Cold Rotary Forming of Thin-wall Component From Flat-disc Blank_E Kayali

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j o u r n a l h o m e p a g e : w w w . e l s e v i e r . c o m / l o c a t e / j m a t p r o t e c

Cold rotary forming of thin-wall component

from flat-disc blank

C.C. Wong, A. Danno, K.K. Tong, M.S. Yong

Singapore Institute of Manufacturing Technology, Forming Technology Group,

71 Nanyang Drive, Singapore 638071, Singapore

a r t i c l e i n f o

Article history:

Received 18 October 2006

Received in revised form

22 October 2007

Accepted 23 December 2007

Keywords:

Rotary forming

Flow forming

Incremental forming

Finite Element simulation

a b s t r a c t

Flow forming, one of the rotary-forming processes, is used mainly to produce thin-walled

high-precision tubular components. Due to its flexibility and low tool load requirement,

the process has great potential to be extended to the forming of net-shape components for

thin and intricate features from bulk raw materials, such as solid bar ingot, cast and forged

performs. In the work reported in this paper, a flow-forming facility was established to

investigate the feasibility of forming thin-walled cups from flat-disc blanks by investigating

the effects of roller geometry, degree of material reduction and roller geometry on material

flow. In addition, a 3D Finite Element (FE) model was developed to simulate the bending

process, based on the experimental conditions.

The results showed that it is possible to adopt a two-step forming process, bending and

flow forming to enable material flow along the mandrel in order to form a thin-wall cup

component using two different profiles and adopting an axial roller movement. Quality of

thecups formeddependson thediameterreduction, starting disc thicknessof theblank and

thenumber of pass in theflow-formingstage. Theresults predictedby theFE simulation was

compared with the experimental results and showed close agreement. This work illustrates

the possibility of adopting flow-forming processes for the production of thin section, which

would be difficult and expensive to produce by press forming. In addition, it also showed

that although FEM is an effective tool to optimize process parameters, computational time

remains as the main barrier for its prevalent usage especially for incremental processes

such as flow forming and spinning processes.

2008 Elsevier B.V. All rights reserved.

1. Introduction

In recent years, there is a growing demand for light-weight

and higher value-added components by the OEMs of trans-

portationindustries.These can be achieved withlower density

materials and new structural designs. As component shapes

are becoming more complicated, machining is not a cost-

effective process for producing these components and should

be minimized as a production operation. As a result, precision

Corresponding author. Tel.: +65 67938449; fax: +65 67925362.E-mail address:[email protected](C.C. Wong).

forging,or net-shape forging,has become increasinglypopular

due to savings in material, energy and finishing steps. How-ever, as manufacturers strive to reduce weight andcost, many

of the new components, because of their shape complexity

and complicated tool design and high load requirements, are

challenging the current precision forging technologies beyond

its current level of technology. In order to meet this require-

ment, there is a renewed interest in incremental forming,

especially rotary-type incremental forming processes, such

0924-0136/$ see front matter 2008 Elsevier B.V. All rights reserved.

doi:10.1016/j.jmatprotec.2007.12.123
mailto:[email protected]://localhost/var/www/apps/conversion/tmp/scratch_7/dx.doi.org/10.1016/j.jmatprotec.2007.12.123http://localhost/var/www/apps/conversion/tmp/scratch_7/dx.doi.org/10.1016/j.jmatprotec.2007.12.123mailto:[email protected]


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54 j o u r n a l o f m a t e r i a l s p r o c e s s i n g t e c h n o l o g y 2 0 8 ( 2 0 0 8 ) 5362

as swaging, cross-wedge rolling, ring rolling, rotary forging,

conventional spinning and flow forming. As these processes

involved plastic deformation of small volume of the work-

piece at a time, the power and working forces required are

reducedsignificantly, allowing more complicatedcomponents

to be produced on relatively small machines using simple tool

shapes. In addition, tool life is much improved as compared

with forging processes.In the last two decades or so, flow forming (including

shear-forming process) has gradually matured as a rotary

metal-forming process for the production of engineering com-

ponents in small to medium batch quantities. Due to its

inherent advantages such as flexibility, simple tooling, low

forming loads and consequently smaller equipments, flow

forming has enabled customers to optimize designs and

reduce weight and cost, all of which are vital, especially in

the automotive industries.

