LZ50车轴钢在复合微动条件下的研究

Study on LZ50 Axle Steel under Condition of Composite Fretting

微动疲劳损伤广泛存在于各种机械接触变载荷作用的构件上,如螺栓,轴承,键槽和榫槽等。微动疲劳会加速受微动作用构件的接触处表面及表层裂纹的萌生和扩展,在微动疲劳的早期阶段裂纹生长速率较高,导致了在微动条件下金属构件过早失效,大幅度降低构件寿命。本文以LZ50车轴钢为主要研究对象,实现了在圆形和椭圆形路径加载下的拉扭复合微动疲劳试验模拟,采用静拉伸的方法测试了材料的力学性能,在圆形和椭圆形路径加载下,LZ50钢微动疲劳表面磨屑的演变分为三个过程,轻度氧化——进一步氧化——高度氧化;LZ50钢在多轴非比例加载下的复合微动疲劳接触表面损伤可分为四个阶段,分别为表面膜去除阶段、表面直接接触阶段、形成第三体保护层阶段和动态平衡阶段;在圆形和椭圆形路径加载下,LZ50钢微动疲劳裂纹是在微动与未微动分界线上局部应力集中而萌生的,由于疲劳裂纹的扩展和连接而导致材料断裂。

Fretting fatigue damage widely lies in machine components which interfaces bear alternating load,such as bolts,axletrees,slots and tenors.Fretting fatigue will accelerate the crack initiation and growth on the surface and the sub-surface of the fretting contact components.In the early stages,fretting fatigue crack grows fast,which leads to early failure of metal components and cause a significant reduction on the working life.In this study,the fretting fatigue test of LZ50 steel is executed in the round and oval-shaped path of the pull-torsional loading fretting fatigue test simulation,using the method of static tensile to acquire the mechanical properties of material.In the round and oval shaped loading path,LZ50 steel debris fretting fatigue evolution of the surface is divided into three processes,namely the light oxidation-the further oxidation-a high degree of oxidation.LZ50 steel under multiaxial nonproportional loading fretting fatigue contact surface damage can be divided into four stages,namely the surface film removal phase,the surface of direct contact with the stage,the formation of protective layer of the third stage and the dynamic balance of body stage.In the round and oval-shaped loading path,LZ50 steel fretting fatigue cracks are initiated in the dividing line between micro-initiation and non-micro-initation of local stress concentration,due to fatigue crack propagation and fracture