Numerical Simulation of the Initiation and Growth of Small Inner Cracks

In this chapter, regarding small inner cracks in creep-fatigue of austenitic stainless steel SUS304, we proposed a numerical simulation method to estimate the spatial distribution of small inner cracks and its changes that cannot be directly and continuously observed, based on the observations of intergranular cracks on the stress axis longitudinal section of specimens obtained from interrupted tests. The small inner crack model, which is the basis of this simulation, is created by a computer model of a stack of planes (multiplanes) consisting of grain boundary facetsGrain boundary facet projected on a plane perpendicular to the stress axis, and cracks are assumed to initiate and grow on grain boundary facets with a temporal and spatial distribution in units of grain boundary facetsGrain boundary facet. By selecting an appropriate crack initiation driving force F and crack propagation driving force K, the crack density, mean crack length, and crack length distribution actually measured on a longitudinal section can be well reproduced from early to late life.