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Published by Scientific technical
Union of Mechanical Engineering
International virtual journal for science, technics andinnovations for the industry
YE
AR
VIII
9
Is
su
e
IS
SN
13
13
-02
26
/ 2014
MACHINESTECHNOLOGIESMATERIALS
MACHINES, TECHNOLOGIES, MATERIALS
INTERNATIONAL VIRTUAL JOURNAL
PUBLISHER
SCIENTIFIC TECHNICAL UNION OF MECHANICAL ENGINEERING
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ISSN 1313-0226 YEAR VIII ISSUE 9 / 2014
EDITORIAL BOARD
Editor-in-chief: Prof. Dr. Mitko Mihovski – Chairman of the Scientific Council of the STUnion of Mechanical Engineering
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CONTENTS
DAMAGE QUANTIFICATION RELIABILITY IN BEAMS USING INCOMPLETE STATIC INFORMATION Štimac Grandić I., D. Grandić D. ................................................................................................................................................... 3 SATELLITE PUMP AND MOTOR Sliwinski P. .................................................................................................................................................................................... 8 SOCIAL RESPONSIVENESS OF RUSSIAN BIG INDUSTRIAL BUSINESS AGANIST THE BACKDROP OF A GLOBAL FINANCIAL CRISIS Kuznetsova O., V. Kuznetsov, V. Makarov ................................................................................................................................ 12 APPLYING ULTRASONIC PRESSING IN MANUFACTURING SLIP BEARINGS MADE OF COMPOSITE MATERIAL BASED ON POLYTETRAFLUOROETHYLEN Eremin E., D. Negrov .................................................................................................................................................................. 15 COMPACT SATELLITE HYDRAULIC UNIT Patrosz P., P. Śliwinski. ............................................................................................................................................................... 17 CORROSION RESISTANCE OF LASER WELDED JOINTS OF TP347HFG AND VM12-SHC STAINLESS STEELS Scendo M., B. Antoszewski, J.Trela, S. Tofil .............................................................................................................................. 21 PROBABILITY STRESS CONDITIONS IN MACHINE ELEMENTS Popov A. ...................................................................................................................................................................................... 24 PENETRATION KINETIK OF BISMUTH MELT INFO COPPER POLYCRYSTALLINE STRUCTURE Apyhtina I.V., M.Sc. Novikov A.A., Novikova E.A., Orelkina D.I., Petelin A.L. ..................................................................... 26 RISK MANAGEMENT IN INDUSTRIAL ENTERPRISES Mihova T., V. Nikolova – Alexieva, T. Gigova .......................................................................................................................... 28 SCIENTIFIC BASES OF CREATION OF HIGHLY EFFECTIVE BIOACTIVE COATINGS FOR BONE IMPLANTS Lyasnikov V., S. Speransky ......................................................................................................................................................... 32 COMMERCIALLY PURE COPPER AND LOW-ALLOYED CHROME BRONZE IN TRIBOLOGICAL CONTACT WITH GRAPHITIFEROUS MATERIAL Semenov V.I., L.Sh. Shuster, S.-J. Huang, P.-Ch. Lin, R. Rajendran ......................................................................................... 36 DYNAMIC PARAMETERS OF A CHAIN TRANSMISSION IN METAL AND POLYMER DESIGN Pilipenko O., A. Poluyan ............................................................................................................................................................. 40 RAPID PROTOTYPING – DEFINITION OF TERMS AND HOW TO APPLY DURING A STUDENT PROJECT Pointner A., H.P. Schnöll, M. Friessnig, P. Heinzle .................................................................................................................... 44 VIBRATION MONITORING FOR FAULT DETECTION AND PROCESS CONTROL OF THE MOTOR-MIXER AGREGATE IN FENI INDUSTRY-MACEDONIA Geramitchioski T., Lj.Trajcevski ................................................................................................................................................. 47 COMPUTER AND PHYSICAL SIMULATION OF ANGULAR PRESSING Sosenushkin E.H., E.A. Yanovskaya, A.E. Sosenushkin ........................................................................................................... 52
DAMAGE QUANTIFICATION RELIABILITY IN BEAMS USING INCOMPLETE STATIC INFORMATION
Ass. Prof. Dr. Eng. Štimac Grandić I.1, Ass. Prof. Dr. Eng. Grandić D.2
Faculty of Civil Engineering, University of Rijeka, Croatia 1,2
E-mail: [email protected] Abstract: In the paper a new procedure based on the simple arithmetic operations for location and quantification of damage in beams
using incomplete static information is presented. The grey system theory is employed to locate damage in beam structure using static displacements for two structural stages. Once the location of damage is known, the damage quantification can be done by comparing the displacement curvatures of intact and damage stage of structure. The set of numerical simulations on simply supported beam is conducted to determine the damage quantification reliability of proposed procedure for different damage severities. Also, the results of laboratory test are employed to verify results obtained by numerical simulations.
Keywords: DAMAGE DETECTION, STATIC TEST, DISPLACEMENT, BEAM STRUCTURE
1. Introduction In the past decades a lot of researches dealt with damage
detection, damage localization and damage quantification in different structures such as beams [1,2], plates [3,4], frames or trusses [4]. In general, the damage detection methods can be categorized as: methods based on static structural responses [1,5,6] and methods based on dynamic structural responses [2,4,7]. Also, some researchers combine foregoing structural responses [3]. Some of developed methods can detect and locate the damage [1,8,9] and some of them, beside detection and location, are able to determine the damage severity (quantified the damage) inside the damaged section [2,5,7]. The main problem in both, static and dynamic damage detection methods is incompleteness of structural response information (displacement, mode shape, etc.) i.e. sparseness of measurement [8,9]. Often, algorithms for damage quantification using sparse measurement include solving complicated inverse problems, solving nonlinear optimization problems or using iterative methods [10]. In this paper a new procedure based on the simple arithmetic operations for location and quantification of damage in beams using incomplete (sparse) static displacement is presented. Results of the numerical study and laboratory test are used to determine the damage quantification reliability of proposed procedure for different damage severity.
2. Theoretical formulation of damage detection and quantification method
Damages in the structures may cause a degradation of structural properties which manifest itself as a change in static responses of a structure. It can be concluded that if there is damage present in the structure its static response will not be the same as the response of an intact structure.
In bent beams, where influence of transversal force on curvature may be neglected, the relationship between curvature, bending moment and bending stiffness can be written as:
)()()(
xEIxMx =κ (1)
)()()(
xEIxMx d
dd =κ . (2)
where M(x), EI(x), κ(x), Md(x), EId (x), κd (x) are bending moment, bending stiffness and curvature for intact and damaged state of structure. In statically determinate beam, where bending moment is not dependent of the bending stiffness, M(x)=Md(x), equating the equations (1) and (2) gives relationship between bending stiffness and curvatures for two stages of the structure:
)()(
)()(
xx
xEIxEI
d
d
κκ
= . (3)
If damage is defined as EId=(1-δ)EI , the decrease in bending stiffness δ can be express as:
)()(1)(x
xx dκκδ −= (4)
The curvature of a geometrically and materially linear intact and damaged beams can be written as:
2
2 )()(dx
xwdx =κ ; 2
2 )()(dx
xwdxd
d =κ (5)
where w(x) and wd(x) are displacement lines of intact and damaged structure, respectively.
Due to limited number of measurement equipment, only a limited number of displacements can be measured on the structure, i.e. structure may be treated as it is divided in limited number of segments j between measured displacements in positions i=1 to n (Figure 1).
x
i-2 i-1 i i+1
j-1 j j+1
xi-1xi
xi+1
1 nn-1 n 0 1
w
Fig. 1 The beam's segments “j” and measuring positions “i”
The decrease in bending stiffness δj inside the segment j, can be now rewritten as:
jdj
jκ
κδ −= 1 (6)
where κj and κjd are intact and damaged curvature of the segment j.
Unfortunately, κj and κjd cannot be calculated directly from known
discrete values of displacement.
The curvature of discrete values of displacement can be calculated at the point xi using next equation:
)()()()(2)()(
11
11
iiii
iiii xxxx
xwxwxwx−⋅−+⋅−
≈+−
+−κ (7)
where w(xi) is the value of displacement at the point xi, w(xi-1) and w(xi+1) are the values of displacement at the points xi-1 and xi+1, respectively.
Similar equation can be written for displacement curvature of damaged structure κd(xi) using values wd(xi), wd(xi-1) and wd(xi+1).
3
As it can be seen form Eq. (7), the curvatures κ(xi) and κd (xi), at the position xi (i=1 to n-1) are calculated taken into account the values of displacement in positions xi-1, xi, xi+1. Bearing that fact in mind the curvature at the position xi can be treated as average curvature κ at the adjacent segments j and j+1
)()( 1)(ixix jjix +== κκκ (8)
)()( 1)(ixix j
dj
di
d x +== κκκ . (9)
Then
)()( 1)(
)(1)(
ixix jji
di
ix
xx +==−= δδ
κ
κδ . (10)
Measured or calculated values of displacements usually contained some errors due to different causes, thus, theoretical assumption of zero curvature difference in intact segments will not be fulfilled. Hence, the grey relation coefficient ζ(xi) is employed to detect the position of significant changes in curvature associated with the damage position [1, 10]
RxRRRx
ii max5.0)(
max5.0min)(⋅+⋅+
=ζ (11)
where R(xi) =κ(xi)-κd(xi).
In the points where ζ(xi)≥0.6 it will be assumed that there is no significant changes in curvatures, i.e. 0)( =ixδ [1,10].
Suppose the damage is situated within a single segment j. The grey relation coefficients at the point xi-1 and xi, which are situated at the beginning and at the end of the damaged segment j, will be less than 0.6, i.e. δ(xi-1)≠0 and δ(xi) ≠0. According to Eq. (10) calculated vales δ(xi-1) and δ(xi) shows the average value of decrease in bending stiffness in segments j-1 to j and j to j+1, respectively. As we know that there are no damages in segments j-1 and j+1 the decrease of bending stiffness in segments j=2 to n-1 can be calculated as follows:
)()(2
)(2)(21
1ii
ij xxxx δδδδδ +=
⋅+⋅= −
− (12)
Determination of decrease of bending stiffness in edge elements (j=1 and j=n) can be obtained by using following equations
)(2 11 xδδ ⋅= (13)
)(2 1−⋅= nn xδδ (14)
because the curvatures in the points i=0 and i=n cannot be determined according to Eq. (7).
Based on the previous considerations, the following damage quantification algorithm is proposed:
a) define κ(xi) and κd (xi)
b) R(xi) =κ(xi)-κd(xi).
c) RR
RRxi max5,0max5,0min)(
⋅+⋅+
=ζ
d) if 6,0)( ≥ixζ then 0)( =ixδ
e) if 6,0)( <ixζ then )(
)(1)(
id
ii
xx
xκκ
δ −=
f) )()( 1)(
ixix jjix +== δδδ
g) if 0)1(1 =
xδ then 01 =δ
h) if 0)1(1 ≠
xδ and 0
)2(2 =x
δ then )1(11 2
xδδ ⋅=
i) if 0)1(=
−nxnδ then 0=nδ
j) if 0)1(≠
−nxnδ and 0)2(1 =
−−
nxnδ then )1(12
−⋅=
nxn δδ
k) if 0)(=
ixjδ or 0
)1(=
−ixjδ then 0=jδ , when i=2 to n-1
l) if 0)(≠
ixjδ and 0
)1(≠
−ixjδ then )()( 1 iij xx δδδ += − , when
i=2 to n-1
m) print jδ .
3. Numerical examples The analysis has been carried out for simply supported beam
with different damage severities inside the damaged section of the beam. The span length of the beam is L=9.955 m. The cross section area of the beam is A=2.19⋅10-3 m2, the moment of inertia of intact beam is I=3.83⋅10-6 m4 and Young's modulus is E=2.1⋅108 kN/m2. The applied force at 4.252 m from the left support is F=0.484 kN.
1 2 3 4 5 6 7 8 9 10 11
L=11⋅0.905=9.955 m
F=0.484 kN
0 1 2 3 4 5 6 7 8 9 10 11
Fig. 2 The beam model
The beam is modelled using beam finite elements with knots at both ends of the element (Figure 2). The model has 11 finite elements (1-11) of 0.905 m length and 12 knots (0-11). The displacement have been computed at every finite element knot for both the intact and the damaged state. The bending stiffness of damaged section is reduced by reducing the moment of inertia of intact section for 9 damage scenarios: DS1=10%, DS2=20%, DS3=30%, DS4=40%, DS5=50%, DS6=60%, DS7=70%, DS8=80% and DS9=90%.
3.1 Example 1
The damage has been simulated by reducing the bending stiffness of the whole 5th finite element (at the distance of 3.62 m to 4.525 m from the left support) as it can be seen in Figure 3. According to the proposed algorithm in Chapter 2 the values of decrease of bending stiffness for each finite element are calculated.
1 2 3 4 5 6 7 8 9 10 11
damagedsection
3.62 m4.525 m
Fig. 3 The position of damage (example 1)
Comparison of identified (calculated) and present (simulated) damage for all damage scenarios can be seen in Figures 3-7.
05
1015
1 2 3 4 5 6 7 8 910
11
10,8 10
[%]
element number
identifiedpresent
0
10
20
1 2 3 4 5 6 7 8 910
11
22,9020[%]
element number
identifiedpresent
Fig. 3 Damage quantification for DS1 (left) and DS2 (right) – example 1
4
010203040
1 2 3 4 5 6 7 8 910
11
36,3030
[%]
element number
identifiedpresent
0204060
1 2 3 4 5 6 7 8 910
11
51,3040
[%]
element number
identifiedpresent
Fig. 4 Damage quantification for DS3 (left) and DS4 (right) – example 1
0204060
1 2 3 4 5 6 7 8 910
11
69,10
50[%]
element number
identifiedpresent
0306090
1 2 3 4 5 6 7 8 910
11
87,50
60
[%]
element number
identifiedpresent
Fig. 5 Damage quantification for DS5 (left) and DS6 (right) – example 1
0306090
120
1 2 3 4 5 6 7 8 910
11
109,5070
[%]
element number
identifiedpresent
050
100150
1 2 3 4 5 6 7 8 910
11
135,40
80
[%]
element number
identifiedpresent
Fig. 6 Damage quantification for DS7 (left) and DS8 (right) – example 1
050
100150
1 2 3 4 5 6 7 8 910
11
164,80
90
[%]
element number
identifiedpresent
Fig. 7 Damage quantification for DS9 – example 1
3.2 Example 2
The damage has been simulated by reducing the bending stiffness of a 1/2 of 5th finite element (at the distance of 3.846 m to 4.298 m from the left support) as it can be seen in Figure 8.
1 2 3 4 5 6 7 8 9 10 11
damagedsection
3.846 m4.298 m
Fig. 8 The position of damage (example 2)
According to proposed algorithm in Chapter 2 the values of decrease of bending stiffness for each finite element are calculated. In Figures 9 to 13, the comparison of identified and present damage for all damage scenarios is presented. Present values of damage are expressed as the mean values of damage in the whole 5th element (i.e. for DS1 the mean value of damage in the whole element is 5%).
0
5
10
1 2 3 4 5 6 7 8 910
11
5,65
[%]
element number
identifiedpresent
05
1015
1 2 3 4 5 6 7 8 910
11
12,110
[%]
element number
identifiedpresent
Fig. 9 Damage quantification for DS1 (left) and DS2 (right) – example 2
0
10
20
1 2 3 4 5 6 7 8 910
11
20
15[%]
element number
identifiedpresent
0102030
1 2 3 4 5 6 7 8 910
11
29,520
[%]
element number
identifiedpresent
Fig. 10 Damage quantification for DS3 (left) and DS4 (right) – example 2
0
25
50
1 2 3 4 5 6 7 8 910
11
4125
[%]
element number
identifiedpresent
0
30
60
1 2 3 4 5 6 7 8 910
11
56
30
[%]
element number
identifiedpresent
Fig. 11 Damage quantification for DS5 (left) and DS6 (right) – example 2
0
40
80
1 2 3 4 5 6 7 8 910
11
75,4
35
[%]
element number
identifiedpresent
04080
120
1 2 3 4 5 6 7 8 910
11
102
40
[%]
element number
identifiedpresent
Fig. 12 Damage quantification for DS7 (left) and DS8 (right) – example 2
050
100150
1 2 3 4 5 6 7 8 910
11
140
45
[%]
element number
identifiedpresent
Fig. 13 Damage quantification for DS9 – example 2
3.2 Example 3
The damage has been simulated by reducing the bending stiffness of a 1/3 of 5th finite element (at the distance of 3.922 m to 4.223 m from the left support) as it can be seen in Figure 14. According to proposed algorithm in Chapter 2 the values of decrease of bending stiffness for each finite element are calculated.
In Figures 15 to 19, the comparison of identified and present damage for all damage scenarios is presented. Present values of damage are expressed as the mean values of damage in the whole
5
5th element (i.e. for DS3 the mean value of damage in the whole element is 10%).
1 2 3 4 5 6 7 8 9 10 11
damagedsection
3.922 m4.223 m
Fig. 14 The position of damage (example 3)
0
2,5
5
1 2 3 4 5 6 7 8 910
11
3,603,33
[%]
element number
identifiedpresent
0
5
10
1 2 3 4 5 6 7 8 910
11
8,30
6,67
[%]
element number
identifiedpresent
Fig. 15 Damage quantification for DS1 (left) and DS2 (right) – example 3
05
1015
1 2 3 4 5 6 7 8 910
11
13,8010
[%]
element number
identifiedpresent
0
10
20
1 2 3 4 5 6 7 8 910
11
20,00
13,33
[%]
element number
identifiedpresent
Fig. 16 Damage quantification for DS3 (left) and DS4 (right) – example 3
0102030
1 2 3 4 5 6 7 8 910
11
29,50
16,67
[%]
element number
identifiedpresent
0
25
50
1 2 3 4 5 6 7 8 910
11
41,20
20
[%]
element number
identifiedpresent
Fig. 17 Damage quantification for DS5 (left) and DS6 (right) – example 3
0
30
60
1 2 3 4 5 6 7 8 910
11
57,60
23,33
[%]
element number
identifiedpresent
0
50
100
1 2 3 4 5 6 7 8 910
11
81,80
26,67
[%]
element number
identifiedpresent
Fig. 18 Damage quantification for DS7 (left) and DS8 (right) – example 9
04080
120
1 2 3 4 5 6 7 8 910
11
121,80
30
[%]
element number
identifiedpresent
Fig. 19 Damage quantification for DS9 – example 3
4. Test examples Experimental validation is done by using results of measured
deflection on simply supported intact and damaged beam presented in paper [8]. The properties of the test intact beam are the same as those of the numerical example described in Chapter 3. The deflections due to force F=0.484 kN acting at 4.252 m from the left support were measured at every 0.905 m from the supports (at positions N2-N11 in Figure 20).
The damage was introduced by subsequently grinding cuts inside the 5th segment as it is shown in figures 20, 21 and 22 [8]. The decrease in bending stiffness in damaged cross section is about 60% in comparison to intact cross section in both test damage scenarios.
Fig. 20 Test beam specimen [8]
Fig. 21 Test damage scenario 1 [8]
Fig. 22 Test damage scenario 2 [8]
The identified values of decrease of bending stiffness calculated using the proposed algorithm and real decrease of bending stiffness are shown in Figure 22 for test damage scenario 1 and 2 (TDS1 and TDS2), respectively.
0306090
1 2 3 4 5 6 7 8 910
11
68,6
36
[%]
element number
identifiedreal
Fig. 23 Damage quantification for TDS1 (left) and TDS2 (right) – test example
0306090
1 2 3 4 5 6 7 8 910
11
87
60
[%]
element number
identifiedreal
Fig. 23 Damage quantification for TDS1 (left) and TDS2 (right) – test example
6
The real value of decrease in bending stiffness due to grinding cuts of 60% of intact bending stiffness at the 60% of segment of 0.905 m for TDS1 is expressed as the mean value of damage to the whole segment.
5. Discussion and conclusion As it can be seen form conducted numerical and test examples
the damage is successfully located in all cases.
The comparison of identified and present/real values of decrease in bending stiffness are shown in Tables 1 and 2 as deviation of identified values to present/real values of decrease in bending stiffness.
As it can be seen from Chapter 3 and Table 1, all identified values in numerical examples are greater than present/real values of decrease in bending stiffness. Generally, proposed method give overestimated values of damage severity. In Chapter 3.1, in case of damage scenarios DS7-DS9, as well as in Chapter 3.3 in case of DS9, identified decrease in bending stiffness is greater than 100% what is fiscally impossible. This phenomena is a result of using algorithm based on simple arithmetic operation and insufficient number of structural response data.
Tab. 1 Deviation of identified and present values of decrease in bending stiffness for numerical examples [%]
Damage scenario Example 1 Example 2 Example 3
DS1 8 12 9
DS2 15 21 24
DS3 21 34 38
DS4 28 48 56
DS5 38 64 77
DS6 46 87 106
DS7 56 115 147
DS8 69 153 206
DS9 83 211 306
In cases where a present damage is the smallest (10%) the
deviation of identified over present damage is approximately 10%. In cases of the greatest damage severity of 90% the deviation of identified over present damage is between 83 and 306%. If we compare the same damage scenario it can be seen that overestimation of damage is greater in case where damage is situated on the smallest section, i.e. overestimation of damage is greater if sparseness of data is greater.
Tab. 2 Deviation of identified and real values of decrease in bending stiffness for test examples [%]
Damage scenario Test Examples
TDS1 96
TDS2 45
The results of using test data confirm numerical conclusion.
Test damage scenario 1 (TDS1), where damage covers approximately 60% of length of 5th segment can be compared with damage scenario 6 in numerical example 2 (DS6-2) while test damage scenario 2 (TDS2), where damage covers approximately the whole 5th element can be compared with damage scenario 6 in numerical example 1 (DS6-1). The deviation of identified and present/real values of decrease in bending stiffness for TDS1 is 96% and for DS6-2 is 87%. The deviation of identified and present/real values of decrease in bending stiffness for TDS2 is 45% and for DS6-1 is 46%.
If we suppose that overestimation up to 50% of identified over present/real damage is acceptable in engineering purposes it can be concluded that presented method can be successfully used in detection and quantification of those damages where decrease of bending stiffness is not greater than 40%.
Acknowledgement This work has been partially supported by University of Rijeka
through grant No. 13.05.1.1.01.
6. References [1] Abdo M. A-B., Parametric study of using only static response in structural damage detection, Engineering Structures, 34, p. 124–131, 2012 [2] Choi F.C., Li J., Samali B., Crews K., Application of the modified damage index method to timber beams, Engineering structures, 30(4), p. 1124-1145, 2008 [3] Yam L.H., Li Y.Y., Wong W.O., Sensitivity studies of parameters for damage detection of plate-like structures using static and dynamic approaches, Engineering Structures, 24(11), p. 1465-1475, 2002. [4] Qiao P., Lu K., Lestari W., Wang J., Curvature mode shape-based damage detection in composite laminated plates, Composite structures, 80(3), p. 409-428, 2007. [5] Yang Q.W.; Sun B.X., Structural damage localization and quantification using static test data, Structural Health Monitoring, 10(4), p. 381-389, 2011. [6] Štimac I., Uporaba utjecajnih linija progiba u otkrivanju oštećenja konstrukcija, Disertacija, Split, 137 p. 2006. (in Croatian) [7] Zou Y., Tong L., Steven G.P., Vibration-based model-dependent damage (delamination) identification and health monitoring for composite structures—a review, Journal of Sound and Vibration, 230(2), p. 357–378, 2000. [8] Choi I.-Y., Lee J. S., Choi S., Cho H.-N., Development of elastic damage load theorem for damage detection in statically determinate beam, Computer and Structures, 82(29-30), p. 2483-2492, 2004. [9] Guan H., Karbhari V.M., Improved damage detection method based on element Strain damage Index using sparse measurement, Journal of Sound and Vibration, 309(3-5), p. 465-494, 2008. [10] Chen X-Z., Zhu H-P., Chen C-Y., Structural damage identification using test static data based on grey system theory, Journal of Zhejiang University SCIENCE (JZUS), 6A(8) p. 790–796, 2005.
7
SATELLITE PUMP AND MOTOR
PhD. Eng. Sliwinski P. Faculty of Mechanical Engineering – Gdansk University of Technology, Poland
Abstract: The article describe the design and operation of a prototype of satellite pump and a prototype of satellite motor. In both machines, the operating mechanism consists of a non-circular gear with external teeth (rotor), non-circular gear with internal teeth (curvature), and ten gear wheels which cooperate with the rotor and the curvature. The differences between the commutation unit in the pump and the commutation unit in the motor are described. The principle of axial clearances compensation in the pump and in the motor is also presents. The article contains the values of the losses and the efficiency of these machines supplied with rapeseed oil, HFA-E emulsion and pure tap water. The results of durability tests of motor supplied with HFA-E emulsion and rapeseed oil are also presented.
Keywords: SATELLITE MOTOR, SATELLITE PUMP, GEAR MECHANISM, HFA-E EMULSION, WATER, RAPESEED OIL
1. Introduction In recent years, at the Gdansk University of Technology, started
research work on first satellite pump (marked PSM) with axial clearance compensation (Fig. 1). The developmental research of satellite motor (marked SM) with small geometrical displacement (5÷34 cm3/rev) are also conducted (Fig. 1). Production of the SM motors was undertaken by Stosowanie Maszyn company [13].
In Poland are already produced and well-known low-speed (to 400 rev/min), high-torque hydraulic satellite motors (marked HS) with geometrical displacement 0,4÷6,3 dm3/rev (Fig. 2) [12].
Fig. 1. General view of the newest satellite motor type SM (on the left) and the newest satellite pump type PSM (on the right) [5].
Fig. 2. General view of satellite motor type HS [2].
The research problems stemmed from the requirement to
develop and implement new constant displacement self-priming satellite pumps and satellite motors mostly useful for driving systems and low mechanization of mining equipment in the mining industry. Due to fire safety non-flammable liquids are used in coal mines. The most commonly used liquid is emulsion of oil in water type HFA-E, which contains from 95-99% of water. In extreme situations pure water applications may occur, such as mine rescue equipment or other devices. Motors with a small geometrical displacement are also needed to drive the devices and portable tools in the food industry. Therefore, it is recommended testing the engine fed with vegetable oil. In Gdansk University of Technology the research of the lubricating properties was conducted. Refined rapeseed oil (edible) showed a good lubricating property [3].
