Multiaxial cyclic plasticity model including elastic modulus variation

In the present work a multiaxial model is proposed to describe the elastoplastic behaviour of a structural steel in the presence of loading-unloading cycles. The activity is a part of a more estensive research carried out in collaboration with Baker & Hughes aimed at developing an accurate model for accurately predicing residual stresses caused by autofrettage processes in thick cylinders and its experimental verification. It has been demostrated that in order to obtain estimates of the residual stress with errors within a few percent, the constitutive behavior of the material has to be reproduced very accurately. To this purpose, both the Bauschinger effect and the variation of the elastic modulus with the accumulated plastic deformation have to be accurately measured and properly included in the constitutive model.