The flow-forming process, which grew out of spinning, is

a process during which the workpiece is rotated while the

tool, which rotates about its own axis, may also move axially

or radially to the axis of rotation of workpiece, manipulat-ing it to the final desired shape. It is most widely used to

produce thin-walled, high-precision tubular products where

tubular workpiece is held onto the mandrel and the material

is being displaced axially by one or more rollers moving axi-

ally along the mandrel. Several researchers have conducted

experimental and theoretical analysis in the flow forming of

tubes to evaluate the power and load requirements as well

as the effects of process variables such as feed rate, approach

angle andpercentage reduction on surface finish of the formed

workpiece andforming load (Yao andMakoto, 2002; Jahaziand

Ebrahimi, 1997; Park et al., 1997; Singhal et al., 1990; Hayama

and Kudo, 1979; Wang et al., 1989; Gur and Tirosh, 1982).The

analyses have been based mainly on energy method (Hayamaand Kudo, 1979), slip line fields (Wang et al., 1989), upper

bounds (Park et al., 1997)as well as experimental work was

conducted byGur and Tirosh (1982),Yao and Makoto (2002),

Jahazi and Ebrahimi (1997),as well asSinghal et al. (1990).

Several researchers have also attempted to use the Finite

Element method to analyse the flow-forming process.Li et al.

(1998)developed a 3D FE program, 3D spin, to simulate the

process of backward flow forming of tubes. In their model,

the internal surface nodal points of the tube contacting the

mandrel are restrained in the radial direction and the nodal

points at the end of the upspun tube are restrained in three

directions. Xu et al. (2001)built a 3D rigidplastic FE program,

which is suited to the nature of flow forming of tubes, to anal-yse thedistributionof stress andstrain rate of thedeformation

field. In their 3D model, in order to improve the calculating

efficiency and accuracy, only one-third of the tubular blank

was modelled.Xue et al. (2001)adopted the dynamic explicit

FE code, ADINA, to analyse the tube stagger spinning process,

where the rollers are offset or staggered at a particular dis-

tance in theaxial andradial directions. A one-third model was

adopted and the influence of inertial force in the calculation

was ignored. Hauk etal. (2000)adoptedboth2Dand3DFEanal-

ysis for the simulation of combined flow forming and splitting

of disk blanks. For the 2D model, an axisymmetrical approach

was adopted and a comparison between results obtained from

commercial FE code, DEFORM D and NARC/Autoforgewas con-

ducted. For their 3D model (Hauk et al., 2000),only a sector at

the outer disk blank and half thickness of the original blank

were modelled.

Recently,Hua et al. (2005)developed a 3D elastic plastic FE

model for the three-roller backward flow forming of cylindri-

cal tubes. The phenomenon such as bell mouthing, build-up,

bulging in front of and between rollers, diametral growth as

well as the axial forming load was simulated. Wong et al.(2004)have reported the use of explicit FE code to analyse the

flow forming of solid cylindrical shaft using commercial FE

software, ABAQUS Explicit. He reported that although compu-

tational time can be reduced using mass scaling, care has to

be taken as it canresult in considerable dynamic effects which

can result in unreliable simulation results.

Flow-forming technology is applicable to a wide range of

raw material types and a greater range of shapes than has so

far been attempted. For instance, there seems to be a useful

opportunity to flow form cast or forged shapes, to utilize the

best featuresof two different processes. Hence, the aim of this

work is to examine the aspect of expanding the capabilities of

flow-forming process, by undertaking experimental and mod-elling work, to form a thin-wall cup using a simple perform

shape (disc).

