MODELING FOR TRANSCRYSTALLINE AND INTERCRYSTALLINE FRACTURE BY VOID NUCLEATION AND GROWTH

A criterion has been formulated for transcrystalline and intercrystall ine 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 p olycrystalline material. The criterion does not require the introducti on of any empirical parameters, such as critical void size, critical s ize of ligament between voids and critical void volume fraction, which are used in most models. Modelling has been performed for void nuclea tion and growth in a grain and on grain boundaries for elastic-plastic deformation and under creep conditions. A scheme is proposed to descr ibe the transition from transcrystalline to intercrystalline cavitatio n fracture as a function of strain rate and temperature. The effect of stress triaxiality on the critical strain and the lifetime for both t ranscrystalline and intercrystalline fracture has been investigated. A comparison of the results predicted by the suggested criterion with a vailable empirical data has been performed.