Approximate yield criterion for voided anisotropic ductile materials

As most fractures of ductile materials in metal forming processes occurred due to the results of evolution of internal damage - void nucleation, growt h and coalescence. In this paper, an approximate yield criterion for voided (porous) anisotropic ductile materials is developed. The proposed approxim ate yield function is based on Gurson's yield function in conjunction with the Hosford's non-quadratic anisotropic yield criterion in order to conside r the characteristic of anisotropic properties of matrix material. The asso ciated flow rules are presented and the laws governing void growth with str ain are derived. Using the proposed model void growth of an anisotropic she et under biaxial tensile loading and its effect on sheet metal formability are investigated, The yield surface of voided anisotropic sheet and void gr owth with strain are predicted and compared with the experimental results.