A novel model to predict microvoid evolution in tensile necking using macroscopic deformation behavior

Abstract

Using the final state analysis method (fracture morphology analysis), it is difficult to establish the dynamic changes that would have occurred during the process of necking under tensile load. In this paper, the time-dependent observations, the critical hole expansion ratio model and the Bridgeman equation is applied to establish the relationship between the dynamics of necking and the microscopic parameters that describe fracture in samples made from the low-carbon steel. The results show that the axial (x) and radial (y) displacements observed in the necking process are described by the Gaussian function. And the curve of the neck contraction (yc) and time (t) indicates that the macroscopic deformation process behind necking can be divided into three stages, which correspond to microcrack propagation in the fiber area, the radiation area, and the shear lip area. Following, by considering the fitted model of x-y, the critical hole expansion ratio model and the Bridgeman equation, a novel model between the macroscopic deformation (parameters of yc and εt) observed in necking and the formation of micropores (parameter of Rc) is established, which can disclose the effect of macroscopic deformation on the formation of the micro-voids, and plays a role in the study of plastic deformation mechanisms in a wide range of materials.

Keywords

• Time-dependent observations
• Necking
• Plastic deformation
• Gaussian distribution
• Critical hole expansion ratio model
• Bridgeman equation