2. Satellite working mechanisms The working mechanism of HS motor, the working mechanism
of SM motor and pump PSM are different gear mechanism. In HS motor applied mechanism, which consist of internally toothed eight-hump curvature, externally toothed six-hump rotor and fourteen satellites (Fig. 3). And in the motor SM applied mechanism, which
consist of six-hump curvature, four-hump rotor and ten satellites (Fig. 4).
Fig. 3. HS motor satellite working mechanism: C – curvature, R – rotor, S - satellite [2].
Fig. 4. Satellite working mechanism of the motor type SM and the pump type PSM [8,9,10]
Working chambers are created by the curvature, the rotor and every two neighboring satellites. The satellites act as movable sealed baffles between the chambers. The working chambers in satellite mechanism are closed by two commutation plates (Fig. 5). These plates are made of sintered carbide. In these plates we can find the inflow and outflow holes. The number of these holes is equal to the number of humps on the curvature.
Fig. 5. Commutation plate of satellite motor [1].
The pressure of the working medium causes the satellites roll around the stationary curvature. The effect of the pressure in the working chamber is a force which does not pass through the axis of the rotor. This creates a torque which forces the rotation of the rotor. The particular configuration of the rotor humps and the curvature humps causes during rotation of the rotor chamber periodically change their working volume. Supplied chambers increase the volume, while the chambers reducing the volume extruding the working fluid.
The satellites act as inflow and outflow distributors. The satellite close corresponding holes in the commutation plates at the
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time of the transition of the chamber from the filling phase to the extrusion phase.
Number of working chambers and number of satellite is equal to the sum of curvature humps and rotor humps. Number of cycles of filling and emptying chambers, per one rotation of the shaft, is equal to the product of the number of humps of the curvature and rotor. So, in the working mechanism of the HS motor the number of cycles is 48 and in the mechanism of SM motor (and PSM pump) the number of cycle is 24.
Geometrical displacement of satellite working mechanism depends on the teeth module and the height of mechanism. In HS motors are used modules 1,5 mm and 2,5 mm. While in the SM motors and PSM pumps are applied teeth modules: 0,4 mm, 0,5 mm, 0,6 mm and 0,75 mm.
In HS motors are applied mechanisms with involute tooth profile or circular-arc tooth profile (Fig. 6).
Fig. 6. Involute (on the left) and circular-arc tooth profile (on the right).
For mechanism with the involute profile nominal working pressure is only 20 MPa. The working mechanism with circular-arc tooth profile has been developed to increase the nominal working pressure up to 35 MPa. However, as research has shown, the mechanism with circular-arc profile of tooth is characterized by accelerated wear. The reason is too large the surface pressure of cooperation teeth. It turned out, that the permissible surface pressure is higher for teeth with involute profile. Therefore the optimal solution is involute-arc profile of tooth. Such a profile of the tooth is a hybrid [4,6]. In the area of tooth contact the profile is involute. But in the remaining area the tooth profile is arched (Fig. 7). The tooth with involute-arc profile characterized the greater bending strength than the tooth with involute profile. The FEM calculation results showed a difference about 30%.
Fig. 7. The satellite with involute-arc profile of the teeth [7].
The operating mechanism with involute-arc profile teeth is making by spark machining method. This mechanism is made from tool steel Nimax and sulfonitrided [16].
In satellite working mechanism the most unfavorable position of the satellite relative to the rotor is in area of five teeth on the rotor hump (Fig. 8). In this area the pitch diameter PD-R of the rotor is smallest. Due to the small number of teeth (ten) on the satellite receives a small tooth contact ratio. This affects the unfavorable distribution of inter tooth force.
Fig. 8. The characteristic position of the rotor and satellites: RT – rotor teeth most loaded, HPC – supply channel (high pressure), LPC – outflow channel (low pressure), PD-R – pitch diameter of the rotor hump, PD-S – pitch diameter of the satellite.
Satellite is pressed against the rotor and the curvature with a force resulting from the pressure difference ∆p. At ∆p = 25 MPa the nominal force acting on the tooth is 1500 N. Numerical calculations of tooth were performed, assuming that the mechanism is stationary. The calculation results showed that the stresses at the base of the tooth are 500 MPa (Fig. 9). The contact stresses at the contact point of teeth reach a value of 2000 MPa. Furthermore, after the load of motor shaft, deforms both the shaft and the planet.
Fig. 9. Stress distribution at the contact point of the rotor with satellite (on the left) and stress distribution along the length of the tooth (on the right).
During the motor operation, the teeth of operating mechanism are subject to variable loads. It was calculated that: a) allowable stress σFp for fatigue break the tooth are 520 MPa; b) allowable stress σHp for fatigue tooth surface amounts to 710
MPa. So the condition for the fatigue strength of the surface has not
been met. Furthermore, it should be noted that the satellites are moving freely in the tip clearances. Thus, as a result of the pressure difference, in the teeth cooperation area occurs slippage. This is an additional reason for accelerating the process of tooth wear. In the operating mechanism, on one shaft revolution, the number of loads of each tooth is: a) 4 – for curvature (equals the number of the humps on the rotor); b) 6 – for rotor (equals the number of the humps on the curvature); c) 5 – for satellite (equals the average of the amount of humps of
the rotor and the curvature).
The conclusion is that the rotor teeth will use up the fastest. In the engine running at 1500 rev/min for one hour the number of load cycles of each tooth of the rotor is 540 thousand. In addition, on the durability of the operating mechanism has an impact rotational speed. When rotor speed is 1500 rev/min, then satellites move with flat, with variable speed, in the range of 2849 ÷ 3501 rev/min. This causes additional forces of inertia loading teeth.
3. Satellite motor type SM The overall view of the newest satellite motor is presented in
Fig. 2 and the cross-section is presented in Fig. 10. In this motor is applied working mechanism with involute-arc teeth.
Fig. 10. Cross section of the satellite motor type SM [5]: C – curvature, S – satellite, R – rotor, 1 – shaft, 2 – body, 3 – front body, 4 – rear body, 5,6 – in- or outflow manifold, 7,8 – commutation (compensation plate).
In motor satellites and rotor are lower than curvature with value of 5±1 µm (Fig. 11a) parameter A). Motor operating mechanism includes axial clearances compensation of rotor and satellites (Fig. 11). On the one side of the compensation plate acts pressure from working chambers and on the other side acts pressure from inflow manifold channel. The force of compensation Pc is bigger than the force given by working chambers (Pwc+Pgr+Pgs) and then the
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compensation plates is bending down. In this way total axial clearances are lower, internal leakage is lower and volumetric efficiency higher in effect.
Fig. 11. Idea of axial compensation in satellite motor: a) state before tighten up of clamp (X – high of curvature, A – axial clearance of satellites and rotor, Di – inside diameter of compensation area, Do – outside diameter of compensation area); b) state after tighten up of clamp and under load (B – value of decrease of high of curvature after tighten up of clamp, A’ – real axial clearance in loaded motor, C – value of bend of compensation plate, Fs – force of press down curvature generated by clamp, Pc – pressure in exhaust manifold, Pwc – pressure in working chambers, Pgs – pressure in satellite gaps, Pgr – pressure in rotor gap) [8,9].
Between the rotor and compensation plates there are no leek stoppers. Thus, existing leakage goes from working chambers to the chamber of shaft. Then the leakage drains to outflow manifold channel. Therefore, the pressure in the shaft chamber is higher than in the motor outlet port. It was found that especially in hydraulic mining installations, the pressure in the outflow port can be up to 2 MPa. In addition, at the shaft speed of 1500 rev / min, the speed of shaft spigot surface relative to the seal is more than 2 m/s. Consequently shaft seals are exposed to rapid destruction.
Experimental studies have shown that the best shaft seals for satellite motor should be the seal named TurnRing or R9 (Fig. 12) [6]. The sealed surface of the shaft spigot should have a low roughness – Ra=0,1 being the best. It is also recommended to cover the shaft spigot surface with the low friction, hard coating, like Balinit C [15]. Balinit C is a low-friction coating, made on the basis of amorphous carbon with the addition of tungsten (designation of the coating material: WC / C (aC: H: W)) with a micro-hardness 1500HV.
Fig. 12. The seal TurnRing [14] and R9 [15].
4. Satellite pump type PSM The newest satellite pump (Fig. 2) was built based on the
satellite motor design. The newest construction of satellite pump is showed in Fig. 13. Construction of the high side of the pump is the same as in the motor. And different is the design of the low pressure side (suction side in pump). Moreover, another is in the shape of holes in compensation plate 7 (Fig. 13). In this plate are the noncircular holes SH. In pumping plate 6 are circular holes like in the motor SM. The field of the suction hole SH is 25% greater than the outflow hole in plate 6. The commutation plates 6 and 7 play the role of the compensation plates simultaneously. In this way the satellite pump includes axial clearances compensation. Construction and principle of operation the compensation on the pressure side is the same as in the engine (Fig. 11).
In contrast to the engine was designed and applied compensation on the suction side of the pump. In the suction port 3 was placed compensation chamber CC. This chamber has the shape of a ring having an outer diameter D2 and inner diameter D1. The compensation chamber CC is connected at least one compensation
hole CH to the high pressure working chambers. Laboratory results have shown, that at a pump speed 1500 rev/min, the pressure in the compensation chamber CC is about 20% lower than the discharge pressure.
Fig. 13. Cross section of the newest satellite pump PSM: C – curvature, S – satellite, R – rotor, 1 – shaft, 2 – body, 3 – front body, 4 – rear body (suction port), 5 – pumping manifold, 6 – pumping commutation plate, 7 – suction commutation plate, detail A – construction of compensation on suction side, SH – non circular suction hole, CH – compensation hole, CC – compensation chamber, CA – compensation area.
Application of compensation to the suction side is only possible in the pump due to the constant fluid flow direction.
5. Test results of SM motor and PSM pump Laboratory test of the motor SM-0,6/20 and the pump PSM-
0,75/15 have been carried out. These machines parameters are given in Tab. 1.
Table 1: Parameters of tested motor and pump SM-0,6/20 PSM-0,75/15
Tooth module 0,6 mm 0,75 mm Height of the operating mechanism 20 mm 15 mm
Theoretical displacement 16,7 cm3/rev 18,6 cm3/rev
Prior to designing the satellite motor assumed nominal working pressure 25 MPa. However, calculations have shown that for pressure 25 MPa the condition is satisfied only for tooth bending. That is the working pressure of 25 MPa can be intermittent or instantaneous pressure. Losses and efficiencies of tested motor and pump, for ∆p=25MPa, are given in Tab. 2.
Table 2: Losses and efficiencies of tested motor and pump.
W – tap water E – HFA-E emulsion*
RO – rapeseed oil Viscosity of RO: µ=40cSt C
lear
ance
s of
roto
r /
sate
llite
[µm
]
Vol
umet
ric
loss
es [l
/min
]
Vol
umet
ric
effic
ienc
y [-]
Torq
ue o
f lo
sses
[Nm
] H
ydr-m
ecan
. ef
ficie
ncy
[-]
Motor SM-0,6/20
n=1500 rpm; ∆p=25 MPa
W 7 / 6,7 4,5 0,83 6,1 0,90 E 6 / 4,5 4,2 0,84 12,3 0,81
RO 4,5 / 6,2 1,5 0,94 10,4 0,83 Pump PSM-
0,75/15
n=750 rpm; ∆p=25 MPa
W 5 / 4,5 3,2 0,77 10,9 0,87 E 5 / 4,5 3,2 0,77 10,0 0,88
RO 5,4 / 5,8 1,8 0,88 7,5 0,90 *) 1% concentrate ISOSYNTH VX110-BF in tap water
Nevertheless it was decided, to check what will be the durability of the operating mechanism of motor at the pressure 20 MPa. For comparison, it was decided to check the durability of the engine at a lower load, corresponding to a pressure of 15 MPa. The elements of SM-0.6/20 engines which were running in different mode were studied. Modes were marked as: “A”, “B” and “C” and their characteristic was showed below in Tab. 3.
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Table 3: Various engine operating modes Mode Working fluid Speed Decrease
pressure A 1% emulsion HFA-E*) 1500 rpm 20 MPa B
refined rapeseed oil 1500 rpm 20 MPa
C 15 MPa D 10 MPa
*) 1% concentrate ISOSYNTH VX110-BF in tap water Laboratory tests showed low durability of rotor teeth. Time
after which occurred the destruction of mechanism is for mode: a) A – 4 hours (2,16 million load cycles of the rotor teeth); b) B – 35 hours (18,9 million load cycles of the rotor teeth); c) C – 46 hours (24,8 million load cycles of the rotor teeth);
For mode D after 111 hours test was discontinued. There was no destruction of working mechanism.
Fig. 14 (on the left) shows an example of tooth wear on the rotor hump. Further exploitation leads to breaking the tooth and clutch action of the entire mechanism (Fig. 14 on the right).
Fig. 14. Tooth wear on the rotor hump (on the left) and destroyed elements of the working mechanism (on the right).
The durability test of motor, for mode D, has shown interesting property of rapeseed oil. On the end of surface of the rotor forms a layer of scorched oil (Fig. 15). The thickness of this layer corresponds to the height of the gap between the rotor and the compensation plate. On the compensation plate is created distinctive annular discoloration. The result of this phenomenon is to reduce the leakage from the working chambers to the chamber of shaft.
Fig. 15. Scorched rapeseed oil on the end face of the rotor (on the left) and distinctive annular mark on the surface of the plate (on the right).
6. Summary The compensation plates are made of sintered carbide. The
satellite mechanism is made of special tool steel and sulfonitrided. Therefore satellite pumps and motors can work not only with mineral oil but also with other liquid like vegetable oils, emulsions and tap water.
The experimental research shows that the satellite mechanism is characterized by a very low durability under overload condition. Application of liquid with poor lubricant properties (like water and HFA-E emulsion) causes accelerated wear of the working mechanism teeth. The following factors on the durability of the motor operating mechanism have an impact: a) the construction of the operating mechanism; b) the type of steel used for the elements of the mechanism; c) the kind and quality of the thermo-chemical treatment; d) the working fluid.
In hydraulics, it is assumed that the durability of the hydraulic motor should be about 10 thousand hours. Assuming that the engine is running at a speed of 1500 rev/min, the durability of the teeth should be at least 900 million cycles. Thus, the stability under overload conditions, at the pressure drop in the engine 20 MPa, is at least 36 times less than the nominal. Therefore, should be lowered rated working pressure of the engine, reduce its speed and should be chosen of higher strength steel with a suitably chosen heat treatment. At this stage, in order to maintain proper engine durability, it is proposed to reduce the operating pressure up to 10 MPa and the speed to 400 rev/min.
The great advantage of satellite motors and pumps are their small size. Satellites motors can be an excellent alternative to orbital motors. The dimensions and weight of these engines are similar. And the motor efficiency of satellite is greater. Moreover, the orbit motors are not suitable for operation with water and HFA-E emulsion.
Acknowledgment I would like to mention that presented work has been financed
as part of the R&D grant LIDER/35/102/L-2/10/NCBiR/2011 “New elaborate of hydraulic satellite machines for drives with environmentally friendly and non–flammable liquids” from the Polish National Centre for Research and Development.
References [1] Balawender A., Sliwinski P. and others: Developmental research of
hydraulic satellite motors and satellite pump with small geometrical displacement supplied with water, emulsion and oil. Report of research project no. R0300103. Gdansk University of Technology, 2010.
[2] Balawender, A., Elgert K., Sliwinski P. and others: Research on development of satellite hydraulic motors of III generation. Report of research project no. 8T07C04720. Gdansk University of Technology, 2003.
[3] Lubinski J., Sliwinski P. Multi parameter sliding test result evaluation for the selection of material pair for wear resistant components of a hydraulic motor dedicated for use with environmentally friendly working fluids. Conference Wear Processes 2012. Szczecin 2012.
[4] Patrosz P.: New possibilities for generating of shapes of planetary working mechanisms. International Scientific and Technical Conference: Drives and Hydraulic and Pneumatic Controls 2012. Wroclaw, 2012.
[5] Sliwinski P.: The flow of liquid in flat gaps of satellite motors working mechanism. Article accepted for publication in the Polish Maritime Research. 2014.
[6] Sliwinski P.: High pressure rotational seals for shaft of hydraulic displacement machines. Hydraulics and Pneumatics, No. 3/2014.
[7] Sliwinski P. Patrosz. P.: Patent application nr P. 401821. Satellite operating mechanism of hydraulic positive displacement machines. 2012.
[8] Sliwinski P.: R&D of satellite pumps and motors with small geometrical displacement supplied with oil and non-flammable liquids. Developments in mechanical engineering nr 5/2012. Gdansk University of Technology Publishers, Gdansk 2012.
[9] Sliwinski P.: New satellite pumps. Key Engineering Materials nr 490/2012. Trans Tech Publication, Switzerland.
[10] Sliwinski P.: Results of developmental research of hydraulic satellite motors series of types SM. Chapter in the monograph: „Research, design, production and operation of hydraulic systems”, Cylinder Library. Komag Mining Mechanisation Centre, Gliwice 2010.
[11] Sliwinski P., Sliwinski P. and T. Szwajca, Patent applications nr P.392624. Inflow and outflow channels in side plates of satellite working mechanism of displacement machine. 2010.
[12] FAMA. Product catalogue. www.fama-gniew.pl [13] Stosowanie Maszyn. Product catalogue. www.stosowaniemaszyn.pl [14] Trelleborg. Product catalogue. www.trelleborg.com [15] TEST. Product catalogue. www.test.pl [16] Udeholm. Product catalogue. www.udeholm.pl
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SOCIAL RESPONSIVENESS OF RUSSIAN BIG INDUSTRIAL BUSINESS AGANIST THE BACKDROP OF A GLOBAL FINANCIAL CRISIS
СОЦИАЛЬНАЯ ОТВЕТСТВЕННОСТЬ КРУПНОГО ПРОМЫШЛЕННОГО БИЗНЕСА РОССИИ В
УСЛОВИЯХ МИРОВОГО ЭКОНОМИЧЕСКОГО КРИЗИСА
Prof. Dr. of Economics Kuznetsova O. Associate Prof. Ph.D. in Engineering Kuznetsov V. Associate Prof. Ph.D. in Engineering Makarov V.
Omsk State Technical University, Omsk City, Russia [email protected]
Abstract: Modern society is developing in conditions of pressing social, economical and ecological problems. Since Russian big
industrial business as part of society has an effect on its development, social responsiveness becomes increasingly important. Value of social responsiveness is in minimizing negative implications of company production operation, in solving climate, global and local development. Thanks to social responsiveness business becomes more well-established socioeconomically, gets an opportunity of increasing its intangible assets.
KEY WORDS: INDUSTRY, BIG BUSINESS, SOCIAL RESPONSIBILITY
Modern society is developing in conditions of pressing social, economical and ecological problems. Since Russian big industrial business as part of society has an effect on its development, social responsiveness becomes increasingly important. Value of social responsiveness is in minimizing negative implications of company production operation, in solving climate, global and local development. Thanks to social responsiveness business becomes more well-established socioeconomically, gets an opportunity of increasing its intangible assets.
Broad introduction of corporate social responsibility to the practice is dated to 70-s of the XXth century. Nowadays governments of all leading countries associate socio-economic development with expansion of social responsibility of business organizations. This approach - to economic growth through the social responsibility as a factor of permanent development – is the basis of issued in 2000 Lisbon Strategy as a policy document of socio-economic development of European Union [10].
Any company aims to maximize efficiency, which allows to produce and sell high-quality products, to pay dividends to shareholders etc. However, the activities of commercial organizations also have a pronounced social part. Social responsibility of business in economy is the corresponding quality of goods and services, high security of production, normal working conditions for staff etc.
Till now foreign management theory has no classical definition of corporate social responsibility. The meaning of this concept may be defined in many ways and it is very subjective, but one can highlight its main characteristics. In contrast to legal responsibility, social responsibility does not involve hard standards [9]. It is a voluntary businessmen’s duty to follow the policies to make such decisions and to follow such activities that are desirable from the point of view of aims and values of the society. In other words, it is a kind of a social contract between employers, communities and the state, and the purpose is to promote the welfare of the whole society.
One usually classifies socially responsible behavior as [5]: - Charity; -Development of social programs (health, education, etc.) to
support the company staff; - Development of social programs aimed to support the local
community; it is completed by companies; - Additional (i.e. over and above the legally stated) informing
customers about the company's products; - Voluntary withdrawal of products in the event of hazard for
the consumer. The main problem is to define the level owners are ready to be
included in the work on social situation analysis on their management facilities and in the regions. It is obviously that the big businessman primarily is busy making money and counting profits.
Social responsiveness becomes especially important against the backdrop of a global financial crisis. At period of economic recovery some companies viewed a socially responsible policy as advantageous process of self -image investment, but in new conditions the pure economical efficiency of such investment becomes dubious as minimum. This highlights social aspects of responsiveness facing the society.
When discussing the issues of corporate social responsibility, the emphasis is usually done on corporate responsibility. There are many reasons. Large companies are powerful, they are able to bring great benefit and great harm. They employ a large number of people who fall under their influence. In their turn cities and regions where the corporations locate their production, also depend on them. Mass production creates a lot of waste, often toxic one[9].
Criteria for assessing corporate social responsibility may vary depending on several factors. For example, the region the company operates in, its value, the capital structure, etc. Among the criteria there can be security assessment of the environment, the quality of produced goods and services, employee relations, activity in a variety of charitable programs.
2008-2009 crisis decreased social programs volume, performed by Russian industrial companies. In 2010 incremental recovery of different social projects became. But in 2012-2013 because of long -term overcoming of global financial crisis ramifications and expecting new economic malaise in the world most big industrial enterprises significantly decreased their social projects.
The development of socially responsible business concept is important today because tendency of masse industrial enterprises restructuring appears. These processes are accompanied with serious social risks: amid the crisis going with the reduction of output, industrial capacity, the task of decreasing appeared social risks gets priority for industrial companies and its performing is possible only under conditions of socially responsible business.
Now to activate suitable solution the next questions should be studied:
1. Russian industrial business should activate the process of transmitting social responsiveness into legal basis;
2. Government and society are the main distributors of modern industry in Russian conditions;
3. Government has economical, political administrative and media resources and industry has financial, expert innovative ones, which could be used more effective to execute social policy in the country;
4. Industry social responsiveness against government and society is multy leveled and executed according to four models: model of suppression and enforcement, model of patronage, model of government noninterference, model of social partnership of power and industry.
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In view of prevailing conditions Russian industrial organizations influence little on government policy. Among reasons for such situation is insufficient development of civil society and legislation gaps. Lack of finance and all Russian industrial unions loyalty to their leaders impede social responsiveness and that prevents effective government relations. At the same time public and locals should be kept informed regularly of charity and its development meeting state interests, that charity movement is considered by government positively.
Social responsiveness should be realized as providing needs of current Russian generation and developing opportunities of meeting future generation requirements.
Genuine social responsibility of business is not only heavy donations to people education, but such an organization, which would provide stable financial state of workers, social protection, education and opportunities for inner growth.
Russian business history researchers came to the conclusion that only in the beginning of the XXth century individual entrepreneurs, mainly the younger generation began to abandon patronage and charity in favor for the immediate social protection of their workers. There were established kindergartens, hospitals, schools, trade schools, libraries at factories, and there were organized visits to the theaters and charity concerts. And this was done not out of pure philanthropy, but primarily because of awareness of the prudent owner needs in disciplined, skilled and socially prosperous workforce [5].
In Russia after the mid-90s years of the XXth century social responsibility of business initially was manifested as individual social programs at individual enterprises. According to foreign specialists estimates some Russian factories were the best in the world, not only in terms of devices and equipment, but also in terms of solving social problems. [7] Companies are responsible for the society where they operate, above and beyond to ensure the effectiveness, employment, profits, and following the laws. Companies should therefore devote part of their resources and efforts to the social development of the society; they are obliged to sacrifice for the benefit and improvement of the society. Moreover, the society has certain reposes and stereotypes of an organization should behave to be considered a good corporate member of the society.
To encourage charity on state's part at the period of global financial crisis uneconomic methods come to the fore. The aim of such activity is moral encouragement of all charity participants, public and prospective investor motivation strengthening, inspiration of charity involvement. Appreciation of local philanthropist's merits and energy of charity movement on official government institutions' part are significant factor of public opinion formation and industrial company charity activation.
Moral encouragement using at the federal level is limited. Some departments only start their attempts to use them in the form of conferring decorations, certificates of honor for charity activity.
Such ways are used more active at Russian region level. Here being engaged in solving lots of social problems, facing closely specific results of industrial company charity activity, authorities highly appreciate its significancy and possibilities. Attraction of industrial company extra resources as part of charity to perform many tasks including additional budgetary institution financing becomes the main and an integral part of regional policy in social field. In regions of Russia there are a lot of examples of industrial company charity programmes, focused on child support, education, science, culture, local associations and civic initiatives.
Also, realizing that not only industrial investments, but social ones should be effective, directed to achieve stable positive results becomes more obvious in Russia. For industrial organizations smart management in the field of corporate social programme goes to the frontburner. Information dissemination on positive experience in this field becomes problem number one at present.
Russian charity of industrial companies is at the very outset of establishment. There is the process of current charity tradition realizing going on. At the moment we can say, that up-to-date activity of Russian industrialists is similar to neither pre-
revolutionary one with its Christian benevolence nor Western one with its tough minded amelioration.
One of perspective forms of interaction non-commercial and industrial sectors is social entrepreneurship, realized as entrepreneurial business based on principle of self-repayment, innovativeness and soundness, focused on solving pressing social problems by accumulative saving, that has long-term positive changes in the society. Such industry can be named as business with social mission. Social entrepreneurship combines both charity organization elements and business firm using entrepreneurial approach. This is a new approach to perform social tasks.
