Effect of self heating on the torque vs. equivalent tensile strain plot inhigh temperature torsion of visco-plastic material

In hot forming as simulated by the torsion test, a temperature rise due to self heating is simulated within a FEM approach. The numerical results allo w for a "natural" explanation of the maximum experimentally observed for th e torque vs. equivalent tensile strain plot. There is no longer any need fo r assumptions of microstructurally conditioned strain softening during the test. With increasing cumulated strain (time) the radial temperature gradie nt in a cross section of the useful centre part of the test specimen is sho wn to change in sign; in the beginning the temperature is highest at the su rface and at the end the temperature maximum is at the centre. (C) 2001 Klu wer Academic Publishers.