Dynamic characteristics of wheelset-track system under corrugation excitations in metro

There are few systematic researches on the dynamic characteristics of wheelset-track system under different corrugation excitations. In order to study the influence of different corrugations on the wheelset-track dynamic characteristics, a three-dimensional wheelset-track rolling contact model is established and the model rationality is analyzed. Then, the wavelength and wave depth of the initial corrugation irregularity for simulation analysis are determined according to the measured data. Finally, the wheel-rail vertical force and wheel vertical vibration acceleration are selected as the output variables, and the wheelset-track dynamic responses under excitations are studied. The results show that comparing with the middle/long wavelength irregularity, the short wavelength irregularity will not increase the amplitude of wheel-rail dynamic action, but will increase the frequency of wheel-rail dynamic action. The initial irregularity wave depth will not affect the frequency of wheel-rail dynamic action, but will affect the amplitude of wheel-rail dynamic action, and the greater the amplitude of the wave depth is, the greater the impact on the dynamic responses of wheelset-track system is. The main characteristic frequencies of output variables are close to the initial irregularity passing frequency, and the other peak frequencies are in a frequency multiplication relationship with the initial irregularity passing frequency.

Dynamic Response of a Rectangular Plate With Initial Imperfections Under Large In-Plane Forces

This paper presents an analysis of the response of an imperfect, finite, simply-supported, rectangular plate under an in-plane above-critical force applied during a short time at one of the edges in the direction perpendicular to the edge. The influence of the initial irregularities on the overall response during and after load application is analyzed. The results indicate that the frequency spectrum of free vibrations, after removal of the load, is controlled by the initial irregularity distribution, the plate geometry, and the load level.

Thermoelastic instabilities in the sliding of conforming solids

If two sliding solids are nominally in contact over a large area, the inevitable irregularities in the surfaces will cause the pressure distribution to be non-uniform. The generation of heat due to friction at the interface will also be non-uniform and the solids will be distorted by thermal expansion. The highest parts of the surface will carry the greatest pressure, reach the highest temperature and consequently expand more than the surroundings. Thus the thermal distortion tends to exaggerate the initial irregularity of the surface. The wear at the interface has the opposite effect, but under suitable conditions the process can be unstable. Experiments are described in which the effects of this instability are observed: the load is concentrated into a few small parts of the surface causing high local temperatures. After a few seconds, the load is transferred to a new part of the surface and, when the original contact area has returned to the temperature of the surroundings, it contracts leaving an observable depression in the surface. The scale of this process is large in comparison with the size of the surface asperities. An experimental model has been produced which demonstrates the characteristics of the instability in a simplified form. The thermal expansion drives the surfaces apart at the beginning of the cycle and this movement has been observed experimentally. An analysis of the instability is produced and a good correlation is obtained with experiment.