The problem of social responsibility of business development is particularly relevant today in Russia. This is due to the fact that the process of capital accumulation was primitive. Privatization was carried out simultaneously with the formation of the state, when there were no market economy laws. All that was accompanied with corruption growth and criminalization of the society. As the consequence there was the domestic business negative image in the West and in Russia. As a result, due to the extremely low valuation of intangible assets, Russian companies were undercapitalized. [9]
Should the business be socially responsible? For Russia, this way is just beginning. Russian companies, on the one hand, try to develop specific approaches to social responsibility, to implement international principles of transparency, environmental safety, labor relations, public support. On the other hand, they are forced to build their policies in a state of social sphere crisis in Russian regions, unstable socio-economic situation. So the decision could be the development of such approaches to social responsibility, which would be based on generally accepted international principles, but would take into account the realities of Russia today. Therefore, the question if business should be socially responsible, is still not solved for many local businessmen. But the answer is quite simple: it should be. First of all, socially active behavior has a direct impact on business reputation. In addition, the business gets a competitive advantage over other firms operating in this market: they have an access to the intellectual capital, increase brand value, reduce costs. Corporate and social responsibility of business affects the value of companies’ shares, increases reputational capital of business. [10]
The processes of globalization, which allowed firms in different countries to increase their income by expanding their market position, led to wider gap between income of population. Society, as it was divided into two classes: the elite (owners, managers, employees of world-wide corporations), and the population serving to the elite. However, the growing income gap of these classes did not cause major corporations response on how to improve the security of the society, the level and quality of life [13]. It is particularly noticeable in Russia
If Russian companies implement corporate codes, it is mainly to declare to the capital market and potential investors that they have a code of corporate governance, that they are willing to disclose their "transparency", that they are ready to carry out civilized norms of business conduct.
There is an urgent need for unified corporate social responsibility to the society as a whole, understanding the importance of social policy as a necessary condition of "decision" of all groups of corporate audience.
Most of Russian industrial companies which came into the Western markets had to use standards of corporate social responsiveness, adopted in developed countries. Foreign experience in this field is rather important to understand social responsiveness, but Western standards imitating without taking into account Russian specificity can't be successful problem solving. For Russian practice formation of new approaches to social responsiveness with maximum consideration of Russian reforms implications is required. At the period of privatization large industrial institutions were concentrated on national wealth, but didn't take on the mantle for social economic development of Russia.
The theme of social responsibility becomes more actualized in minds of Russian business, as companies and corporations are not only the basis of economic relations, but they will affect the social processes taking place in modern society. Business becomes more
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involved in society life, it goes out beyond the scope of its professional orientation. It must build relationships with a variety of related parties, as its activities, in addition to the internal environment, is influenced with external environment - authorities, non-profit organizations, consumers, mass media, international organizations and partners, people on the territory where the enterprise is located, and so on.
References: 1. Business as a subject of social policy. M .: HU-HES, 2005. 2. Philanthropy in Russia: the concept of transformation into
an effective instrument of social policy: an analytical report of the Union of Charitable Organizations of Russia. M., 2012.
3. Buksha K. Management business reputation. Russian and foreign PR-practice. M., 2013.
4. Socially responsible business problems and cross-sector collaboration. M .: IP RAS, 2009.
5. Zhigar O.V., Vybornaya G.A. The problem of social responsibility within the business ethics [Electronic resource]. URL:http://www.lib.csu.ru/vch/128/015. pdf
6. Ivchenko I., Liborakina M. City and Business: the formation of the social responsibility of Russian companies. M .: Institute for Urban Economics, 2007.
7. The research study "Social responsibility of business - the experience of Russia and the West." Moscow, 2004
8. Lyubinin V. The objective necessity of social responsibility of business. Russian Entrepreneurship. 2013. № 4.
9. Lyakhovetskaya E. The problem of development of social responsibility of business in Russia today is particularly relevant [Electronic resource]. URL: http://kadet.news-22.ru/index.php/2009-09-02-04-41-03/87-2009-10-06-03-47-08
10. Mingaleva Zh., Smilevskaya I. The social responsibility of enterprises as the foundation of successful business and socio-economic development. Russian Entrepreneurship. 2012. № 17 (215)
11. Ovtcharova L.A. Business as a subject of social policy: a debtor, a benefactor, a partner? M .: INEC 2011.
12. Social policy business in Russian regions. M., 2005. 13. Fomina E. Social Responsibility of Russian business
[Electronic resource]. URL: http://sr.fondedin.ru/new/fullnews_arch_to.php?subaction=showfull&id=1101387589&archive=1101388796&start_from=&ucat=14&"decision" all groups corporate audience.
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APPLYING ULTRASONIC PRESSING IN MANUFACTURING SLIP BEARINGS MADE OF COMPOSITE MATERIAL BASED ON POLYTETRAFLUOROETHYLEN
ПРИМЕНЕНИЕ УЛЬТРАЗВУКОВОГО ПРЕССОВАНИЯ В ТЕХНОЛОГИИ ПРОИЗВОДСТВА ПОДШИПНИКОВ СКОЛЬЖЕНИЯ ИЗ КОМПОЗИЦИОННОГО МАТЕРИАЛА НА ОСНОВЕ
ПОЛИТЕТРАФТОРЭТИЛЕНА
Prof., Dr. of Technical Sciences Eremin E., Doc., Cand. of Technical Sciences Negrov D. Omsk State Technical University – Omsk, Russia
E-mail: [email protected] Abstract: The influence of parameters of ultrasonic pressing on the mechanical and tribological properties of composite
materials on the basis of polytetrafluoroethylene is considered. A new technology for the friction bearings production is proposed and its advantages are shown.
KEYWORDS: FRICTION BEARING, ULTRASONIC PRESSING, POLYTETRAFLUOROETHYLENE, MECHANICAL PROPERTIES, WEAR RATE, FRICTION COEFFICIENT
1. Intriduction Frictional components made from various metals and alloys are gradually being replaced by polymers and polymer composites – in particular, composites based on polytetrafluoroethylene (PTFE) [1]. These materials reduce costs and improve reliability and durability. However, the applicability of these materials is very limited, since they are characterized by poor strength and elasticity, with consequent wear and deformation of the surface layers in friction. These problems are partially addressed by existing means of improving the mechanical and tribological properties of PTFE, such as the introduction of modifiers in the polymer matrix and adjustment of the manufacturing conditions (grinding and mixing of the components, pressing, and heat treatment). However, we need new methods permitting significant improvement in polymer properties, with accompanying gains in applicability. Components are generally made from polymer composites by pressing from powder and subsequent sintering. Pressing creates the basic properties of the eventual product – its density, strength, elasticity, and wear resistance – and distributes them uniformly throughout the volume [2]. To improve pressing, we may employ vibration [3]. Under the action of vibration, coagulation of the particles is reduced. Consequently, the fluidity of the powder is improved and the particles are packed more uniformly; any arch structures that form quickly disintegrate. 2. Precondition and means for resolving the problem Ultrasound treatment is also promising, because it lends itself readily to plastic deformation of the powder particles, with improvement in the frictional forces. Such treatment permits shaping of complex products with relatively small forces. In the present work, we consider the influence of ultrasonic pressing on the mechanical and tribological properties of polymer composites, so as to develop a manufacturing technology for slip bearings. We investigate a PFTE-based composite (State Standard GOST 10007-80) with a complex filler containing 8 % cryptocrystalline graphite, 6 % carbon fiber, and 2 % MoS2. The experiment consists of two stages. In the first stage, we determine the basic technological parameters of ultrasonic pressing (the amplitude of waveguide vibrations and the pressing time and force), as well as the influence of these parameters on the composite's mechanical properties (strength and elastic modulus). The mechanical properties of samples in tensile tests are determined on an R0.5 rupture machine at a strain rate of 20 mm/min. In the second stage, we investigate the influence of ultrasonic pressing on the tribological properties of the material (wear rate, frictional coefficient, and frictional torque). Special equipment based on an MT-50 hydraulic press is
developed for the manufacture of polymer-composite components by ultrasonic pressing (Fig. 1). The ultrasound source is a PMS 15-A-18 magneto-strictional converter (resonant frequency 17,8 kHz), with a UZG 3–4 ultrasound generator (input power 5 kW; frequency 17,5–23 kHz) [4].
Fig. 1. Equipment for ultrasonic pressing of PTFE components:
(1) base; (2) ball bearing; (3) mold; (4) waveguide; (5) crosspiece; (6) magnetostrictive converter; (7) directional column; (8) handle;
(9) hydraulic cylinder; (10) hydraulic system
The manufacturing technology is as follows. Polymer composite powder from a mixer (blade speed at least 2800 rpm) is packed into a closed mold, attached to ball bearing. The ultrasound is switched on when the waveguide touches the powder surface. Under the action of the waveguide vibration, the powder particles oscillate. Small particles are distributed and ordered between the large particles; this facilitates compression and increases the contact between the particles [5]. After ultrasonic pressing, the blank is sintered: heating to 360 ± 5°C at 1,5–2,0°C/min; holding at this temperature (8–9 min per 1 mm of wall thickness); cooling to 327 °C at 0,3–0,4 °C/min; and cooling from 327 °C to the normal temperature with the furnace. For comparison, we manufacture samples without ultrasonic treatment but with the same sintering conditions. 3. The results and discussion We find that the optimal pressing time t = 90 s (Fig. 2). For samples manufactured by ultrasonic pressing, the strength is 15 % higher and the elastic modulus is 23 % greater than for samples produced without ultrasound. Further increase in pressing time does not change the strength or elastic modulus.
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Fig. 2. Dependence of the strength σb (a) and elastic modulus E (b) of polymer composites on the pressing time t, with (1) and
without (2) ultrasound
The dependences of the strength and elastic modulus on the force are characterized by an extremum at P = 65 MPa (Fig. 3). The strength and elastic modulus are greater for the samples produced with ultrasonic pressing.
Fig. 3. Dependence of the strength σb (a) and elastic modulus E
(b) of polymer composites on the force P, with (1) and without (2) ultrasound
The influence of the amplitude of vibration on the strength of the composite is extremal, with maximum strength at an amplitude of 14 μm when the force applied is P = 65 MPa and the pressing time t = 90 s (Fig. 4).
Fig. 4. Dependence of the strength σb of polymer composites on
the vibrational amplitudeA of the waveguide On the basis of the results, we recommend the following conditions: waveguide amplitude A = 14 μm; force P = 65 MPa; pressing time t = 90 s. Samples obtained in these conditions are tested on special-purpose MDS-2 equipment at a slip rate v = 0,75 m/s and force P = 2 MPa, with no lubricant [4]. The results of tribological tests are shown in Fig. 5.
Fig. 5. Tribological properties of polymer composites produced by
the traditional technology (■) and with ultrasound (□): I – wear rate; Mf –, frictional torque;ffr – frictional coefficient
4. Conclusions The use of ultrasonic pressing in the production of slip bearings (t = 90 s, P = 65 MPa, A = 14 μm) increases the strength by 15 % and the elastic modulus by 23 %. The wear rate is reduced by 23 % and the frictional coefficient by 15 %. This technology is used to produce slip bearings for Tenzilor M equipment. 5. Literature 1. Mashkov, Yu. K. Composite materials based on polytetrafluoroethylene. structural modification. Moscow, Mashinostroenie, 2005, 240 p. (Mashkov Yu. K., Z. N. Ovchar, V. I. Surikov) 2. Mashkov, Yu. K. Friction and modification of frictional materials. Moscow, Nauka, 2000, 196 p (Mashkov Yu. K., K. N. Poleshchenko, S. N. Povoroznyuk, P. V. Orlov) 3. Agranat, B. A. Ultrasound in powder metallurgy. Moscow, Metallurgiya, 1986, 168 p (Agranat B. A., A. P. Gudovich, L. B. Nezhevenko) 4. Negrov, D. A. Development of an ultrasonic tool for the fabrication of articles from polymer composition materials. – Tekhnology Mashinostroenia, No. 5, 2012, P. 44-47. (Negrov, D. A., E. N. Eremin). 5. Negrov, D. A. The influence of hipersonic oscillations on the structure of the polimeric composite materiak. – Omsk scientific vestnik, No. 2 (90), 2010, P. 12-15. (Negrov, D. A., E. N. Eremin).
16
COMPACT SATELLITE HYDRAULIC UNIT
M.Sc. Patrosz P.1, PhD. Śliwinski. P.1 Faculty of Mechanical Engineering – Gdansk University of Technology, Poland 1
Abstract: The article describes the design and operation of a prototype hydraulic unit. It is based on an inversed kinematics, satellite pump in which the body rotates around the shaft. The pump is placed inside the electric motor. Thanks to that the compact and low mass construction was achieved. Thanks to new commutation unit with enlarged channels, lower pressure losses were obtained. The article presents the construction and results of preliminary tests.
Keywords: HYDRAULICS, PUMPS, SATELLITE MECHANISM
1. Introduction In nowadays there is a strong tendency to integrate hydraulic
equipment with electrical control. There are many electro-hydraulic elements such as valves and electrically controlled variable displacement pumps and motors. However the integration process didn’t significantly affect the coupling of electrical motor and a hydraulic pump. Only a few companies managed to successfully build a compact hydraulic unit with a pump completely combined with an electrical motor. Most of them are the classic constructions of an electrical motor permanently coupled with a pump using a coupling or a common shaft. As an example of these machines the HAWE MP and SAUER DAIKIN J-RP Rotor pump can be given.
Fig. 1 HAWE MP pump[8].
Fig. 2 SAUER DAIKIN J-RP Rotor pump [7].
The HAWE construction (Fig. 1) is an electric motor equipped with a dedicated connection for a hydraulic pump that is installed directly on motor’s shaft without an additional coupling. DAIKIN pump (Fig. 2) is more compact and consolidated construction. The cylinder block of an axial piston pump is built into the rotor and the pump is completely hidden inside the casing of the electric motor.
At Gdansk University of Technology new type of compact hydraulic unit has been designed. The construction of the unit was a part of a project LIDER/35/102/L-2/10/NCBiR/2011 funded by Polish National Center of Research and Development. The common name of the machine is “SLON”, which means “Elephant”. The name has been given because of the bulky shape of the machine and two elastic hoses connected to the motor, like a trunk and a tail of an elephant (Fig. 3). “SLON” can work with typical hydraulic fluids such as oil and polymer based fluids but also oil-water emulsion,
vegetable oil and pure water. However the machine is most efficient with higher viscosity fluids like oil or vegetable oil.
Fig. 3 Compact Hydraulic Unit “SLON” at the test stand.
2. Principle of operation The machine is based on the construction of satellite pump with
inversed kinematics [1, 5]. The pump is installed inside a casing of an electric motor. The size of the pump is small enough to fit it in an electric motor but also has enough power to make full use of motors capabilities. To entirely explain the principle of operation of the pumping unit, it is necessary to first present the satellite mechanism which is a heart of the machine.
The mechanism (Fig.4) [6] consists of three basic elements: - Perimeter (O), - Planet (P), - Satellites (S).
Fig. 4 Satellite mechanism (P – planet, S – satellite, O – perimeter, C – fixed shaft, PB – side plate, 1 – high pressure hole, 2 – low pressure hole).
The perimeter and a satellites are moving and the planet is fixed. The chambers separated by the satellites constantly change their volume. When they expand, the fluid is sucked into them. When they contract, the fluid is pushed out. The expansion and contraction of the chambers is a cyclical process. To correctly control the direction of fluid flow during suction and pumping process, two side plates where added. Every side plate has four holes (1, 2), which connect the chambers with low (blue color) and high pressure (red color) channel at the right time. The holes in plate PB1 are connected to the high pressure channel and in the plate PB2 to low pressure channel. The holes in the plates are periodically
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covered by satellites which is the principle of operation of satellite pumps’ commutation (Fig.5).
Fig. 5 Commutation of working mechanism satellite pump
3. Design of compact hydraulic unit As it was said before, the satellite pump is fitted inside an
electric motor (Fig 6, 7). The shaft of an electric motor has been replaced with a tube which connects the suction and pumping port of the unit. The pumping port is an integral part of a pump. The rotor (14) is connected with a shaft (4) with a key (12), and the shaft is connected with a perimeter of a pump (1). The rotation of a perimeter begins the suction and pumping process as it was described in a previous chapter
Fig. 6 Compact Hydraulic Unit “SLON” (2,3 – covers, 4 – shaft, 5 – clamping nut, 11 – suction port, 12 – key, 13 – stator, 14 – rotor, 16 – ball bearing, 18 – seal).
Fig. 7 Compact Hydraulic Unit “SLON”-detailed view of a pump (1 – pump, 6,7,8 – distance rings, 9 – key, 10 – mounting flange, 15 – ball bearing, 17 – O-Ring seal, 19 – mounting balls).
The “SLON” construction was developed for maximum working pressure equal to 25MPa. But the nominal operating pressure is expected to be 20 MPa. The unit was built on the basis of mass-produced electric motor (11kW and 750rpm).
During the design process of “SLON” the Finite Element Method was used to determine the deformation of unit’s elements [2,3] and using this information the proper form and material were chosen. The conducted analysis goal was to get the optimal area of axial clearance compensation. The axial clearance compensation is a feature of satellite pumps which enables them to pump the fluid under relatively high pressures without a significant increase of volumetric losses. The mechanism of clearance compensation is based on balancing the forces generated in satellite mechanism by the force generated by the counterpressure applied on the side of one of the side plates (Fig. 8). It is necessary to correctly define the size of compensation area. Too big area will generate too much force which will deform the side plate and clamp the rotating elements of the pump (Fig. 9). Too small area will cause internal leakage (Fig. 10). Thanks to FEM analysis proper size of the compensation area was defined.
Fig. 8 Pressure fields on the side plates (red-pumping pressure, blue-average pressure).
Fig. 9 Exemplary result of FEM Analysis – too big compensation area.
Fig. 10 Exemplary result of FEM Analysis – too small compensation area.
4. Test stand and test methodology To determine the efficiency of the machine it was necessary
build a test stand and measure basic parameters like: pressure, flow rate, rotational speed and torque.
The test stand (Fig.11) consists of the tested unit and pressure relief valve. The unit’s rotational speed can be controlled and measured. So is the torque necessary to drive the pump. The relief valve is needed to control the load of the pump by controlling the pumping pressure which is measured by the manometers. The test stand enables the user to measure both pumping and suction pressure. Additionally the flow rate can be measured by mass flow meter.
The tests were conducted in order to determine the maximal pumping pressure and to calculate the basic efficiencies of the machine. The methodology of the tests was carried out starting
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Fig. 10 Test stand scheme (M – electric motor, P – pump, RV – pressure relief valve, T – torque transducer, n – encoder, Q – flow meter, p1 and p2 – manometers).
from the low pressure and then rising it to the maximal value. This way the risk of the premature damage was minimized. The rotational speed changed from 200 to 740 rpm. The tests were conducted to measure the parameters in full range of speed adjustments, from low to high pressure setting. Every test series were carried out using two hydraulic fluids: oil and water-oil emulsion.
5. Results and discussion The tests were carried out in the entire speed range (up to
750rpm) and the entire operating pressure range (up to 200bar).
The tests’ results were presented in a charts where the abscissa is either the rotational speed or the pumping pressure. The ordinate is presenting the value of different efficiencies. The volumetric efficiency describes the losses of fluid volume. The main factors which lower the volumetric efficiency are: − internal leakage, − compressibility of the fluid, − cavitation.
It is very difficult to separate the hydraulic efficiency from the mechanical efficiency. Therefore hydraulic-mechanical efficiency is presented on a charts. Generally speaking it describes the losses in pressure. The main factors influencing it are: − mechanical friction, − flow resistance, − inertia.
The total efficiency is defined as product of volumetric and hydraulic-mechanical efficiencies. It is calculated using the equation:
𝜂𝑐 = 𝜂𝑣 ∙ 𝜂ℎ−𝑚𝑒𝑐ℎ (1) where:
− 𝜂𝑣 – volumetric efficiency, − 𝜂ℎ−𝑚𝑒𝑐ℎ – hydraulic-mechanical efficiency.
All efficiency charts are presented on figures 11÷22. It is noticeable that total efficiency for oil and for emulsion is quite similar. This origins from the fact that oil is more viscous than emulsion which significantly lowers the leakage and improves volumetric efficiency. That fact also causes more flow resistance which should lower the value of hydraulic-mechanical efficiency. However oil is much better lubricant than emulsion which lowers the friction. Thanks to that the hydraulic-mechanical efficiency is only a little higher for emulsion. Nevertheless the product of this two basic efficiency gives similar results for oil and emulsion.
The shape of the charts is typical for all hydraulic equipment. The charts presenting volumetric efficiency in function of pressure (Fig. 11 and Fig.17) drop with the rising pressure. It is explained by the fact that pressure rises the leakage, which significantly lowers the efficiency. However the hydraulic-mechanical efficiency (Fig. 13 and Fig. 19) rises with the pressure. This is a result of lowering the shear of pressure losses caused by flow resistance comparing to the pumping pressure. The pressure losses generally depend mainly of fluid flow speed and they aren’t changed significantly by the pumping pressure. Therefore when the pumping pressure rises and the pressure losses don’t change the efficiency must rise.
Fig. 11 Volumetric efficiency as a function of pressure (fluid: oil).
Fig. 12 Volumetric efficiency as a function of rotational speed (fluid: oil).
Fig. 13 Hydraulic-mechanical efficiency as a function of pressure (fluid: oil).
Fig. 14 Hydraulic-mechanical efficiency as a function of rotational speed (fluid: oil).
Fig. 15 Total efficiency as a function of pressure (fluid: oil).
Fig. 16 Total efficiency as a function of rotational speed (fluid: oil).
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Fig. 17 Volumetric efficiency as a function of pressure (fluid: oil-in-water emulsion).
Fig. 18 Volumetric efficiency as a function of rotational speed (fluid: oil-in-water emulsion).
Fig. 19 Hydraulic-mechanical efficiency as a function of pressure (fluid: oil-in-water emulsion).
Fig. 20 Hydraulic-mechanical efficiency as a function of rotational speed (fluid: oil-in-water emulsion).
Fig. 21 Total efficiency as a function of pressure (fluid: oil-in-water emulsion).
Fig. 22 Total efficiency as a function of rotational speed (fluid: oil-in-water emulsion).
There is one basic efficiency which doesn’t have typical behavior. It is a volumetric efficiency in function of rotational speed. Typically it should rise with the rising speed. The tests however show something different. The drop of volumetric efficiency with the rising speed is not explained. The test stand was checked and all measuring equipment was recalibrated. The test every time gave similar results. There is an assumption that it can be caused by the rotation of the fluid inside a long channel inside a
rotor. The other theory says it can be caused by the commutation but it is not verified.
The total efficiency for oil reaches 83% and for water-oil emulsion 80%.
6. Conclusion The tests of the prototype proved that the machine is working
and the efficiencies are on satisfactory level. However there are still some possibilities to improve the machine. There are some results that still need explaining like volumetric efficiency, and some factors that hasn’t been tested like the work of commutation and the flow through a rotating pipe in rotor.
The next stage of the prototype was built basing on the permanent magnet motor and the future test will be carried also on this prototype. The permanent magnet motor is much smaller than the typical asynchronous motor and it has higher torque which makes it the best choice as pumps drive. The first photo of a prototype build form a permanent magnet motor is presented on Fig. 23.
Fig. 23. The demonstrator with the new prototype of “SLON” based on permanent magnet motor.
7. References; [1] Śliwiński P.: Satelitowy agregat pompowy, Hydraulika i
Pneumatyka 5/2013. [2] Patrosz P.: Symulacja odkształceń w węźle kompensacji luzów
satelitowego agregatu pompowego, Gliwice 2013, KOMAG, Conference CYLINDER 2013.
[3] Patrosz P.: Odkształcenia w węźle kompensacji luzów satelitowego agregatu pompowego, Hydraulika i Pneumatyka 1/2014.
[4] Soltys P.: Projekt agregatu pompowego, M.Sc Thesis, Gdansk 2013, Gdansk University of Technology.
[5] Patrosz P., Sliwinski P., Osiecki L.: Płynowa maszyna wyporowa z satelitowym mechanizmem roboczym o odwróconej kinematyce. Patent application no. P.403060 date: 07.03.2013r.
[6] Patrosz P., Sliwinski P.: Satelitowy mechanizm roboczy hydraulicznej maszyny wyporowej. Patent application P.401821 date: 29.11.2012r.
[7] SAUER DAIKIN catalogue: www.daikin.com. [8] HAVE catalogue: www.hawe.com.
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CORROSION RESISTANCE OF LASER WELDED JOINTS OF TP347HFG AND VM12-SHC STAINLESS STEELS
Prof.UJK dr hab. Scendo M.*1, Prof. dr hab. Antoszewski B.2, M.Sc.Trela J.1, M.Sc.eng. Tofil S.2
1 Institute of Chemistry, Jan Kochanowski University in Kielce, Swietokrzyska 15G, PL- 25406 Kielce, Poland
2 Centre for Laser Technologies of Metals, University of Technology in Kielce, 1000-lecia Panstwa Polskiego 7, PL-25314 Kielce, Poland Abstract:The CO2 laser welding technique was suggested as a method of joining dissimilar materials. The corrosion resistance at high temperatures of the joint of TP347HFG and VM12-SHC stainless steel was investigated. The stainless steel was butt welded. Materials were examined by the thermogravimetric method. The surface and microstructure of the sample were observed in a scanning electron microscope (SEM). The results showed the substantial intermixing of both substrates within the fusion zone. The thermogravimetric data indicate that at high temperatures and air condition the joint and the stainless steel undergo chemical corrosion. The joint has acquired medium resistance for chemical corrosion in relation to both steels.
KEYWORDS: LASER WELDING; JOINT, AUSTENITIC, MARTENSITIC, CROSS-SECTION, THERMOGRAVIMETRIC ANALYSIS, CHEMICAL CORROSION
*Corresponding author. Tel.: +41 349 7045; Fax: +41 349 7062.E-mail address: [email protected] 1. Introduction
Stainless steels are Fe-Cr-Ni alloys which are widely applied in various industrial sectors such as marine, chemical, desalination and petrochemical industries. Austenitic and martensitic stainless steels are most widely used to produce modern energetistic devices. They can work at high and low temperatures [1-5]. These steels are usually used for a wide range of applications such as steam generators, pressure vessels, mixer blades, cutting tools and off-shore platforms for oil extraction [6]. The joining of dissimilar materials is one of the most challenging tasks facing modern manufactures. Dissimilar metal joints are widely used in various industrial applications for both technical and economic reasons. Stainless steels are seldom welded because of their high hardenability and susceptibility to hydrogen induced cold cracking. Austenitic and martensitic stainless steels with their chromium and carbon contents are resistant to various environmental conditions. Moreover, nickel and molybdenum content provides the elevated-temperature strength through the formation of stable carbide both metals [7]. The laser welding technique was suggested as a modern method of joining two metals of different properties. Laser welding is a high energy density process and well-known for its deep penetration, high speed, small heat-affected zone, fine welding seam quality, low heat input per unit volume [8]. A butt joint is one of the most common laser welded materials used to produce tubes and tailor welded blanks. It is of profit to all welding, but even more important to laser welding. Unfortunately, in the case of dissimilar materials the butt joint is subject to chemical and electrochemical corrosion at high temperatures or in an aggressive environment, particularly in the presence of chloride ions [9-16]. The present paper deals with the corrosion resistance of the CO2 laser welded joint of TP347HFG (austenitic) and VM12-SHC (martensitic) stainless steels. The samples were examined using a thermogravimetric analyzer (TGA) in air atmosphere. The surface and microstructures were observed by a scanning electron microscope (SEM). 2. Experimental 2.1. Materials The materials of TP347HFG and of VM12-SHC stainless steels were designed for the laser welding. Samples for welding were prepared by cutting to the size of 150×200×5 mm from the base material. 2.2. CO2 laser welding system The CO2 laser welding system was used for the melting of two stainless steels. A TRUMPF LASERCELL 1005 (TLC 1005) with 6 kW power made it possible to produce short and long series of different materials at low costs and in a short time.
