The Effect of Shot Peening on the Bending Strength of Carburized Gear Teeth

Abstract

The quantitative effects of hardness and residual stress produced by shot peening on the bending strength of carburized spur gears of m=5 are investigated. The residual stress of every test tooth is measured by an X-ray diffraction method. The intensity of shot peening has little effect on the fatigue strength. The mean strength is about 1200 MPa, which is about 1.3 times that of carburized gears without shot peening. When a tooth surface is electropolished and a higher compressive residual stress is applied to the fillet, the fatigue strength is still 250 MPa higher than that of the shot-peened gears. In this study, the improvement of fatigue strength is assumed to be caused by an increase of both hardness and residual stress, and an experimental formula is proposed to estimate the fatigue strength.