2. Experimentation

2.1. Flow-forming equipment

In this work, a Mazak NC lathe was utilized as a flow-forming

machine.Only oneroller wasusedin each experiment. A roller

tool was designed and built to accommodate the lathe tool

post. The mandrel was clamped using the lathes chuck and

the workpiece was fixed onto the mandrel and tightened bya bolt. In addition, in order to minimize radial deflection of

the mandrel during flow-forming operation, a mandrel holder

was designed, to fix onto the lathe bed. Fig. 1 shows the exper-

imental set-up.

Two different rollers were used, as shown inFig. 2.Roller A

(shown in Fig. 2a) has an approachangle of 60and the secondroller, roller B, has an approach angle of 20, shown inFig. 2b.

2.2. Workpiece

In order to reduce the loading on the machine and prevent

severe radial deflection of the roller tool, an annealed alu-

Fig. 1 Experimental set-up.


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Fig. 2 Roller geometry and workpiece.

minum alloy, A6061 was used as the workpiece and mounted

onto the mandrel. The hardness of the aluminum disc is

approximately 49 HV. A flat-disc blank of diameter 70 mm and

thickness of 5 mm and 10mm, as shown inFig. 2cwas used as

the starting workpiece.

2.3. Flow-forming sequence

Two flow-forming steps were proposed in this experimental

study to investigate the feasibility of forming thin-wall cups

from flat-disc blanks. In the first step, roller A ( Fig. 2a) wasproposed to bend the disc blank to the preset diameter into

a cup-shape product. In the second step, roller B (Fig. 2b) was

used to flow form the wall of the cup onto the mandrel to

obtain uniform wall thickness, desired internal diameter and

increase height of the cup.

For both forming sequences, the mandrel and the work-

piece were rotating andthe roller was fedalong theworkpiece

parallel to its axis at a preset interference (diameter reduction)

for a pre-defined length. The roller path for both sequence are

shown inFig. 3.

2.4. Flow-forming conditions

The rotation of the workpiece was fixed at 250 rpm and the

axial feed rate of the roller was set at 1 mm/s (0.24 mm/rev).

Cutting oil was used at the interface between the roller and

the workpiece as well as the interface between the workpiece

and mandrel. The initial thicknesses of the workpieces inves-tigated were 5 mm and 10 mm.

The diameter reduction, red (%) of the blank was defined

as

red (%)=

Diameter reduction

Initial diameter

100

Fig. 3 Flow-forming sequence.


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3. Finite Element modelling

3.1. Difficulties in modelling and simulating

flow-forming process

The flow-forming process by nature, like other incremental

forming processes, is very difficult to model due to the follow-ing factors:

(i) Asit involves only localizeddeformation,only a small por-

tion of the workpiece is in contact with the roller at any

given time and due to the cyclic character in the applica-

tion of forces, there is frequent and rapid change in the

contact condition.

(ii) As the workpiece rotates continuously and its transient

plastic deformation is very small, fine mesh discretisa-

tion is necessary in order to allow continuity of contact as

nodal forces transfer from one element to the next.

(iii) Large number of rotations of the workpiece may result in

volume change in FE analysis and also increases compu-

tational time.

(iv) For most incremental forming processes like rotary forg-

ing, cross wedge rolling, spinning and flow forming, good

representation of the actual process can be achieved only

by using 3D model.

As a result of the above factors, modelling of incremen-

tal forming processes is inherently very time consuming and

involves large computational resources. Thus, efficient Finite

Element software with robust and unique features to model

as well as simulate the flow-forming process is necessary.

Although, the author has proven in previous studies that theexplicit FE code is ideal to tackle some issues in simulating

flow-forming process, the main drawback has always been the

inherent existence of the dynamic effects which user has to

control if he/she were to increase the very small time step

required for explicit formulation.

3.2. Proposed FE model

In this study, Finite Element modelling and simulation using

the commercial FE implicit code, DEFORMTM 3D V6.0 was

attempted to model the first step of the cup-forming pro-

cess, i.e. the bending step. The initial meshes and model

set-up are shown in Fig. 4. The workpiece was considered as anelasticplastic model andthe roller andmandrelwas modelled

as a rigid surface. In order to overcomethe difficultiesin simu-

lation with regards to rotating the workpiece (as mentioned in

the previous section), the workpiece was fixed and the roller

was chosen to rotate around the axis of the workpiece at the

same rotational speed as that of the rotating workpiece in the

actual process. By adopting this method, not only can volume

be controlled, butalso a significant reductionin computational

time can be achieved. In addition, to model the free spinning

of the roller around its own axis, a negligible torque value was

prescribed around the rollers neutral axis.

