Small punch test for determining a flow stress by using a hybrid inverse procedure

A flow stress of the structural materials used in nuclear and fossil power plants is determined by using the small punch test. An inverse method is proposed to deal with a non-uniform deformation in a specimen used for the small punch test. The objective function of the inverse analysis is the difference between the measured load–displacement response and the calculated one during a deformation. The convergence of the objective function to a global minimum is assured by adopting a simulated annealing. During the optimization process, the load–displacement response under given material parameters is calculated by means of an artificial neural network. Material parameters are accurately identified for the numerical test data. The present method is verified by applying it to the experimental data for the as-received and ex-service materials. The results show that the flow stress of the materials used in this study is predicted with a reasonable accuracy.