Surface defects, such as surface cracks and non-metallic inclusions, are decreased the fatigue strength of vehicle parts. However, the study on overcoming the surface defects by using surface refining methods is hardly reported. The cavitation peening (CP) is a high possibility as a new surface refining method, which is a shot-less peening method and increases compressive residual stress. On studying the effects of the CP to the defects, an experiment using the two types of specimens with an artificial semi-circular slit, whose slit depth (a)=0.04, 0.075 and 0.10mm on the surface of specimens, was conducted and their refined surface characteristics and fatigue limits were evaluated. Consequently, it is concluded that by using CP, the acceptable defect size (slit depth: a) with the smooth and that with notched specimens can be estimated less than 0.04mm and 0.075 mm, respectively.
