The localized internal necking process between microvoids in a plastic solid

Ductile fracture of metals may result from the nucleation, growth and sudden catastrophic coalescence of microvoids. In this paper, the interaction between two microvoids in a plastic solid under uniaxial tension at infinity is considered, and the localized internal necking process in the intervoid matrix is investigated. Firstly, the growth rate of an elliptic-cylindrical void in a power law viscous material is numerically studied. It is found that the influence of the nonlinearity of the material was underestimated by previous researchers. Secondly, by means of Riemann's analytical integration the slip-line field of Cauchy problem for plane-strain plastic flow between adjacent elliptical voids is constructed, and the relationship between this slip-line field and the remote strain is discussed. Thirdly, a critical condition for the incipient microvoid coalescence is suggested. Finally based on a step-by-step computation of the velocity distribution in the plastic slip line field, the process of the internal necking and the distortion of the microvoids are quantitatively studied. Obviously, the present results may be of great importance in the study of the fracture mechanisms in ductile materials under low stress triaxiality condition.