Prediction and analysis of ductile fracture in sheet metal forming-Part II: Application of the modified Ayada criterion

Ductile fracture occurs due to micro-void nucleation, growth, and final coalescence into micro-crack. In this paper, a modified Ayada ductile criterion is implemented for prediction and analysis of the ductile fracture in sheet metal forming. To enhance calculation efficiency, an algorithm for efficient calculation of damage value is proposed. The finite element formulations for obtaining the generalized strain distribution and the damage value distribution by using the modified Ayada ductile criterion are presented. Case studies show that the simulation-based predictions with the built-in modified Ayada ductile fracture criterion have a good agreement with the experimental results. Furthermore, the comparison of the predictions by using the Ayada and the modified criteria shows that the latter is more conservative and hence safer for the design of deformed parts, forming processes, and tooling.