Research On Temperature Field And Thermal-mechanical Stress Of Rail In Rail Grinding Process

With the increase of operating length and transportation density of railway,the surface damage becomes one of main damage forms of rail.The rail grinding can effectively repair the damage of rail surface.However,unreasonable grinding parameters may lead to high temperature on the rail head,which leads to rail bluing and even rail burns.Meanwhile,the thermal stress caused by high temperature will further increase the surface fatigue damage of rail.Thus,it is significant to explore the influence of grinding parameters on the temperature of grinding rail and the distribution of thermal stress,which can guide the parameter settings in the process of rail grinding.The method of moving heat source was applied and the grinding wheels were simplified as a moving heat source on the rail.Combined the classical theory of heat transfer and the process of rail grinding,this study established a heat transfer model of rail grinding.Based on the finite element theory,the numerical solution was carried out to analyze the heat transfer process.At the same time,a three-dimensional finite element model was established to explore the effect of grinding parameters on the temperature field of grinding rail using ABAQUS.According to actual condition,the pre-grinding and reparative grinding were simulated.Finally,the study explored the relationship between the grinding parameters and thermal stress and mechanical stress.The main conclusions are drawn as follows.(1)The lower power of grinding motor,wider grinding surface width,faster moving velocity,lower rotate speed of grinding stone and smaller feed depth can help to decrease the grinding temperature of rail.The distribution of temperature field is like an ellipse where the higher temperature is near the center and the lower temperature locates around the edge.As the temperature increases first and then decrease with the particle size of grinding stone increasing.Therefore,appropriate particle size of grinding stone must be used for controlling the grinding temperature.(2)The highest temperature of grinding rail dose not continue to rise when the whole grinding train grinds the rail.The highest temperature of grinding rail continues to rise when the first car passes the rail,but no longer rises when the second car passes through.The temperature of pre-grinding mode is higher than that of reparative grinding.Compared with the condition that two grinding stones act on the same surface,two grinding stones distributing on the adjacent surfaces can help to lower the grinding temperature.(3)The mises stress caused by the grinding stone decreases with an increase in rotational speed and increases with the grinding pressure increasing.The maximal stress distributes on the edge of the contact zone.The thermal stress increases with the increase of the temperature in the rail grinding process.The distribution of thermal stress is similar to the distribution of the grinding temperature,which presents an ellipse.The bigger stress is near the center of high temperature zone.The maximum principal stress distributes along the moving direction of grinding train.(4)The thermal stress is a thousand times bigger than the mechanical stress.Thus,controlling the grinding temperature is an only effective way to reduce the rail grinding stress.