考虑变摩擦系数的轮轨系统滑动接触热弹塑性应力分析

Thermo-Elasto-Plastic Analysis of Wheel-Rail Sliding Contact Stress with Variable Friction Coefficient

以LM型踏面车轮和60kg·m-1钢轨为例,采用双线性塑性模型和平面应变热力耦合单元实现轮轨的热弹塑性耦合,传热过程中考虑轮轨接触斑处的非稳态热传导以及轮轨与周围环境间的热对流和热辐射,建立轮轨滑动接触二维热弹塑性有限元模型,分析轮轨接触斑间全滑动时不同相对滑动速度下,与温度变化相关的变摩擦系数对轮轨接触表面温度和等效应力的影响,并与取0.334的常摩擦系数时进行对比。结果表明:钢轨在轮轨接触斑附近的摩擦温升主要分布在其接触表面大约1.8mm的深度范围内,而车轮的主要分布在其接触表面大约2.5mm的深度范围内,采用变摩擦系数得到的轮轨摩擦温升要比采用常摩擦系数时低57%左右;轮轨接触斑附近钢轨和车轮的最大等效应力出现在车轮和钢轨的次表面上,采用变摩擦系数时得到的车轮和钢轨等效应力的影响范围比采用常摩擦系数时略小;轮轨间相对滑动速度对车轮接触表面的温度和等效应力影响不明显,但对钢轨接触表面温度和等效应力的影响明显,相对滑动速度越大,钢轨接触表面的温度也越高。

With LM tread wheelset and 60 kg m-1 rail as examples, a bilinear plasticity model and thermo-mechanical coupling plane strain elements were used to simulate the thermo-elasto-plastic coupling of wheel and rail. In the process of heat transfer, the non-steady heat conduction in wheel-rail contact patch, the heat convection and thermal radiation between wheel-rail and ambient environment were considered. A two-dimensional thermo-elasto-plastic finite element model of wheel-rail sliding contact was established. The effects of temperature-dependent friction coefficient on the temperature and equivalent stress of wheel-rail contact surface were investigated under different relative sliding speed of wheel-rail sliding contact at pure sliding in wheel-rail contact patch, and the results were compared with those using the constant friction coefficient of 0. 334. Calculation results show as follows. The frictional temperature rise affected zone of rail near the contact patch is mainly distributed in the 1.8 mm depth range of rail contact surface, while the temperature rise affected zone of wheel is mainly distributed in the 2.5 mm depth range of wheel contact surface. The friction temperature rise with variable friction coefficient is 57% lower than that of using constant friction coefficient. The maximum equivalent stress of the rail and wheel near contact patch occurs on the subsurface of wheel and rail. The influence scope of equivalent stress with variable friction coefficient is slightly smaller than that with constant friction coefficient. The effect of wheel-rail relative sliding speed on the temperature and equivalent stress near wheel contact surface is not obvious, but the effect on the temperature and equivalent stress of rail contact surface is significant. The higher is the relative sliding speed, the higher temperature of rail contact surface will be.