The effect of void shape on the ductile behavior of tension-compression asymmetric materials

This paper presents an in-depth investigation into how matrix tension-compression asymmetry and initial void shape impact the ductile behavior of porous materials, offering new insights that have not been explored in previous studies. To achieve this, finite element computations in ABAQUS/Standard are used to model three-dimensional unit cells with various void shapes -spherical, oblate, and prolate- embedded in a matrix material characterized by the CPB06 constitutive model, implemented via a UMAT user subroutine. The simulations span a range of stress states with variations in stress triaxiality from 0 to 2 and Lode parameter from −1 to 1, focusing on the evolution of void volume fraction and void geometry. The findings indicate that, while the initial yield locus is found to be similar for spherical and non-spherical (oblate and prolate) voids, significant variations in void growth and shape evolution occur depending on the void shape. Non-spherical voids, especially in materials with pronounced tension-compression asymmetry, exhibit significantly different growth patterns and morphological changes when compared with the spherical case.