Effect of localization criteria and yield criteria in predicting the forming limit diagram (FLD) of DP590 steel sheets

Abstract

ABSTRACT The main objective of the present work is to study the effect of different localisation criteria and yield criteria in predicting the forming limit diagram (FLD) of dual phase (DP) 590 steel sheets. DP590 steel is used in automotive applications for structural and safety parts such as cross members, longitudinal beams, B-pillar reinforcements and bumper reinforcements. Limit dome height (LDH) tests were performed for DP590 steel sheets and experimental FLD is plotted. Tensile tests and plastic strain ratio ‘r’ tests were performed at different rolling directions to evaluate the mechanical properties The evaluated mechanical properties were used in finite element (FE) simulations to predict the FLD of DP590 steel sheet. Three material models namely Transversely anisotropic elastic plastic, 3 parameter Barlat yield law and Hill 3 R which includes diverse yield criteria Hill 48, Barlat 89 and Hill 3 R, respectively, were used in FE analysis. Three different localisation criteria namely equivalent plastic strain criterion, thickness criterion and localisation criterion based on true strain gradient were used to predict the FLD of DP590 steel sheets. It was found that predicted FLD is close to experimental FLD when localisation criterion proposed, based on true strain gradient and Hill 48 yield criterion is used.