Numerically produced forming limit diagrams for metal sheets with voids considering micromechanical effects

A numerical study of how changes in the micromechanical modeling affect the formability of voided metal sheets is conducted. A homogenization technique, where periodic representative volume elements are used, permits investigations of the global formability where the local material mechanisms and the microstructure are accounted for. A nonlocal material model, containing a constitutive material length, is used to include size dependence in the formulation. When the nonlocal material assumption is adopted, the formability is shown to be lowered as compared to the response of the local material assumption. Altering the void distribution, to a more clustered state, is also found to decrease the formability. Increasing the initial volume fraction of voids affects the formability by lowering and reshaping the formability curve. When the strain hardening exponent is increased the formability curve is found to be lowered.