An evaluation of three material models used in the finite element simulation of a sheet stretching process

Hemispherical punch stretch tests were simulated using an in-house dynamic explicit finite element code which incorporated three material models: J2 flow, Gurson and Taylor crystalline, and results are compared with those obtained from experiments carried out on a Nakajima type test rig. Only the Gurson and crystalline models predicted material instabilities, though the former had a much more sudden characteristic. Although there was an enormous disparity between the computational times, the accuracy with which the crystalline model predicts the strain distribution throughout the loading history, the necking geometry and the load–displacement relationships, justifies, in this case, the additional expense.