Subjects on Fatigue Crack Generation in High Strength Alloys for Long-Life Design

Abstract

The very localized deformation processes have been found to be decisive for subsurface fatigue crack generation at the lower stress level such as the elastic incompatibility at boundaries where only a very small fraction of plastically deformed grains was detected. The material design and its microstructure modification to achieve higher fatigue resistance in long-life range are needed for the high strength alloys, which is one of the ways developing an ecomaterial. Novel systems have employed to clarify the substance crack generation and growth mechanisms of high strength alloys. The initial crack size highly depends on the maximum cyclic stress range, which implies a threshold of stress intensity range controlling mechanism. Heterogeneous microplasticity due to planar slip and restricted system is considered to play an important role on making the subsurface crack. Then, it should be progressed in the understanding of damage stage in high-cycle fatigue fracture process.