| Abstract | In recent years weight reduction of suspension springs has been increasingly required from the viewpoints ofimprovement in fuel efficiency of automobiles and global environmental concerns. To realize further weightsaving of the suspension spring, it is important to increase its fatigue strength and it is imperative tounderstand shot peening techniques, which affect improvement in the fatigue strength. However, the relationbetween surface roughness, residual stress distribution, which affects the fatigue strength, and shot peeningconditions has yet to be sufficiently clarified while it is qualitatively comprehended. Moreover, the quantitativerelation between the surface roughness, the residual stress distribution, and the fatigue strength has also notbeen fully understood.If the fatigue strength can be predicted quantitatively from the shot peening conditions, shot peening can beused as a tool for the optimal design of the suspension spring. This quantitative prediction will also be veryuseful in knowing processing conditions to improve the fatigue strength.In this study, various shot peening conditions, such as shot size and spring steel hardness, were examined toobtain a regression formula to estimate the residual stress and the surface roughness. Further, a method topredict the fatigue limit from the regression formula and the fracture mechanics was examined, and itspracticality was verified. |