Simulation of deep drawing of dual phase steel sheets incorporating tribological behaviour predicted by advanced friction modelling

Abstract

In a deep drawing process, friction at the sheet metal-die contact interface affects the material flow in the flange as well as at the die entry affecting product quality significantly. The accuracy of predicted drawing force and thinning in deep drawing simulation strongly depends on friction modelling. The Coulomb friction model with a constant coefficient of friction is generally assumed in simulations. In reality, the actual friction coefficient depends on process variables such as local contact pressure, relative sliding velocity, and strain in the sheet material. In this work, an approach is presented for deep drawing simulation of dual phase (DP600) steel sheets incorporating the effect of these variables on the friction coefficient. Strip drawing tests under conditions similar to that exist in the flange area during deep drawing have been carried out. Deep drawing simulations have been performed using two friction models taking into consideration the variation of friction coefficient with respect to pressure and velocity. The predicted punch force and thickness variation are validated using deep drawing experiments. A considerable improvement in the accuracy of predicted results has been observed when compared to a constant coefficient of friction.