COMPARATIVE STUDY OF THE EFFECT OF DWELLING THE … · 2016-06-10 · metal forming. He has also elaborated about the applications of these presses in various sheet metal forming

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International Journal of Mechanical Engineering and Technology (IJMET)

Volume 7, Issue 3, May–June 2016, pp.249–266, Article ID: IJMET_07_03_023

Available online at

http://www.iaeme.com/IJMET/issues.asp?JType=IJMET&VType=7&IType=3

Journal Impact Factor (2016): 9.2286 (Calculated by GISI) www.jifactor.com

ISSN Print: 0976-6340 and ISSN Online: 0976-6359

© IAEME Publication

COMPARATIVE STUDY OF THE EFFECT

OF DWELLING THE PUNCH AT THE BDC

VS WITHOUT DWELLING AT THE BDC ON

THE DEEP DRAWING PROCESS BY FE

SIMULATION

Priya B. Vhangade

M.E. Cad/Cam & Robotics Student,

Fr. Conceicao Rodrigues College of Engineering,

Bandra, Mumbai, India

D.S.S. Sudhakar

H.O.D, Department of Mechanical Engineering, Fr. Conceicao Rodrigues College of Engineering,

Bandra, Mumbai, India

Rajeev A. Solanki

Manager, Department of New Product Engineering,

M/S Larsen & Toubro, Powai, Mumbai, India

Basappa U. Vhangade

H.O.D, Department of physics,

Mahatma Phule Arts, Science & Commerce College,

Panvel, Mumbai, India

ABSTRACT

Since past many years the manufacturing industry has made use of the

conventional presses for sheet metal forming. Many advantages as well as the

limitations of the conventional presses are known by now. The servo presses

came into existence many years ago but are now starting to gain popularity

because of its flexible slide motion programming and other significant

characteristics which are unique to the servo presses. Majority of the

components in various industries are made by deep drawing sheet metal

process. So these growing demands need new sheet metal forming techniques

which improve the quality, increase production and save time. To be able to

dwell at the BDC for some time is a unique characteristic of the servo press

compared to the conventional press.

Priya B. Vhangade, D.S.S. Sudhakar, Rajeev A. Solanki and Basappa U. Vhangade


This paper presents an investigation of the effect of the punch dwelling at

the BDC in a servo press vs. without dwelling at the BDC in a conventional

press to find their influence on the deformation behavior of the sheet metal by

finding the variation in formability, contact forces, displacement, % thinning,

stress distribution and von misses stress of a deep drawn cup using finite

element simulations. The finite element simulation analysis is carried out by

using Altair Hyperform and Radioss solver.

Key words: Deep Drawing, HYPERFORM, Simulation, Dwell, Servo Press,

RADIOSS, Bottom Dead Centre (BDC)

Cite this Article Priya B. Vhangade, D.S.S. Sudhakar, Rajeev A. Solanki and

Basappa U. Vhangade, Comparative Study of The Effect of Dwelling The

Punch at The BDC Vs without Dwelling at The BDC on The Deep Drawing

Process by Fe Simulation. International Journal of Mechanical Engineering

and Technology, 7(3), 2016, pp. 249–266.

http://www.iaeme.com/currentissue.asp?JType=IJMET&VType=7&IType=3

1. INTRODUCTION

The sheet metal forming technology is utilized by majority of the automotive,

manufacturing and appliances producing industries. With the increasing popularity of

the finite element simulations, they are performed repeatedly in the design feasibility

studies of die design and production tooling [1]. Deep drawing is one of the most

important forming processes in any industry. Deep drawing is a process for shaping

flat sheets into cup like cylindrical component by radially drawing metal blank into

the die cavity with the help of a punch without fracture or excessive localized

thinning. The control and design of a deep drawing process depends not only on the

equipment used, geometry, workpiece material, but also on the condition at the tool

workpiece interface and the mechanics of plastic deformation [1]. Hence the

upcoming servo press technology makes use of various other additions in the sheet

metal forming process due to its programmable slide motions as compared to that of

the conventional press. The servo press eliminates the need of flywheel, clutch and

brake and replaces it with high power servo motor as shown in figure 1 [2].

