Comparative study of various hardening models for the prediction of plastic responses under strain path change conditions

This work is aimed at investigating the influence of hardening models on the prediction of plastic responses of sheet metals under strain path change conditions. An enhanced back-stress restoration evolution hardening model was proposed, considering that the back stress accumulated in preloading stages was restored gradually in the subsequent loading stage. A comparative study was conducted between the proposed model and other two hardening models, i.e. Chaboche combined hardening model and Yoshida-Uemori hardening model, in terms of their prediction accuracy of work-hardening and r-value evolution behaviors under reverse and orthogonal loading conditions. The parameters in the models were determined by the experimental results of uniaxial tension and uniaxial compression-tension-compression tests using 6061O aluminum sheet. Associated with the Yld2000-2d yield function, these three hardening models were further employed to simulate a two-stage deep drawing process of a cylindrical cup. The predicted punch load-stroke curves, the height distribution of the drawn cup, and the split-ring springback were compared with the experimental ones. Obvious difference between the predictions was observed in the second drawing stage, which indicates the significant influence of hardening model on the prediction of plastic response under strain path change conditions. Among these three hardening models, the proposed hardening model presented a good prediction result which matched well with the experimental outcome.