Thefriction between the roller andthe workpiece interface

was expressed as a number known as the friction factor m,

Fig. 4 Proposed FE model.

defined as follows:

= mk=m 3

where is the shear stress, k is the shear strength and is

the flow stress of the workpiece material. The constant shear

friction factor was chosen for this study because flow form-

ing is a process which involves bulk material deformation.

Since constant lubricant was being fed between the interface

of theroller andworkpiece during theactual flow-forming pro-

cess, the friction is considered low and is assumed at a value

ofm = 0.1 between them. For the interface between the man-

drel and workpiece, a sticking friction was prescribed to best

simulate the experimental conditions as the workpiece is not

supposed to slide along the mandrel.The material properties were determined using the uniax-

ial compression test andexpressed in the form of a power law,

= Kn, wherekis the strength coefficient andnis the strain-hardening exponent. The workpiece was meshed using 3D

tetrahedralelementswhere theforming areahas a higher den-

sity than the rest of the workpiece, which resulted in 45,000

elements. In order to ensure continuity of contact as nodal

forces transfer from one element to the next and to reduce

severe mesh deformation, a very small and appropriate time

step of 0.0025 s/step was chosen after several trials. The gen-

eral conditions for the model are shown inTable 1,which are

similar to the experimental conditions.

Table 1 FE simulation parameters

Condition Description

Material A6061 aluminum (annealed condition)

Material properties = K n,K =220MPa,n =0.211Flat-disc diameter 70 mm

Flat-disc thickness 5 mm

Friction model Shear friction

Friction factor 0.1

No. of elements 45,000

Axial feed rate (mm/rev) 0.24

Time-step size 0.0025


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Fig. 5 Deformed shape with diameter reduction for starting thickness of 5mm and 10 mm.

4. Results and discussion

4.1. Step 1bending process

Fig. 5shows the final deformed shape of the disc blank after

the forming process for thicknesses of 5 mm and 10 mm at

different diameter reductions andFig. 6shows the metal flow

predicted by FE simulation as well as cross-section of a exper-

imental profile for a thickness of 5mm. For both starting

thickness of thedisc blanks, it canbe observed experimentally

that a cup-shaped component was produced by simply trans-

lating the roller in the axial direction after a certain diameter

reduction was set. However, on the other hand, too small a

reduction, e.g. 3%, will result in insignificant cup height and

wall thickness due to insufficient material being deformed.

At the outset of the roller deformation as shown inFig. 7,

the metal is mainly being deformed towards the mandrel in

a bending mode. As the roller traversed axially, the material

also flows predominantly in the axial direction, with a flange

Fig. 6 Deformed shape predicted by FE simulation.


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Fig. 7 Predicted metal flow at different roller strokes and comparison with experimental profile.

Fig. 8 Formation of step along the internal diameter of the cup.

occurringin frontof the roller. Theflange will gradually reduce

in height as the roller moved further axially and will deform

under the roller to produce a step (Fig. 8)along the internal

diameter. This is being confirmed by the experimental profile

shown inFig. 8where a step is visible for all reductions. The

formation of the step along the internal diameter is mainly

caused by the bending mode during the initial stage of form-ing that resulted in the exterior of the flange that is in direct

contact with the roller to flow faster than the interior sur-

face facing the mandrel. In general, the final profile predicted

by FE simulation is in close agreement with the experimenta

l profile.

Fig. 9 shows the variation of cup height and wall thick-

ness with diameter reduction. It can be seen from the figure

that for both starting disc thicknesses, cup height increased

linearly with increased in diameter reduction. However, for

diameter reduction above 19%, theheight of thecup increased

drastically. This is because for diameter reduction above 19%,

the material that was being deformed contacted the mandrel

at the beginning of roller axial translation, which forced the

Fig. 9 Variation of cup height and wall thickness with

diameter reduction.


