Aplicação de curvas limite de conformação na previsão de rupturas em bordas de peças estampadas

Abstract

Several authors have studied the Forming Limit Curve limitation for predicting failures on the flanges of Advanced High Strength Steels stamped parts, mainly in the Dual Phase steels. This limitation comes from the work hardening and the edge defects generated during the cutting operation which decreases the materials ductility in this region, causing premature fractures. The hole expansion test is used to evaluating the ability of deformed edges. However, the major concern with this test is the maximum percentage expansion of the hole, not considering the maximum strains in the region adjacent to it. This study aimed to develop an experimental method for predicting edge fracture on stamped parts. Two test methodologies were evaluated, called Circular Mesh and Double Bending Methods. The maximum strain supported by edge during stretching efforts were quantified for two different steels, IF and DP600. The techniques showed different strain limits. In both, the FLC could not predict the edge punching and stretching failure for the DP600 steel. From the results obtained, it was proposed to use a modified FLC, offset from the original FLC.