扣件胶垫刚度的幅频变对轮轨耦合系统随机频响特征的影响

INFLUENCE OF AMPLITUDE-AND FREQUENCY-DEPENDENT STIFFNESS OF RAIL PADS ON THE FREQUENCY-DOMAIN RANDOM VIBRATION OF VEHICLE-TRACK COUPLED SYSTEM

以热塑性聚氨酯弹性体(TPEE)的扣件胶垫为研究对象,首先利用万能试验机测得其荷载-位移非线性曲线。然后,借助非线性静力分析的有限元模型,计算车辆静载与弹条扣压共同作用下该类扣件胶垫的位移幅值及其对应的静刚度。最后,运用车辆-轨道垂向耦合随机振动分析模型,探讨聚氨酯胶垫的常量刚度、频变刚度与幅频变刚度对车辆-轨道耦合系统随机振动频响特征的影响规律。研究结果表明:聚氨酯胶垫的静刚度具有显著的非线性特征,而且在20 k N扣压力与80 k N静轮载共同作用下聚氨酯胶垫的静刚度在19.1 k N/mm^37.9 k N/mm范围内变化,其均值与规范中假设的线性常量静刚度26.7 k N/mm相近;另外,与聚氨酯胶垫的幅频变刚度相比,它的常量刚度会严重低估轮轨系统65 Hz^150 Hz的频域响应。因此,如果车辆-轨道系统中有刚度非线性较强的高分子材料,就必须综合考虑这些材料刚度的幅变与频变特征,否则将难以准确预测轮轨系统及其周边环境振动的频域响应。

Taking the rail pads of the thermoplastic polyurethane elastomer（TPEE） for example, the nonlinear curves between the static loads of TPEE rail pads and their corresponding compressed deformation were plotted by a universal testing machine. A rail-fastener finite element model used for the nonlinear static analysis was established to calculate the compressed deformation of rail pads and their corresponding static stiffness under the static vehicle weight and the preload of the rail fastener. Finally, the vertical vehicle-track coupled model was applied to investigate the influence of the constant stiffness, the frequency-dependent stiffness, the amplitude-and frequency-dependent stiffness of TPEE rail pads on the frequency-domain random vibration responses of the vehicle-track coupled system. Results indicate that the static stiffness of TPEE rail pads nonlinearly increases with the increase of their compressed deformation, and the static stiffness of TPEE rail pads ranges from 19.1 k N/mm to 37.9 k N/mm under 1/8 vehicle weight of 80 k N and rail fastener＇ preloading of 20 k N, with an average approximately equivalent to the hypothetically linear constant stiffness of 26.7 k N/mm in the national standard. Additionally, compared with the amplitude-and frequency-dependent stiffness of TPEE rail pads, their hypothetically linear constant stiffness leads to a severe underestimate of the random vibration levels of wheel-track coupled system at frequencies of 65 Hz^150 Hz. Thus, only if there are polymer materials with strong nonlinear stiffness in the vehicle-track coupled system, it is necessary to comprehensively consider its amplitudeand frequency-dependent stiffness; otherwise, it is difficult to accurately predict the frequency-domain responses of both the wheel-track coupled vibrations and the train-induced environment vibrations.