A MICROMECHANICAL MODEL OF CYCLIC DEFORMATION AND FATIGUE-CRACK NUCLEATION IN f.c.c. SINGLE CRYSTALS

摘要

Abstract-We have developed a micromechanical finite-element model of fatigue-crack initiation in nominally defect-free pure f.c.c. metals. The scale of observation envisioned is that of a single persistent slip band (PSB) intersecting the free surface of a single crystal. The nucleation event is identified with the formation of a sharp surface crack, whose subsequent growth obeys the laws of fracture mechanics. Basic building blocks of the theory are: a model of cyclic plasticity tailored to PSBs which accounts for the Bauschinger effect, PSB elongation due to pair annihilation, and vacancy generation; and a model of Vacancy diffusion which accounts for pipe diffusion and the surface motion resulting from the outward Flux of vacancies.