抄録
Stress relief groove has been used to improve the fretting fatigue strength at fitted part between mechanical components. However, in the limited mechanical components such as railway wheelsets, applicability of the groove has not been fully evaluated and there are insufficient investigations to determine optimal shape of the groove. In this study, fretting fatigue tests were done using several kinds of grooved specimen. The shape of groove was systematically changed with parameters groove radius R and tangential angle θ. FEM stress analyses were also done to investigate stress conditions and to evaluate the fretting fatigue limit of the grooved specimen. In the fretting fatigue test, fatigue limit of a grooved specimen had a peak with increase of θ. The maximum improvement of fatigue limit was achieved at the transition point of the failure mode from the fretting fatigue at contact part to the fatigue at groove root. The radius of groove has an influence on the improvement of fatigue limit, since stress conditions at groove root become severe when the size of groove is too small. In the simple elastic FEM analysis, a highly compressive stress field was generated near the contact edge, where small cracks could never propagate. Thus, as an assumption to relieve the contact pressure concentration, the local plastic deformation at the contact edge was simulated by elasto-plastic FEM deformation analysis. As the results, it was found that fretting fatigue limit of grooved specimen could be evaluated using the maximum axial stress near the contact edge. The estimation of fretting fatigue limit using a relationship between K_t /K_<t0> and θd gave a good correlation with the experimental results and it would be a useful method to select the optimal groove shape.
