An inverse computational method for determining the constitutive parameters using the hot torsion test results

Recently a number of inverse computational methods were presented for determining constitutive parameters from the results of mechanical tests. These are based on minimization of the least square errors of the measured and calculated load-displacement results of the given test. Uniqueness of the minimum obtained from these methods has not been investigated properly. This paper presents an approximate solution for the minimum error in the inverse computational determination of constitutive parameters using the hot torsion test. The approximation is based on an analytical solution for the torsion test. It shows that for the hot torsion test, the existing inverse computational methods based on a load-displacement objective function fail to predict a unique set of constitutive parameters for an assumed rigid-viscoplastic constitutive relationship. A new objective function was developed to ensure the uniqueness of the solution for the constitutive parameters. An algorithm is presented for applying the new method to the hot torsion test results.