Failure prediction for nonlinear strain paths in sheet metal forming

The Forming Limit Curve (FLC) is a conventional failure criterion to estimate sheet metal formability for proportional loading conditions in Finite Element Analysis. Previous studies found that a standard FLC is not suitable for predicting the influence of nonlinear strain paths. This paper introduces a new method for the description of failure behavior in two-step forming operations by using a metamodeling technique. The main objectives of this approach are the cost effectiveness of the required experimental calibration and its practical applicability. The predicted forming limits determined with the proposed method are presented and validated by experimental results.