Investigation Of Wheel-Rail Interface By Ultrasonic Wave

The relationship of the wheel-rail contact is a foundamental research topic in railway transportation, which has a significant impact on traveling safety and stability. With the development of high-speed and heavy-haul trains, the research on wheel-rail interface status has the important role in the high-quality wheel-rail contact, such as media, roughness, contact pressure, etc.When locomotive and carriage are running, track conditions and the relative positions of wheel and track are always changing. A non-ideal boundary model between two solids was proposed, in order to achieve real-time monitoring of the wheel-rail contact status. The research is based on Physics, Wave Dynamic and Friction fractal theory. The simulation of the wheel-rail contact states by COMSOL Multiphysic provides the experimental feasibility.Firstly, three surface topography models such as perfect contact, partial contact and completed separation are established, based on the W-M function. Realistic boundary conditions were set to evaluate the wheel-rail contac tstates by ultrasonic longitudinal wave.Secondly, the investigation of interface roughness indicates reflective wave amplitude decreasing with h/λwaterdecrease, if frequency was the same.It can be used to distinguish layer media at the same proportion of contact. When the medium is water, the scale coefficient of the same fractal dimension is related to the fractal dimension by the appropriate ultrasonic frequency. While the medium is air, they are not related.Finally, the actual wheel-rail interface model was established, based on the experimental results by Knothe.D=1.622and G=6.0144x10-8m were calculated. The contact pressure monitored has increased with drifting frequency. Based on the acousto-elasticity theory, the effect of acoustic impedance on acoustic reflection becomes less significant as contact pressure increased. The research also explored the distribution of acoustic reflection pressure with the frequency at the different proportions of wheel-rail contours. The results show that wheel-rail contours model can be simplified when the frequency is greater than10MHz.