Effect of Imposing Temperature Gradient in Stretch Forming Process for Ferritic Stainless Steel Sheets

A new stamping method developed by the authors, in which a temperature gradient is imposed on the workpiece during stamping, is capable of improving stretch formability in stamping of ferritic stainless steel sheets. Unlike the conventional warm stamping method, the temperature gradient is utilized in order to diffuse the strain distribution induced in the material. Basically, the portions of the sheets which are in contact with the top of the punch and die face are heated, while simultaneously, the portions in contact with the punch corners and die corners are intensively cooled The authors developed a finite element simulation model of stamping which analyzes mechanical and thermal behaviors simultaneously utilizing LS‐DYNA3D. The numerical analysis, combined with a numerical model which evaluates the ductile fracture limit of the material in the high temperature region, confirmed that the new stamping method improves stretch formability and the optimal temperature gradient is given. In order to verify ...