| With the high-speed development of the railway vehicles in recent years, in order to meet the design requirements of the vertical large deflection, horizontal small stiffness and vibration isolation, more and more new locomotives adopt flexicoil spring as the secondary suspension. In flexicoil spring mixed system, rubber pads become the key to reduce the lateral stiffness with its hyperelasticity and large deformation.As each stiffness of the secondary suspension is key factor that affect the locomotive vehicle dynamic performance, so it’s important to get the accurate stiffness. At present, it is mainly used the method of experience formula and test method to analyze the stiffness of the flexicoil spring with rubber pads mixed system in in domestic and foreign.However, formula method is linear estimation, the resulting stiffness values can’t respond the stiffness character of the rubber pads in the operation of the vehicle, and it is more difficulty for representing the nonlinear character of the mixed system; Test method, though reliable, but it can’t be put into effect when the rolling stock is in the design stage. With the constant improvement of the nonlinear computational simulation, it becomes possible to analyze the locomotive secondary suspension by the method of nonlinear FEM. Using the nonlinear finite element method to analyze each stiffness of the flexicoil spring mixed system could be more realistic to simulate the actual situation. Therefore, rubber pads and flexicoil spring are analyzed with the nonlinear method based on Abaqus nonlinear finite element software, and then compare it with the results of experience formula and quasi-linear, these work are done in the paper:(1) In order to obtain the reasonable parameters of the Mooney-Rivlin constitutive relation, the axisymmetric finite element model of rubber bearing is established, and by analyzing the axial stiffness with different coefficient values, the parameter of the Mooney-Rivlin constitutive model is C2/C1=0.25.(2) The nonlinear finite element model of the rubber spring is established based on Mooney-Rivlin constitutive relation, and the vertical stiffness, lateral stiffness and bending stiffness are analyzed. Among them, the axial stiffness and bending stiffness increases with the increase of displacement, and the curves show strong nonlinear; The lateral stiffness decreases gradually and shows weakly nonlinear. Compare with the results of the formula method and quasi-linear finite element method, the maximum error of the axial stiffness up to50%, the maximum error of the lateral stiffness is only4%。(3) A complete flexicoil spring with rubber pads mixed system FEM is established, and the nonlinear stiffness of the axial and lateral direction of the mixed system is analyzed, the axial stiffness is568.5～571.1N/mm, the lateral stiffness is154.5-133.2N/mm. The influence of the rubber pads on each stiffness and stress of the flexicoil spring is studied further, the results show that rubber pads have little influence to the axial stiffness of the mixed system, and decrease the lateral stiffness obviously; The rubber pads can reduce the normal stress7%and shear stress9%.(4) The paper also calculate the axial stiffness and lateral stiffness of the flexi coil spring mixed system by both the formula method and quasi-linear FEM. Compare with the analysis results of the nonlinear FEM, the calculation error of the axial stiffness by formula method is about11%, but it is just less than1.6%by the quasi-linear FEM. Respectively, the lateral stiffness has a calculation error of20.2%and19.5%by the formula method and quasi-linear FEM. Therefore, the nonlinear FEM is more accurate and reliable to calculate the stiffness of the flexi coil spring mixed system, especially the lateral stiffness. |
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