A new method for predicting Forming Limit Curves from mechanical properties

Forming Limit Curves (FLCs) are an important tool in steel sheet metal forming. Experimental measurements of FLCs are costly, and therefore, empirical prediction methods are of practical use. Difficulties in accurately defining FLCs for new steel grades, such as AHSS, have necessitated a review of the existing prediction methods. Four points were defined to characterise an FLC, and correlations between the coordinates of these points and the mechanical properties from tensile testing were found. The results show that the total elongation, Lankford coefficient and thickness are strongly related to the FLC values. Predictive equations were derived from the statistical relations between the measured FLC points and the mechanical properties. To verify the predictive equations, predicted FLCs for approximately fifty steel grades in various thickness ranges were compared with measured FLCs. It was found that the newly developed method accurately predicts the FLCs.