EXPERIMENTAL STUDY AND CRITICAL CONDITION COMPUTING FOR PREVENTING OUTER WRINKLING IN THE USE OF DRAW BEAD

A round draw bead can prevent the forming of inner wrinkling.Before the drawn piece is formed,the material outside the draw bead will undergo complex changes.All these changes will affect the forming process of outer wrinkling,in other words,they will decide whether outer wrinkling will be brought about or not.This situation is analyzed theoretically and tested by experiment.Finally,a critical condition expression is given which shows the way to prevent outer wrinkling in the use of the round draw bead,and an experience formula is derived which tells the best location of the draw bead.