Figure 1 Mechanical press vs. servo press [2]

Hence, it is possible to obtain flexible slide motions in a servo press due to the use

of servo motors. The capacity to dwell at the BDC is one of the most important

functions of a servo press because it helps in easy forming of advanced high strength

steels and other high strength materials. Also it helps in reducing the number of

forming steps otherwise required and hence increases productivity in lesser time. In

the figure 2 we can see the comparison between press cycles of a mechanical press vs.

servo press.

http://www.iaeme.com/currentissue.asp?JType=IJMET&VType=7&IType=2

Comparative Study of The Effect of Dwelling The Punch at The BDC Vs without Dwelling at

The BDC on The Deep Drawing Process by Fe Simulation


Figure 2 Slide motion flexibility in servo drive presses [3, 4, 2].

Hence it is important to analyse the effect of dwell on the sheet metal forming

process. The finite element analysis software is regularly used in the design

assessment of dies and stamping tooling in the manufacturing industry.

In the current work case is studied for a deep drawing process of a cup in which

the cup is first drawn without providing dwell at the BDC and then by providing

dwell at the BDC. The finite element simulation of these two processes are carried out

and the variation or effect on formability, contact forces, displacement(mag),

%thinning, stress and von mises stress(scalar value) are studied by the FE simulations.

2. LITERATURE REVIEW

Kozo Osakada, D., (2009) [5] conducted a study on mechanical servo press

technology for metal forming. Here he has explained about the various aspects of

servo presses which include the different slide motions, their applications, various

designs of the servo presses, arrangement etc. Servo drive presses have capabilities to

improve process conditions and productivity in metal forming.

T. Altan, A. Groseclose, (2009) [3] studied and reviewed the servo drive presses

and their capability to improve productivity and to improve process conditions in

metal forming. He has also elaborated about the applications of these presses in

various sheet metal forming processes such as deep drawing, blanking, warm forming

etc. the literature also describes about various press designs and major applications.

Long Ju [6] performed the investigation of forming speed and friction on

drawability of Al 5182-O using a servo press with CNC cushion. Lubrication and

forming speed effect the productivity and part quality. Servo presses have the

capability to provide variable ram motions for various stamping operations. In the

present study, deep drawing tests were conducted in a servo press to investigate the

effects of forming speed on the drawability for Al alloy (5182-O) sheets at room

temperature. The results and discussions gave insights into the effects of forming

speed on deep drawing process of aluminum alloys at room temperature.



Ryo Matsumoto, (2013) [7] studied about Shape accuracy in the forming of deep

holes with retreat and advance pulse ram motion on a servo press. Since the ram speed

and motion of servo presses can be programmed with a servomotor through CNC

control, servo presses have led to new forming processes. Here the shape accuracy of

the formed hole is discussed with experimental and finite element simulation results

in terms of lubrication state and temperature change.

From above findings and discussions, it is clear that researchers have been

working on the various programmable slide motions of the servo press and on their

benefits in the forming process. It is also evident that for this purpose the researchers

are using FE approach to know about the effects of their study. The FE approach also

helps in reducing cost which would otherwise be caused by time consuming

experimental trial and error method.

3. RESEARCH GAP

After the analysis of the literature, it was found that the servo presses are gaining

importance quickly due to its various benefits and customizable abilities as compared

to the conventional presses. Researchers have conducted various experiments and

tests on the servo press which shows various benefits in forming operations due to its

programmable slide motions. Hence, the servo press not only consists of the speed of

a mechanical press but can also provide tonnage as by a hydraulic press. Many

researchers have investigated regarding the effect of forming speed for different sheet

metal forming processes, analysis of friction with advance pulse ram motion in a

servo press, shape accuracy of deep holes on servo press and other such related topics

but very few researchers have carried out the differences caused in the sheet metal by

dwelling at the BDC vs. without providing dwell at the BDC with the help of FE

simulations. There lies an immense future scope in studying different motions of the

servo press and what effects they carry. Hence, the aim of the present work is to

investigate the effect of dwelling at the BDC vs. without dwelling at the BDC on the

variation in stress distribution, displacement, contact forces, von misses stress and

formability of a deep drawn cup using finite element simulations.

4. RESEARCH METHODOLOGY

The research methodology used for the current work is as shown in the figure 1

below.