The welding velocity was 160 mm/min in X-direction for the trial tests to perform a successful welding. The laser beam was positioned at the joint (and moved) 2 mm in relation to the surface of a sample. Helium gas at the pressure of 200 Pa and speed of 18
L/min was used as a shield gas to protect the heated surface against oxidation. 2.3. Laser welded joint The materials were butt welded. The full joint penetration was applied. The joint was initially examined in an optical microscope. The cross-section of the weld fillet was observed to determine the geometry, depth of penetration and cracks in the heat-affected zone (HAZ) as well as in the welded zone (WZ) of the joint. Moreover, no special heat treatment was carried out after laser welding. 2.4. Thermogravimetric measurements
Thermogravimetric measurements were carried out on an NETZSCH STA Jupiter 449 thermogravimetric analyzer (TGA). The sample in the furnace was heated up from 25 to 1380 0C with the heating rate of 5 0C min-1. A analyzer was applied for the thermal analysis of TP347HFG or VM12-SHC stainless steels, and the joint of both steels. 2.5. Additional measuring instruments
The cross-section of the surface and microstructure of a sample was observed in a scanning electron microscope (SEM), Joel, type JSM-5400.
To evaluate the mechanical properties, microhardness values were determined along the cross-section by the Vickers (HV) method using a Microtech MX3 tester under of 0.4 N load. 3. Results and discussion 3.1. Thermogravimetric measurements and kinetic studies
The thermogravimetry curves for TP347HFG, VM12-SHC stainless steels and the joint are presented in Figure 1. Fig. 1. Thermogravimetry curves for stainless steel and joint: (a) TP347HFG, (b) joint, and (c) VM12-SHC. Heating rate of 5 0C min-
1.
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The weight gain of samples were observed after the achievement of the critical temperature conversion in which the increase of the mass of a sample achieved the value of 0.1% in relation to the mass of the initial specimen, Table 1. TP347HFG was the most resistant to oxidation whereas VM12-SHC stainless steel was the least resistant to it. It is noteworthy that the critical temperature conversion for the joint was placed between both stainless steels. Moreover, Table 1 contains the weight gain of samples after the measurement. Table 1. Critical temperature conversion, weight gain of stainless steel and joint.
Materials
Critical temperature conversion
(0C)
Weight gain sample
(mg)
TP347HFG
1145
20.01
Joint
1101
41.71
VM12-SHC
1049
62.69
The largest increase in mass was registered for VM12-
SHC, but the smallest for TP347HFG stainless steel. However, for the joint a medium increase in the mass of the sample was observed.
Kinetic studies, based on the change of mass, were obtained by the TG curve analysis. The corrosion rate of materials was calculated from the following equation:
tAmk ∆
= (1)
where ∆m is the change mass of sample, A is the surface area of the test specimen, and t is the time of measurement. The corrosion rate was expressed in mg cm-2 h-1.
The corrosion rate of samples were calculated on basis of Equation (1). The results are shown in Figure 2. The corrosion rate of samples increased with increase of temperature. The joint achieved the medium values of corrosion rate in comparison with both steels.
Fig. 2. Corrosion rate as function of temperature for stainless steel and joint: (a) TP347HFG, (b) joint, and (c) VM12-SHC. Heating rate of 5 0 min-1.
The thermogravimetric process in the atmosphere of air depends on the oxidation of the sample surface. The process of forming an oxide layer on the surface of the clean metal begins from the adsorption of oxygen:
4 Fe + 3 O2 → 2 Fe2O3. (2)
The product of the iron corrosion (reaction (2)) at high-temperature has a stratified structure. The spatial structure of layers of oxide is of ion character. The process of forming a layer of oxide on the metal depends on the diffusion of Fe2+ through the layer in the direction of the gas phase (from pithy diffusion). Moreover, the diffusion ions of oxide from the layer in the direction of the metallic basis (to pithy diffusion) is also possible [17]. The tight and suitable thick of the oxide layer should effectively protect the metal against the significant progress of the corrosion process. The high temperature (higher than 1300 0C) causes the dissociation pressure of the oxide layer according to the equation:
6 Fe2O3 (s) ↔ 4 Fe3O4(s) + O2(g). (3)
The compositions of scales for multiple alloys are usually varied.
In the case of TP347HFG and VM12-SHC stainless steels the compiled composition concerns the scale of the joint because it contains oxides of chrome, nickel, or cobalt.
Figure 3 shows the images of the joint, TP347HFG and VM12-SHC stainless steels after thermogravimetric measurements. It can be seen that on the surface of TP347HFG the compact, uniform and hard oxide layer was formed, which protects the steel prior to high-temperature corrosion.
Fig. 3. Images stainless steel and joint after thermogravimetric measurement: (a) TP347HFG, (b) joint, and (c) VM12-SHC.
However, in the case of VM12-SHC and the joint, due to the dissociation pressure the top oxide layer undergoes cracking on small pieces, exposing the deeper layers of materials.
3.2. Microhardness profiles and microstructures
The microhardness profiles of the specimen were analyzed using the Vickers method. The results are presented in Figure 4.
(a)
(b)
(c)
22
Fig. 4. Vickers microhardness profile along the cross-section in specimen.
In the heat-affected zone an increase in microhardness of both steels was observed. The maximum hardness value is located in the weld zone (about 580 HV0.4). The hardness of the joint increased about twice as much in comparison to the hardness of steels. The HV value indicates that the joint is fragile, and has low strength on hitting in relation to stainless steels. In this case special heat treatment should be applied after laser welding. The scanning electron microscope images of the microstructure of the sample is shown in Figure 5.
a) b) c)
Fig. 5. Scanning electron microscope images of microstructure: a) TP347HFG, b) joint, and c) VM12-SHC stainless steel. Magnification 1000×.
The characteristic austenitic microstructure (Fig. 5a) is observed for TP347HFG as well as the martensitic microstructure (Fig. 5c) for VM12-SHC stainless steel. Moreover, observations revealed a fine grained microstructure, and basically dendritic in the weld zone (Fig. 5b). The material which possesses dendrite microstructure is usually very hard. However, this type of microstructure is a result of high cooling rates typical of the laser welding process.
4. Conclusions 1. The CO2 laser welding technique was suggested as a method of joining dissimilar materials.
2. The thermogravimetric data indicate that at high temperature under air conditions the joint and stainless steels undergo chemical corrosion. The product of the corrosion of iron, Fe2O3 , has a stratified structure at high-temperature.
3. The joint has the medium resistance to chemical corrosion in relation to both steels, and the chemical composition of the joint is different in comparison to both steels.
4. The weld zone revealed a fine microstructure and was basically dendritic, due to the high cooling rate which is characteristic of the laser welding process.
5. The value of Vickers microhardness indicates that the joint is fragile, and has low strength on hitting in relation to stainless steels.
References [1] Zhang L, Fontana G. Autogenous laser welding of stainless steel to free-cutting steel for the manufacture of hydraulic valves. J Mater Process Technol 74, 1998, 174-182. [2] Katayama S. Laser welding of aluminum alloys and dissimilar metals. Weld Inter 18, 2004, 618-625. [3] Mackwood AP, Crafer RC. Thermal modeling of laser welding and related processes: a literature review. Opt Laser Technol 37, 2005, 99-115. [4] Kwok CT, Lo KH, Chan WK, Cheng FT, Man HC. Effect of laser surface melting on intergranular corrosion behaviour of aged austenitic and duplex stainless steels. Corros Sci 53, 2011, 1581-1591. [5] Baghjari SH, Akbari Mousavi SAA. Experimental investigation on dissimilar pulsed Nd: YAG laser welding of AISI 420 stainless steel to kovar alloy. Mater Des 57, 2014, 128-134. [6] Nasery Isfahany A, Saghafian H, Borhani G. The effect of heat treatment on mechanical properties and corrosion behavior of AISI 420 martensitic stainless steel. J Alloys Comp 509, 2011, 3931-3936. [7] Lippold JC, Kotecki DJ. Welding Metallurgy and Weldability of Stainless Steel. NJ USA, Ed. John Willey & Sons, 2005; pp 63-70. [8] Weichiat C, Paul A, Pal M. CO2 laser welding of galvanized steel sheets using vent holes. Mater Des 30, 2009, 245-251. [9] Chan LC, Chan SM, Cheng CH, Lee TC. Formability and weld zone analysis of tailor-welded blanks for various thickness ratios. J Eng Mater Technol Trans ASME 127, 2005, 179-185. [10] Lee H, Hamb HS. Optimization of Nd:YAG laser welding parameters for sealing small titanium tube ends. Mater Sci Eng A 415, 2006, 149-155. [11] Cheng CH, Chan LC, Lai CP, Chow CL. Formability of Ti-TWBs at elevated temperatures, SAE 2006. J Mater Manuf 01-0353, 2006, 327-335. [12] Fratini L, Buffa G, Shivpuri R. Improving friction stir welding of blanks of different thicknesses ratios. Mater Sci Eng 459, 2007, 209-215. [13] Scendo M. Potassium ethylxanthate as corrosion inhibitor for copper in acidic chloride solutions. Corros Sci 47, 2005, 1738–1749. [14] Scendo M. Corrosion inhibition of copper by potassium ethylxanthate in acidic chloride solutions. Corros Sci 47, 2005, 2778–2791. [15] Scendo M, Trela J, Radek N. Purine as an effective corrosion inhibitor for stainless steel in chloride acid solutions. Corros Rev 30, 2012, 33–45. [16] Dzoba I, Pała T, Pała R. The material properties of different zones of welded using a laser -terotechnology. Adv Mmater Res 874, 2014, 3-9. [17] Danielewski M. Coupled diffusion in the multicomponent system, derivation of the general formula for interdiffusion coefficient. Solid State Ionics 45, 1991, 245-251.
23
PROBABILITY STRESS CONDITIONS IN MACHINE ELEMENTS
ВЕРОЯТНОСТНИ ЯКОСТНИ УСЛОВИЯ ЗА МАШИННИ ЕЛЕМЕНТИ
Assoc. Prof. PhD Popov A. Institute of Mechanics – Bulgarian Academy of Science, Sofia, Bulgaria
E-mail: [email protected]
Abstract: Ordinary in the theory of machine elements a deterministic stress conditions are used. In general case there are relationships between “acceptance stress” and “working stress”. In practice the stresses are random values. Therefore the stress conditions have got probabilistic formulation. In this paper the probabilistic formulation of stress conditions for machine elements are presented. KEY WORDS: PROBABILITY, STRENGTH, MACHINE DESIGN 1.Introduction In the theory of machine elements a deterministic stress conditions are used [1]. In general case there are relationships between “acceptance stress” and “working stress”. In practice the stresses are random values. Therefore the stress conditions have got probabilistic formulation[2].
This paper the probabilistic formulation of stress conditions for machine elements are presented. 2. Probability stress condition for body free of imperfections In general case the formulation of deterministic stress condition is ACCσ – WORKσ ≥ 0 [1]. The probabilistic of stress condition is [2]
Pr ( ACCσ – WORKσ ≥ 0 ) (1)
where ( )3,2,1};{ =ijijWORK σσ , ( );...; UTSYSACC σσσ ,
3,2,1; =ijijσ - tensor of mechanical stress, UTSYS σσ ; -
yield stress limit and ultimate tensile stress respectively. The condition (1) is generalization to concept of “reliability”. The reliability R for safety work for machine design free of imperfections is define by the probability Pr { S – M ≥ 0 } [3]
R = Pr { M - S ≥ 0 } (2) where for a construction clement the mechanical characteristics is start diving by the vector M≡ );;;;( νσσ GEM UTSYS ,
where ν;;GE are elastic modulus [4] and stress-deformation state
is the vector S≡ ( )3,2,1};{};{ =ijS ijij εσ , where
( )3,2,1};{};{ =ijijij εσ - tensors of stress and deformation
respectively. The relationship (2) is transform to
R = dMdSSpMpS MM∫ ∫
∞
∞−
∞
)()(
(3)
If in (3) the densities of distribution - )(MpM и )(SpS are with Weibull’s distributions, then
)(xpW =X
X
ϑβ
X
XXxϑ
β 1)( −−
−−
X
X
Xxβ
ϑexp with
parameters XX ϑβ ; , X = );;;;( νσσ GEM UTSYS and X
= ( )3,2,1};{};{ =ijS ijij εσ , then relationship (3) transform to
{ }dyyheR y∫∞ − −−=
0)(exp1
(4)
where S
M
SS
M SMyyhβ
β
ϑϑϑ
−+= /1)( [3].
3. Probability stress condition for body with imperfections
In this case the probabilistic of stress condition is
Pr ( KIC - KI ≥ 0 ) (5) where KI - stress intensity factor, KIC – critical coefficient of stress intensity if load, imperfection geometry is know. The values
IK and KIC are know from fracture mechanics [4]. In overt type the probabilistic of stress condition (5) is
R = ( ) ICICICK dKKIKpIC∫
∞
∞−)(
(6)
where ( )ICKI = ∫∞
S IIK dKKpI
)( .
In (6) the densities of distributions )( IK KpI
and )( ICK KpIC
are known. If )( IK Kp
Iand )( ICK Kp
ICare not known, then
the numeric characteristics: mathematical expectation Е( IK ),E( ICK ) and dispersion D( IK ), D( ICK ) [8] are used. In this case the probabilistic of stress condition is Chebishev’s inequality [2]
{ } ( ) )(2)()()(. DI
EIC
EIC
EII KKKKK −
≤≥− (7)
where )(EIK =Е( IK ), )(D
IK =D ( )IK , )(EICK =E( ICK );
[E( ICK )]2 = 3
1 E( D ). ( )νξ ,E ( )ψση ,S ;
24
( )νξ ,E ≈ E(E){1 + [E(ν )]2 }; ( )ψση ,S ≈E( Sσ ){E(ψ ) - 0.5[E(ψ )]2 }.
The evaluation of ( )D , E(E), E(ν ), E( Sσ ), E ( )ψ is look at [8]. 4.Evaluation of IK and KIC
For evaluation of IK look at plate with crack (fig.1.).
h ∞σ ∞σ fig.1. Depth of crack evaluation– h, by means
ultrasonic measures [8] with transducer type CDS (300-700-700), PANAMERTICS, САЩ Measurement by EN 583-1, EN 583-5.
In this case [4]
IK = ∞σ h.π )(λF (8)
where θτ cos21
∆= XTVh - crack length (fig.1.), θ - reflection
angle, 21 τττ −=∆ - time derivation in propagation of longitudinal and transversal ultrasonic waves with velocity
XTV ; )(λF =∑
=
−4
0)1(
k
KK
K a λ ;λ =bh
< 0.7 ;
0a =1.12, 1a =0.23, 2a =10.6, 3a =21.7, 4a =30.4.
The value KIC is material characteristics. For KIC there is relationship with mechanical characteristics
( )UTSYSE σσν ;,, and structural characteristic D of the material [5].
( ICK )2 =
31 . ζξσ ... YSD
(9)
where
−
= 21 νξ E
;
+
+=YSUTS σσ
ζ.2
4201ln .
The average grain size D is obtain by [8]
( ) 0.321125
.4 3
553
42
=−
+ L
TLL
T DfVVV
V απ (10)
where fVV LTL ;;; α are respectively velocity, attenuation and frequency in ultrasonic propagation [8].
The values LTL VV α;; are measure by means digital ultrasonic
flow detectors. The methods for measure of LTL VV α;; in according ASTM E 494:2010 are presented. The yield stress limit – YSσ by Holl – Petch’s model [9] is obtained
( ) 2/10
−+= DK yS σσ
(11)
The material constants yK;0σ are evaluation by means
experiment [8,9]. The elastic modulus [8] are obtained by means
2
2
)/(1)/(5.0
LT
LT
VVVV
−−
=ν (12)
22
2
)/(1)/(43
TLT
LT VVVVVE ρ
−−
= (13)
where ρ - material density.
The relationship between ultimate tensile strength UTSσ and Brinel’s hardness is [6]
HBB 31
=σ (14)
where НВ – Brinel’s hardness. The value of HB is obtain by means Leeb method of hardness testing, according ASTM A 956:2012 5.Conclusion The probabilistic of stress condition are written for body free of imperfections. A body with imperfections is look. In this case probabilistic of stress condition is written by Chebishev’s inequality. The method for evaluation of the
value IK and KIC and average grain size D by means ultrasonic measure are shown.
Reference
1. Lefterov L., &, Machine elements, Tehnika, Sofia, 1994 (In Bulgarian). 2. Svetlickii V.A., Statistical mechanics and theory reliability, MGTU im.N.E.Baumana, Moskow, 2002 (In Russian). 3. Alexandrovskaia D.N., &, Safety and reliability technical systems, Logos, Moskow, 2008 (In Russian). 4. Hellan K., Introduction to fracture mechanics, McGraw-Hill Book Company, New York,1984. 5. Andreykiv A.E., Three-dimensional problems in crack theory, Naukova dumka, Kiev, 1982 (In Russian). 6. Markovec M.P., Non-samples methods to evaluation of mechanical properties of metals, MEI, Moskow, 1983 (In Russian). 7. Physical acoustics, vol. IV, B, Edition by U. Mezon, Fizmatlit, Moskow, 1963 (In Russian), Papadakis E., Ultrasound attenuation dependent from scattering in polycrystalline materials. 8. Popov l., Probabilistic methods in evaluation of mechanical properties in ferro-carbon alloys (Mon0graphy). Edited by Institute of mechanics – Bulgarian Academy of Science, Series “Mechanics”, April 2014 (ISSN 1314-3034), (In Bulgarian). 9. Trefilov V.I., &, Deformation at strengthen and destruction of polycrystalline materials, Naukova dumka, Kiev, 1987 (In Russian).
25
PENETRATION KINETIK OF BISMUTH MELT INFO COPPER POLYCRYSTALLINE STRUCTURE
M.Sc. Apyhtina I.V. PhD., M.Sc. Novikov A.A., M.Sc. Novikova E.A. PhD., M.Sc. Orelkina D.I., Prof. M.Sc. Petelin A.L.
National University of Science and Technology «MISIS»
Abstract: The liquid bismuth network formation along grain boundaries (GB) and triple junctions (TJ) was investigated in copper
polycrystalline samples. The experimental observation in situ technique of Bi penetration through the Cu plate was used. The temperature dependence of the penetration rate of the melt through the wafers of polycrystalline copper and the effective activation energy of penetration of Bi along the GBs are found.
Keywords: KINETIC, COPPER, BISMUTH, PENETRATION, GRAIN BOUNDARY 1. Introduction The problem of solid-liquid metal phases interaction described
in several tens of theoretical and experimental researches [1,2]. It is well known that liquid-metal grooves formation occurs on the liquid-solid interface at the exiting places of grain boundaries (GBs). This effect can lead to the solid metal embrittlement. The samples destruction along GBs was observed on copper (solid) - bismuth (liquid) system [3]. In polycrystalline samples the wetting GBs transformation is a complex process, which occurs in the area near the wetting temperature – Tw. The triple junctions (TJs) as a GBs are subject to wetting transformation. The spread velocity of the liquid phase along TJs is more than along grain boundaries [4]. Co-wetting of GBs and TJs in polycrystalline metal samples leads to formation and growth of a continuous liquid-metal channel net. The appearance of the liquid phase channels net was observed by GB wetting investigations of liquid bismuth interaction with polycrystalline copper samples [5]. However, until now there were not experimentally obtained kinetic characteristics of molten bismuth penetration into polycrystalline copper structure near the wetting temperature. The aim of present work is the experimentally research of the kinetics of liquid bismuth penetration into polycrystalline copper in the Tw temperature area.
2. Experimental For the experiments there were used high purity metallic
materials, copper - 99.995 wt.% and bismuth - 99.999 wt.%. Copper samples were the plates which were made on electro erosion machine ARTA 200-2. Plate’s thickness was from 150 to 500 microns. The average grain size of copper samples was about 40 microns. It was achieved by pre-deformation and following heat treatment of cooper plates.
Deformation of copper was carried out by upsetting (30 – 40 %) after which the samples had two-step recrystallization annealing. Annealing includes exposure for 15 min. at T1=900 C and then holding for 120 min. at T2=650 C. Isothermal exposures of copper samples in contact with liquid bismuth were carried out in the temperature range from 560 ºC to 590 ºC.
The experiments were performed in the heating micro-furnace in thermal cell TS1500. This device is accomodated for observations of high-temperature processes in situ, i.e. directly during the heating. This method is used for the analysis the process of metal melt penetration along GBs in solid metal matrix for the first time. All treatments were carried out in inert atmosphere - there was used Ar of high purity. During the penetration, on the test surface appeared liquid bismuth points. (Fig. 1).
Fig.1. Appearance of melt on the opposite sample’s surface. Arrows
show the penetration points Bismuth appearance on copper’s free surface was observed
using a continuous visual microscopic analysis of the surface (using an optical microscopes LEICA-DMILM, LEICA-L2). After experiments copper samples were investigated by scanning electron microscope HitachiS-800, including using electron microprobe analysis.
These results were confirmed the observation data of optical microscopy. The appearing points of bismuth on the free surface of the copper plates correspond to TJs in which there was happened through-penetration. This was confirmed by following chemical etching of the free surface. This fact indicates that the TJs are the fastest ways of the liquid phase penetration through a polycrystalline sample, as previously was noted in [6]. The appearance time of series of bismuth point’s on the free cooper surface was fixed during the observation of bismuth penetration process through copper plates at each temperature. Such time was named through-penetration time (t) for definite experimental conditions.
3. Results To study the morphology of the forming network of melt
channels inside the samples of polycrystalline copper after holdings, we prepared transverse slices with planes perpendicular to the contact surfaces of the liquid and solid phases. When investigating the slices, it was established that the melt channels inside copper samples are formed both at GBs and along the lines of TJs. A photograph presented in Fig. 2 shows the region near the separation interface of the bismuth melt (the upper part of the photograph) and solid copper wafer (the lower part of the photograph). Funnel-like melt grooves along the GBs are seen; a thin GB melt channel moves away from one of them and is hampered by the TJ (triangular rosette in the lower part of the photograph). Being branched, it propagates farther into a depth of a copper plate.
26
Fig. 2. Morphology of the liquid bismuth penetration The experimental results for all temperatures conditions -
through-penetration times (t) and the total average lengths of liquid bismuth channels (h1) which were determined by measuring of the copper plate’s thicknesses (h) with account of copper polycrystalline structure – are present in Table 1. An average velocity of liquid metal channel net formation was determined using the results of measurements of through wetting penetration.
Under the assumption that the rate-limiting stage of channels formation has the diffusion nature there were made the estimations of the effective diffusion coefficients (D*) by the
correlation t*D1h ⋅≈ . The estimations of D* were made for all experimental
temperatures (see Tabl 2). The base equation of the diffusion
coefficient temperature dependence
−=
RTEDD
**0
* exp ,
where E* - is the effective activation energy, ∗0D - is the effective
pre-exponential factor, allows to estimate the E* with the help of graphic dependence Ln(D*)÷1/T (Fig.3).
Table 1: The experimental results of average velocity of liquid metal
channel net formation into polycrystalline copper structure
T, °C V, µm/min
550 ± 1 20 ± 5 560 ± 1 23 ± 5 570 ± 1 27 ± 5 580 ± 1 35 ± 5 590 ± 1 42 ± 5
Table 2: The experimental results of liquid Bi spreading into
polycrystalline copper structure
T, K t, min h1, μm D*, m3/s
550 13 1,0·10-4 8,7.10-11 560 13 9,4·10-5 1,2.10-10 570 9 8,2·10-5 1,1.10-10 580 7 7,0·10-5 1,4.10-10 590 6 8,4·10-5 1,8.10-10
Fig3. Estimation of E* with the help of linear temperature diffusion coefficient dependence
The effective activation energy (E*) was defined from the slope of the linear dependence. It’s significant is equal 94±22 kJ/mol. This value correlates with the activation energy of GB Bi-Cu hetero diffusion - 156.2 kJ/mol [7]. But obtained experimental data of activation energy is less than the activation energy of GB diffusion of bismuth in copper. This may be connecting with the contribution of the TJs bismuth diffusion in the copper polycrystalline samples.
4. Conclusions
1) The fact of complete liquid bismuth penetration through the copper plate was established in conditions of GBs and TJs complete wetting.
2) The average effective rate of liquid Bi penetration along GBs was determined. It increased from 20 to 42 µm/min with temperature increasing from 550 to 590ºC.
3) The activation energy of Bi penetration process is equal to 94±22 kJ/mol. It was assumed that the GB diffusion is the limiting process of GB wetting. Low value of activation energy may be due to the Bi diffusion along TJs.
5. References [1] B.B. Straumal, Grain boundary phase transitions, Nauka
publishers, Moscow, 2003. [2] B.S. Bokstein, N,A. Dolgopolov, A.L Petefin et at., Izvestiya
vuzov tsvetnaya metallurgiya 6 (2006) p.42 (in Russian). [3] I.V. Apykhtina, S.A. Gulevskii, N.A. Dolgopolov et al.,
Defect and Diffusion Forum. Vol. 237240 (2005) p.855. [4] S.A. Gulevskii, N.B. Emelina, A.L. Petelin, Russian Journal
of Non-Ferrous Metals 47 (2006) p.38. [5] B.S. Bokstein, N.B. Emetina et al., Materiallovedenie 8
(2007) p.13 (in Russian). [6] S.A. Gulevskii, L.M. Klinger, A.L. Petelin, Tekhnologiya
metallov 8 (2007) p.13 (in Russian). [7] S.V. Divinski, M. Lohmann, Chr. Herzig et al., Phys. Rev.
