表面凹坑对活塞-缸套摩擦生热过程的影响

Frictional heat influenced by the surface pits of piston-cylinder

针对表面规则凹坑可以改善活塞-缸套摩擦副的热效应这一物理现象,建立了热应力耦合的有限元模型。对该模型进行接触非线性分析,求得接触力,从而得到摩擦力所做的功,将功转化为热能作为表面热流输入到温度场控制方程中,实现了应力场与温度场的耦合。仿真结果表明:相对于光滑活塞,加工有凹坑的活塞表面虽然在局部存在较高的温度点,但整体上实现了温度的均匀分布,而光滑裙部表面的温度分布集中使导热较差是引起光滑裙部局部磨损的主要原因之一。凹坑可使裙部热量分散,不易引起磨损以及高温黏着现象,从而提高裙部表面的耐磨性,延长活塞的使用寿命。

A coupling thermal stress finite element model is proposed to investigate the physical phenomenon that the surface pits can improve the thermal performance of piston liner. First, non- linear analysis is carried out on the contact problem, and the contact force and the friction work are obtained. This friction work is then converted into thermal energy as a surface heat flux, which is taken as the boundary condition of the governing equations of temperature field, thus, the coupling between stress field and temperature field is achieved. Simulation was conducted and results show that the maximum temperature on the piston surface with pits is locally higher than that of smooth piston surface, but the overall temperature distribution is uniform. One of the main reasons for local wear of smooth piston skirt is due to the temperature focus which can induce poor heat conduction. The pits can disperse the heat of the piston skirt that avoids the wear and high-temperature adhesion.Therefore, the surface pits can enhance the wear resistance of the piston skirt and prolong the service life of pistons.