Evaluation of constitutive models for voided solids

In this work four constitutive models for voided solids are reviewed and ev aluated; namely, Gurson's, Green's, Liao's et al. and Shima-Oyane's models. Two modified forms of Gurson's model and a non-quadratic form of Green's m odel are developed for normal anisotropy prevailing in the analysis of shee t metal forming. A simplified version - more amenable to analytical derivat ions - of Gurson's yield function and its modified forms an proposed for pl ane stress conditions. The associated flow rules are presented and the laws governing void growth with accumulated strain are derived using the above models. Their predictions are compared with experiments. As an application, the flow curves of voided materials of known initial porosities are predic ted and compared with experiments. (C) 1999 Elsevier Science Ltd. All right s reserved.