An Approach for Prediction of Coil Specific Forming Limit Curves

Forming limit curves (FLCs) are widely used for predicting failure in sheet metal forming operations. FLCs are determined in the laboratory according to ISO 12004‑2 using the Nakajima test. The testing procedure involves stretching a series of dog-bone shaped blanks with a hemispherical punch until failure occurs. This measurement procedure is extremely time-consuming. Consequently, a variety of statistical models have been proposed for predicting FLCs based on tensile test data. Unfortunately, practically all existing models are targeted for carbon and alloy steels, and thereby these models cannot be directly applied to stainless steels. In the present study, an approach for prediction of coil specific forming limit curves is developed. Predictive equations are derived based on statistical correlations between measured FLCs and steel properties. The application of the method to prediction of FLCs of stabilized ferritic stainless steels is described.