1995 Volume 35 Issue 1 Pages 56-62
The technology of deep drawing of commercially pure Ti cold-rolled sheet for obtaining drawn cup without defects was developed. Oil hydraulic press of 490 kN punch force and 98 kN blank holding force (BHF) and 300 mm/min drawing speed were used. Ti sheets (TP28C) of 0.8 mm sheet thickness (t) were used. The punch diameter is φ40 mm, and various radii were used.
First, blanks lubricated with machine oil were deep drawn. BHF values were calculated by Dr. Fukui's formula. The limiting drawing ratio (LDR) was about 1.8, inferior to steel sheets.
Next, two 30 μm polyethylene (PE) films were used on each side of Ti sheet and BHF values were calculated by Dr. Fukui's formula. When LDR increased to e.g. 2.5, large and numerous wrinkles were found. By BHF increasing to 98 kN, only traces of wrinkles were found.
Last, punch lubrication was eliminated. The LDR increased to 2.6, but severe earing was formed.
By the consideration of characteristics of test piece of each direction, the breaking mechanism was qualitively explained. By adequate blank shape, this earing was nearly eliminated.