1. An experimental study on the examination of springback of sheet metals with several thicknesses and properties in bending dies Zafer Tekiner Accepted 25 July 2003 Presented by Jared Moyer September 22, 2004

2. Bending Background Used anciently-5000 BC Utensils and jewelry A common shaping process today Seams, flanges Automotive-car bodies Aircraft fuselages Beverage can Metal desks

3. Modern forms

4. Advantages Low cost Good strength Light weight Formability characteristics no necking or tearing Versatile shapes

5. Disadvantages Cracking Springback –Sheets –Rod –Wire –bars SB = (A’ – Ab’)/ Ab’

6. Reducing Springback Over bending part Elevated temperatures Bottoming the punch High-localized compressive stresses between the punch and die surface Stretch bending Part is in tension while being bent

7. Purpose of Paper Find a springback values –Bending die designers –Acceptable tolerances Experimental methods Time Money

8. Test Set Up Several materials: Steel, Copper, Brass, Aluminum, Galvanized and stainless steels Dimensions: 25 mm x 50 mm Different thicknesses:.5,.75 & 1.00 mm Measured bending by optical profilometer (1 min) Used four different methods Results graphed by Microsoft Excel software

9. Forces Needed Force Equations –C = 1 + (4*T/W) –P*v = C (B*T^2*dd*b-/W) x 10

10. Method 1 Punch doesn’t touch die corners Gap thickness between punch and die equaled to sheet metal thickness Punched left for 20 sec. Repeated each material and thickness

11. Method 1 Results

12. Method 1 overall results

13. Method 2 Punch on the sheet metal No maintaining load

14. Method 2 Results

15. Method 2 overall Results

16. Method 3 and 4 Method 3 –No gap between punch and die –Load left for 20 sec Method 4 –No gap between punch and sheet metal –No holding load Results –Too complicated –Crushing material –Depth of descending punch not considered

17. Conclusions Changed with material and die Reduced by leaving loads Developed equations help produce more precise results

18. My conclusions Are the springback values valid with multiple bends? Experiments have been preformed Machinists use charts

19. References Fundamentals of Modern Manufacturing, Mikell P. Groover Manufacturing Engineering and Technology, Kalpakjan and Schmid

20. Questions