DISCRETE TIME TRANSFER MATRIX MODELING OF FlEXIBLE WHEELSET AND VERTICAL VIBRATION

For the dynamic simulation problems of elastic vibration and high-frequency exciting test for railway wheelset, the discrete time transfer matrix method is applied to establish the flexible wheelset vibrating model. The discrete time transfer matrixes of distributed mass elastic axle, lumped mass wheel and spring-damping element in wheelset are derived based on the Newmark- βintegration formula. Both the Riccati method and Newmark- βmethod are applied to solve the vertical vibrating accelerations, velocities and displacements of wheelset system. The wheelset dynamic model is then introduced into the bogie frame and rail roller submodels to form an integrated dynamic system, in which the latter submodels are solved by the new explicit integration method. The single-wheelset rolling and vibration dynamic model of railway vehicle is then completed. The solution flow of dynamic simulation in the mixed integral modes is presented subsequently. Based on the vibrating and rolling test rig, the high-speed running test within the speeds of 300 ~ 400 km/h is carried out in the conditions of surface initial roughness, grinded polygon and local depression for rail rollers. The corresponding dynamic simulation under the same running conditions is carried out simultaneously. Both the simulation and test results are compared in time-frequency domains to verify the theoretical model. Viewed from the perspective of time-frequency characteristics and amplitude distribution of vibration accelerations, the results indicate that, the flexible wheelset dynamics model can well reflect the medium-high frequency vibration rules for the system vibrations below the frequency of 500 Hz. The dynamic excitations such as wheel out of round, polygonal wear and local depression can be captured effectively. The amplitude errors of calculated axle-box accelerations under the above three roller surface conditions are lower than 9% in general. The model has good adaptability and precision. However, the application of relevant modeling methods in the complex spatial structures needs further exploration.