A Comparative Investigation on Theoretical Models for Forming Limit Diagram Prediction of Sheet Metals

This study provides a coherent comparison among four theoretical models including Swift’s instability, Hill’s localized neck, Storen-Rice bifurcation analysis, and Hora’s MMFC criteria for explicitly estimating the forming limit diagram (FLD) of sheet metals. These explicit solutions for FLD are derived based on a power hardening law coupling with J2 flow theory. Accordingly, the advantages and limitations of each model are discussed from the points of view of metal physics, which appears to be a useful suggestion for selecting a proper theoretical model to evaluate FLD of sheet metals without conducting experimental tests. To verify the effectiveness of those suggestions, the predicted FLD of AA6016 and DP590 sheet materials are compared with experimentally measured data from a series of Nakazima tests.