Simultaneous determination of flow stress and interface friction by finite element based inverse analysis technique

A finite element based inverse analysis technique has been developed to determine the flow stress and friction at the tool/workpiece interface simultaneously from one set of material tests. The inverse problem is aimed at minimizing the error between experimental data and predictions made by rigid-plastic finite element simulations. The ring compression test and the modified limiting dome height test (sheet blank with a hole at center stretched with a hemispherical punch) were selected for evaluating the method for bulk forming and for sheet forming, respectively. The determined flow stress data were compared with corresponding data obtained independently using the well-lubricated cylinder compression test and hydraulic bulge test. Results show that the method discussed in the study is efficient and accurate.