Analysis Of Dynamic Properties Of Rubber Side Bearing In Locomotive And Its Influences

Rubber elastic components are widely used in locomotive suspension due to viscoelastic characteristics,high load carrying capacity and maintenance-free characteristics.Rubber-metal laminated components are used in secondary suspensions of most freight locomotives as the elastic support,which is called rubber side bearing.In the suspension design of freight locomotives,the static deflection of the rubber side bearing is very small,which is usually matched with primary suspensions of large static deflection,so that the locomotive can not only have good adaptability to line irregularities,but also have the advantage of small axle load transfer.The three-way stiffness and viscoelastic characteristics of the side bearing make the design of secondary suspensions simplified.However,the static deflection of the rubber side bearing is too small,it has a negative impact on the vertical and horizontal stability of the locomotive.Therefore,some locomotives have increased the static deflection of the secondary suspensions.In addition,the rubber elastic components also has elastoplasticity,the vibration amplitude and frequency have a certain effect on the mechanical properties of the rubber side bearing,so it is of great significance to study the dynamic characteristics and dynamic effects of the rubber side bearing under complex excitation.The main research contents are:(1)The static and dynamic characteristics of rubber are introduced.The superelasticity of rubber based on static characteristics are discussed.The phenomenological model based on strain energy density function and the hyperelastic model based on statistical model of molecular chain network are discussed.The viscoelasticity and elastoplasticity of rubber based on dynamic characteristics are discussed.The frequency-dependent viscoelastic constitutive model and the amplitude-dependent elastoplastic constitutive model are discussed.The theoretical basis of selecting a suitable constitutive model for rubber finite element simulation is provided.(2)A constitutive model is select and a model parameter identification method is proposed.The model parameters is obtained by NR65 rubber material shear experiments.Based on this,A rubber material model is established in finite element software ANSYS and the accuracy of the parameters verified by shear simulation.Then the superimposed finite element model of the side bearing is established and the dynamic stiffness of the rubber side bearing is calculated with different amplitudes and frequencies.(3)A method of superposition force elements is proposed in SIMPACK.A superposition force element capable of describing amplitude and frequency dependence is established.And the parameter fitting method of rubber side bearing superimposed force element are given.In the fitting method,the parameters are identified by the dynamic stiffness of the rubber side bearing with different amplitudes and frequencies.(4)Taking a diesel locomotive as the research object,the traditional dynamic model without considering the dynamic characteristics and the variable stiffness dynamic model with the dynamic characteristics of the rubber side bearing are established respectively.The nonlinear critical velocity,lateral wheelset force,vertical wheel rail force and derailment coefficient,etc of the vehicle in the two models are compared and analyzed.The impact of the dynamic characteristics of the rubber side bearing on the dynamic performance of the locomotive is analyzed in detail.Through simulation analysis,the following main conclusions are obtained:(1)The superposition constitutive model where the generalized Maxwell viscoelastic model is used to represent viscoelasticity and multiple hysteresis models are used to represent elastoplastic can better fit the frequency dependence and amplitude dependence of rubber materials.The parameters of the superposition constitutive model obtained through the damping modulus identification method can be used in finite element software.(2)The superposition model finite element method is a modeling method by superimposing multiple finite element models and ensuring that multiple nodes of the finite element model are shared and that the elements are not shared.The rubber finite element model established by the superposed constitutive model parameters have high accuracy.(3)A method of superposition force elements is proposed in SIMPACK.Force elements 102 and 205 are superimposed to establish a superposition force element capable of describing amplitude and frequency dependence.The parameter fitting method of rubber side bearing superimposed force element have high accuracy.When fitting the transfer function of force element 102,the MATLAB toolbox has a better fitting effect.(4)When the vehicle is in a straight section,the longitudinal dynamic stiffness of the rubber side bearing of the variable stiffness model increases,while the lateral dynamic stiffness of the rubber side bearing decreases significantly.When the vehicle is in a curved section,the longitudinal and lateral dynamic stiffness of the rubber side bearing decreases significantly.The amplitude dependence of the rubber side bearing has a greater impact on the stiffness.(5)In straight line conditions,the lateral stability of the variable stiffness model is better than that of the traditional model.In curve conditions,lateral wheelset force,vertical wheel rail force and derailment coefficient of the variable stiffness model are smaller than those of the traditional model.These are caused by the reduction of longitudinal and transverse dynamic stiffness,indicating that the amplitude dependence of the rubber side bearing has a greater impact on the dynamic performance of the locomotive.The dynamic performance of the variable stiffness model is better than the traditional model.