A SIMULATION OF COLD-ROLL FORMING FOR ELASTOPLASTIC MATERIALS

A kinematical approach was proposed in a previous paper for predicting the optimal shape and the deformed length of a rigid-plastic metal sh eet during cold-roll forming. Because the elastic effects are importan t in this kind of process, the method has been extended here to elasto plastic materials. In the new formulation, the sheet is still consider ed as a thin shell and its middle surface is described as a Coons patc h depending on one geometrical parameter. Moreover, the material now s atisfies a constitutive rate equation in which the corotational rate o f stress is used. The Prandtl-Reuss model, including the von Mises yie ld criterion and the normality flow rule, is used. In order to integra te the elastoplastic constitutive equations,a radial return Scheme is adapted so that the plastic power rate is calculated, using a Gauss me thod. Its minimization gives the optimal shape for a strain hardening elastoplastic material, as well as the optimal velocity field. This ap proach has been implemented on workstation and, as for rigid-plastic m aterials, it gives a very fast simulation of the cold-roll forming pro cess. (C) 1997 Published by Elsevier Science Ltd.