Effect of Surface Treatment on Torsional Fatigue Properties of Machine Structural Steel

Abstract

As more than 90% of failure cases are initiated from stress concentrated portion and more than 90% are due to fatigue, it is practically very important to improve the fatigue strength of notched portion. Some of the authors have been investigating to improve the fatigue strength of to improve the fatigue strength of notched portion applying plastic deformation method. In this study, the torsional fatigue test about roller-worked specimen had been performed. The material was carbon steels (JIS standards S25C). The main results obtained were as follows; When the plastic deformation value is 1mm, the torsional fatigue strength of notched specimen by roller-working increases 68MPa than that of the notched specimen by non roller-working. The photographs of surface condition roller-worked before failure showed many blocks like cracks, which were not observed in the case of non roller-worked specimen.