Effect of Initial Void Shape on Void Growth of Structural Steels Based on Micromechanical RVE Models

Abstract

This paper aims to study the effect of initial void shape on void growth of structural steels, which is a critical stage for ductile fracture of steel. Typical void shapes of structural steels were characterized by an in situ high-resolution micro X-ray computed tomography (μXCT) technique, including spherical, elliptical, and cylindrical voids. Then, a micromechanical representative volume element (RVE) model containing a single void was established with periodic boundary conditions. On this basis, impacts of the void shape on void growth were analyzed through Python-based parametric modeling in ABAQUS with respect to the stress triaxiality, aspect ratio, orientation, and initial void volume fraction, respectively. The results indicate a significant effect of the void shape on void growth under low stress triaxialities, and the effect tends to decrease with the increase of the stress triaxiality. Under low stress triaxialities (e.g., 0.33), there is a remarkable void growth difference between cylindrical and elliptical voids with the same initial aspect ratio, and this difference tends to disappear when the stress triaxiality increases to a high value, e.g., 0.8. Compared with the void orientation aligned in a coordinate axis, the off-axis one presents a smaller void growth difference induced by the void shape when the stress triaxiality is low, but reverse under high stress triaxialities. Finally, accurate and simplified formulas were proposed to consider the effects of void shape on void growth at the mesoscale.