Study on Influences of Curved Ratio and Reverse Drawing Technique on Thinning of Curved Bottom Cup

This work studied the influences of the punch head curve ratio on thickness changing of cup by deep drawing process using one step or conventional drawing and reverse drawing (2-step) from 1 mm thick Aluminum 5052 H32. For conventional drawing, it was found that the curve bottom part of cup was thinner than other area when deep drawing with lower curve ratio punch. The maximum thinning area was found on curve bottom part of cup. While deep drawing with high curve ratio punch, the thinnest area had shift to straight wall close to bottom of cup. Deep drawing of 2 steps using reverse drawing could reduce thinning with low curve ratio punch and short straight wall cup. The mechanism for deep drawing of curve bottom cup could be divided into two parts; the curve bottom with main stretching was formed initially and followed by forming the straight wall with main radial tensile stress. Thus, reverse drawing could help reduce thinning only on the first part of curved bottom cup forming.  Therefore, using reverse drawing had less effect on thinning for cup with high curve bottom ratio with large straight wall due to second part of forming straight wall area was dominated.