Abstract
Effects of shot peening on the bending fatigue strength of spring steel SUP9A (470HV) containing an artificial small hole were investigated. Shot peening (SP) and stress shot peening (SSP) were carried out with the specimens containing an artificial drilled hole 0.1, 0.2 and 0.4 mm depth. Then, bending fatigue tests were carried out with the specimens. The fatigue strengths of specimens containing an artificial small hole were increased by shot peening. Stress shot peening (SSP) was effective in improving fatigue strength. It was found that an artificial drilled hole under 0.1 mm depth and 0.2 mm depth could be made acceptable by SP and SSP. The acceptable defect size by SP and SSP were evaluated based on fracture mechanics.
