A New Model to Describe Yield Surface Distortion Based on the Baltov and Sawczuk’s Model

In the present study Baltov and Sawczuk’s yield surface model is modified to represent compatible results with experimental observations. The proposed yield surface is determined during tension-torsion loading by considering kinematic hardening model and monotonic loading paths. The experimental results represent the nosed and flattened region in the loading and reverse loading direction respectively. The nosed region is dominant in tension than in torsion. The cross-effect is negligible in the small plastic strain amount. The Baltov and Sawczuk’s yield surface has nosed and flattened regions in both loading and reversed loading directions for negative and positive added material parameter respectively. Thus the elliptic Baltov and Sawczuk’s yield surface is modified by changing the sign of this parameter continuously from loading to reverse loading direction and the needed relations of the new model are obtained. The new model was able to predict properly the shape of yield surface. The experimental results compare well with the new model yield surface distortion predictions.