B.71 (2005) p.104104.
27
RISK MANAGEMENT IN INDUSTRIAL ENTERPRISES
Assos.Prof. Toni Mihova , PhD 1, Assos.Prof.Valentina Nikolova – Alexieva, PhD.2
Assistant Prof. Tania Gigova1
Technical University – Sofia, branch Plovdiv, Bulgaria 1
University of Food Technologies – Plovdiv, Bulgaria 2
[email protected]; [email protected]; [email protected]
Abstract: The authors report on the essence of risk management in the enterprise as an effective management tool in today's rapidly changing business environment. The report targeted to indicate the attitude of the managers in this process, based on a survey, as demonstrate the need for a more comprehensive approach to risk management.
Keywords: RISK MANAGEMENT, INVESTMENT RISK, FINANCIAL RISK, BUSINESS RISK
1. Introduction Risk management in industrial enterprises is very hot topic
today on the one hand because of the extremely important role of industry in the global and national economies and on the other - from the growing uncertainty in the results that industrial enterprises rely as their goals and expect to achieve by its activities. Processes of globalization and increasingly rapid technological development contribute to this uncertainty.
The report aims to show the current state of risk management in Bulgarian enterprises also formulate more substantive issues, and the author's view of what needs to be done to fully improvement of this activity. The report summarized the results of research carried out for this purpose in two hundred large industrial enterprises in Bulgaria. This report summarizes information provided by respondents who completed Risk Management Survey between January 2012 and April in 2014. The respondents of this survey are registered members of Confederation of the Employers and Industrialists in Bulgaria and they are more managers and practitioners interested in a comprehensive approach to process management and related concern like risk management. The main goal of this survey is to draw picture of the ways that risk management is being used in the Bulgarian organizations today and the results reflect the perspectives of a broad base of Bulgarian managers interested in. Report offers to reader’s insights into the kinds of risk management development efforts currently underway and the ways their own company’s risk management efforts compare with those of other companies.
2. What is the essence of risk managemen? According to the Deloitte’s definition of risk "The risk is the
possibility of losses - or reduced profits - caused by factors that may adversely affect the achievement of the organization", which according to the authors most accurately expresses its essence. [1].
The concept of risk management has been developed in recent years and has different definitions. According to the experience of Marsh key points in the definition of company’s risk management (RM) are as follows: "Basic structured approach that supports the alignment of strategy with processes, people, technology and knowledge to assess and manage the uncertainties that an organization faces while creating value. For this purpose, the organization must be provided with information about the quality management making decisions in a more effective manner and with more confidence".[2].
The essence of risk management in the enterprise is built around his pragmatic use as an effective management tool that also be a major boost to increase in value. In contemporary business environment, the need for a more comprehensive approach to risk management that ensures the development of alternative responses to risks has a major importance. Every business carries risks. Therefore, risk management is essential for any business process. It prevents foreseeable risks prevents bad investments and reduces damage from unforeseen events. Enterprise Risk Management (ERM) is a process, which organize and control activities in order to
minimize the effects of risk. In the 'risk' here includes not only the risk of unexpected losses, but also financial, strategic, operational and other types of risks, i.e more comprehensive approach to risk management.
Widespread popularity has acquired following COSO ERM’s definition of risk management "process performed by a board of directors, management and other personnel, applied in setting the company's strategy, designed to identify potential events that could have an effect on company, and manage risk to be within the risk appetite, to provide reasonable assurance regarding the achievement of company objectives" [3]. The term "risk appetite" is a risk that the organization is ready to take to be in line with the strategic and operational objectives to maximize value for stakeholders. Risk management in the organization requires the company to have a versatile look at risk.
More significant basic principles of risk management are: raising awareness of the risk; specific action plans; the lowest risk capital requirement; better link between strategy and operations; effective management and change control; organizational culture should encourage an environment that promotes opportunities for managing risks, not eliminating them overall.
Risk management is a process including: development and implementation of strategies, identification of risk assessment and risk measurement, risk responses, testing and risk control, monitoring, maintenance and continuous improvement .
At the consulting practice there is using the framework COSO ERM, which defines the main components offers a common language and provides a clear purpose and direction for risk management in the organization.
Eight interrelated components are typical for this framework: internal environment, setting targets, identifying events, risk assessment, risk response, control activities, information, communication and monitoring. [1]
In summary it can be concluded that the most salient features of this framework is as follows:
- establishes the philosophy of risk management;
- formed a risk culture within the organization;
- take into account all other aspects concerning how the actions of the organization could affect the risk culture;
- includes the identification of these incidents occur internally or externally, which would affect the strategy or achievement of the objectives set out therein;
- examines the way in which internal and external factors combine and interact with each other, and how they influence the risk profile of the company;
- allows an organization to acquire an exact picture to what extent the potential events might affect the achievement of objectives;
- using a combination of qualitative and quantitative risk assessment methodologies;
28
- мanagement identifies, captures the relevant information and transmits it in a form and timeframe that enables people to carry out their responsibilities;
- the communication has a broader scope and it is distributed horizontal and vertical within the organization.
It is essential to clarify the concepts associated with a risk intelligent organization and risk policy.
Risk intelligent organization starts to manage the risk with
determination of the strategic objectives; unfies operations management and risk management; creates links between units; understand the interactions between different risks; manage risks as a daily activity.
Risk policy is a long term action plan consists of guidelines and principles designed to achieve the objectives of risk management. Key elements are: goals, risk management vision, risk appetite, risk management framework, the risk management process; minimum requirements; roles and responsibilities. [3]
What kind of risks are faced industrial enterprises?
In economic theory, regarding the individual company most attention is given to the three main types of risk - investment, financial and economic risk (business risk).[4] Although they address different aspects of business, they are closely related and affect complex activities and state of the enterprise.
Investment risk is the probability that actual cash flows (earnings) of an investment to be lower than expected. The financial risk associated with the use of foreign capital in the business. This is the risk of insolvency and more severe form - failure due to accumulation of financial obligations that can not be repaid. Business risk is defined as the possibility of adverse changes in market and economic conditions in which the entity operates. These changes directly or indirectly affect the economic fundamentals of the enterprise, such as sales, revenues, financial results, cash flow, return on capital, economic value added, etc. Business risk includes several components: macroeconomic and political risk; industrial risk; market risk; internal company risk; risk in terms of factor markets.[4] Macroeconomic risk is related to the general economic situation of the country and the business. The significance of this risk is determined by the phase of the business cycle, inflation, interest rates, trade and tax legislation including Government tax policy, the level of GDP; growth rates, investment, exchange rates, foreign trade, balance of payments, unemployment,etc. There has been a decline in the gross domestic product (production) and investments when the economy is in recession. At the same time, unemployment is increased . This inevitably affects the volume of sales of both consumer and investment goods [5] . In the practice it is considered that when the decline in production (GDP) remains at least six months there is a recession. Stagnation is a prolonged and deep recession, which is characterized by massive bankruptcies of companies with uncertain market positions whose financial result is highly sensitive to changes in sales volume, ie companies with a high level of business risk. In contrast, under stable economic conditions, sales and financial performance of companies is constantly increasing. Different types of business and individual firms are differently exposed to macroeconomic risks. For example, cyclical companies, ie those companies who are more sensitive to the macro cycles should have higher beta- coefficients. Such are, for example, construction companies and car manufacturers. At the times of crisis, sales of these companies fell dramatically, while in periods of economic boom sales mark unbelievable growth. In contrast, companies in the food and tobacco industry [6], [9] for example, are less sensitive to economic conditions and have lower beta coefficients.
Industry risk is related to the status and organization of the industry, the degree of monopolization and competition, legal and administrative restrictions [8] in the sector and others. When analyzing the business risk of an enterprise must be given the specifics of the industry and its organization, the market share of the company and competition. As a rule, companies with larger market
share, monopolies and oligopolies are favored in terms of business risk because of their ability to influence the product and factor markets, respectively on prices, production and consumption. Usually the sales and profits of such companies are stable and have little variation for a certain period of time [10], [11] . Largely, the business risk is determined by the nature of the activity and specificity of the procedure. Companies from heavy industry and high-tech industries are characterized by high investment absorption. For this kind of business are required huge investment.
Market risk is defined as the probability of a reduction in sales volume due to the adverse impact of market factors - reducing consumption, the emergence of competitors, the emergence of substitute goods and other market reasons character [7] . We should note that sometimes the loss of sales could be due to reasons internal to the enterprise, rather than external (market) factors. Such circumstances may include quality deterioration, ineffective advertising, improper marketing and pricing policy, etc. Changes in sales volume greatly influence the amount of cash flows and financial results, and therefore on the performance indicators and added value. A potential decline in sales will affect the financial situation of the company. It is clear that the business risk and financial risk are closely related. Not only managers and owners, but also potential investors (and sometimes business partners and creditors) need information about any changes in sales volume and how they would affect the profitability and value of the enterprise.
Intercompany risk can be defined as the probability of a reduction in sales and efficiency due to adverse impact of internal company factors. Very often, reducing sales and efficiency due to reasons of internal, rather than external (market) factors. Such circumstances may include quality deterioration, ineffective advertising, improper marketing and pricing policy, poor organization of the production process, supply problems, problems with staff and others.
Risk in terms of factor markets is associated with any adverse changes in these markets, such as raising the prices of factors of production (materials, energy, fixed assets, payroll, etc.)., loss of suppliers, supply delay, the emergence of deficiency and others. This reflects negatively on the cost of production or services on the organization and timing of production and sales, and ultimately affects profit, added value and performance indicators. Let us imagine, for example, industrial company, whose production has a high material consumption (higher share of material costs in the cost price). Rising prices of production materials will significantly increase the cost of production [7]. Often, however, companies in this situation can not afford to increase selling prices adequately and in a timely manner, if there is no competitive advantage since risk their sales to fall dramatically (at high competition in the industry and high price elasticity of sales). This risk classification is used in research conducted by the authors in two hundred large Bulgarian industrial enterprises.
3. What are the results from the study? For settle what is the importance of risk management and how it
is being used in the Bulgarian organizations today this survey was held in 200 Bulgarian enterprises between January 2012 and April in 2014. In this case we sent an e-mail to the membership of Bulgarian Chamber of Commerce and Confederation of the Employers and Industrialists in Bulgaria – CEIBG invited them to participate in the survey. We had 200 people completed the survey in this period. Partial completes are not included in the tabulations. In the charts and tables that follow the survey, some of the totals will add to less than 200 because some questions are not relevant to some respondents, or because some questions allowed respondents to select more than one answer. In addition, total percentages do not always sum to exactly 100% because of rounding, or because the question allowed the respondent to select more than one answer.
The respondents were asked to identify the industry in which they worked. The categories match those used by Bulgarian Department of Labor. The largest group (68%) chose
29
“Food/Beverage”, and second largest group is from Financial services – 58%. The companies from Food/Beverage industry and from financial services industry is very competitive, generates high profit margins, and depends on computer systems to support or implement its services. Thus, they have always been quick to invest in any new IT hardware or software that might give them a competitive advantage. The next largest groups (53%) is in telecommunications and from the computers/consumer electronics/software industry (48%) and retailing (48%). Most of those choosing computers/consumer electronics/software are probably in the software area. The problem with this industry group comes in distinguishing those who are vendors of business process products and services, and those whose companies use BPM products to support their internal process work [6]. Other groups are as follows: Education -42%, Energy-35%, Light manufacturing – 33%,Business consulting -32% , Travel/Entertainment- 29%, Heavy manufacturing – 19%, Health care/Medical Equipment – 18% and Chemicals- 14%. The largest group (23%) chose “Other”, and most of those identified their industry as consulting.
Questions in the questionnaire and interview with managers of companies are focused on exploring the capabilities of risk management in the enterprise. For this purpose we used COSO scheme to assess the level of "maturity" in risk management. Fig. 1.
The first question of the survey is related to the development of a risk management strategy in the enterprise. 60% of respondents answered negatively, 30% say they have developed such a strategy, while 10% say that they are in a stage of preparation for strategy development. The next part of questions are directed to the eight components of the framework COSO ERM - internal environment, setting objectives, identifying events, risk assessment, risk response, control activities, information and communication and monitoring. Analysis of the results from the study allows to divide survey participants into five groups according to the scheme of assessment "maturity" level in risk management.
Fig. 1 Stages of Risk Management Capability Maturity [3]
The first group is the most numerous and covers 40% of the managers of establishments that fall into the “Fragmented” maturity level. Characteristics of this stage are:
- uncoordinated activities of risk management; - limited focus on the links between risks; - limited consistency between risk and strategies; - diverse functions for monitoring and reporting.
The second group of participants - 30% are related to "Top-down“ maturity level , for which is typical:
- general framework, program and policy; - routine risk assessment; - vertical communication about the biggest company risks with the top management; - conscious action; - formal risk consultations; - reliable team.
The third group includes 20% of managers of industrial enterprises who have the lowest level of maturity - "Unaware", characterized by:
- chaos and - individual qualities and abilities.
To the fourth stage of maturity level "Systematic" belong 5% of the interviewed managers. Its distinctive features are:
- coordinated action to manage the risk between the units; - risk appetite is clearly defined; - the risk is observed, measured and recorded throughout the company; - contingency plans; - risk management trainings.
To the fifth stage of maturity level so called "Risk intelligent" belong also 5% of the interviewed managers. Its distinctive features are:
- conducting discussions related to risks that are involved in strategic planning, capital allocation, product development, etc.; - use of preliminary indicators of risks; - link between assessment and performance incentives; - modeling / development of risk scenarios; -benchmarking and regular use of measurement standards by the industry; - evaluating the capabilities of risk management in the organization.
The main conclusions resulting from the analysis are:
1. 60% of large enterprises surveyed have policies and strategies for risk management.
2. 60% of them belong to the lowest maturity levels of risk management, namely - "Unaware" and "Fragmented".
3. Only 10% of companies manage risk systematically and intelligently.
The above conclusions enable us to systematize the major problems concerning risk management as follows:
1. Process identification and risk assessment is perceived as a single action that held once a year and it is implemented as a daily activity. [5], [7] ,[8]
2. Uncertainties and inadequate management of the full spectrum of risks. [6], [9]
3. The lack of education and awareness prevent the introduction of risk management as an integral part of management . [10], [11]
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4. Conclusion The main question is “What needs to be done to improve risk management in Bulgarian enterprises”? 1. Deep understanding of the overall framework for risk management.
2. Clear allocation of responsibilities for risk management in the enterprise.
3. Implementation of risk management as an integral part of the enterprise’s organizational activities .
4. Adequately prepared team.
5. Strictly defined control and supervision.
Overall, the major conclusion of this survey is that most Bulgarian organization remain relatively immature. Only a handful of firms are able to realize consistent, repeatable results. The firms that are achieving results are those that have made a commitment to a dedicated RM practice area, most notably, a COSO ERM framework. The leading companies are focused on moving from level 4 to level 5. Applying the framework COSO ERM can help Bulgarian enterprises to understand where they are today and to serve as a navigator on the way to achieving maturity in the risk management . Any enterprise can be placed at the appropriate level of maturity in terms of risk management. World's leading companies today focus their efforts to move to the fifth level and they have already created process architecture that shows how to combine the basic and auxiliary process risks, which helps to build a risk management system that distributes the responsibilities of process managers provides resources, monitoring and measurement of risk.
In the contemporary rapidly changing business environment, managers need to rethink the overall philosophy of risk management in order to build a comprehensive approach to managing various types of risk in industrial enterprises. The report made an attempt to cover the main issues and point out the directions in which must be oriented risk management.
Literature [1].Въведение в управлението на риска, Deloitte, http://ns.nssi.bg/
[2].Управление на риска в предприятието, http://bg.marsh.com/risk/enterprise/
[3] COSO Enterprise Risk Management – Integrated Framework. 2004
[4] Тодоров, Л. Oценка на бизнес риска (част 1) – дефиниране на понятията, http://cfo.cio.bg/
[5] Gigova Т., Mihova Т. (2013), Industrial growth in Bulgaria - background and opportunities, 3rd EmoNT 2013, Vrnjačka Banja, Serbia, , ISBN: 978-86-6075-039-8 (рр.187-190)
[6] Alexieva V., “Exploring The State of Business Processes Management In The Bulgarian Enterprises”, WCBEM -2012, Procedia - Social and Behavioral Sciences, ISSN: 1877-0428 by ELSEVIER
[7] Karev, N., The shoe manufacture in the structure of subsector “Processing of leathers and manufacture of leather articles” Journal of the University of Chemical Technology and Metallurgy – volume 47, issue 5, 2012, p. 582-587
[8] Марков, К. Трансформация на контролната дейност в административната система, ISBN: 978-619-160-264-3, „Авангард Прима“, 2014
[9] Mihova T. Small and medium enterprises - economic development and competitiveness of the Bulgarian state industry in
the global economic crisis, Scientific conference with international participation "TechSys 2013", 2013
[10] Nikolova N., T.Penev, L.Dimitrov, A classification of risk management methods in complex electrotechnical systems, European International Journal of Science and Technology, Vol.2, № 6, July 2013, p.217-225 (ISSN 2304-9693)
[11] Nikolova N., T.Penev, L.Dimitrov, Conceptual Model of Risk-Management in complex Energy Systems, International Journal of Business, Humanities and Technology, Vol.3, № 8, December 2013, p.85-98 (ISSN 2162-1357 – print; ISSN 2162-1381 – online)
31
SCIENTIFIC BASES OF CREATION OF HIGHLY EFFECTIVE BIOACTIVE COATINGS FOR BONE IMPLANTS
НАУЧНЫЕ ОСНОВЫ СОЗДАНИЯ ВЫСОКОЭФФЕКТИВНЫХ БИОАКТИВНЫХ
ПОКРЫТИЙ НА КОСТНЫХ ИМПЛАНТАТАХ Prof.Dr.End.Lyasnikov V.1, Ass.Prof. Speransky S.1
Yuri Gagarin State Technical University of Saratov, Russia1
E-mail: [email protected], [email protected]
Abstract: In this paper, we present an object detection system and its application to plasma sprayed coatings implants with the classifier based on the Principal Component Analysis (PCA). In order to improve performance of the classifier, we used combinations of halftone images and gradient images generated by the Sobel operator. To improve the quality of plasma coatings we apply intelligent control methods based on artificial neural networks and Bayesian network for optimization the weights Keywords: OBJECT DETECTION; PRINCIPAL COMPONENT ANALYSIS (PCA); IMPLANTS; PLASMA SPRAYED COATINGS; ARTIFICIAL NEURAL NETWORKS; BAYESIAN NETWORK
1.Introduction
The use of dental implants is an effective way to treat defects of dentition. However, despite many constructions created for implants, application of different bioactive coatings and bioactive materials, biocompatibility and mechanical properties for possible exclusion remains up-to-date. Radical solution to the problems of exclusion of implants is forming a structure on the surface of the implant using plasma technology layer with a porous structure, surface morphology, adhesive and other properties, which would apply maximum functional qualities to the design of the natural tooth root (Fig.1). At this time, there exist well-researched technological and medical aspects of bioactive hydroxyapatite and compositions on its basis [1].
Fig. 1 Some of the design: plate and cylindrical implants
To achieve a secure and lasting insertion of the implant in a bone,
we put different methods for creating special bioactive coatings at its surface. Currently, most methods use plasma spraying with an additional energy effects on substrate and coating. Achieving significant results requires scientific approach for creating the technologies of forming bioactive nanostructured coatings [1].
2.Preconditions and means for resolving the problem
Hydroxyapatite (HA), glass ceramics with active component as well as their compositions with various metals and alloys are now widely used as a bioactive material. An important factor in this case is high mechanical durability of the metal base of the implant along with better biological compatibility of the implant surface (Fig. 2).
б
Fig.2 Integration of the implant: without spraying (left); with plasma sprayed coatings (right)
Microstructure analysis of data shows that coatings have
strongly developed structure consisting of deformed melted particles with spherical shapes.
Developing the algorithms and software for automatic detection of microparticles in digital images is of practical importance. With these tools available, we are able to create the automatic
evaluation system for specific parameters of sprayed-on materials in the digital photos depicting their surfaces. We will be able to know the relative number of spheroidal particles and thereby forcast technological and operational properties of a coating.
3. Results and discussion
Major improvement of qualitative characteristics of bioactive coatings is achieved by optimizing the technological modes of spraying materials. In this respect, an important area of research is the study of selecting and using modern modeling methods for creating nanostructured surface layers on dental implants. The main source of information was data collected in the study of the morphology of the surface after different modes of plasma spraying [2]. The following research equipment has been used: scanning electron microscope LMU TESCAN MIRA II and device for electronic dispersion spectral analysis Ynka Energy 350 with acceleration voltage 20-30 kW (Fig. 3a). To prevent charge generation, which gives worse image quality, electrons on the surface should be leaking off the surface. Fig. 3b shows magnetron spray gun used for putting a thin layer of gold (10 < nm) on the surface and connected to the substrate, wherewith electrons stream down from the surface. Experiments have shown that spraying regimes affect the quality of the coating (Fig.4).
Fig. 3 Instruments used to study plasma coatings: a -scanning
electron microscope; b- magnetron spray gun
Spherical micro-particle detection task for halftone image of some surface can be formulated as a classifying task for each of snapshot sections containing or lacking microparticles. Microparticles have different sizes. That is why detection sections vary in size too. On the other hand, all microparticles have a similar spherical shape, which prevents using different classifiers, and the detection process can be conducted with a single classifier and scaling of the original image.
For proper functioning of the algorithm, all training examples must be the same size. We chose the size of 100 x 100 pixels because it was the average micro-particle image size obtained by an electron
32
microscope. Besides, we decided to use both halftone images and their gradient versions. When micro-particle contours are similar, gradient images supply additional information that provides more reliable detection (Fig. 5).
Fig. 4 Bioactive coatings image generated by different modes of
spraying
Fig.5 Positive (left) and negative (right) snapshots used as training examples with corresponding gradient representations
Principal component method (PCA) used in this publication is a
way to reduce the dimensionality of data with minimal loss of information [3]. When using PCA method we look for a smaller space dimension, the orthogonal projection on which variation is maximized. PCA creates a linear model that reflects the maximum variation of the data images. On the one hand, we can find the vector υi which minimizes the medium quadratic error Eγ between the source data and the data di projection on the υ (1) ∑ −=
ii
Tir ddE 2)( υυ
On the other hand, we can try to find a vector υ, which maximizes the variance of the data vector projection υ.
(2)
∑= −
=−
=N
i
TTTi DD
Nd
N 1
22
11)(
11 υυυσ ,
where D is the matrix, in which columns are the vectors of data di. In both cases, the results will be similar. The vector υ can be
found as a solution to an optimization problem. The Lagrange multiplier λ was introduced to the target function in order to make the vectorυ singular:
(3) )][(maxarg
))1((maxarg
λυλυ
υυλυυυ
υ
υ
−−
=−+=
IDDDDTT
TTT
First, we should find an optimum value of υ taking the derivative of (3) and equating it to zero:
(4)
[ ]( ) 0=−⋅− λυλυυ
IDDdd TT
After a simple conversion of expression (2), we obtain the expression, which can be defined as the task of finding eigenvectors 𝜈 and eigenvalues λ matrix C=DDT: (5) λυυ =][ TDD
After the eigenvectors and eigenvalues are calculated, we can calculate the so called eigenimages A that are, essentially, the components of our images in the course of the image recognition process. The latter involves comparing the principal components of an unknown image with components of all known images: (6)
λυDA =
After their eigenimages are calculated, we can design an original plot image to a limited number of eigenimages, and then restored the original image from the projection. The more appropriate set of eigenimages was selected for projections, the more the restored image resembled the original snapshot since less information was lost during transformations [4,5]. Three hundred positive and 300 negative snapshots were used to train the detector.
This method was implemented in the Matlab environment for detection of microparticles in halftone images obtained by means of an electronic microscope (Fig.6). Using the approach implemented in this work will identify the optimal regimes of spraying to obtain desired properties.
In a first time, an estimation scheme based on artificial neural network [6-8] is proposed to predict the density and amount of spherical particles as a function of the process power parameters: arc carrent, dispersion of powder, spraying distance(Fig.7).
Fig. 6 Detection results
An important step in developing an artificial neural network
model is the determination of its weight matrix through training. This part intends at minimizing the mean sum of squares of the network errors between the network outputs and the target outputs. A training mechanism called back-propagation training algorithm method is so far one of the most popular.
In this work, the batch gradient decent with momentum al-gorithm was used as the training of propagation at each level. (7) 𝑌𝑁𝐸𝑇 = 𝑓(∑ 𝑤𝑖𝑗
𝑞𝑗=1 𝑓𝑗�∑ 𝑤𝑗𝑙𝑚
𝑙=1 𝑥𝑙 + 𝑤𝑗0� + 𝑤𝑖0) where f is the hyperbolic sigmoid function, wij is a weight for an input hidden layer, wji is a weight for an input component x1 and wio, wjo are a bias unit which always equals one. Each weight is adjusted to coincide with output and target by a gradient method.
33
The neural network parameters can be optimized by minimizing the error function e over the example. Thus:
𝑒(𝑘) = 𝑦(𝑘) − 𝑦𝑛𝑒𝑡(𝑘) In the training step, the connection parameters were ad-
justed in such a way that, for the given input dataset, the neural network-predicted output dataset matched with the real output dataset. At the beginning of the training phase, the network connection weights are randomized values (generally close to 0).
Fig. 7 Artificial neural network
For a given set of inputs to the network, the response of each neuron in the output layer is then calculated and compared with the corresponding real output response. Then the prediction error associated with the output response is computed according to the error quadratic function defined by (8) 𝐸 = 1
2∑ 𝑒𝑖2(𝑘)𝑁𝑖=1
The weights are adjusted to reduce the prediction errors through a back propagation algorithm where the error is back distributed to the previous layers across the network. The optimization of the connection weights is indeed performed by minimizing the error according to: (9) ω𝑗𝑘 = ω𝑗𝑘
0 − µ 𝜕𝐸𝑘𝜕ω𝑗𝑘
where wik0 is the initial connection weight and µ the learning
coefficient. This coefficient controls the degree at which the connection weights are modified during the training phase. Once the weights are modified, the next dataset is fed to the network and a new estimation is performed. The error is calculated again and back distributed across the network for the next modification. This iterative process is repeated until the prediction error decreases to defined criteria.
