柴油机主轴承轴瓦微动损伤可靠性分析

Fretting Reliability Analysis of Main Bearings of Diesel Engine

车用柴油机功率密度和轻量化要求不断提高,往往导致发动机零部件的刚度不足,部件接触面之间产生微位移和微动磨损,对零部件和整机的可靠性产生较大影响。对一款车用柴油机,建立曲轴、轴瓦、螺栓、机体、连杆多体接触有限元模型,根据发动机运行工况,分析一个循环内的载荷和应力分布变化规律;结合微动磨损的Archard模型和微动疲劳的SWT(Smith,Watson and Topper)准则,分析机体-轴瓦的微动磨损和疲劳规律;考虑结构和材料参数的分散性,结合可靠性理论,得到微动损伤可靠性随时间的变化规律。结果表明第四主轴承下轴瓦侧面和第二主轴承上下瓦结合面分别是微动磨损和疲劳的危险点;微动磨损的可靠度下降要快于微动疲劳的可靠度。研究结果为提高整机的可靠性提供了建议和参考。

Requirements for power density and lightweight of automotive diesel engines often lead to insufficient stiffness of engine parts,and causing micro-displacement and fretting wear between contact surfaces,which have a great impact on the reliability of parts and the whole engine.A finite element multibody contact model,including crankshaft,bearings,bolts,engine block and connecting rods has been established.Loads and Stresses of multibody are analyzed during one complete engine cycle.Based on Arc hard model offretting wear and SWT(Smith,Watson and Topper)criterionof fretting fatigue,fretting damage between main bearing and bore are analyzed.Considering the dispersion of structural and material parameters,the reliabilities offretting wear and fatigue of bearings are analyzed based on the theory of reliability.The simulation results show that the dangerous points offretting wear and fatigue situate at the low side face of the fourth main bearing,and the split face of the second main bearing respectively.The decreasing of reliability of fretting wear is faster than that of fretting fatigue.The results provide suggestions for improving the reliability of the whole engine.