This project was aimed for study of springback effect in perforated sheet metal with variation in various controlling parameters like percentage of open area, ligament ratio,shape of hole, size of hole, pattern of hole arrangement.

1. FINITE ELEMENT ANALYSIS OF
SPRINGBACK EFFECT ON
PERFORATED SHEET METAL
GUIDE:
Prof. G.Venkatachalam
TEAM MEMBERS:
Ashish Devarth (08BME037)
Bhupendra Singh (08BME055)
Ravi Shekhar (08BME181)

2. Introduction
• The elastic strain recovery in the formed part after deformation is called
springback effect.
• Springback is the increase in included angle of the formed part relative
to the included angle of the forming tool after the tool is removed.
• With the knowledge of springback, tool dimensions, die design, force
and punch motion can be modified to produce the products with
required dimensions.
• Perforated sheet metal is made through sheet metal stamping and sheet
metal manufacturing process.

3. Contd..
Springback Effect in Bending
Manufacturing processes by S. Kalpakjian and S. Schmid
αi: bend angle before springback
αf: bend angle after springback
Ri: bend radius before springback
Rf: bend radius after springback

4. Literature Review
 Cho et.al studied the effect of punch corner radius, the punch-die
clearance and friction coefficient on Springback effect.
 Chan studied spring-back angles of the work piece by varying the punch
angle, punch radius and die-lip radius.
 Panthi et.al studied the effect of material properties (yield stress, Young’s
modulus, strain hardening) and geometric parameters (thickness of sheet,
die radius, sector angle) on springback effect at minimal load condition.
 Lia et.al studied the material’s hardening model and its affect on the
accuracy of springback calculation.
 Chakrabartty et.al studied the elastic/plastic analysis of the sheet bending
process under conditions of plane strain.

5. Contd..
 Romen et. al studied that the spring back's increasing classical trends are
related to radius decrease, yielding stress increase, bending radius increase
and Young’s modulus decrease.
 Tan et.al studied that due to the non-homogeneous plastic deformation
across thickness, springback will result in redistribution of internal stress
and residual stress can be observed in a bent specimen.
On the basis of Literature Survey following observations were drawn:
Parameter Value Springback
Yield Strength of Material Increase Increase
Thickness of Sheet Metal Decrease Increase
Modulus of Elasticity Decrease Increase
Punch Die Clearance Increase Increase

6. Contd..
Parameters Value Springback
Friction Coefficient Increase Increase
Punch Velocity Decrease Increase
Force Applied Decrease Increase
Bend Radius Increase Increase
Punch Radius Decrease Increase
Punch angle Decrease Increase
Valley Springback angle Decrease Increase
Area of Plastic Deformation Decrease Increase

7. Problem Statement
• Springback effect is a major cause of concern for sheet metal forming
industries which leads to inaccuracies in the final product produced and
eventually leads to problems in assembly.
• From literature review it is clear that springback effect in case of
perforated sheet metal has not been studied . The problem being taken
for the project is to study the effect of springback phenomenon on
perforated sheet metal.
• The study accounts for various controlling parameters for perforation of
sheet metal .

8. Methodology

9. Design of Perforated Sheet Metal
The various controlling parameters on which the design of
perforated sheet metal depends are:
• Percentage of open area
• Ligament ratio
• Size of the hole
• Shape of the hole
• Pattern of hole arrangement
• Area of sheet
• Thickness of sheet
• Material of sheet

10. Circular holes arranged in Square Pattern

11. Design of Bending Process
Punch
Assembly
Die

12. Material Chosen
• The material chosen for Punch and Die is Cast Iron having Young’s
modulus 210 Gpa and Poisson’s Ratio 0.25.
• The material chosen for perforated sheet metal is commercial pure
aluminium having Young’s modulus 70 Gpa and Poisson’s Ratio
0.33.
• Plastic properties of commercial pure aluminium are :

13. Meshing
• Element type : Solid45
• Meshing type : Mapped meshing
• Element size : For sheet metal 0.75 mm and for punch and die 10
mm.

14. Contact Pair
• Surface-to-Surface contact: CONTA174
• Node-to-Surface contact: CONTA175
• Target Element: TARGET 170
Surface-to-surface contact Node-to-surface contact

15. Boundary Condition
• Die : Constrained in all DOF
• Punch: Constrained in X and Z direction
• Perforated Sheet: Constrained in X and Z direction

16. Simulation
X - Component Y - Component
Von mise Stress Von mises Strain

17. After Bending

18. After Unloading

19. Results and Discussion

20. Springback Vs Open Area (Circular Hole)

21. Springback Vs Open Area ( Square Hole)

22. Springback Vs Load ( Circular Hole)

23. Springback Vs Load ( Square Hole )

24. Springback Vs Ligament Ratio ( Circular Hole)

25. Springback Vs Ligament Ratio ( Square Hole)

26. Springback Vs Load ( Circular Hole )

27. Springback Vs Load ( Square Hole)

28. Springback Vs Hole Size ( Circular Hole )

29. Springback Vs Hole Size ( Square Hole )

30. Springback Vs Load ( Circular Hole )

31. Springback Vs Load ( Square Hole )

32. Springback Vs Thickness

33. Springback Vs Load

34. Springback Vs Shape

35. Springback Vs Pattern

36. Conclusion
The springback effect was studied on perforated sheet metal and the
following conclusions were drawn:
• The value of springback effect increases with increase in the percentage
of open area for circular hole as well as square hole when the hole size,
ligament ratio and thickness of sheet metal were taken as constant. Sheet
metal with square hole showed greater springback than those with circular
hole because strength of square hole is less than strength of circular hole.
• The value of springback effect decreases with the increase of load on the
perforated sheet metal. This holds good for both the square and circular
hole.
• The value of springback effect decreases with increase in hole size for
both circular as well as square holes when open area, ligament ratio and
thickness of sheet metal is kept constant. The values are higher for square
holes.

