EFFECT OF A THIRD INVARIANT ON THE EFFECTIVE REACTION OF DUCTILE POROUS BODIES. II. LOADING SURFACE OF POROUS BODIES WHOSE PROPERTIES ARE SENSITIVE TO A TRIAXIAL STRESSED STATE

摘要

The lower and upper boundary approximation for describing the yield condition of porous bodies whose behavior is sensitive to a third strain rate invariant is obtained. Together with porosity the constitutive equations contain a material parameter that is responsible for the change in pore shape. This approach makes it possible to present the macroscopic yield condition in a compact form convenient for analysis and various applications. In particular, generalization of well-known plasticity conditions of Gurson and Green-Shima is presented. The lower estimate generalizes the Gurson model and the upper estimate corresponds to the Green-Shima model. Octahedral contours of the loading surface are constructed that agree with experimental data for loose materials and porous powder bodies.