For date we use fuzzy logic which replaces the role of the mathematical model and replaces it with another that is build from a number of smaller rules that in general only describe a small section of the whole system. The process of inference binds them together to produce the desired outputs. The purpose of control is to vary the behavior of a system by changing an input or inputs of this system according to a rule or a set of rules that model how the system operates [9, 10].
A fuzzy expert system is an expert system that uses a collection of fuzzy membership functions and rules, instead of Boolean logic, to reason about data. As a term-set of the first input variable X1 - arc current T1 = {"SMALL", "MEDIUM", " HIGH "}, or in symbolic form T1 = {SC, MC, HC} with the membership functions of the terms shown in Fig. 8.
As the term set of the second input variable X2 dispersion of the powder used set T2 = {''SMALL "," MID ","LARGE"} or in symbolic form T2 = {SP, MP, LP} with the membership functions of the terms looks like Fig. 7. As the third term set of the linguistic variable X3 - spraying distance is used a lot of T3 = {"LOW", "MID", "HIGH"} or in symbolic form T3 = {LD, MD, HB} with the membership functions of the terms looks like Fig. 8.
As a term-set output variable Y - parameter coating - the number of spherical particles will use a variety of Y = {"very SMALL ", " SMALL", "medium", "BIG", "very BIG"} or symbolically TY = {VS, S, M, B, VB} (see Fig. 9).
Fig. 8 The membership function of the input variable arc current
Fig. 9 The membership function of output parameter - the number of spherical particles
In our research for this purpose we used: a genetic algorithm and
Bayesian network. They differ parallel processing a plurality of alternative solutions, concentrating on the search of the most promising.
In operation, the first algorithm used operators: selection, crossover, mutation [6]. When training the neural network is preferably used a method of regulation based on a probability of Bayes [11], which allows to determine a weighting vector w, in which the dependence of the output signal from the input has a smooth appearance. Based on Bayes theorem for conditional probability density describing the distribution of the weight vector w, we can write:
(10) 𝑝(𝑤 𝐷𝐾⁄ ) =𝑃(𝐷𝐾 𝑤⁄ )𝑃(𝑤)
𝑃(𝐷𝐾),
where P (DK) - probability density, which is a constant; P (w) - a priori probability density at which most likely are small values of the weighting coefficients; P (DK/w) - the posterior probability density is determined by the formula: 𝑝(𝐷𝐾 𝑤⁄ ) = �
12π𝜎2�
𝐾𝑚∕2
𝑒𝑥𝑝 �−1
2𝜎2 ��(𝑦𝑖𝑘 − 𝑦𝑖(𝑥𝑘 ,𝑤))2𝑚
𝑖=1
𝐾
𝑘=1
�
In this formula:𝑦𝑖(𝑥𝑘 ,𝑤) - a deterministic function and meet the expectation of the output variable; yik - output value of at standard deviation σy; K, m - the number of neurons and layers. The most probable weight vector w found from the condition: 𝑤 = 𝑎𝑟𝑔max𝑤 𝑝(𝑤 ∕ 𝐷𝐾)
34
4.Conclusion 1. We designed reliable developed method of the spherical micro-
particle detection made by the Principal Component Analysis in the Matlab environment.
2. We use neural network for plasma spraying with Bayesian framework for backpropagation optimization the weights of the networks. We have developed an interface (Fig.10) for setting parameters of this process, to produce the necessary properties of surface.
3. The modern process unit (Fig.11, Fig.12) for plasma spraying was used in our research
4. In the future we will try to develop new system of structure investigation based on theory of Fractals.
Fig. 12 Apparatus UPS 28 for plasma spraying on dental implant
Fig. 10 An on-line interface for set of the spraying
Fig.11 Process of plasma spraying on titanium with bioactive materials inside chamber
5. Literature
1. Лясников В. Н. Плазменное напыление в электронике и
биомедицинской технике [Текст] : учеб. пособие для студ. физ.-техн. спец. / В. Н. Лясников, Н. В. Протасова ; Саратовский гос. техн. ун-т. - Саратов : СГТУ, 2010. - 285 с.
2. Кудинов В.В., Пекшев П.Ю. Нанесение покрытий плазмой.- М.:Наука,1990.-408 с.
3. L.Malagon-Borja, O.Fuentes, Object detection using image reconstruction with PCA, IVC, 27: 2–9, 2009
4. Jolliffe I.T. Principal Component Analysis, Series: Springer Series in Statistics, 2nd ed., Springer, NY, 2002, XXIX, 487 p. 28
5. Turk, M. and Pentland, A. (1991). Eigenfaces for recognition. The Journal of Cognitive Neuroscience, 3(1): 71-86.
6. Методы робастного, нейро-нечеткого и адаптивного управления: учебник; под ред.Н.Д.Егупова.- М.:Изд-во МГТУ им.Баумана, 2002.-744.
7. Усков А.А.Интеллектуальные технологии управления: Искусственные нейронные сети и нечеткая логика/ А.А.Усков.- М.:Горячая линия - Телеком.2004.-143с.
8. Jia Li, Yinlun Huang Bayesian – based on-line applicability evaluation of network models in modeling automotive paint spray operations. Computers & Chemical Engineering 30 (2006) 1392-1399
9. Леоненков А.В. Нечеткое моделирование в среде MATLAB и fuzzyTECH.- СПб.: БХВ-Петербург, 2003. – 736 с.
10. Мелихов А.Н. Ситуационные советующие системы с нечеткой логикой /А.Н. Мелихов, Л.С.Бернштейн, С.Я.Коровин. – М.:Наука, 1990. – 272 с.
11. В. Г. Матвейкин Использование байесовского подхода в обучении нейронных сетей. Уч.пос. Изд-во Тамбовского ун-та,-2006,-37стр
35
COMMERCIALLY PURE COPPER AND LOW-ALLOYED CHROME BRONZE IN TRIBOLOGICAL CONTACT WITH GRAPHITIFEROUS MATERIAL
ТЕХНИЧЕСКИ ЧИСТАЯ МЕДЬ И НИЗКОЛЕГИРОВАННАЯ БРОНЗА В ТРИБОЛОГИЧЕСКОМ КОНТАКТЕ С ГРАФИТСОДЕРЖАЩИМ МАТЕРИАЛОМ
Dr. Eng. V.I. Semenov 1,2+, Prof. L.Sh. Shuster 2, Prof. S.-J. Huang 3, PhD Stud. P.-Ch. Lin 3, Prof. R. Rajendran 4
1Institute of Oil and Gas Technologies and New Materials 2Ufa State Aviation Technical University, Ufa, Russia
3National Taiwan University of Science and Technology, Taipei, Taiwan 4BS Abdur Rahman University, Chennai, India
+corresponding author, e-mail: [email protected]
Abstract: This work presented the results of tribological studies of commercially pure copper (Cu 99.9%) and low-alloyed chrome bronze Cu-1%Cr in contact with a graphitiferous plate EK-40. Samples from copper and copper alloy were prepared to obtain two kinds of grain size of microstructure. Two schemes were used for tribological studies. The first scheme was used during reciprocal movement to evaluate the friction coefficient. The second scheme was employed to evaluate the shear strength of adhesive bonds and the adhesive component of the friction coefficient.Besides, the fulfilled studies determined that the tribological properties of materials depended on the grain size of microstructure. It is shown that an ECAP–Conformed specimen with UFG exhibits 20-30% lower friction coefficients than that of annealed specimen with CG structure. The tribological test results showed that the coefficient of friction decreased, with the decreasing grain size. Therefore, were conclude the coefficient of friction of proposed materials is microstructure-sensitive. KEYWORDS: TRIBOLOGICAL PROPERTIES, COMMERCIALLY PURE COPPER, CHROME BRONZE, MICROSTRUCTURE, SEVERE PLASTIC DEFORMATION. 1. Introduction Recent four decades of the 20th century have faced intensive development of high-speed passenger rail transport systems. Such systems allow achieving speeds up to 300-400 km/h, while the average speeds are 160-200 km/h. A whole number of special requirements is imposed on structural materials, in particular, on materials for contact wires in order to secure proper functioning of high-speed lines. These requirements are difficult to be met using conventional technologies. The tension stress of contact wires of conventional electrified railway lines does not exceed 100 MPa, the tension stress of contact wires of high-speed lines is 250 MPa (2.5 times higher than that for conventional lines). The permissible temperature of long-term heating is 150ºС [1]. Therefore, a problem of contact wire wear arises. It is known that harder materials provide lower wear and friction coefficient [2]. There are various ways to enhance hardness in alloys for most cases due to thermal treatment [3, 4]. However, thermal treatment of such materials as copper-based alloys aimed at increasing the hardness does not always allow achieving the desired effect. This makes employment of copper-based alloys in friction assemblies rather restricted. Various types of chemical and thermal treatment [5-7] and surface plastic treatment [6-8] are used for such materials. They enable enhancing the surface strength of the processed materials. The disadvantage of these techniques is rather a small thickness of the strengthened surface layer; therefore, they can be used only for finishing treatment and for relatively simple and low-loaded parts of tribological couplings. Influence of the structural and phase compositions of metal materials on their tribological properties has been studied in [6, 7, 9 - 11]. In these works the tribological studies were conducted on the materials subjected to various kinds of thermal treatment, as a result of which changes in the microstructure were observed. At present the technology of effective and multiple enhancement of strength with retention of high technological ductility has received development. The technology is based on severe plastic deformation (SPD) techniques and enables producing high-strength bulk billets from metal materials [12]. One of the SPD techniques is equal channel angular pressing (ECAP) [13], which is fulfilled in several deformation cycles. The essence of this technique aimed at enhancement of material strength is in the maximum refinement of the grain structure to submicrocrystalline (SMC) and nano-sizes [14]. Therefore, the complex approach to tribological studies of copper and its alloys in different structural states after annealing and SPD processing is of scientific and practical interest.
2. Methods of assessment of the integral value of the friction coefficient and its molecular component Two schemes displayed in Fig. 1 were used for tribological studies.
Fig. 1. Schemes of tribological tests: (a) 1 – lower sample (graphitiferous plate); 2 – upper sample (to be tested); 3 – holder; (b) 1 – tested samples; 2 – spherical indenter; 3 –
cable; 4 – disc with a groove; 5 – conductor lines; 6 – electric insulating pads.
The first scheme during reciprocal movement (Fig. 1, (a)) was used for evaluation of the friction coefficient in the pairs “commercially pure copper – graphitiferous plate EK-40” and “chrome bronze Cu-1%Cr – graphitiferous plate EK-40”. The testing conditions are as follows: the normal load Р is 80 N, the rate of relative sliding – 0.1 m/s, time of testing – 60 min. The normal load is chosen on the condition of the maximum force of hold-down of a contact wire to a graphitiferous current collector on a rail transport. The testing rate is confined by the capacity of the used tribometer. The time is set on the basis of test experience. The tests were conducted at room temperature. The second scheme (Fig. 1, (b)) was used to evaluate the shear strength of adhesive bonds and the adhesive component of the friction coefficient in the contact pair “commercially pure copper – graphitiferous material EK-40”. The test samples were prepared in the shape of discs with a diameter 20 mm and thickness 5 mm from commercially pure copper in tow structural states, coarse-grained (CG) after annealing and submicrocrystalline (SMC) after ECAP-Conform. The spherical indenter was produced from graphitiferous material EK-40 and had a sphere radius 2.5 mm. The tests were conducted at 20; 150; 250 and 450оС on a one-ball adhesiometer [15]. According to this model, the spherical indenter 2, pressed by two flat parallel samples 1, rotates about its own axis under a load. The force F, spent for the indenter rotation and applied to the cable 3, bedded in the disc groove 4, is connected with the shear strength of adhesive bonds τn. Special equipment was created with the aim to
36
use this technique as applied to the conditions of elevated temperatures of a contact. It enables conducting electrocontact heating (through lines 5, isolated by pads 6 from the casing) of the contact zone. The initial roughness of contact surfaces of the tested samples and the indenter in both testing schemes was 0.06 – 0.16 µm in the Ra-scale. The roughness of samples was measured by a profilometer SE-3500K 2D-3D.
The shear strength of adhesive bonds nτ (МPа) was calculated via:
,
2
75,0 32,1
⋅
⋅=dM
n
π
τ (1)
where d1,2 – diameters of the prints on the tested samples, mm; М – the indenter rotation torque, N mm. The adhesive (molecular) component of the friction coefficient was calculated as:
r
пa р
fτ
= , (2)
where pr – the normal pressure, МPа 2
2,1
2π
⋅
=d
Ррr (3)
where Р – the compression force of samples, N. The microhardness Hµ of pure copper samples under research was measured on a Micromet-5101 device at a load 0.98 N for 15 s before tribological tests via the first scheme (Fig. 1 (a)) and after them. Commercially pure copper M1 and chrome bronze Cu-1%Cr in the annealed (coarse-grained) states were chosen as materials to be subjected to severe plastic deformation by equal channel angular pressing via the “Conform” scheme with the aim of strain hardening and subsequent studies. The materials were processed at room temperature. A billet was rotated about its longitudinal axis at 90о after each cycle. The ECAP-Conform scheme [16, 17] is displayed in Fig. 2. The angle of channels intersection was 90о.
Fig. 2. Scheme of one of SPD techniques – equal channel angular
pressing-Conform (ECAP– Conform): 1 – die; 2 – punch; 3 – billet. The accumulated strain degree was calculated via formula (4).
ε = N 3
)2/cot(2 ϕ , (4)
where N – the number of deformation cycles; φ – the angle of channels intersection.
3. Results 3.1. Determination of the friction coefficient, shear strength of adhesive bonds and adhesive component of the friction coefficient The studied materials were in the annealed state with a coarse-grained structure and after SPD processing with a SMC structure. As a result of metallographic studies it was established that the average grain size in the annealed commercially pure copper was 80 μm. After four cycles of ECAP-Conform submicrocrystalline structure with the average grain size 0.22 μm is observed. The average grain size in chrome bronze Cu-1%Cr in the annealed state was 70 μm, and after SPD it was 0.30 μm. The results of tribological tests via the first scheme (Fig. 1, (a)) in the friction pairs “commercially pure copper - graphitiferous plate EK-40” and “chrome bronze Cu-1%Cr – graphitiferous plate EK-40” are presented in Fig. 3.
Fig. 3. Dependence of the friction coefficient on the friction way: 1 – commercially pure copper in the annealed condition with a CG
structure; 2 – commercially pure copper with a SMC structure after SPD processing by ECAP – Conform technique; 3 - chrome bronze of the composition Cu-1%Cr in the annealed condition with a CG structure; 4 - chrome bronze of the composition Cu-1%Cr with a
SMC structure after SPD processing by ECAP – Conform technique.
As it is seen from the displayed graph, the values of the friction coefficient obtained in the annealed samples of commercially pure copper (curve 1) and chrome bronze Cu-1%Cr (curve 3) are higher than those in the samples with the SMC structure after ECAP-Conform (curves 2 and 4). It is stated that the friction coefficient practically does not change in commercially pure copper samples after annealing during the whole testing time. The friction coefficient reduces slightly in the samples subjected to SPD processing with the friction contact path increasing. Apparently it is connected with additional strengthening of the surface of the material with the SMC structure in the sliding friction contact due to work hardening. This observation suits well to explain the results of tribological tests obtained for chrome bronze Cu-1%Cr samples. The results of determination of the strength of adhesive bonds enabled establishing that the adhesive component of the friction coefficient practically did not change when using commercially pure copper with the test temperature increasing from room one to 150оС. The adhesive component was 0.082 for GG materials and 0.061 for SMC ones. Further increase of the temperature from 150оС to 250оС results in growth of the adhesive component of the friction coefficient from 0.082 to 0.09 for material with the CG structure and from 0.061 to 0.069 for material with the SMC structure. The observed change is apparently connected with structural and phase transformations and diffusion processes along grain boundaries within the temperature range 150 – 250оС. This assumption requires further studies. The adhesive component values of the friction coefficient do not practically change with further increase of the temperature to 450оС. Fig. 4 displays the curves reflecting the results of assessment of the shear strength of adhesive bonds conducted on a one-ball tribometer according to the scheme shown in Fig. 1 (b).
37
Fig. 4 Dependencies of the adhesive component of the friction
coefficient on the temperature: 1 – commercially pure copper in the annealed condition with a CG structure; 2 – commercially pure copper with a SMC structure after SPD processing by ECAP – Conform technique; 3 - chrome bronze of the composition Cu-
1%Cr in the annealed condition with a CG structure; 4 - chrome
bronze of the composition Cu-1%Cr with a SMC structure after SPD processing by ECAP – Conform technique.
The adhesive component of the friction coefficient grows monotonously in both structural states at some stabilization of values within the temperature range 350 – 450оС in low-alloyed chrome bronze Cu-1%Cr samples with the temperature increase. On the basis of the analysis of the results of determination of the shear strength of adhesive bonds in the contact pairs “commercially pure copper – graphitiferous material” and “chrome bronze – graphitiferous material”, it was stated that the adhesive component of the friction coefficient in CG samples after annealing is higher than that in SMC-structured samples after SPD processing in the whole considered temperature range. Table 1 lists the values of the shear strength of adhesive bonds (τn) and normal pressures (pr) at room temperature for commercially pure copper and chrome bronze in different structural states. The values were obtained experimentally.
Table 1. Values of shear strength of adhesive bonds (τn), normal pressures (pr), adhesive and deformation components of the friction coefficient at room temperature
Material Shear strength of adhesive bonds
(τn), MPa
Normal pressure (pr), MPa
Adhesive component of the friction coefficient
(fa)
Strain component of the friction
coefficient (fd)*
Cu(annealing) 29.4 358.0 0.082 0.008 Cu(ECAP-Conform) 32.9 539.3 0.061 0.010 Cu-1%Cr(annealing) 26,5 481,8 0,055 0,028 Cu-1%Cr(ECAP-Conform) 29,7 582,4 0,051 0,024
* The strain component of the friction coefficient is found as: fd = f - fa [5]. Table 1 demonstrates that the adhesive component has a prevailing meaning in the studied frictional pairs in the dynamic contact both for materials with CG and SMC structures after severe plastic deformation through ECAP-Conform. The deformation component of the friction coefficient (fd) in chrome bronze samples is higher than that in commercially pure copper samples. The analysis of the complex tribological test results enabled stating that the largest tribological effect of SPD processing was observed in commercially pure materials. The obtained results correlate with the previously conducted studies
[18, 19].
4. Conclusions 1. As a result of overall studies of tribological properties of commercially pure copper and chrome bronze in different structural states in the conditions of elastic contact, the values of the friction coefficient during reciprocal movement and their molecular components were measured on a one-ball adhesiometer. It was established that the adhesive component of the friction coefficient prevailed in the contact pairs “commercially pure copper - graphitiferous material” and “chrome bronze – graphitiferous materials”; 2. The deformation component of the friction coefficient (fd) in chrome bronze samples is higher than that in commercially pure copper samples. The analysis of the complex tribological test results enabled stating that the largest tribological effect of SPD processing was observed in commercially pure materials.
References [1] Yu.E. Kuptsov, Dialogues about current collection. — M.: “Modern-A”, 2001. - 256 p.
[2] Friction, wear and lubrication (tribology and triboengineering)/ A.V. Chichinadze, E.M. Berliner, E.D. Brown et al., edited by A.V. Chichinadze. – M.: Mashinostroenie, 2003. – 576 p. (in Russian)
[3] Yu.V. Futoryanskiy, Effective methods of hardening of steel items. Kuibyshev: Kuibyshev Publishing House. 1978. 87 p. (in Russian)
[4] V.Ya. Kirschenbaum. Mechanical and thermal formation of friction surfaces. M.: Mashinostroenie, 1987. 230 p. (in Russian)
[5] D.G. Gromakovskiy, N.D. Kuznetsov, et al. Enhancement of fatigue life of friction assemblies by applying carbon-fluorines //Vestnik mashinostroenia, 1987, № 8. (in Russian)
[6] A.V. Belyi, G.D. Karpenko, N.K. Myshkin, Structure and methods of formation of wear-resistant surface layers. M.: Mashinostroenie, 1991. 208 p. (in Russian)
[7] D.N. Garkunov, Triboengineering. M.: Mashinostroenie, 1989. 327 p. (in Russian)
[8] L.G. Odintsov, Hardening and finishing of items by surface plastic deformation: Reference book. M.: Mashinostroenie, 1987. 327 p. (in Russian)
[9] Pearlite in carbon steels / V.M. Schastlivtsev, D.A. Mirzaev, I.L. Yakovleva et al. Ekaterinburg: UrB RAS, 2006. ISBN 5-7691-1713-3. (in Russian)
[10] V.M. Schastlivtsev, V.I. Zeldovich, D.A. Mirzaev et al. Development of ideas of Academician V.D. Sadovskiy. Collected works. Ekaterinburg, 2008. ISBN 5—900474—58—5. (in Russian)
[11] L.M. Rybakova, L.I. Kuksenova. Structure and wear resistance of metals. M.: Mashinostroenie, 1982. 212 p. (in Russian)
[12] R.Z. Valiev, I.V. Alexandrov, “Nanostructured Materials Produced by Severe Plastic Deformation”, 2000, Logos Pub., Moscow, 272 p. (in Russian).
[13] G.I. Raab, R.Z. Valiev, Equal channel angular pressing of long-length billets. Tsvetnaya metallurgia. 2000. №5, pp.50-53. (in Russian)
[14] Equal channel angular pressing of metal materials: achievements and directions of development (Topical collection of
38
publications edited by V.M. Segal, S.V. Dobatkin, R.Z. Valiev)//Metally 2004, № № 1, 2.
[15] L.Sh. Shuster. Adhesive interaction of solid metal bodies. - Ufa: Ghilem, 1999. 198 p. (in Russian)
[16] Equal channel angular pressing of metal materials: achievements and directions of development (Topical collection of publications edited by V.M. Segal, S.V. Dobatkin, R.Z. Valiev)//Metally, 2004, № 1. pp. 5-119, № 2. pp. 5-63. (in Russian)
[17] R.Z. Valiev, Y. Estrin, Z. Horita, T.G. Langdon, M.J. Zehetbauer, Y.T. Zhu Producing Bulk Ultrafine-Grained Materials by Severe Plastic Deformation.//JOM, Vol. 58, No. 4 (2006) pp. 33-39.
[18] V.I. Semenov, L.Sh. Shuster, S.V. Chertovskikh, G.I. Raab. Influence of integral parameter of plastic friction contact and material structure on the strength of adhesive bonds//Friction and wear. 2005. V. 26. № 1. pp. 74 – 79. (in Russian)
[19] V.I. Semenov, L.Sh. Shuster, S.-J. Huang, P.-Ch. Lin Tribological Behavior of Low-Carbon Steel Depending on Treatment and Structural State//Journal of Friction and Wear, 2011, Vol. 32, No. 3, pp. 205–211. Allerton Press, Inc., 2011.
39
DYNAMIC PARAMETERS OF A CHAIN TRANSMISSION IN METAL AND POLYMER DESIGN
Dr. Sc. Pilipenko O., Phd Student Eng. Poluyan A. Chernihiv National Technological University, 14027, Chernihiv city, st. Shevchenko 95, Ukraine
E-mail: [email protected], [email protected]
Abstract: Today the development of formalized methods of synthesis of chain transmission for mechanical engineering are observed. Solving it gives the opportunity to raise designing quality and labor productivity of the designer and the constructor when applying these methods directly in computer-aided design.
Comparative analysis of dynamics 3D computer design modeling of chain transmission in metal and polymer design by means of program complex SolidWorks are presented. From the analysis of graphic dependences precisely traced advantages of application components of polymer composites as compared with traditional metal parts of chain transmission: dynamic loads in chain contour, force of the impact between the oncoming roller and sprocket, dynamic irregularity of rotation the sprockets.
KEYWORDS: CHAIN TRANSMISSION, PARTS OF POLYMER COMPOSITES, COMPARATIVE DYNAMIC PARAMETERS
1. Introduction
Today the development of formalized methods of synthesis of chain transmission for mechanical engineering are observed. Solving it gives the opportunity to raise designing quality and labor productivity of the designer and the constructor when applying these methods directly in computer-aided design.
A multi mass chain drive is the system, which consists of interactive and intercaused indivisible elements, has many possible realization in the process of functioning and that is why behaves to the complicated systems. The new approach to calculation and designing of chain drives must be based on the account of the real dynamic processes which take place during their work, use of polymeric composites for making of sprockets and chains and change-over to the automated optimal design, which will enable to choose the aggregate of values of their parameters, at which yet on the stage of design high dynamic quality of transmissions and drives will be provided. The majority of machines demands advancing their drives, in particular chain drives, with the purpose of a decrease of specific consumption of materials and power costs of speeding up and braking of driven parts. One of basic directions of achievement of this aim there is the use of modern CAD of the programs [1-3]. Main reason of the use of CAD of the programs is ability of realization of computer experiment on the terms of work of machine or mechanism, near to the real.
The decline of the dynamic loading, pin tensions and wear of parts of chain drive is reached at by application of polymeric and metal-polymeric sprockets and chains. Production of parts for chain-drives from the polymeric compos of low-waste and not very much power-consumption. From polymeric compos it more easily to make the parts of complicated form, they are so technological, that allow to create the so-called integrated parts production of that from a metal far more expensive or it is impossible in general.
2. Preconditions and means for resolving the problem
2.1. Theoretical Model A linear dynamic analysis is based on frequency researches.
Software expects the reaction of model by means of summation influences of every mode (functions, equation) on loading [4]. Influence of mode depends on the frequency spectrum of loading, value, straight, duration and coordinates of location of model. The equations of motion are not only linked the parameters of mass, rigidity and damping, but depends on the coordinate system used to describe them.
In cases where the linear dynamic analysis generates false results, such as a violation of the assumptions on which it is based, uses a non-linear dynamic analysis is based on the incremental method of managing loading. It is used to solve the problems of nonlinearity, caused by material behavior, large displacements and contact conditions.
