非比例加载下两相介质弹塑性特性的有限元分析

在Ｉｌｙｕｓｈｉｎ五维应变空间下，利用弹塑性有限变形的有限元法。研究了两相介质在非比例加载下的弹塑性特性，提出了应力模、延迟角随应变路径、转折角变化的近似计算公式，计算结果还表明，工程材料的许多复杂本构特性都是由第二相介质引起的．

A STUDY ON THE ELASTO-PLASTIC MECHANICAL BEHAVIOR OF TWO PHASE MEDIA UNDER NONPROPORTIONAL LOADING

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.