A UNIFIED MODEL FOR DISLOCATION NUCLEATION, DISLOCATION EMISSION AND DISLOCATION-FREE ZONE

In this paper, a unified model for dislocation nucleation, emission an d dislocation free zone is proposed based on the Peierls framework. Th ree regions are identified ahead of the crack tip. The emitted disloca tions, located away from the crack tip in the form of an inverse pileu p, define the plastic zone. Between that zone and the cohesive zone im mediately ahead of the crack tip, there is a dislocation free zone. Wi th the stress field and the dislocation density field in the cohesive zone and plastic zone being, respectively, expressed in the first and second Chebyshev polynomial series, and the opening and slip displacem ents in trigonometric series, a set of nonlinear algebraic equations c an be obtained and solved with the Newton-Raphson Method. The results of calculations for pure shearing and combined tension and shear loadi ng after dislocation emission are given in detail. An approximate trea tment of the dynamic effects of the dislocation emission is also devel oped in this paper, and the calculation results are in good agreement with those of molecular dynamics simulations.