An Effect of Compressive Residual Stress on a High Temperature Fatigue Crack Propagation Behavior of The Shot-peened Spring Steel

압축잔류응력이 스프링강의 고온환경 피로크랙 진전거동에 미치는 영향

The lightness of components required in automobile and machinery industry is requiring high strength of components. In particular, manufacturing process and new materials development for solving the fatigue fracture problem attendant upon high strength of suspension of automobile are actively advanced. In this paper, the effect of compressive residual stress of spring steel(JISG SUP-9) by shot-peening on fatigue crack growth characteristics in high temperatures($100^{\circ}C,\;150^{\circ}C,\;180^{\circ}C$) was investigated with considering fracture mechanics. So, we can obtain followings. (1) Compressive residual stress is decreased in high temperature, that is, with increasing temperature. (2) The effect of compressive residual stress on fatigue crack growth behavior in high temperature is increased below ${\Delta}K=17{\sim}19MPa\sqrt{m}$. The fatigue crack growth rate is increased with increasing temperature. The fatigue life is decreased with increasing temperature. (3) The dependence of temperature and compressive residual stress on the parameters C and m in Paris' law formed the formulas such as equations (3),(4),(5),(6),(7),(8),(9),(10). (4) It was investigated by SEM that the constraint of compress residual stress for plastic zone of fatigue crack tip was decreased in high temperature as compared with room temperature.