Study of Fatigue Processes Occurring in the Plastic Zone In Front off the Tip of a Microcrack in Austenitic Steels

摘要

Optical microscopy and scanning electron microscopy were used to study the plastic zone in front of the tip of a fatigue macrocrack. Slip bands and isolated microcracks were revealed in the plastic zone which reaches 300-350 mu m in size. The nucleation sites, length, and distribution of slip bands in the plastic zone were studied. The angular orientation of slip bands relative to the direction of the macrocrack propagation was measured. It was found that repeated fatigue tests lead to the formation of new bands with different angular orientations. The statistical distributions of the lengths of the slip bands and their angular deviations from the macrocrack direction were determined. A correlation of the slip bands with the structural elements of steel was found. The sizes of the isolated microcracks in the plastic zones were measured, and their statistical distribution was determined. It was shown that the isolated microcracks and slip bands coincide in length only in the region of small values.