Effects of Shot Peening Process on Fatigue Strength of 50CrV4 Steel Contaning an Artifical Surface Defect
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It is well known that surface defects have a very significant effect on the fatigue strength of engineering materials. The shot peening process is a mechanical surface treatment to enhance surface properties and fatigue strength. In this study, it is aimed to investigate the effects of surface defects on the fatigue strength of 50CrV4 spring steel and the effect of shot peening process effects. Samples including a semicircular slit sized 0,2 mm or a hole sized 3 mm throughout the sample were shot-peened by S230 steel balls. 3point bending tests were performed on defected and non-defected samples. It was found that the defects acted as a pre-existent crack and samples with hole and semicircular slit significantly reduced the fatigue strength by 85% and 80% (for 672 MPa), respectively. While shot peening enhanced the fatigue strength of the semi -circular slitted sample by 126%, it had almost no effect on the holed sample. Although shot peening increased the fatigue strength of the semi -circular slotted sample, it could not reach that of the non-defected sample. According to the results, it can be concluded that 3 mm hole and 0,2 mm scratch defects cannot be made harmless by the Shot Peening method.