微动损伤对车轴疲劳寿命的影响

Effects of Fretting on Fatigue Behavior of Axle

微动损伤会降低车轴的疲劳强度，缩短疲劳寿命。本文采用模拟轮对，对试验轴进行模拟车轴工况的微动损伤试验。经过１．２×１０７次循环后卸载，采用扫描电镜分析试验轴磨损面及疲劳断口形貌，Ｘ射线电子谱仪分析磨损面的氧化物，Ｘ射线衍射仪分析磨屑的成分和物相，显微硬度计被用来测定磨损面下剖面的微区硬度。分析证明，试验轴磨损面有塑性流变、蚀坑和加厚的氧化层，在接触面的应力集中部位有疲劳裂纹，其最初是在微动应力作用下沿着与表面成３０°～４５°角的方向扩展。

Fretting damage is caused when two surfaces in contact experience slight periodic relative motion(usually<100μm), and is known to have a deleterious effect on fatigue behavior. In this paper, fretting test was carried out with an apparatus which imitates axial working condition to investigate the effect of fretting on the fatigue life of the axle. After 1.2×10 7 circles, scanning electron microscopes (SEM) and X ray photoelectron spectroscop (XPS) techniques were used to examine the appearance and oxides of the axial fretted surface and the fatigue fracture side. X ray diffraction was also used to identify loose wear particles. Plastic flow and pits,a thicker oxide film and fatigue cracks were observed on fretted surface. Fretting is thought responsible for the propagation of the fatigue crack being oblique to the axial surface at an angle of 30°￣45°at initial stage.