Author(s)

F. Ma & K. Kishimoto

Abstract

Based on a detailed finite element computations on yielding of axisymmetric unit cell models, the accuracy of Gurson's yielding function as well as Tvel- gaard's modification of it for porous plasticity was examined. It was found that the cell with aspect ratio of n/4 exhibits isotropic yielding, and it is described well by setting ?i = 1.35 and # = 0.95 in Tvergaard's model. A non- associated flow rule was introduced to describe precisely the post-yield responses of the porous material. 1 Introduction The microscopic voids plays a crucial role in ductile fracture of materi- als. The constitutive description including such mechanisms has received a great deal of attentions in the past decades. Gurson* derived an approxi- mate yield function for the idealized porous material from the upper-bound solutions

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