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Fig. 10 Cracking due to large diameter reduction.

material to flow axially along the mandrel, thereby elongating

the formedcup. Onthe other hand, fordiameterreduction less

than 19%, the cup was practically formed in air, i.e. without

any support on the inner walls of the cup (see Fig. 3a), and

there is no contact between the inner wall (internal diame-

ter of the formed cup) and the mandrel, and the cup formed

was parallel to the horizontal axis of the mandrel. The rea-

son for this phenomenon is that the rigidity of the cup formed

by the roller is able to withstand the localized deformation

that is induced by the roller during the forming process. This

phenomenon is also confirmed by the final deformed profile

predicted by FE simulation for diameter reduction of 10 mm

(14%) and 12mm (17%), shown in Fig. 6.It can be seen from

the cross-section profile shown inFig. 6that the inner diam-

eter of the cups are smaller that the outer diameter of the

mandrel for both reduction of 14% and 17%.

It can also be seen from Fig. 9 that for various diameter

reduction, the variation in wall thickness for disc thickness

of 5 mm and 10 mm is not very significant. Moreover, taller

cups were produced for starting disc thickness of 10 mm. The

taller cups produced using larger starting disc thickness may

be explained by the fact that higher volume of material was

displaced axially compared to smaller disc thickness. In other

words, the heightof thecups is directly affected by the diame-

ter reduction. On the other hand, the diameter reduction does

not affect the wall thickness. Wall thickness is largely affected

by the nose radius (seeFig. 2)of the roller which determines

the amount of plastic deformation induced along the wall. As

a result, the variation in wall thickness for both starting disc

Fig. 11 Bulging phenomenon at bottom of the cup formed.

thickness of 5 mm and 10 mm is not significant as the same

roller nose radius was used.

A critical forming limit occurred at diameter reduction of

25%. For both starting disc thicknesses of 5 mm and 10 mm,

severe breakage occur during the initial forming stage for

diameter reduction above 25%, as shown inFig. 10.This may

be due to the heavy material accumulation in front of the

roller for high diameter reduction, resulting in material flow-

ing predominantly in the radial direction as the roller moved

axially. In addition, the heavy accumulation at the front of the

roller, from high diameter reduction, gave rise to very high

axial stress. This in turn causes severe bulging which leads to

instability and ultimately cracking of the flange in front of the

roller.

For blank disc thickness of 10mm, bulging of material

appeared at the bottom of the cup, i.e. at the beginning of

the roller axial path, as shown inFig. 11.This may be due to

the fact that for higher starting disc thickness, more mate-

rial was being deformed by the roller which led to some

material escaping underneath the roller, flowing in the oppo-

site direction of the roller axial translation. Another reason

for this phenomenon is the relative larger radial deflection

due to high diameter reduction, which encouraged mate-

rial to flow circumferentially. Moreover, this bulging effect

Fig. 12 Effective stress distribution on the outside of the cup.


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Fig. 13 Effective stress distribution along cup wall.

did not occur at all reductions for disc thickness of 5mm

as well as small diameter reduction at disc thickness of

10mm.

Fig. 12 shows the predicted effective stress distribution

between the workpiece and the roller contact. From the fig-

ure, it can be seen that only localized deformation occurred

between the workpiece and the roller during the forming pro-

cess which is typical of incremental rotary-forming processes.

The maximum effective stress value increased as the roller

stroke increased with maximum stress occurring towards the

end of the rollerstroke andhas a valueof about 450MPa. Fig. 13

shows the effective stress distribution alongthe cupwall. Max-

imum effective stress occurred along the region when theroller contacts the workpiece and decreases along the height

of the cup wall.

Fig. 14shows the axial stress distribution along the cup

wall. It can be seen from the figure that tensile stress mainly

occurred at the region where the roller contacted the work-

piece. This is due to the fact that as the roller moved

axially, material underneath the roller is mainly flowing in

the opposite direction to the roller. Axial compressive stress

Fig. 14 Axial stress distribution along cup wall.

