Evaluation of LS-DYNA Material Models for the Analysis of Sidewall Curl in Advanced High Strength Steels

Accurate modelling of the Bauschinger effect and anisotropic plasticity in advanced high strength steels (AHSS) is essential in order to accurately predict sidewall curl. In this study, the performance of several constitutive models from the LS-DYNA library was evaluated for the prediction of sidewall curl in a plane-strain channel draw process for two grades of AHSS (TRIP780 and DP980). Since the profile of the channel section after springback results from the recovery of elastic strains in a plastically deformed sheet metal, the stress distributions in the channel section after the forming stage were carefully examined. Deformation modes in the sheet metal included sliding under the binder pressure, successive bending-unbending through a drawbead and drawing over the die entry radius. Material types 24, 36, 37 and 125 were used with shell element formulation 16 in order to select the most accurate combination for predicting sidewall curl. An investigation of simulation results showed that MAT125 predicted the sidewall curvature more accurately than the other models.