Wrinkling behaviour of cold-rolled sheet metals when drawing through a tractrix die

✍ Scribed by R. Narayanasamy; R. Sowerby

• Publisher: Elsevier Science
• Year: 1995
• Tongue: English
• Weight: 462 KB
• Volume: 49
• Category: Article
• ISSN: 0924-0136
• DOI: 10.1016/0924-0136(94)01331-t

✦ Synopsis

This paper deals with the deep drawing of circular blanks into cylindrical cups through a Tractrix die using flat-bottomed and hemispherically-ended punches. It is well established that the use of a Tractrix die can enhance the limiting draw ratio as compared with that obtainable in a conventional drawing operation. When the Tractrix 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 stage of a drawing process in which thin sheet blanks are employed. For the present work, cold rolled commercially-pure aluminium and copper blanks of different diameters are drawn through the Tractrix die under dry lubrication (with no lubricant) condition, until the appearance of a first-stage wrinkle. An attempt is here made to relate the amount of draw obtainable in the drawing process with the initial diameter of the blank. It is also shown that the onset of wrinkling takes place when the percentage change in thickness reaches a critical value, this value being found to be generally the same for both aluminium and copper sheets.