Study On Dynamic Characteristics Of Rubber Spring

The rubber damper material is widely used in the railway vehicles for its good isolation performance. As is known to all, the rubber damper material has serious nonlinear dynamic characteristics, while the existing dynamic softwares treat the rubber components as the linear isolators, which will bring a certain degree of limitation to the dynamic simulation of the railway vehicles. Besides, the dynamic characteristics of rubber material are affected by the temperature, and most of the existing models haven’t considered this factor. Therefore a new nonlinear model that can reflect the effect of the exciting frequency, the exciting amplitude and the ambient temperature is needed.The widely used mechanical model can improve the accuracy of the dynamic characteristics fitting, however, which is based on the cost of more complex forms, and it’s usually more difficult to solve. Moreover, the mechanical model can’t describe the dynamic characteristics over the broad frequency area, and it can’t reflect the effect to the mechanical characteristics of the exciting amplitude.To describe the rubber viscoelastic modulus over the broad frequency area with less parameters, the double-fractional derivative model is built, which can describe asymmetry around the loss modulus peak and the loss factor peak. Based on the polymer thermodynamics, the temperature-frequency conversion factors are introduced by the Time-Temperature Superposition, and then the complex themo-viscoelastic model is set up. On the other side, the Berg friction unit is introduced to describe the effect of the exciting amplitude. Finally a new nonlinear model (TPLN model) is put forward by paralleling the complex themo- viscoelastic model and the Berg friction unit.The experiments of the rubber mat of axle box are carried out to test and verify the TPLN model, and the experiments include the vertical static mechanical characteristic test, the vertical dynamic mechanical characterstic test and the dynamic mechanical thermal analysis (DMTA) test. By fitting the parameters of the Kelvin model, the Maxwell model, the Zener model and the TPLN model with the test data, the contrast result shows that the traditional models can’t describe the effect of the exciting frequency, the exciting amplitude and the temperature, while the TPLN model can describe the mechanical characteristic accurately within the engineering application error scope, and the TPLN model can also forecast the high frequency characteristic very well.In order to study the isolation performance of the rubber isolator, the single-degree-of-freedom vibration isolation system of four models mentioned before are set up. A series of sinusoidal excitation are loaded on the bottom, and the Runge-Kutta numerical integration method is used to solve the isolation systems of traditional model, while the Newmark-β numerical integration method is used to solve the isolation system of the TPLN model. The result shows that the vibration transmitting rate and the vibration acceleration differ greatly between the traditional models and the TPLN model, which means that building the accurate nonlinear model of rubber material is very important to the simulating of the vibration isolation. What’s more, the effect of the exciting amplitude can be reflected by the TPLN model, while the other conventional model can’t deal with it.