1. Finite element analysis of springback in L-bending of sheet metal
Y.E. Ling H.P. Lee B.T. Cheok
7 February 2007
A Presentation by:
Rose Wieland

2. Overview Introduction Set up Effects of Die Clearance
Effects of Step Size
Conclusion/Recommendations

3. Introduction Increasing demand for tight tolerances
Springback is biggest problem to tolerances
FEM models allow for effect of die clearance, die radii, and step size to be analyzed
Idea of how to minimize springback

5. History 1958 – first mathematical model for springback corrections
1991/1992 – FEM models used to analyze springback
Never in the paper is the accuracy of FEM models versus real experimental data discussed!

6. FEM Model Die, punch, and pressure pad rigid
Workpiece is a deformable mesh
Die step height, step distance, die clearance, and
die radii varied
Material used : AL2024-T3

7. Effects of Die Clearance

8. Bend Leg analysis
Bend leg curves between clearances of 1t and 0.8 t with maximum between 0.9 t and 0.95 t
Otherwise, bend leg remains strait

9. Stress Analysis

10. Effects of Die Radius K = springback factor
A = bend angle after springback
A1= bend angle during bending
Springback factor of 1 most desirable

11. Effects of Step Height and Distance

12. Design Recommendations
Die radius, clearance, and step height and distance all effect springback
Die radius and clearance have greatest effect
Effects are exclusive and additive i.e.
die radius = 2.0t die clearance = 0.75t;
step height = 0.2t step distance = 0t.
springback reduction for die radius 2.0t and die clearance 0.75t is 1.37◦
springback reduction for using a step height of 0.2t and step distance 0t at that die radius and clearance is 1.08◦
The total springback reduction is 1.37◦ ◦ = 2.45◦
(values from Table 2 and Table 3)

13. Beware bend leg elongation

14. Accounting for Elongation
Radius most important factor to elongation
Bend leg elongation only happens at clearance less than the thickness
Step height and step distance do not alter bend allowances significantly

15. Conclusion
Established trends for effect of die clearance, die radius, step height and distance
Need for research with other materials
This research took hours
Perhaps small samples of other materials could be tested to show trends

16. References
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