Effect of fretting wear on very high cycle bending fatigue behaviors of FV520B steel

In order to investigate the effect of fretting wear on very high cycle bending fatigue behaviors of FV520B steel, fatigue tests with and without fretting wear were carried out by using ultrasonic fatigue testing system. The specimens for two fatigue testing methods were designed and the stress and displacement distributions were obtained by finite element method. The S-N curves were compared and analyzed based on fatigue data. The micromorphology characteristics of specimen surface and fracture surface were observed. The experimental results indicate that there exists no “conventional fatigue limit” and fatigue life decreases with the increase of applied stress for two fatigue testing methods. For fatigue test without fretting wear, the initiation and propagation of fatigue crack are mainly ascribed to surface machining defects and surface stress concentration. For fatigue test with fretting wear, surface damage including adhesive wear, abrasive wear and surface material removed in sliding contact promotes the initiation and propagation of numerous cracks on surface, which brings about the higher deviation of fatigue data. So the fatigue life is significantly reduced compared to that of the smooth specimen.