Formability Index: A New Accurate Approach to Evaluate Material Formability

In sheet metal forming simulation, Forming Limit Diagram (FLD) has long been used to evaluate sheet metal formability. In conventional method, FLD is obtained by assuming linear strain path (Fig.1); while in real production environment, strain path can be very non-linear due to the complexity of geometry or different forming steps. Both experimental observations and theoretical analysis show that strain history will affect the final limit strain (Fig. 1). As a result, large safety margin has to be used for FLDs.