Finding the pad load to suppress wrinkling in free bending of ultra-high tensile strength steel sheets

Abstract

The critical pad load to suppress wrinkling in free bending is derived by linking the pad lifting behaviour and the wrinkle disappearing condition that depends on the clearance between the punch and the blank generated by pad lifting at the early stage of bending. The clearance is estimated based on the simulated results that the contacting zone of the blank with the pad at the early stage of bending is confined to the vicinity of the punch shoulder. The usefulness of the critical pad load is confirmed by forming experiments of a T-shaped product from high strength steel sheets.