Explicit numerical study of softening in porous ductile solids

Abstract

Axisymmetric unit cell model calculations are widely used to study void growth to coalescence in a material containing a periodic array of ellipsoidal voids. The objective of the present paper is to compare the predictions of a proposed cell model quasi-static explicit calculations with the results from numerical implicit cell model analyses. The unit cell is presumed to be remotely loaded in an axisymmetric fashion with predominant axial stress and overall stress triaxiality kept constant during the whole process of deformation. Computations with different void shapes, overall stress triaxiality and material parameters are performed. A global view of the obtained results indicates that there is reasonably good agreement between both approaches. As an example, the proposed numerical technique is used to study the plastic collapse of an axisymmetric unit cell with a primary spherical void embedded in a porous matrix material. Consistent with experimental and theoretical results available in literature, the obtained results substantiate the sensitivity of coalescence to the presence of the secondary voids. It is found in particular that failure mechanisms depend on both initial void volume fractions and stress triaxiality essentially.