Modelling for Transcrystalline and Intercrystalline Fracture by Void Nucleation and Growth

Abstract

A criterion has been formulated for transcrystalline and intercrystalline fracture caused by the evolution of voids located both in a grain and on grain boundaries. The criterion is based on the idea of plastic collapse for a unit cell that is a regular structural mezovolume of polycrystalline material. The criterion does not require the introduction of any empirical parameters, such as critical void size, critical size of ligament between voids and critical void volume fraction, which are used in most models. Modelling has been performed for void nucleation and growth in a grain and on grain boundaries for elastic–plastic deformation and under creep conditions. A scheme is proposed to describe the transition from transcrystalline to intercrystalline cavitation fracture as a function of strain rate and temperature. The effect of stress triaxiality on the critical strain and the lifetime for both transcrystalline and intercrystalline fracture has been investigated. A comparison of the results predicted by the suggested criterion with available empirical data has been performed.

Modeling for fracture in materials under long-term static creep loading and neutron irradiation. Part 1. A physico-mechanical model

“…The authors [17][18][19] came up with a model for intergranular fracture under static and cyclic loading, which is based on the equations for void nucleation and growth and the so-called criterion for "microplastic collapse" or a unit cell plastic instability. This criterion requires no empirical parameters of fracture.…”

“…The present paper elaborates on a physico-mechanical model for intergranular fracture [17][18][19] for predicting creep rupture strength and plasticity of neutron-irradiated materials.…”

“…Fracture Criterion. The microplastic collapse criterion proposed in [17][18][19] for describing fracture caused by void propagation will be used as an intergranular fracture criterion in this model. A polycrystalline material is represented as an aggregate of unit cells.…”

“…1). The critical state of a unit cell with voids, i.e., the cell fracture, is defined as a microplastic collapse that can be represented as [18] ∂ ∂κ…”

“…Following the Kachanov's procedure [6] we introduce effective stresses σ ij which are give by [17][18][19] σ ij…”