Figure 3 Methodology of deep drawing simulation

The die and blank geometry is prepared by using the modeling software PRO-E

and then is imported into the preprocessor Hyperform. The preprocessing steps are

carried out in which boundary conditions such as die and blank meshing, clearance,

material properties etc. is applied to generate the required tooling setup for carrying

out the deep drawing simulation analysis. The material used is CRDQ steel which is

elastic plastic material of thickness 1.2mm. The material properties are shown in the

given table 1.



Table 1 Properties of CRDQ steel

Sr. No. Properties Values

1 Young’s modulus (E) 210 Gpa

2 Poisson’s ratio (ν) 0.3

3 Frictions coefficient (µ) 0.1

4 Density (ρ) 7800 kg/m3

5 Yield Stress (σy) 250 Mpa

6 Ultimate tensile Stress (σt) 550 Mpa

7 Tangent modulus (Et) 0.5 Gpa

8 Strain hardening exponent (n) 0.22

4. FINITE ELEMENT MODEL

Drawing of a circular cup is shown in fig 2 [8]. All the important dimensions of the

punch, die and blank holder are shown in figure 3 [9] and are mentioned in table 2.

Figure 4 Cylindrical cup




Figure 5 Geometry of Drawing Dies Assembly [9]

Table 2 Geometric Parameters

Blank thickness (t) 1.2 mm

Blank size radius (BR) 17 mm

Punch radius (PR) 9.64 mm

Die radius (DR) 10 mm

Punch nose radius (rp) 6 mm

Die shoulder radius (rd) 2 mm

Radial clearance (wc) 0.33 mm

Cup Height of the draw (h) 15 mm

Figure 6a, 6b shows simulation setup of a deep drawing process generated at the

end of preprocessing in hyperform software.



Figure 6(a) Setup Consisting Of Die, Binder, Blank and Punch

. Figure 6(b) Front View of Setup

6. RESULTS AND DISCUSSION

Here we are going to study the effects of providing dwell for few seconds at the BDC

which is possible by a servo press. We are comparing the results for slide motion

without dwell vs. the slide motion with dwell at the BDC for 4 sec. The blank holder

force provided is 28000 N. We conduct the simulation preprocessing in Hyper form

and Post processing in Radioss. And then view the results in Hyperview. Hence, we

check their effects on following variables:

FLD (Formability)

Contact forces (Mag)

Displacement (mag)

% thinning

Stress (von mises)




Major stress (P1)

Minor stress (P3)

Von mises stress

6.1. FLD (forming limit diagram)

Figure 7(a) FLD without dwell at BDC

Figure 7(b) Fld plot with dwell at the BDC.

In the fld plot without dwell at the BDC we can see that the plot shows near

marginal failure approaching at some points and also the safe zone formation is bit

distorted compared to the safe zone formation in the plot with dwell at the BDC.

Whereas the fld plot with dwell displays almost no marginal failure inspite having all

the same input parameters.



6.2. Contact forces (mag)

Figure 8(a) contact forces without dwell

Figure 8(b) contact forces with dwell.




From the contour plot analysis system results we can see that the maximum

contact force is 2.857E+02 KN in the plot without dwell as compared to the

maximum contact force in the plot with dwell which is 1.952E+02 KN. Hence the

contact force in plot without dwell is more than in plot with dwell.

6.3. Displacement (mag)

Figure 9(a) Displacement without dwell

Figure 9(b) Displacement with dwell

The displacement plot without dwell shows little compressed zone as compared to

that in the plot with dwell. Hence, we can say that the displacement plot of forming

with dwell is safer and has tendency for lesser wrinkle or compression.



6.4. %Thinning

Figure 10(a) % Thinning without dwell

Figure 10(b) % Thinning with dwell.

The maximum % thinning area is more in the plot with dwell as compared to the

plot without dwell. The value of maximum % thinning during forming with dwell is

around 19% while that in without dwell is around 21%. So this shows that the forming

with dwell process can be extremely useful for high strength alloy forming as they

need more tonnage compared to steel.




6.5. Stress (von mises)

Figure 11(a) Stresses without dwell

Figure 11(b) Stresses with dwell

From both the plots above, maximum stress is more in the plot without dwell than

in the plot with dwell. The value of maximum stress in plot without dwell is 637 Mpa

and that of with dwell is 436 Mpa. In the plot with dwell there are very few maximum

stresses induced during forming as compared to the plot without dwell.



6.5.1. Major stress (P1)

Figure 12(a) Major stresses without dwell

Figure 12(b) Major stresses with dwell.

