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Ahmed Hakem, Youcef Bouafia / International Journal of Engineering Research and

Applications (IJERA) ISSN: 2248-9622 www.ijera.com

Vol. 3, Issue 1, January -February 2013, pp.2077-2081

2077 | P a g e

Elasticity of the 42 000 hypoeutectic alloy in longitudinal

vibration mode

Ahmed Hakem*, Youcef Bouafia*

*Laboratory LaMoMS, Mouloud MAMMERI university of Tizi-Ouzou, 15000 Algeria.

ABSTRACTThe Technical Impulse Excitation (IET)

is one of the recent nondestructive techniques

which makes it possible to identify the frequencies

of resonance principal or fundamental on the one

hand and the frequencies of damping or internalfriction on the other hand of a specimen of

standardized and well defined form. These

frequencies of resonance or damping are closely

related to the chemical composition, the form,

dimensions and the density of the test specimenmachined from one of metals selected and which

governs our study. The fundamental

characteristics of the test specimen for this

purpose are the uniformity of their form and

their dimensions, the precision of their

measurements thus of that of their density andmainly metal studied must be isotropic. Once the

principal frequencies are determined, the

software Resonency Frequency Dumping Analys

(RFDA: Resonance Frequency Damping

Analyzes) calculates the Youngs Modulus, the

shear Modulus and the Poisson's ratio

The Technical Impulse Excitation allowsmeasurements which can be taken with the

ambient temperature or high temperature. The

standardized test piece can be of form

rectangular, cylindrical full or hollow and of a

disc full or pierced with a hole in the center. Liketechnique IET has a great advantage of being

nondestructive, the test piece can be thus used in

several experiments and on real parts

with ambient temperature or low or high

temperature (cryogenic temperature). [3, 4, 5]

Keywords - IET, elastic characteristics,

principal frequencies, vibration, longitudinal.

I. INTRODUCTIONThe study of the elastic properties of solid

materials is of a great importance from the scientificpoint of view as well as industrial and practical. .

Indeed, in industrial applications, it is required ofthe builder and the engineer to know in advance andwith precision, the elastic characteristics ofmaterials used to ensure proper operation of their

realizations. This importance is not one of less fromthe scientific point of view, since these properties

also inform us about the nature of the the atomic

bonding, i.e. of the atomic bonding strengths. Thus,we can estimate the energies of atomic interactions.

In order to answer this requirement so much desirednot only by the scientists but also by the

manufacturers, the method of investigationTechnical Excitation, who belongs to the besttechniques used until now, allows to determine in a

simple way and specifies the elastic characteristicsof various solid materials. Moreover, knowing thatthis method is nondestructive, it is very interesting

to follow the evolution of these characteristics

during different heat treatments as well asmechanical operations on the same test piece. [1,

14]

II. PRINCIPE OF THE METHODThe Technical Impulse Excitation (IET), is

one of the recent nondestructive dynamictechniques, which makes it possible to determine theelastic characteristics of various solid materials

to room temperature.The elastic properties are intimately linked

to particular frequencies of resonance, called

primary or fundamental frequency, mechanical

vibration of a specimen. They depend greatly on thechemical composition (intrinsic elastic properties),the mass and geometry of the test specimen. Thus,

the elastic properties of a material can be calculatedif and only if the geometric shape (rectangular,cylindrical ... etc..), The mass and the resonantfrequencies of vibration of a given sample areknown. Using this technique, one can determine thedynamic Young's modulus E and the dynamic shear

modulus G (stiffness modulus) respectively bymeasuring the resonant frequency of vibration in thelongitudinal mode. Then the formula connecting E

and G is used to evaluate the Poisson's ratio.

The Technical Pulse Excitation is of greatimportance because it can also follow the evolution

of the elastic properties of solid materials during thetemperature variation: cryogenic and raisedtemperatures, on condition that making

modifications appropriate to the equipment ofmeasuring equipment in order to compensate for theheating effect. Using this method, to calculate thevalues of the elastic characteristics, one determines

initially the principal frequencies of resonance of thetest piece of a given geometry.