In nonlinear dynamic analysis equation equilibrium of dynamic system in the time interval t + Dt, will have the form [4]:
[ ] { }( ) [ ] { }( ) [ ]( ) [ ]( ) { } { }( )1 −++++++ −=++ itDttDtitDtitDtitDtitDt FRDUKUCUМ , (1)
where [ ]М – matrix of mass system; [ ]С – damping matrix of the system;
[ ]( )itDt К+ – stiffness matrix of the system;
{ }( )itDt R+ – vector of external nodal loads applied;
{ }( )1−+ itDt F – vector of internal forces generated in the nodes upon repetition (і – 1);
[ ]( )itDt DU+ – vector of nodal displacements at increasing repetition (і);
{ }( )itDt U+ – complete displacement vector to repeat (і);
{ }( )itDt U+ – vector full speed on repeat (і);
{ }( )itDt U+ – vector of full acceleration on repeat (і). Using implicit time integration schemes such as Newmark-Beta
or Wilson-Theta and using the iterative Newton method, equation (1) has the form:
[ ]( ) { }( ) { }( )itDtiitDt RDUK ++ = ,
where { }( )itDt R+ – effective loading vector;
{ }( ) { } { }( ) [ ] { }( ) { }( ) { } { }( )[ ] { }( ) { }( ) { } { }( )UaUaUUaC
UaUaUUaMFRRtttitDt
tttitDtitDttDtitDt
541
1
321
01
++−−+
+++−−+−=−+
−+−+++
[ ]( )itDt K+ – effective stiffness matrix;
[ ]( ) [ ]( ) [ ] [ ]CaMaKK itDtitDt10 ++= ++
а0, а1, а2, а3, а4 і а5 – constants implicit integration methods. Iterative schemes for solving nonlinear dynamic analysis
available: Newton-Raphson algorithm (NR) and variable algorithm Newton-Raphson (MNR).
Equation contact force between two contacting parts, N [4]:
( ) ( ) dtdg,c,dg,StepgkF MAXMAXe
n ⋅+⋅= 00 , where k – stiffness of the material at the boundary interaction between two contacting parts;
g – penetration of one body into another geometry; е – rate of perceived exponential force compared with offset
model; dMAX – limit penetration; сМАХ – maximum damping on the boundary interaction;
dtdg – speed of penetration at the point of contact. Consider the example of using SolidWorks to analyze the
dynamic parameters of the chain transmission according to [5] in the metal (Fig. 1) and the polymer performance (Fig. 2). In 3D simulation used parameters and qualitative characteristics of sprockets chain transmission ГОСТ 592-75; metal chain - ГОСТ 13568-97, corresponding to ISO 606-94, and polymer – according to [6]. Unfortunately, Fig. 1, 2 not fully reflect the actual movement of the chain contour (exists authored animated version).
40
Fig. 1. 3D model of experimental stand in metal performance
Fig. 2. 3D model of experimental stand in polymer performance
The main dynamic parameters conducted analysis of motion 3D models of chain contours SolidWorks software package are:
- change of kinetic energy with a change in velocity of the metal (Fig. 3) and polymer (Fig. 4) performance;
- change of impulse force oncoming on the sprocket in a metal joint (Fig. 5) and the cylindrical part of the elastic monolithic link [6] in the polymer (Fig. 6) performance;
- the power contact (impact) between the leading sprocket and oncoming joint chain (Fig. 7) in metal and elastic monolithic link in the polymer performance (Fig. 8);
- dynamic irregularity rotation driving mass with metal an sprocket (Fig. 9) and polymeric sprocket (Fig. 10);
- dynamic load of metal (Fig. 11) and polymeric (Fig. 12) performance contours.
Changes in the value of the velocity u1 to u2 leads to the changes of the kinetic energy:
( )21
222
uumWк −=∆
Fig. 3. Change of kinetic energy in metal performance (J)
Fig. 4. Change of kinetic energy in polymer performance (J)
The maximum change in kinetic energy is several times greater in metal chain transmission (Fig. 3), as compared to its performance polymer (Fig. 4). The reduction of the kinetic energy increases the reversibility of chain transmission, ie to change the motion direction of the system it is necessary to apply less force.
Fig. 5. Changing impulse force along the axis Y, (N · s) in metal performance
Fig. 6. Changing impulse force along the axis Y, (N · s) in polymeric performance
The upper graph peaks characterize the changing in force impulse of joint chain (Fig. 5) and of elastic monolithic link (Fig. 6) during contact with the driven sprocket, and lower peaks are with the driving. The intervals of time between the contacts with the sprocket joint chain and elastic monolithic link are in driving and driven branches of the chain contour. The graphs (Fig. 5, 6) clearly show the advantages application of chain transmission parts of polymeric materials: maximum and minimum values of change impulse force is several times smaller.
Fig. 7. Power contact between the sprocket and the driving oncoming joint
41
Fig. 8. Power contact between the driving sprocket and elastic
monolithic link
Figures 7 and 8 show that the force of contact (impact) between the driving sprocket and oncoming joint chain (Fig. 7) higher compared to monolithic elastic contact links and driving sprocket (Fig. 8).
Fig. 9. Dynamical irregularity rotation of driving mass with metal sprocket
Fig. 10. The dynamic irregularity rotation of driving mass with
polymeric sprocket
The curve of the graph (Fig. 10) clearly shows a decrease of dynamic range values dynamic irregularity of rotation driving sprocket and its constancy and stability in performance compared to the metal (Fig.9), in which it is much more.
Fig. 11. The dynamic loading chain contour in metal performance
Fig. 12. The dynamic loading contour in polymeric chain
performance
Fig. 12 clearly shows the decrease of dynamic load in polymeric performance chain contour (mean 134N) in comparison with a dynamic load (Fig. 11) in a metal contour (mean 182N).
2.2. Experimental stand In Fig. 13 and 14 are photos of the experimental stand [5]
equipped a metal and polymeric chains and sprockets. In experimental researches used 4 sensors ohmic resistancethat
are sealed in a special link measurement (2 - on the outside of the link and 2 - on the inside), which fixed the change in tension-squeeze deformation. For greater sensitivity of sensors connected by half-bridge scheme. In order to amplify the signal from the sensors used instrumentation amplifier AD 8555.
Fig. 13. The experimental stand is equipped with a metal chain
transmission
Fig. 14. The experimental stand is equipped with polymeric
chain transmission
As a result of experimental research of chain drives (Fig. 13, 14) were obtained oscillograms dynamic loading of the chain contour (Fig. 15).
42
Fig. 15. Experimental oscillograms dynamic loading: - blue curve - a metal chain drive at speed n1 = 300s-1, - red curve - polymer chain drive at speed n1 = 290s-1.
From the analysis of oscillograms (Fig.15) that the average value of the dynamic loading in metal chain contour is 191N, and his performance polymeric - 128N.
3. Conclusion
From the analysis of the curves as the experiment and the simulation shows that the chain transmission to polymer performance provides: - reducing the kinetic energy that allows to obtain greater reversibility, ie to change the direction of motion of the system is necessary to apply less force; - reducing the force impulse oncoming on the sprocket joint several times that allows to put less force to change the direction of rotation of the contour; - reducing the contact force (impact) due to greater damping coefficient of the material; - lowering range, stability and constancy values dynamic irregularity rotation of driving mass.
Analyzing the graphs (Fig. 11, 12) and oscillograms (Fig.15), one could argue that the difference of theoretical and experimental mean values of dynamic loading in the chain contours does not exceed 5%, which demonstrates the possibility to use SolidWorks software for the calculation of any chain contours.
Application of SolidWorks software allows not only to modeling and simulation of real work chain drives, but also conduct their analysis with a view to switching to automated optimal design for high dynamic quality of material and energy consumption.
4. Literature
1. Алямовский А.А. COSMOSWorks. Основы расчёта конструкций на прочность в среде SolidWorks. – ДМК Пресс, 2010 – 789 с. 2. Paul M. Kurowski. Engineering. Analysis with COSMOSWorks Professional. – Schroff Development Corporation (SDC), 2005. – 248 р. 3. Кудрявцев Е. М. КОМПАС-3D V10. Максимально полное руководство. В 3-х томах.: ДМК Пресс, 2008. – 1184 с. 4. http://help.solidworks.com. 5. Пилипенко О.И., Лабудько В.А., Радченко С.В.Стенд для испытаний и исследований передач гибкой связью. А.с. № 1717988 Б.И. № 9, 1992. 6. Пилипенко О.І., Козар І.Ф., Степенко А.П. Пружна монолітна ланка ланцюга. Патент України 23341А. Бюл. №4, 31.08.98.
43
RAPID PROTOTYPING – DEFINITION OF TERMS AND HOW TO APPLY DURING A STUDENT PROJECT
Dipl.-Ing. Pointner A.,BSc1; Dipl.-Ing. Schnöll H.P.2; Dipl.-Ing. Friessnig M.,BSc2; Heinzle P., BSc1
Institute of Production Science and Management – Graz University of Technology, Austria 1
Institute of Industrial Management and Innovation Research, Graz University of Technology, Austria 2
[email protected]; [email protected]; [email protected]; [email protected]
Abstract: Nowadays the field of Rapid Prototyping is rapidly changing and providing a clear overview is challenging. One of the biggest problems in this context is that different operations are often named similar. In the beginning of this paper the most important related terms are defined and classified. Afterwards the major Rapid Prototyping techniques, called generative manufacturing methods, are explained. Alternatives to these generative methods as well as 3D-scanning methods are dealt with too. All in all these emerging technologies around 3D-printing and 3D-scanning are revolutionizing the way Rapid Prototyping laboratories look like. They offer new possibilities and reduce the complexity of prototyping. One of the future trends is so called Fab Labs which are currently stretching the boundaries of the common Rapid Prototyping laboratories. At Graz University of Technology the second Fab Lab in Austria has been established lately. Especially its implementation in University education as part of the Product Innovation Project is discussed in detail.
Keywords: RAPID PROTOTYPING, 3D-PRINTING, 3D-SCANNING, GENERATIVE METHODS, STEREOLITHOGRAPHY,
GENERATIVE SINTERING, FUSED DEPOSITION MODELING, FABRICATION LABORATORY, PRODUCT INNOVATION PROJECT, FAB LAB MOVEMENT
1. Introduction As the field of Rapid Prototyping has been growing quickly
during the past few years, several definitions for Rapid Prototyping are known. Also the term of 3D-printing is often used across the board and is seldom clearly defined. If one takes a closer look at the field, these circumstances increase the risk of confusion. Especially the use of the term 3D-printing as an umbrella term is crucial in this regard. Therefore as a precaution the most important terms of the field are defined and classified before going deeper into the topic. Besides the major generative and conventional Rapid Prototyping methods, which are the essential basic tools in prototyping, are presented.
Connected to the quick advancement of Rapid Prototyping possibilities is also the so called Fab Lab movement. Its main ambition is to simplify prototyping and enable more and more people all over the world the possibility to manufacture their individual items themselves. The worldwide exchange of prototyping and manufacturing knowledge is only one benefit that is generated when being part of the network. As there exists a course called “Product Innovation Project” at Graz University of Technology, which deals with the development of prototypes, the establishment of a new Fab Lab made perfect sense.
In the second part of this paper the Fab Lab movement, the new Fab Lab in Graz and its application within the “Product Innovation Project” course will be described in detail.
2. Rapid Prototyping The term Rapid Prototyping stands for an application of the
generative manufacturing methods. These methods are based on the layering principle, which implies that an object is made up of plenty of thin layers. [1] In numerous steps the layers of material are added onto each other and an energy source ensures that they get adhered and hardened. The layer material can either be in powder form, fluid or in hard condition. The major advantage of these methods compared to conventional ones is that there are hardly constraints concerning the shape of the desired object. [2]
Beside other applications like Rapid Tooling, which stands for the fabrication of moulds, tools and equipment for production processes, Rapid Prototyping is defined as the fabrication of models and prototypes without product character. When custom-specific final products are produced in individual or small series the application is called Rapid Manufacturing. On the contrary Additive Manufacturing describes the application of generative methods in case of serial production. [1]
According to VDI guideline 3404 nine generative manufacturing methods can be distinguished in total: [3]
• Stereolithography
• Laser sintering and electron beam melting
• Fused layer modeling (Fused deposition modeling)
• Multi-Jet modeling
• Poly-Jet modeling
• 3D-Printing
• Layer Laminated Manufacturing
• Mask sintering
• Digital light processing
A description of each method would go beyond the scope of this paper. Therefore the focus is on the three major ones, which are stereolithography, laser sintering / electron beam melting and fused layer modeling (fused deposition modeling). [3]
The company “3D System” introduced Stereolithography in 1987. It is known as the oldest generative manufacturing method. [3] The principle of stereolithography is the layer by layer solidification of fluid or pasty monomers through polymerization. Within the group of stereolithography several different sub-methods can be distinguished. Whereof the laser-scanner-stereolithography can be seen as the prime father in case of industrial used rapid prototyping processes. [4] The necessity of supporting structures and the poor thermal and mechanical resilience of the objects produced are offset by the high level of detail and the achievable refinement of their surface. [5]
In the early 1990s the generative sintering was known as laser sintering due to the fact that all common systems used a laser as energy source. Nowadays machines using an electron beam or infrared radiator for the fusion and solidification of the layers are frequently used too. The basic raw materials are densely packed and precompressed powder particles out of metal, ceramic or resin-bonded sand. These particles get fused by the energy source and so layer by layer the object is built up. [6] Although there are basically no supporting structures needed because of the supporting effect of the solid raw material, however they are often used to ensure a good heat dissipation to prevent warping of the metal material. [7] Temperature control is crucial because already small deviation can lead to poor sintered or discolored useless objects. [8]
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The company Stratasys introduced the fused layer modeling or fused deposition modeling method. In most of the applications ABS or PLA plastic filaments are used as basic raw material. By passing a heated nozzle the temperature of the filament rises close to the melting point of its material. Once the filament is pasty it’s deposited onto the previous layer. Through heat conduction the material cools down, fuses with the prior layer and hardens immediately afterwards. Although the surface quality is often quite poor and overhanging sections of the objects require supporting structure, the method is quite popular because of its low costs and office suitability. [9]
Another generative method is called 3D-printing. Although it only represents one of the nine generative manufacturing methods, it is more and more used as an umbrella term for all of them. Obviously this can easily cause confusion. Therefore it is essential to use the correct terms while working professionally in this field. [10]
After all prototyping doesn’t necessarily have to be done by using one of the named generative methods. There are also possibilities to build up prototypes with conventional manufacturing techniques like a CNC-milling or laser cutting. [11] While laser cutting is suitable for building up prototypes out of piled thin layers and is commonly used in architecture, prototyping with CNC-milling can be very challenging especially if the structure of the desired object is complex. The achievable excellent accuracy is offset by the constraints regarding the accessibility of narrow and angled areas of the object. Clever combinations of generative and cutting processes offer great potential. Through using the generative manufacturing methods to build the object there are hardly limitations regarding the shape of the object. Refining it afterwards by using cutting methods, enables the achievement of excellent accuracy and surface quality. [12]
Prototyping with all of these methods requires a 3D-CAD-model as a starting point. This can either be designed by using common CAD-software or, if the object already exists, it can be scanned through using a 3D-scanner. The technology of 3D-scanning is advancing rapidly in the past few years. Beside applications in different fields like medicine, historic preservation or the packaging industry, it is also widely used for quality assurance and digital archiving of prototypes. [13] Especially the technology of desktop-3D-scanning is emerging hand in hand with office suitable 3D-printers.
Basically contact and non-contact 3D-scanning methods can be distinguished. As in desktop-3D-scanning the disadvantages like the high costs, the low speed and big effort of the contact based methods outweigh the achievable accuracy of the scans, the focus is on non-contact methods. The most common methods used in desktop-3D-scanning are triangulation-based laser-scanning, structured light technology and photogrammetry.
At the moment the uprising competition among these 3D-scanner devices has been pushing down the prices to a few hundred Euros. It is very difficult to maintain the overview of the market as there are new solutions brought to the market frequently. One of the latest trends is the combination of these desktop-3D-scanners and the already above mentioned 3D-printers in one device.
These emerging technologies around 3D-printing and 3D-scanning for home users are revolutionizing the way Rapid Prototyping laboratories look like. They offer new possibilities and are reducing the effort to build a complexity prototype. One future trend of these Rapid Prototyping laboratories, also called maker spaces, is a Fab Lab.
3. Fab Lab – A Maker Space The first Fab Lab was set up by Neil Gershenfeld at the
MediaLab of the Massachusetts Institute of Technology (MIT) in 2002. The acronym Fab Lab stands for Fabrication Laboratory. The basic idea of these labs is to provide individuals access to
manufacturing tools, so that they are able to produce their own things. As long as commercial activities of the users do not interfere with the access of others, they are tolerated. [14]
There are four main criteria that have to be fulfilled to start a Fab Lab. First of all the lab should be accessible free of charge for everyone at least once a week. Secondly the Fab Charter, which states the principles of the Fab Lab movement, has to be published on site and on the web page of the lab. Furthermore all labs should be equipped with the same basic tools to ensure the exchangeability of designs, knowledge and the reproducibility across borders. In addition the support of other labs and a contribution to the Fab Lab community is expected. [15]
Nowadays the Fab Lab movement is spreading rapidly all over the world and currently there are already more than 330 Fab Labs registered. [15] At the Institute of Production Science and Management of Graz University of Technology the second Fab Lab in Austria has been built up in the last few months. The equipment had been well chosen according to the guidelines of the MIT. These already mentioned common equipment includes a computer-controlled laser cutter, a plotter cutter, several programming tools, a precision milling machine and also a numerically-controlled milling machine. [16] Although there are a lot of commonalities among the different Fab Labs, every lab still has its own identity. Slight differences regarding the services and tools which are provided in the labs and the various user groups determine these identities.
Based on our own experience an extension of the provided tools towards a 3D-printer makes the most sense. Therefore at the Fab Lab at the Institute of PSM additionally a 3D-printer named “3D Touch” is available. Furthermore the required basic tools as a MDX-540 SA precision milling machine from Roland, a CAMM-1 Servo GX-24 plotter cutter from Roland and a VLS 3.50 laser cutter from Universal Laser Systems are provided. Although there is only limited space, additionally a sand blaster, a computer workstation, a workbench and some electrical tools are available. Basically the lab can be used by all students of the University and once a week also by external visitors. The main target group consists of students who are participating the course “Product Innovation Project”.
4. Rapid Prototyping in University Education – The Product Innovation Project
The course "Product Innovation Project" was founded in 2006. The main idea is to bring students of different fields of study together to work on projects and develop new products. The students have to work as a team to be able to create a solution to fulfill complex product development tasks. The outputs of the course are working prototypes. Key elements of organizational framework of “Product Innovation Project” are interdisciplinary, intercultural and international student teams. It shall impart the holistic view on the product development process, from idea generation until the market introduction. An adequate budget – paid by the industrial partners – allows the manufacturing of a working prototype in workshops like a maker space.
“Product Innovation Project” splits up the innovation process in a way that the process steps are carried out by different executing parties according to their strengths and weaknesses. Whereas university acts as a host for the project preparation, organization and contributes its specific technical know-how and facilities, the main actors in the actual innovation process are the student teams. The industrial partners cover the very first (the strategic decision of “what and how to innovate”) as well as the very last phase in the process (refinement, production, and market introduction). The teams of students intermediate carry out the phases from idea generation until the preparation of a working prototype and a product concept, as seen in Fig. 1. [17]
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Fig. 1 Integration of “Product Innovation Project“ into the innovation process according to [17]
In past periods of the project, it was recognizable that in addition to support provided by the industrial partners, the student teams are willing to make various different prototypes on their own instead of hiring a contract manufacturer. But this was not possible due to an inexistent small fabrication laboratory. While analyzing the product development process, it’s worth noting that it is not only necessary to have maker equipment in phase VII and VIII, where the students put all effort on the development and realization of the working prototypes. Especially in the phase II, IV and V a fast and uncomplicated access to manufacturing machines is essential. Students can generate far more ideas or rough product concepts when virtual 3D models are transformed in physically existing prototypes. Experience shows that often only these prototypes allow proper evaluation of product size, materials and other important product attributes. Early prototyping as well as detailed research on the available solutions, their advantages and possible problems, their stage of maturity (research stage or available on the market) are the basis for an outstanding result and a small fabrication laboratory provides the right tools.
In addition, cooperation between the stakeholder groups can provide benefits for each of them, like hands on experience for students in a product development project, additional funding and research fields for universities or access to qualified students for companies. These benefits are the result of an up-to-date learning environment, involving students, industrial partners and scientific staff of universities. It is worth to mention that students are investing the most working hours compared to other stakeholders in such a project. Due to this reason, the members of the student teams play a key role within the stakeholder constellation and it’s very important not only to ensure their motivation but also provide them professional facilities to support the product development process.
5. Conclusion The past few years showed what students are able to create, if
they got the chance to develop their own projects. Students learn through challenges, so it’s important that the university challenge their students. In addition, the idea of having a physical output is a long-term motivation for every student. Due to this reason, Graz University of Technology decided to go one step further and join the Fab Lab community in summer 2014. Through providing such an environment, where students can make their ideas real, it can be ensured that they have the possibility to develop their full potential.
6. References
[1] A. H. Fritz und G. Schulze, Fertigungstechnik 10.Auflage, Berlin: Springer, 2012, p. 106.
[2] M. F. Zäh, Wirtschaftliche Fertigung mit Rapid-Technologien, München: Carl Hanser, 2006, p. 11.
[3] A. H. Fritz und G. Schulze, Fertigungstechnik 10.Auflage, Berlin: Springer, 2012, p. 108.
[4] A. Gebhardt, Generative Fertigungsverfahren 3.Auflage, Erkelenz/Düsseldorf: Carl Hanser, 2007, p. 81.
[5] P. Fastermann, 3D-Druck/Rapid Prototyping, Düsseldorf: Springer, 2012, p. 122.
[6] A. Gebhardt, Generative Fertigungsverfahren 3.Auflage, Erkelenz/Düsseldorf: Carl Hanser, 2007, p. 121.
[7] A. H. Fritz und G. Schulze, Fertigungstechnik 10.Auflage, Berlin: Springer, 2012, p. 109.
[8] A. Gebhardt, Generative Fertigungsverfahren 3.Auflage, Erkelenz/Düsseldorf: Carl Hanser, 2007, p. 122.
[9] P. Fastermann, 3D-Druck/Rapid Prototyping, Düsseldorf: Springer, 2012, p. 120.
[10] A. H. Fritz und G. Schulze, Fertigungstechnik 10.Auflage, Berlin: Springer, 2012, p. 112.
[11] M. F. Zäh, Wirtschaftliche Fertigung mit Rapid-Technologien, München: Carl Hanser, 2006, p. 10.
[12] M. F. Zäh, Wirtschaftliche Fertigung mit Rapid-Technologien, München: Carl Hanser, 2006, p. 80f.
[13] P. Fastermann, 3D-Druck/Rapid Prototyping, Düsseldorf: Springer, 2012, p. 54.
[14] P. Fastermann, 3D-Druck/Rapid Prototyping, Düsseldorf: Springer, 2012, p. 49.
[15] fabfoundation.org, „fabfoundation.org,“ 17 6 2014. [Online]. Available: http://www.fabfoundation.org/fab-labs/. [access date 17 6 2014].
[16] fab.cba.mit.edu, „fab.cba.mit.edu,“ 1 7 2014. [Online]. Available: http://fab.cba.mit.edu/about/faq/ . [access date 1 7 2014].
[17] M. Fallast, H. Oberschmid, "Product Innovation Project" - a novel interdisciplinary student project, in Advances In Production Engineering & Management, Maribor, 2009.
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VIBRATION MONITORING FOR FAULT DETECTION AND
PROCESS CONTROL OF THE MOTOR-MIXER AGREGATE IN FENI INDUSTRY-MACEDONIA
Prof. Geramitchioski T. PhD.1, Doc.Trajcevski Lj. PhD.2
Faculty of Technical Science – University St. Kliment Ohridski Bitola, Republic of Macedonia 1 [email protected]
Abstract: One of the larger aggregates for production nickel in Feni – INDUSTRIES- Macedonia, is assembly machine mixer 1 and
mixer 2. The proper functioning of aggregate depends on the prevention and early detection of damaged parts. Given that the aggregate works non-stop for 24 hours, its failure means termination of operation of furnaces for nickel, and thus the entire production. It means a loss of time, deviation from the production plan, loss of markets and loss of a lot of money. It is a very important to constantly monitor the vital parts rightness. Therefore regularly perform frequency analysis of engine bearings and mixer bearings. Aggregate is composed of: motor, hydro coupling, reducer, mechanics coupling, and mixer. This paper provides the results of frequency analysis of measured vibration of these parts, compared with limited values and recommendations for quick actions in removing the damaged parts in time periods with the least losses. That means pre timely delivery of bearings, preparation of aggregates for quick repairs with a short downtime. You will also be given a techno - economic analysis to save funds by using this method. KEYWORDS: SIGNAL PROCESSING, VIBRATION ANALYSIS, BEARINGS, CONDITION MONITORING 1. Introduction Production of nickel is an intensive process that uses robust and
rotating equipment where it is exposed to intense workload and high temperatures, whereas the susceptibility of equipment failures poses a serious threat. In critical positions in flow of the production process include crushers , rotary dryers (x4), mills (x2), rotary kilns (x2) and the main hydraulic oil lubrication systems that use large electric motors and reduction enclosures , in addition to electric furnaces ( x2), converters (x2), arc furnace (x1), granulation system ( x1 ) and vats that are susceptible to decline bricks and large transformers.
By exploiting the plant comes to unwanted accidents due to the occurrence of illicit vibration. In order to avoid these phenomena are often performed unnecessarily replacing the elements of the plant, although they can still be used.
The latest trends tend to maintain fixed time intervals for replacement of mechanical elements, to be replaced by interval control state of the plant. The basic principle of this system maintenance vibration diagnostics is to defining discrete air forces imply irregular operation of the plant [1].
Modern equipment for measurement, analysis and diagnostics, along with knowledge and experience of professional staff who manage it, guarantee to resolve the complex side effects that occur during the operation of the plant. All rotating machines during operation generate vibrations that are inevitable occurrence in their exploitation. Their full elimination is impossible, but it is the same loft in boundaries defined by the equipment manufacturer or adopted global standards and norms, such as: VDI 2056 recommendations; DIN 45.666 norms ISO 10816 standards; E 90-100 French norm.
