Wrinkling of sheet metals when drawing through a conical die

✍ Scribed by R. Narayanasamy; R. Sowerby

• Publisher: Elsevier Science
• Year: 1994
• Tongue: English
• Weight: 656 KB
• Volume: 41
• Category: Article
• ISSN: 0924-0136
• DOI: 10.1016/0924-0136(94)90166-x

✦ Synopsis

This paper deals with the deep drawing of circular blanks into cylindrical cups through a conical die using flat-bottomed and hemispherical-ended punches. It is well established that the use of a conical die can enhance the limiting drawing ratio compared with that obtainable in a conventional drawing operation. When a conical die is employed, the need for a hold-down or clamping ring is eliminated. However, this enhances the propensity of the blank to fail by wrinkling or buckling, particularly in the early stages of a drawing process in which thin sheet blanks are used. An attempt is made to rank the properties that appear to suppress wrinkling. The wrinkling modes that develop during the different stages of drawing are identified. It is shown also that the onset of wrinkling takes place when the ratio of the plastic strain increment (d~,/d%) reaches a critical value. This value, which is determined experimentally, compares favourably with the results of theoretical analysis.

Nomenclature

a¢ critical compressive hoop stress /~ normal anisotropy AR planar anisotropy a true stress true strain K strength coefficient ~o constant