Analysis of a Test Method of Sheet Metal Formability Using the Finite-Element Method

The rigid-plastic finite element method was used to study the formability of sheet materials. In the finite element simulations, sheet material was assumed to be rigid plastic and to follow Hill’s anisotropic yield criterion and its associated flow rules. The work hardening effect and Coulomb friction were incorporated into the analysis. Hasek’s test, hemispherical punch stretching of the circular blank with circular cutoff, was analyzed in detail by simulation. The computed solutions were obtained using different blank geometries and coefficients of friction between the tool-sheet interface. Strain paths of critical elements were plotted in major and minor surface strain space. Experiments were also carried out using AISI 304 stainless steel sheets, and the results were compared with predictions for load-displacement curves and thickness strain distributions. Further, an attempt was made to construct a forming limit curve based on the detailed analysis of the test by computation.