The fact that irregular work of some mechanical element with particular intensity and frequency determined exactly unique to that part of the plant, is used for determining and defining exactly inertial forces that cause the dynamic state of the plant.
Nature of inertial forces can be various different [2],[3],[7]: - imbalance in the rotating masses ; - misalignment - axis of the shaft ; - mechanical damage in rolling bearings ; - irregularity in the operation of the sliding bearings ; - work in terms of resonance phenomena ; - Excitation aerodynamic and hydraulic forces ; - Electromagnetic vibration and more.
The choice of balancing rotors in their own bearings has that advantage:
- Corrects imbalances of the total rotating mass of the entire composition.
- There are no transport costs; - Avoided mistakes are repeated editing.
The following example will show the measurement and diagnosis of two motor-mixer agregates used permanently in Feni - INDUSTRIES- Kavadarci, R.Macedonia. (fig.1)
Fig.1.FENI INDUSTRY KAVADARCI –MACEDONIA
2. Material and methods The basic goal of this investigation is measuring the vibration of
all rotating machinery in Feni Industry in critical points of the vital slops with PRеsеnoted the results in period before failure of the bearings.
For that purpose was used VIBROTEST 60 (Bruel&Kjaer) instrument with appropriate modules.
All measurements of rotating machines via a memory card of the VIBROTEST 60 were transferred to a computer. The computer has installed XMS software where all measurements are recorded on the machine. XMS (extended monitoring software) is the professional software for optimum implementation of the concept “condition-oriented machine maintenance” and provides perfect support through an intelligent database. By measuring the route covered all machines in the factory (Fig.2). By measuring the vibrations in this program and register at the same time frequency analysis are too. But if there's a problem of the machines are made more frequent measurement to monitor the amount of vibration and to determine whether resulting from lineups: Bad bearings in electric motor or the working circuit. Sometimes a problem with the clutch which can be damaged by irregular lubrication of electric motor with a working circuit, or by imbalances that may occur with consumption of the fins from the working circuit. Spending the fins can occur from hot air and dust that is in him. To determine what caused the vibration, it has been establish measurements and software through the frequency analysis of all bearings, and it is seen from the pictures (Fig.9-). In images, if any of the peaks coincided with the
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red vertical lines (1-5), who read part of the slot is damaged, (read from right image)
Fig.2. xms software used in FENI Industry - Kavadarci If the vibrations are caused by damage to the bearings, then take
a further reading of the frequency analysis. When you determine what caused the vibrations, we look in the documentation that the manufacturer of that machine in which boundaries are allowed to run. According to the number of revolutions we see what the allowable vibrations are.
The bearing frequencies can easily be calculated from the bearing geometry using the formulae given in Fig. 3[1].
Fig.3. Formulas for calculating bearing frequencies
The most widely used standard as an indicator of vibration
severity is ISO 2372 (BS 4675)[1]. The standard can be used to determine acceptable vibration levels for various classes of machinery. Thus, to use this ISO standard, it is necessary to first classify the machine of interest. Reading across the chart we can correlate the severity of the machine condition with vibration. The standard uses the parameter of velocity-rms to indicate severity.
Fig.3. ISO 2372 standard for evaluate vibrations impact
The letters A, B, C and D as seen in Figure 2.13, classify the severity. Class I Individual parts of engines and machines integrally connected with a complete machine in its normal operating condition (production electrical motors of up to 15 Kw are typical examples of machines in this category).
Class II Medium-sized machines (typically electrical motors with 15–75 kW output) without special foundations, rigidly mounted engines or machines (up to 300 kW) on special foundations.
Class III Large prime movers and other large machines with rotating masses mounted on rigid and heavy foundations, which are relatively stiff in the direction of vibration.
Class IV Large prime movers and other large machines with rotating masses mounted on foundations, which are relatively soft in the direction of vibration measurement (for example – turbogenerator sets, especially those with lightweight substructures). Motor-mixer aggregates 1,2 in this paper are in class III, according the parameters they possess. 3. RESULTS AND DISCUSSION 3.1. Results of the measuring vibrations of the motor mixer No1 before the critical moment of failure One of the larger aggregates to production nickel in Feni-INDUSTRIES, are mixer 1 and mixer 2... Its proper functioning depends on the prevention and early detection of damaged parts. Therefore regularly perform frequency analysis of engine bearings and mixer bearings. Each of the aggregates is composed of: electric, hydro coupling, gearbox, mechanics coupling and mixer (Fig.4).
Fig.4. Motor-mixer aggregate No1 – measurement point’s
Frequency of the bearings elements on points 1.2 on motor, for the type SKF 6228 are given in Fig 5.
Fig.5. Frequency of the bearings on points 1.2 types SKF 6228 The aggregate working conditions are very difficult. The air
contents of a high concentration of dust pollution. Its function is mixing ground ore in micron dust and water. The generator runs continuously twenty four hours every day. His problem produced a slowdown in manufacturing with the big negatively consequences on efficiency the whole factory. Because of that, to perform the daily visual, and measurement controls and regular frequency analysis is necessary.
Measuring the frequency analysis is performed on: - Bearing number -1, 2 of the motor with n=1450r/min, -Bearing number 9,10 of the mixer n=86.5r/min (i=16.76)
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The measurement is done horizontally, vertically and axially. Fig.4, 5 shows the measurements performed on bearing type 6228 of motor mixer 1, point 1 and point 2 (see Fig, 6). This measurement is done before the bearings failure. The critical FFT diagram is on fig.6
Fig.6. Bearing SKF 6228 –FFT on motor: a) Measuring on 1
vertically 3.4mm/s max peak a) on 1 horizontally 4.95mm/s max peak
The diagrams present that the point number - 1 (horizontal vibrations on motor) show high amplitude in line 5 and the line 3. It assumed the red line 5 approved bearing damage from the cage, while the line 3 present damage to the bearing balls. This early detection allows us timely preparation and change the bearing. The same can be proved from the vertical vibration - frequency analysis point -1 vertically. And this diagram reflected the damage of bearing balls (fig.7). There are pitting on the balls as results of a high concentration of dust and dirty with the problems in lubrications and high contact pressure between balls and the inner ring... Overlapping line - 3 with the largest amplitude was shown on the diagram on fig.6
Fig.7. Damaged rolling elements of the SKF 6228 on motor
The same situation exists on another main point’s where vibrations are measured in both directions on motor point 2. FFT diagrams shows on fig.8 measuring in time before failure of the bearings.
Fig.8. Bearing SKF 6228 –FFT on point 2-motor before failure
a) Vertical measuring max peak 3,8mm/s b) horizontal measuring 3.6mm/s max peak
Permanent monitoring and measured results of the vibrations (Fig.9,10) at the characteristic points in three directions showed that the rolling bearings SKF 6228 defined with the point 1 and 2 in Fig.3 are most sensitive of the electric motor.
Two types of bearing defects, namely, rolling elements and cage defects were studied. Measurements were carried out on two sets of bearings. The defective bearing was replaced by good bearing after predicting the failure with vibration signal analysis.
After dismantling the bearing, the photo showed the place where it caused the failure of the bearing cage (Fig.9).
Fig.9. Damaged cage of the SKF 6228 rolling bearing
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Fig.10 Damaged outer race SKF 6228 rolling bearing
Defects on the rolling elements (Fig.7, 10) can generate a frequency at twice ball spin frequency and harmonics and the fundamental train frequency. Twice the rolling element spin frequency can be generated when the defect strikes both raceways, but sometimes the frequency may not be this high because the ball is not always in the load zone when the defect strikes and energy is lost as the signal passes through other structural interfaces as it strikes the inner raceway. Also, when a defect on a ball is orientated in the axial direction it will not always contact the inner and outer raceway and therefore may be difficult to detect.
The bearing cage tends to rotate at, typically, 0.4 times inner ring speed, has a low mass and, therefore, unless there is a defect from the manufacturing process, is generally not visible. Unlike raceway defects, cage failures do not usually excite specific ringing frequencies and this limits the effectiveness of the envelope spectrum. In the case of cage failure, the signature is likely to have random bursts of vibration as the balls slide and the cage starts to wear or deform and a wide band of frequencies is likely to occur. 2.2. Results of the measuring vibrations before the critical moment of failure the motor mixer No2 Motor – mixer aggregate No2 is similar the same with No1. Each of the aggregates is composed of: electric, hydro coupling, gearbox, mechanics coupling and mixer (Fig.11).
Fig.11. Motor-mixer aggregate No1 – measurement point’s The frequencies of the elements of bearings 9, 10 Type SKF
22240 (spherical) given on Fig.12
Fig.12. Frequency of the bearings on points 9.10 type SKF 22240
Measuring the frequency analysis is performed on bearings: - number 9 and - 10 of the mixer, spherical bearings with the power to adapting the shaft deformations without any problems of cinematic and dynamics influence.
The measurement is done horizontally and vertically.
Fig.13. Bearing SKF 22240 CC/W33 –FFT on point 9-mixer
a)vertical 10.9 mm/s max peak b)horizontal measuring 29.5mm/s Same can check the diagram in the frequency measurement
point number -10 V. Line Number - 1 coincide with the maximum amplitude of diagram. So it is confirmed that there is damage to the outer ring of the bearing 22240 CC/W33
Fig.14. Bearing SKF 22240 CC/W33 –FFT on mixer
a) measuring on 1vertically 4mm/s max peak a) on 1 horizontally 30mm/s max peak
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Damaged outer ring of bearing 22240 CC/W33 is show on next picture.
Fig.15 Damaged outer ring of bearing 22240 CC/W33
4. CONCLUSION Continuous monitoring of the mechanical assemblies condition
is very important and vital for technological process in FENI Industry. Monitoring was done by periodically measured and analyzed vibration detecting by vibration signature.
In the case of two assemblies of motor- mixers in this paper, there are given vibrations signature only measured at critical points of the motor and the mixer in period before the bearings failure. The analysis was done by FFT diagram, permanent change the bearings parts frequency and the amplitude of vibration which through comparison with ISO 2372 standard definition of impact.
In the case of SKF 6228 bearing in point 1 of mixer-motor 1 that belongs to class III according to ISO 2372 in connection with the driving characteristics and fundaments the maximum amplitude of vibration of 3.6 and 3.8 mm / s are within the eligibility. Changing the frequency of the balls and the cage is a result of the occurrence of misalignment (increased amplitude of low frequency) and large dust pollutants in the atmosphere that violate minimum lubrication.
Amplitudes of vibration measured at a point 9.10 of bearings mixer 2 show another picture. Horizontal vibration of 29.5 mm / s and 30mm / s of SKF 22240 CC/W33 entered the engine-mixer 2 in the area of irregular vibration according to ISO 2372. These results indicate axial looseness of the external to the internal ring and damage rolling elements in the bearings.
The bearing cage tends to rotate at typically 0.4 times inner ring speed, has a low mass and therefore, unless there is a defect from the manufacturing process, is generally not visible.
Unlike raceway defects, cage failures do not usually excite specific ringing frequencies and this limits the effectiveness of the envelope spectrum. In the case of cage failure, the signature is likely to have random bursts of vibration as the balls slide and the cage starts to wear or deform and a wide band of frequencies is likely to occur.
Following are some example of problem that can cause the generation of the fundamental train frequency. These are in addition to other conditions already discussed.
1. In rare cases when one or more rollers are missing from a bearing, the FTF can be generated. The problem occurs as a pulse at the FTF. The frequency spectra contain a series of harmonics of the FTF. The amplitude of the first harmonic is quite low, the second, third, and fourth harmonics are higher in amplitude as determined by the pulse.
2. Sometimes, attempts to lubricate sealed or shielded bearings can cause the seal or shield to deflect inward. If the cage touches the
seal or shield, the FTF and/or two times FTF plus harmonics can be generated.
3. Excessive clearance in an antifriction bearing can cause the generation of a discrete frequency at the FTF and/or modulations of the FTF at rotating speed and harmonics.
Except for defects that occur in bearing components during manufacturing, the cage is usually the last component to fail. The typical failure sequence is as follows: defects form on the races, the balls, and then finally the cage. A severely damaged cage can cause constant frequency shifts that are observable with the use of a real-time analyzer.
When the cage is broken in enough places to allow the balls or rollers to bunch up, wide shifts in frequencies accompanied by loud noises can occur. When these signs are present, bearing seizure is imminent, Trend of overall frequencies and vibration spectrum provide useful information to analyse defects in roller bearings. Trend indicates severity of vibration in defective bearings. Vibration domain spectrum identifies amplitudes corresponding to defect frequencies and enables to predict presence of defects on inner race and outer race of roller bearings. The distinct and different behaviour of vibration signals from bearings with inner race defect and outer race defect helps in identifying the defects in roller bearings.
REFERENCES
[1] Wowk,V., 2006. Machinery Vibration –Measurement and Analysis, McGraw-Hill Inc.
[2] Lindh, T., 2003. On predictive bearing condition monitoring of induction motors, Ph.D. dissertation, Lappeenranta University of Technology, Isbn 951764-3, Isssn 1456-4491,2003.
[3] Henderson, D.S., K. Lothian and J. Priest, 1998. Pc based monitoring IEE/IMechE International Conference on Power Station Maintenance Profitability through Reliability, no. 452, March/ April 1998, pp: 28-31.
[4] Li, Y. and C. Zhang, 2004, Dynamic Prognostic Prediction of Defect Propagation on Rolling Element Bearing. Journal of Vibration and Acoustics, Trans of ASME, vol 85, no. 1, pp: 214-220. July 2004.
[5] Igarishi, T. and Hiroyoshi., 1980. Studies on Vibration and Sound of Defective Rolling Bearing. Bulletin JSME, vol 25, no. 204, pp: 994-1001.
[6] Chaudhary, A. and N. Tandon, 1998. A Theoretical Model to Predict Vibration Response of Rolling Bearings to Distributed Defects under Radial Load. Journal of Vibration and Acoustics, Transactions of ASME, vil 120, no. 1, pp: 214-220.
[7] Taylor, I.J., 1980. Identification of Bearing Defects by Spectral Analysis. Journal of Mechanical Design, Transaction of ASME, Vol. 120: 199-204
[8] T.Geramitchioski, Lj.Trajcevski, 2014, Case Study: Vibration Analysis of a Vertical Pump of Cooling System in Ferro-nickel Industry , 8th International Symposium "KOD 2014", on 12th till 15th June 2014 in Hotel Marina in Balatonfüred, Hungary
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COMPUTER AND PHYSICAL SIMULATION OF ANGULAR PRESSING Sosenushkin E.H., Yanovskaya E.A., Sosenushkin A.E.
Abstract: The results of computer simulation and physical experiment on angular pressing AD1 alloy billets are presented. There were microstructure and dyurametrix researches to confirm the changes in the structure of the structure and its mechanical properties. Keywords: angular pressing, power parameters, simulation, structure, hardness.
1. Introduction. Unfortunately, traditional methods of stamping: cold [1]semi hot [2, 3], the hot volume [4, 5] and hydromechanical [6], can not bring structural changes to the ultrafine grain size, despite significant accumulated strain received by metal. Fragments with low-angle misorientation are obtained mainly these kinds of plastic processing [7]. Equal channel angular pressing is one of popular in the industry and one of perspective ways of severe plastic deformation. This method can generate a deformation of ultrafine-grained structure and improve the mechanical properties of bulk structural metals. Equal channel angular pressing (ECAP) [8-12] occurs with a predominance of mechanical deformation scheme, this corresponds to a simple shift.
Dislocation slip is the main mechanism of new grain boundaries and dominant at the initial stage of restructuring. However, larger values of accumulated deformation lead to some saturation grain size as well as on the hardening of the treated metal. It leads to the predominance of non-crystallographic grain boundary shifts. Shifts cause angular misorientation boundaries increase. The more shear strain more accumulated is and the less structural fragments are, the more intense characteristics of subjected to angular pressing metal change [13].
2. Preconditions and means to solve the
problem. The research is aimed to confirm these theoretical
propositions about the relationship of accumulated deformations and basic geometric characteristics of the channels structure of metallic materials and their properties [14]. For this purpose we use our models [15-17] and need to study the influence of process parameters on the kinematics of the metal flow and energy-power conditions angular pressing [18-20] and to conduct physical simulation [21] to obtain the blanks with shredded structure models.
3. Results of computer simulation. Software QFORM 3D was adopted as a simulation tool. As
a tool for simulation of dependence of influence of conjugation radius at the intersection of channels on angular pressing force parameters was obtained (Fig. 1). Analysis of the results showed a plastic deformation forces decreased with increasing of radius of conjugation channel. Angle of conjugation of the channels is the second process parameter influencing magnitude of the forces pressing. The graph in Fig. 2 illustrates the decrease forces of deformation with increasing angle of conjugation channels.
Fig.1. Dependence of pressing force on the stroke of the punch
when combined radiuses conjugation channels; D - characteristic dimension of channel cross section.
Fig.2. The pressing force dependence on the angle of crossing channels The work deformation increases in the course punch and it also affects the value of the radius of the channel conjugation (Fig. 3).
Fig.3. Dependence of the plastic deformation of the punch stroke at different combinations and not equal to each conjugation radius channels r, R
Analysis of simulation results allowed to design stamping tooling [22, 23] with rational radius conjugation channels and angles of intersection of the channels.
4. Physical simulation. Fig. 4 shows a universal stamp for angular pressing with the
possibility of crossing the channel changeover angles in the range 90 ° ≤ θ ≤ 135 ° c implementations pressing schemes with one and two foci of deformation [24]. First we pressed components samples of lead with the reference grid with scheme of a traditional ECAP with foci of deformation, angle crossing the channels 90 º and the conjugation radius: external - 5 mm; internal - 2 mm. After we had verified the stamping tooling operability, we moved to research pressing AD1 alloy workpieces. All results relate to the angular pressed workpieces with square cross section of 16 × 16 mm and a length of 100.
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Fig. 4. Stamping snap for angular pressing Changing the grid and Lagrangian lines in computer simulations are the same (Fig. 5).
Fig.5. Experimental and theoretical distribution of the grid lines in the workpieces. a) - an experiment; b) - computational simulation.
Comparison of angular pressing forces of in the simulation
based on the known dependence and the results of the experiment is shown in Figure 6. Experimental curve corresponds to a smooth increase pressing force and a slightly larger punch stroke.
Fig. 6. Comparison forces of angular pressing Results of microstructural analysis after one and two passes through the workpieces the deformation foci are shown in (Fig. 7) to confirm the changes of the alloy AD1 structure Microhardness distribution over the cross section after pressing the workpiece shown in Fig. 8 The hardness increases with the increasing number of the workpiece passes through the channels. It indicates that the workpiece material is hardening.
a) b)
c) d)
e) f)
Fig. 7. Dynamics of changes in the microstructure during ECAP: a) - longitudinal ground joint initial billet; b) - transverse section of the initial billet; c) - longitudinal ground joint, 1 cycle ECAP; d) - the cross-sections ground joint, 1 cycle ECAP; e) - longitudinal ground joint, 2 cycle ECAP; f) - the cross-sections ground joint, 2 cycles of ECAP.
а)
b) Fig. 8. Microhardness distribution over the cross section microsections at different number of cycles of ECAP: a) - longitudinal microsections; b) - the cross-sections.
5. Summary / Conclusions. 1. The identity of the experimental results distribution grid
lines in the composite workpiece with the results of computer simulation is installed. This suggests that the data on the flow kinematics and deformed state workpieces are valid.
2. When analyzing the hardening curves revealed that the implementation of two loops ECAP flow stress level values are increased by 60% compared with the initial workpiece and by 50% compared with the workpiece, after one cycle of the ECAP. This confirms the increase in mechanical properties as a result of hardening.
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3. After one cycle ECAP microhardness increased by 30-50%, especially in the longitudinal microsections, and after two cycles ECAP by 40-60% compared to the original workpiece
6. Literature. 1. Сосенушкин Е.Н. Прогрессивные процессы
объемной штамповки. – М.: Машиностроение, 2011. – 480 с. 2. Сосенушкин Е.Н. Развитие систем пластического
деформирования.// Вестник МГТУ «Станкин». – 2010. - №2. – С.12-20.
3. Артес А.Э., Сосенушкин Е.Н. Проблемы производства крупных поковок в отечественном машиностроении.// Справочник. Инженерный журнал с приложением. – 2012. - №9. – С.45-50.
4. Артес А.Э., Сосенушкин Е.Н., Третьюхин В.В. Технологические возможности горячей объемной штамповки деталей арматуры из центробежнолитых чугунных труб.// Кузнечно-штамповочное производство. Обработка металлов давлением. – 2008. - № 10. – С.30-32.
5. Пономарев А.С., Сосенушкин Е.Н., Климов В.Н. Влияние технологических особенностей обработки давлением на микроструктуру и качество деталей трубопроводной арматуры из высокопрочного чугуна.// Металловедениеитермическаяобработкаметаллов. – 2012. - №1. – С.23-27. [Ponomarev A.S., Sosenushkin E.N., Klimov V.N. Effect of process features of pressure treatment on the microstructure and quality of parts of pipeline fittings from higt-strength cast iron.// Metal Science and Heat Treatment. –2012. – T.54. - №1-2. P. 22-27.]
6. Артес А.Э., Сосенушкин Е.Н., Третьюхин В.В., Окунькова А.А., Гуреева Т.В. Новые ресурсо- и энергосберегающие технологии изготовления деталей обработкой давлением.// Вестникмашиностроения. – 2013. - №5. – С.72-74. [Artes A.E., Sosenushkin E.N., Tret’yukhin V.V., Okun’kova A.A., Gureeva T.V. Resorse- and energy-saving manufacturing technologies based on pressure treatment.// Russian Engineering Research. – 2013. T.33. №8. P. 460-462.]
7. Утяшев Ф.З. Современные методы интенсивной пластической деформации. – Уфа: УГАТУ, 2008. – 313с.
8. Сегал В.М., Резников В.И., Копылов В.И. и др. Процессы пластического структурообразования металлов. - Минск: Наука и техника, 1994. – 232с.
9. Боткин А.В., Рааб Г.И., Валиев Р.З. Деформационные и силовые параметры процесса равноканального углового прессования в параллельных каналах // Кузнечно-штамповочное производство. Обработка металлов давлением. -2009. - №6. –С. 3-7.
10. Патент №2509621. Штамп для углового прессования/ Сосенушкин Е.Н., Цфас Г.М., Яновская Е.А., Белокопытов В.В., Сосенушкин А.Е.
11. Сосенушкин Е.Н., Яновская Е.А., Сосенушкин А.Е. Верхняя оценка силовых и деформационных параметров равноканального углового прессования в параллельных каналах// Известия Самарского научного центра РАН, 2012. Том 14.
12. Sosenushkin E., Sosenushkin A. Simulation of the equal channel angular extrusion technology// IX International congress machines, technologies, materials 2012.September 19-21 2012, Varna, Bulgaria. – P. 110-112.
13. Сосенушкин Е.Н., Овечкин Л.М., Климов В.Н., Сосенушкин А.Е., Сапронов И.Ю. Влияние кинематики течения металла на эволюцию микроструктуры и свойства заготовок при равноканальном угловом прессовании. // Кузнечно-штамповочное производство. Обработка металлов давлением. №11. 2012. С. 19-22.
14. Сосенушкин Е.Н., Яновская Е.А., Сосенушкин А.Е. Формирование мелкозернистой структуры металлов комбинированным методом интенсивной пластической деформации. Труды ХХ Международной конференции «Математика, компьютер, образование». М.:- Ижевск, 2013. С.193.
15. Сосенушкин А.Е., Артес А.Э., Сосенушкин Е.Н. Математическое моделирование равноканального углового прессования.// Технология машиностроения. - №12. – 2011. – С.53-56.
16. Сосенушкин А.Е, Сосенушкин Е.Н., Яновская Е.А. Моделирование кинематически возможных полей скоростей процесса углового прессования в пересекающихся каналах для расчета энерго-силовых параметров./ Фундаментальные физико-математические проблемы и моделирование технико-технологических систем. Вып. 15. Материалы II международной научной конференции «Моделирование нелинейных процессов и систем». Том 2. – М.: ФГБОУ ВПО МГТУ «СТАНКИН», 2013 – С.185-193.
17. Сосенушкин Е.Н., Белокопытов В.В., Сосенушкин А.Е. Температурная интенсификация процесса равноканального углового прессования в параллельных каналах. / В сб. докладов и научных статей «Перспективы инновационного и конкурентоспособного развития кузнечно-прессового машиностроения и кузнечно-штамповочных производств». – Рязань: ОАО «Тяжпрессмаш», 2012. – С.271-279.
18. Сосенушкин Е.Н., Овечкин Л.М., Сосенушкин А.Е. Совершенствование процессов интенсивной пластической деформации. // Вестник МГТУ «СТАНКИН» - 2012. – №1 (18). – С.22-25.
19. Сосенушкин Е.Н., Сосенушкин А.Е. Оценка силовых параметров и деформированного состояния заготовки при равноканальном угловом прессовании. / Труды международной научно-технической конференции «Современные металлические материалы и технологии». – СПб: Санкт-Петербургский ГТУ, 2011. – С.233-235.
20. Сосенушкин А.Е. Обобщенная расчетная схема процесса углового прессования и автоматизация построения годографов скоростей перемещений./ Труды XV научной конференции «Математическое моделирование и информатика». – М.: ФГБОУ ВПО МГТУ «СТАНКИН», 2013 – С.188-190.
21. Сосенушкин Е.Н., Овечкин Л.М., Сосенушкин А.Е. Экспериментальная проверка адекватности компьютерного моделирования процесса равноканального углового прессования./ Состояние, проблемы и перспективы развития кузнечно-прессового машиностроения и кузнечно-штамповочных производств. – Рязань: ОАО «Тяжпрессмаш», 2009. – С.169-174.
22. Патент № 133440 на полезную модель. Штамп для углового прессования. Сосенушкин Е.Н., Сосенушкин А.Е., Яновская Е.А. 20.10.2013. – Бюл.№29.
23. Патент №2440210 на изобретение. Штамп для равноканального углового прессования. Сосенушкин Е.Н., Овечкин Л.М., Сосенушкин А.Е. 20.01.2012. – Бюл.№2.
24. Патент №86507 на полезную модель. Устройство для равноканального углового прессования. Сосенушкин Е.Н., Овечкин Л.М., Артес А.Э., Смирнов А.М., Сосенушкин А.Е. 10.09.2009. - Бюл. №25.
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