The IET is particularly suitable to

determine the elastic modules of the homogeneous,

isotropic materials and which do not presentexternal defects the such surface cracks, shrinkage

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Ahmed Hakem, Youcef Bouafia / International Journal of Engineering Research and

Applications (IJERA) ISSN: 2248-9622 www.ijera.com

Vol. 3, Issue 1, January -February 2013, pp.2077-2081

2078 | P a g e

pipes and other deformations. Simple method, it hasmany advantages: This dynamic method as well hasseveral advantages by report with the static

techniques of loading as to those of resonance whichrequire a continuous excitation.a- It is nondestructive and can be used for test piece

intended for other tests.b- Unlike other techniques, one uses a tool of impactand very simple supports to excite by impulse thetest piece.

c- This technique is very useful in quality control ofthe various parts. [3, 4, 5, 6, 12, 13]

III. EQUIPMENT - RFDA - RESONANTFREQUENCY AND DAMPENING ANALYZER.

[3,4]

RFDA SYSTEM 21

RFDA system 21 is used for measurement

of pulse excitation at room temperature. Thesamples are mechanically struck by hand with ahammer small flexible screen. The system RFDA 21is used to measure the resonant frequency and theinternal friction or damping samples al shapes anddetermine the Young's modulus, shear modulus,

Poisson's ratio of rectangular bars, discs, bars ,hollow tubes and disks with a hole in the center.

MOUNTING THE TEST SPECIMEN ON THE

SUPPORT PARTThe test piece is fixed on the support part by means

of special springs.

Window showing the waveform of the longitudinal

vibration (a), the peak of the main frequency (b), the

values of the principal resonance frequency and theattenuation capacity (c), the values of E and E( d).

IV. EXPERIMENTAL PROCEDURE4.1 Investigated material

The material used is donated by SNVI .This is the aluminum-based alloy containing 7%silicon in weight percent, an amount of less than 1%magnesium, and some trace impurities. Afteranalysis, the samples sand cast metal shell and

gravitation have the following chemicalcomposition:

Chemical elements Si Mg Fe

% Depending analysis 6,85 0,35 0,15

Results of chemical analysis of controlsamples after casting sand and shell

4.2 Development of the alloy studied

4.2.1. CastingThe melting of the metal takes place in a

gas oven production is tiltable front to rear,

comprising a graphite crucible capacity 350Kg

whose load is made approximately 40% of ingotsin new AlSi7Mg standard dimensions, compositionand specified characteristics., supplied by theFrench company Pechiney and a mixture of casting

jets 60% return (appendices supply, evacuation,regulation, defective parts and scrap ).

4.2.2 MoldingThis alloy is prepared by two different

methods: sand casting and die casting considering

for three states; crude of casting noted: F,soaked designated: T, aging noted: T46

4.3 Form of the test specimenTo determine the Young's modulus, weused the longitudinal vibration mode.

a b

c

d

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Ahmed Hakem, Youcef Bouafia / International Journal of Engineering Research and

Applications (IJERA) ISSN: 2248-9622 www.ijera.com

Vol. 3, Issue 1, January -February 2013, pp.2077-2081

2079 | P a g e

The measurements were performed on rectangularspecimens (Fig. 1) for the previous mode at roomtemperature. For obtaining reliable and accurate

results and to carry out our measurements, virtuallyall precautions have been taken into account.Among them we can mention the most important

- The measuring accuracy of the coasts of the testpiece is largely higher than 0.1 mm.- The value of the dimension thickness must beuniform along the length and of the width of the test

piece.Before placing the test piece on the door

sample, we carried out the following operations:

- Calculation of the median values of its dimensionsby taking a certain number of measurements (inpreference to less 05) in various places of thesample (it is recommended that the step of

measurement either identical and the taking away orcarried out along dimension considered).

- To carry out the weighing of the sample (at least03 measurements) to determine its average mass. [3,4]

4.4 Measurements in longitudinal mode

Fig. 1 - Form of the specimen for testing Impulse

Excitation Technique dynamic

Fig. 2 -Installation diagram of the fastening deviceof the test piece (1) and excitation of a mechanicalor acoustic vibration mode longitudinal.1 - sample,

2 - Drive, 3 - sensor signal, 4 - system son andspecial springs for fixing the specimen (samplehol