Determination of flow stress and interface friction at elevated temperatures by inverse analysis technique

An inverse analysis technique has been introduced to obtain the flow stress of the bulk and sheet materials at elevated temperatures. The inverse problem is defined as the minimization of the differences between the experimental measurements and the corresponding FEM predictions. As reference material tests, the ring compression and the modified limiting dome height test (sheet blank with a hole at the center stretched with a hemispherical punch) at elevated isothermal conditions were selected. The friction condition at the tool/workpiece interface is identified from the geometrical changes that occur in deformed samples. It is shown that the developed inverse analysis technique is reliable and can determine the flow stress and friction factor simultaneously from one set of material tests.