Multiple-factor dependence of the yielding behavior to isotropic ductile materials

Extensively experimental evidences have shown that the yielding behaviors for many isotropic materials exhibit both the pressure and stress-state dependence. The strength-differential in tension and compression results not only from the hydrostatic stress, but also from the loading type. Different materials often demonstrate different yielding features in stress space even though they have the same ratio of compression yield-stress to tension yield-stress. Bases on a physical hypothesis introduced herein, a yield criterion is proposed to fulfill the experimental observations. The yield criterion can be represented finally with three independent invariants of the stress tensor and the deviatoric stress tensor. The yield criterion can well predict the yielding behavior arising from the yielding mechanism of the multiple-factor dependence. The yielding analysis with the effect of the hydrostatic stress does not have a limit when regardless of the strength-differential in tension and compression. The yield criterion assures the convexity in a wider range of material properties so that it can be used as the plastic potential in the implementation of predicting the subsequent yield surface. The yield criterion reveals a clearly transforming procedure with respect to its simplified form when applied to different materials from a general compressive isotropic material to an ideal incompressive isotropic material, back to the Mises's criterion. Divers experiments on metallic and polymeric materials are compared. The results show that the new yield criterion is in fairly good agreement with all referred experiments.