Fig. 15 Effective plastic strain distribution.

mainly occurred along the approach angle of the roller as

the contact material along the approach angle of the roller

is mainly flowing in the same direction as the roller move-

ment.

Fig. 15shows the predicted plastic strain value along the

outer surface of the cup. Maximum plastic strain occurs along

the cup height as the roller stroke increased with a maximum

value of 0.8.

4.2. Step 2flow-forming process

In order to elongate the cup along the mandrel and to con-

trol the dimension of the formed cup in step 1, flow-forming

processwas proposedas a secondstepto obtainthe final prod-

uct. Attempts were made to conduct flow-forming operation

on cups with inner diameter larger than the mandrel diame-

ter. However, it required an addition of 25 steps just to obtain

the same inner diameter as the mandrel, which is deemed

ineffective. In addition, attempts were also made on cups pro-

duced from starting disc thickness of 10 mm. However, due to

thebulging effectas mentionedin theprevious section, whichresulted in uneven outer diameter, the excess material in the

bulging area flow over the material at the smaller diameter

which resulted in overlapping defects.

Figs. 16 and 17 show the percentage increase in internal

diameter with cup depth having 5-mm initial disc thickness

and diameter reduction of 20% and 22% during the first step.

As this step is similar to the flow forming of cylindrical tubes,

the thickness reduction for the flow-forming operation was

recommended to be controlled at 2030% (Xu et al., 2001)so

as to prevent circumferential flow due to too low a reduction

and bell mouthing defects due to too high a reduction. From

both figures, it canbe seen that after thefirst pass, theinternal

diameterof the cupwas uneven andincreases alongthe height


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Fig. 16 Percent increase in internal diameter for flow

forming of cups for initial starting disc thickness of 5 mm

and diameter reduction of 20%.

Fig. 17 Percent increase in internal diameter for flow

forming of cups for initial starting disc thickness of 5 mm

and diameter reduction of 22%.

of the cup. However,the accuracy of theinternal diameter was

improved witheach subsequent pass and the dimensionof the

internal diameter is tending towards uniformity along the cup

height at about 3rd or 4th pass. It is believed that the internal

diameterwillbeuniformifthematerialcanflowalongalonger

mandrel as compared to the one used in this study.

Moreover, it can be seen fromFig. 18that the wall thick-

ness along the cup height was uniform for both cases. This

shows that the variation of the internal and external diame-

Fig. 18 Thickness variation along cup height for cups after

20% and 22% diameter reduction in the first forming step.

Fig. 19 Hardness measurement position.

Fig. 20 Rotary forming of thin cup shape from flat-disc

blank.

ter of the cup was largely due to the elastic deflection of the

roller which was mainly caused by the increased hardness

along the wall thickness of the cup, as shown in Fig. 19due

to work hardening during the first forming step. The hardness

was measure at the cross-section of the cup in two areas, 1and 2. In each area, the hardness readings at the top, center

and bottom portion of the cup wall were measured. It can be

seen from the readings (Table 2)that the portion of the cup

wall nearer to the roller deformation, i.e. the top portion, has

thehighest hardness value due to thehigh deformation which

Table 2 Hardness values measured

Area 1 (HV) Area 2 (HV)

Top 69.4 81.6

Center 63.4 64.9

Bottom 54.7 57.5


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gave rise to larger work hardening. In addition, it can be seen

that in all portions, area 2 gives a higher hardness reading as

compared to area 1. This is because area 2 was formed as a

result of increasing roller axial translation which induced fur-

ther deformation on the material, leading to increased work

hardening.

The final wall thickness achieved for the tests shown in

Fig. 20 are 0.81 mm, respectively. Further reduction in wallthickness is possible but control in wall-thickness reduction

is critical to ensure stability in the forming mode and surface

finish of the cup.

