Effect of Viscoplastic Flow Rules on the Initiation and Growth of Shear Bands at High Strain Rates

MARCHAND and Duffy have reported detailed measurements of the temperature and strain as a shear band develops in a HY-100 steel. Assuming their torsional tests in thin-wall tubes can be adequately modeled by a viscoplastic block undergoing overall adiabatic simple shearing deformations. we investigate the effect of modeling the viscoplastic response of the material by a-power law. and flow rules proposed by Litonski, Bodner and Partom, and Johnson and Cook. Each of these flow rules is first calibrated by using the test data at a nominal strain-rate of 3300 s-‘. Then predictions from the use of these flow rules at nominal strain-rates of 1400 s-’ and 1600 s-’ are compared with the experimental findings. It is found that the Bodner-Partom law and the dipolar theory proposed by Wright and Batra predict reasonably well the main features of the shear band formation in a HY-100 steel.