ショットピーニングしたマルエージング鋼の破壊機構

概要

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Rotating bending fatigue tests were carried out for a shot-peened managing steel in order to investigate the effects of shot peening on the fatigue strength and the fracture mechanism. Fatigue strength was markedly improved by shot peening because of hardening and generation of compressive residual stress in the surface layer. Origin of fatigue fracture changed from the specimen surface at high stress levels to an inclusion in the interior of specimen at low stress levels. And at the middle stress levels, both fracture modes were observed. Consequently, the shape of S-N curve of shot-peened specimen was complex corresponding to the change of fracture mode. Fatigue strength at low stress levels, where internal fracture occurred, increased by formation of reversion austenite. This is mainly caused by the suppression effects of reversion austenite to the growth of a small crack and the intergranular crack. By formation of reversion austenite, a clear fish-eye was observed.
都城工業高等専門学校の論文