5. Conclusions

In this work, the possibility of forming a thin-wall component

of 0.81mm (Fig. 14) by a two-step rotary-forming process,

using mutli-pass flow forming in the second step has been

demonstrated. Based on the outcomes, the following conclu-

sions may be drawn:

Arollerwithanapproachangleof60can be usedto producean initial cup shape from a flat-disc blank.

In the first forming step, reduction above 25% will result insevere cracking of the disc at roller contact area for starting

disc thickness of 5 mm and 10 mm.

In the first forming step, diameter reduction above 19% willallow the material to flowalong the mandrel therebyachiev-

ing greater height.

In the first forming step, forming of thick disc thickness,e.g. 10 mm, will require higher rigidity for both the mandrel

and machine in order to prevent the bulging phenomenon

which will lead to subsequent defects in step 2.

In the first forming step, wall thickness of the wall depends

on nose radius of the roller and cup height depends on the

initial diameter reduction.

The diameter of the mandrel has to be changed accordingto the required internal diameter for step 2 so as to prevent

unnecessary flow-forming passes, which will lead to galling

effects due to excessive work hardening.

Multi-pass flow forming in the second step can improve thedimensional accuracy and the uniformity of the internal

diameter.

Hardness increases along the cup height and along the wallthickness, with higher hardnessvalue on the exterior of the

cup.

FE modelling and simulation was used with success, to pre-dict formed shapes as well as stresses and strain during the

forming process.

The potential of flow forming to form shapes difficult to beformed by presses, has been demonstrated.

r e f e r e n c e s

Gur, M., Tirosh, J., 1982. Plastic flow instability under compressiveloading during shear spinning process. Trans. ASME J. Eng.Ind. 104, 1722.

Hauk, S., Vazquez, V.H., Atlan, T., 2000. Finite Element simulationof the flow splitting process. J. Mater. Process. Technol. 98 (1),7080.

Hayama, M., Kudo, H., 1979. Analysis of diametrical growth andworking forces in tube spinning. Bull. Jpn. Soc. Mech. Eng. 22,776784.

Hua, F.A., Yang, Y.S., Zhang, Y.N., Guo, M.H., Guo, D.Y., Tong, W.H.,Hu, Z.Q., 2005. Three dimensional finite element analysis oftube spinning. J. Mater. Process. Technol. 168 (1), 6874.

Jahazi, M., Ebrahimi, G., 1997. The influence of flow formingparameters and microstructure on the quality of a D6ac steel.J. Mater. Process. Technol. 103 (13), 362366.

Li, K., Hao, N., Lu, Y., Xue, K., 1998. 3D rigid plastic FEM numericalsimulation on tube spinning. J. Mater. Process. Technol. 79,185188.

Park, J.W., Kim, Y.H., Bae, W.B., 1997. Analysis of tube spinningprocesses by the upper bound stream function method. J.Mater. Process. Technol. 66 (13), 195203.

Singhal, R.P., Saxena, P.K., Prakash, R., 1990. Estimation of powerin shear spinning of long tubes in hard to work materials. J.Mater. Process. Technol. 23 (1), 2940.

Wang, T., Wang, Z.R., Wang, Q., Zhao, Y., Wang, S., 1989. The slipline fields of thickness reduction spinning and theengineering calculation of the spinning forces. In: Proceedings

of the fourth International Conference on Rotary Forming, pp.8993.

Wong, C.C., Dean, T.A., Lin, J., 2004. Incremental forming of solidcylindrical components using flow forming principles. J.Mater. Process. Technol. 153154, 6066.

Xu, Y., Zhang, S.H., Li, P., Yang, K., Shan, D.B., Lu, Y., 2001. 3D rigidplastic FEM numerical simulation on tube spinning. J. Mater.Process. Technol. 113 (13), 710713.

Xue, K., Lu, Y., Zhao, X., 2001. The disposal of key problems in theFEM analysis of tube stagger spinning. J. Mater. Process.Technol. 69 (13), 176179.

Yao, Y., Makoto, M., 2002. An experimental study in paraxialspinning of one tube end. J. Mater. Process. Technol. 128 (13),324329.

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Cold Rotary Forming of Thin-wall Component From Flat-disc Blank_E Kayali