APPROACHES TO CALCULATE THE FORMING LIMIT CURVE UNDER NONLINEAR STRAIN-PATHS

The Forming Limit Curve (FLC) according to ISO 12004 is a standard failure criterion in sheet metal forming simulation. It is well known that the FLC is only valid for proportional loading conditions during the forming process, which unfortunately do not exist in most industrial forming operations. Therefore, the FLC is not capable to correctly predict material failure. To assess this problem, many approaches have been made to improve the FLC's prediction accuracy. In this paper, three different approaches are presented to predict localized necking under nonlinear strain-paths in sheet metal forming. The different approaches are compared and evaluated. Furthermore a new approach to improve the prediction quality of the FLC is presented.