37. Contd..
• During bending process when the ligament ratio between the holes is
increased the value of springback also gets increased while keeping the
other controlling parameter constant.
• When the thickness of perforated sheet metal increases for circular hole
arranged in square pattern then the value of springback value gradually
decreases.
• The value of springback in square hole arranged in square pattern was
found to be more than the value of circular hole arranged in square pattern.
This is because the strength of square hole is less than that of a circular
hole.
• The value of springback for circular hole arranged in triangular pattern
was found to be less than that of circular hole arranged in square pattern
because the strength of triangular pattern is more than that of square
pattern.

38. References
Journal Articles:
[1] J. Chakrabarty, W.B. Lee and K.C. Chan (1999), An Analysis of the Plane-Strain Bending of
an Orthotropic Sheet in the Elastic/Plastic Range, Journal of Material Processing
Technology,104, pp 48-52
[2] You-Min Huang, Tsung-Chia Chen. An elasto-plastic finite element analysis of sheet metal
camber process, Journal of Materials Processing Technology, 2003, pp 432-440.
[3] Xuechun Lia, Yuying Yanga, Yongzhi Wanga, Jun Baoa and Shunping Lib (2001), Effect of the
Material-Hardening Mode on the Springback Simulation Accuracy of V-Free Bending,
Journal of Material Processing Technology, pp 209-211.
[4] Zhong Hu, Elasto-Plastic solutions for springback angle of pipe bending using local induction
heating, Journal of Material Processing Technology (200) pp – 103
[5] Z. Tan, W. B. Li and B. Persson ( 1993), On Analysis and Measurement of Residual
Stresses in the Bending of Sheet Metals, Pergamon, vol 36, pp 483-491.
[6] J.R.Cho, S.J.Moon, Y.H.Moon and S.S.Kang (2003), Finite Element Investigation on Spring-
back Characteristics in Sheet Metal U-Bending Process, Journal of Material Processing
Technology, pp 109-116.

39. Contd..
[7] W.M. Chan, H.I. Chew, H.P. Lee and B.T. Cheok (2003), Finite Element Analysis of
Springback of V–Bending Sheet Metal Forming Processes, Journal of Material Processing
Technology, pp 15 – 24.
[8] S.K. Panthi, N. Ramakrishnan, Meraj Ahmed, Shambhavi S. Singh and M.D. Goel (2009),
Finite Element Analysis of Sheet Metal Bending Process to Predict the Springback, Materials
and Design, pp 657-662.
[9] Z.Tan, B.Persson and C.Magnusson (1994), Plastic Bending of Anisotropic Sheet Metal,
Pergamon, vol. 37, pp 405-421.
[10] F.Pourboghrat and E. Chu (1995), Prediction of Spring-Back and Side-Wall Curl in 2-D
Draw Bending, Journal of Material Processing Technology, pp 361-374.
[11] M.L. Garcia-Romeu , J. Ciurana and I. Ferrer (2007), Springback Determination Of Sheet
Metals In An Air Bending Process Based On An Experimental Work, Journal of Material
Processing Technology, pp 174-177.
[12] Z.T.Zhang and S.J.Hu, Stress and Residual-108, Stress distribution in plane strain bending,
Journal of Mechanical sciences pp- 543-553
[13] M.A.Osman, M. Shazly, A.El-Mokaddem, A.S.Wifi, Springback prediction in V-bending:
modelling and experimentation, Journal of achievement in Material and Manufacturing
Engineering, pp-179-186

40. Contd..
[14] D. Schmoeckel (I) and M. Beth at Institute for Production Technology and Forming
Machines, Springback Reduction In Draw-Bending Process of Sheet Metals, Technical
University Darmstadt Germany, Annals of CIRP, vol. 42, pp 339 – 342.
[15] Fundamentals of Modern Manufacturing: Materials, Processes, and Systems, Third Edition,
by Mikell P. Groover, 4/25/2008.
Books
[16] ANSYS Structural Analysis, ANSYS Release 9.0, November 2004
[17] Manufacturing processes by S. Kalpakjian and S. Schmid, 4th Edition published by Dorling
Kindersley, 2008.
[18] Mechanics of sheet metal forming by Z.Marciniak, J.L.Duncan and S.J.Hu, 2nd Edition
published by Butterworth-Heinemann 2002.
[19] Z.Marciniak, J.L. Duncun, S.J. Hu Text book of Mechanics of Sheet Metal Forming 82-107.
[20] P.S.G. Design Data Book
Lectures
[21] Lecture on Plastic Deformation By R.Ganesh Narayanan, IITG

41. THANK YOU