Mechanism of Improving Fretting Fatigue Strength by Stress-Relief Groove

概要

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The effectiveness of stress-relief groove that significantly improves the fretting fatigue strength has been validated through many fatigue tests using a full-scale railway wheelset. However, the reason for this increase has not been yet fully understood. The objective of this study is to clarify the mechanism responsible for the improvement of the fretting fatigue strength by a stress-relief groove. In this study, fretting fatigue tests using a pre-cracked specimen was done based on the assumption that the fretting fatigue phenomenon can be regarded as a crack propagation problem. In the experiment, the fretting fatigue strength was improved by the stress-relief groove. The result suggested that the propagation of the pre-crack was suppressed by the stress-relief groove. An FEM analysis showed the reason for the suppression of the crack propagation. The mode I stress intensity factor of the pre-crack was reduced by the stress-relief groove. This was achieved by both relaxation of the stress around the contact edge and development of static compressive stress field by severe concentration of the contact pressure due to overhang.