A STUDY ON THE ELASTO-PLASTIC MECHANICAL BEHAVIOR OF TWO PHASE MEDIA UNDER NONPROPORTIONAL LOADING
非比例加载下两相介质弹塑性特性的有限元分析

Under the assumption that the yielding phenomenon is not effected by the meanstress, the strain history of a material can be described by a spatial curve (strain trace) in fivedimensional deviatoric strain space. Stresses are functions of the strain trace. We assume thatthe ideal homogeneous matrix obeys the Mises yielding criterion and isotropic hardening. Butwhen the second particles exist, the stress concentration will occur around the second particlesand the residual stresses occur under unloading. When the strain trace changes its direction theinfluence of the second particles is very complex. In this paper the elasto-plastic behavior of twophase media under nonproportional plane stress loading is studied by finite element method. Thechanges of the stress norm and delayed angle (the angle between the strain rate and stress) with thelength and rotated angle of the strain path are obtained and their approximate formulas are alsogiven. These calculated results are consistent with the previous experimental data well. From thispaper it can be concluded that the complex constitutive behavior of an engineering material canbe quantitatively explained in some degree by its multi-phase (inhomogeneous) character, whichmay exist originally or be produced by the plastic deformation, such as dislocations, micro-cavitiesetc.