In the plots above, the maximum value of major stress induced in plot without

dwell is 727 Mpa and in the plot with dwell is 500 Mpa.




6.5.2. Minor stress (P3)

Figure 13(a) Minor stresses without dwell

Figure 13(b) Minor stresses with dwell

From the plots above, The maximum value of minor stress in plot without dwell is

510 Mpa and that in plot with dwell is 335 Mpa.



6.6. Von mises (scalar value)

Figure 14(a) Von mises stress without dwell

Figure 14(b) Von mises stress with dwell.




From the plots above, the maximum value of von mises stress in the plot without

dwell is 480 Mpa and in the plot with dwell is 325 Mpa. So, we can see that the von

mises stresses developed in the plot with dwell is more safer compared to that in

without dwell.

7. ADVANTAGES OF DWELLING OVER NORMAL SLIDE

MOTION

Dwelling allows the metal flow to arrange itself before the next impact, hence

resulting in better forming as we can see in the FLD.

Dwelling helps in distribute the stresses more evenly.

Dwelling can be the best option for high strength steels and alloy forming.

One most important application is also that the dwell time can be utilized to perform

in-die operations or other secondary operations, which hence helps in saving lot of

time as well as money which would otherwise be spent in putting a whole new set up.

Hence, dwelling helps in increasing the productivity and reducing the production

time.

8. CONCLUSION

Summary of the comparative analysis between the results without and with dwell are

found. Several conclusions can be obtained from the results of the study.

The finite element simulation provides a satisfactory determination in the differences

obtained by with dwell and without dwell.

The results from this work open the platforms for further determining the benefits of

dwell on different HSS and other alloy metal forming.

The simulation results reveal that, due to providing dwell there is more uniform

distribution of stresses, direct impact on the sheet metal is less, also there are some

reduction in wrinkling and the material gets time to flow during the dwell period

which results in more safer forming.

REFERENCES

[1] Anup S. Atal , M. T. Shete, Formability Analysis of Deep drawing Process by

Finite Element Simulation, International Journal of Science and Research, 3(6),

June 2014.

[2] Priya Vhangade, D.S.S. Sudhakar, Rajeev Solanki, Study of servo drive press

technology – A Review, 5(4), April 2016.

[3] Altan, T., Groseclose, A., 2009, Servo-Drive Presses – Recent Developments.

[4] Miyoshi, K., Current Trends in Free Motion Presses, Proceedings of the 3rd

Japan Society for Technology of Plasticity (JSTP), Int. Seminar on Precision

Forming, March 2004.

[5] K. Osakada (1)a*, K. Mori (2)b, T. Altan (1)c, P. Groche (1)d , Mechanical servo

press technology for metal forming, Annals 2011(60) 2.

[6] Long Ju, Tingting Mao, Shrinivas Patil, Taylan Altan, Investigation of forming

speed and friction on drawability of Al 5182-O using a servo press with CNC

cushion.

[7] Ryo Matsumoto, Jae-Yeol Jeon, Hiroshi Utsunomiya, Shape accuracy in the

forming of deep holes with retreat and advance pulse ram motion on a servo

press, Journal of Materials Processing Technology 213 (2013) 770–778.



[8] Sachin s. chaudhari, Navneet K. Patil, Springback Prediction of Sheet Metal In

Deep Drawing Process, IJMET, 6(12), Dec 2015, pp. 9–17.

[9] Mohd Naeemil Mahmudi Bin Mahmud, Reducing Wrinkling and Tearing of

Deep Draw Part, M. Tech thesis, Universiti Malaysia Pahang, May 2012, pp. 16.

[10] Dr.R.Uday Kumar, Dr.P.Ravinder Reddy, Influence of Viscosity on Fluid

Pressure in Hydroforming Deep Drawing Process. International Journal of

Mechanical Engineering and Technology, 3(2), 2012, pp. 604–609.

[11] Dr.R.Uday Kumar, Mathematical Modeling and Evaluation of Radial Stresses In

Hydroforming Deep Drawing Process. International Journal of Mechanical

Engineering and Technology, 3(2), 2012, pp. 693–701.

.

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COMPARATIVE STUDY OF THE EFFECT OF DWELLING THE … · 2016-06-10 · metal forming. He has also elaborated about the applications of these presses in various sheet metal forming