Modeling Research On The Grinding Process Of Rail Grinding Vehicle

Because of the accumulated rail-wheel rolling efforts from the frequent running of railway trains, rails generate corrugations and fatigues which will lower the riding quality and even threaten the running safety. The online grinding maintenance is an effective way which is carried out by rail grinding vehicle. Due to the lack of grinding experiences and mechanism research, the grinding efficiency and quality cannot be guaranteed which even causes the excessive grinding to damage the rail and brings along serious accidents. The rapid expansion of railway transportation makes this problem more and more prominent. Therefore, this thesis builds a theoretical model for the relationship between grinding capabilities and the technological parameters for the rail grinding vehicle by taking the features of operating process and the rail grinding mechanism into consideration. Based on this model, the technological rules of rail grinding can be investigated to be as the theoretical supports for the research and development of the rail grinding operations and the rail grinding equipments.The explicit relationships between the grinding parameters and the rail profile changes are the important bases for exploring rail grinding mechanism. Therefore, spatial geometrical model between the grinding stone and the rail is firstly built by taking the rail grinding forms. Then the rules of changing stone angles and grinding depths can be analyzed by comparing differences between the rail profiles of the pre-and pro-grinding, transversal area and grinding facet lengths. Secondly, the grinding effects are analyzed with several stones arranged into the grinding pattern in which the sequences of stones in the pattern are also noticed. Eventually, the rail grinding patterns can be determined as follows:the grinding positions, tilting angles and the grinding depths are determined for the grinding stones sequentially based on the number of stones and the differences between the aimed profile and the current profile.Although the geometrical relationship between the grinding stone and the rail profile as above can be used to get the general rules and determine the pattern-setting, it is still necessary to get close to the real grinding process by considering the grinding performances of grinding stones. Unlike the grinding processing of ordinary machine tools, the rail grinding stones need to keep their continued grinding capabilities as stable as possible by self-sharpening. And such stability relies on the stabilities of grain distributions on the grinding layers and the stabilities of cutting behaviors of grains.Therefore, it is necessary to construct a grinding stone model which provides stable grinding surfaces as to accomplish the description of grinding process. In detail, by taking the sectional-area sums of grains which belongs to different grinding layers as the stability criteria, the spatial distribution model of equal-distance sphere grains are shook by thousands of times to the stable state model with lowest differences among different layers. The grinding surface can be obtained by choosing a representative slice to reach stochastic steady-state. Meanwhile, the surficial grains are transformed to the grains with random size and angle according to the requirements of cutting edges for grinding. In this way, the surface topography of grinding stone is formed and ready for the research of grinding process.Therefore, the simulation of the grinding surface as above is the foundation of the rail grinding process. Several main factors such as contact length, cutting speed and cutting tracks can be obtained based on the cutting mechanism of grains and the running environments of rail grinding vehicle. Furthermore, the geometry and the force models for cutting grains can be used to get the three-dimensional rail surface after grinding. Then the relationships between the grain cutting depths and the setting powers can be calculated with overall cutting grains involved. Then a verification test for such relationship is carried out by using of the rail grinding test rig, including the tests of the relationship between the setting power and the grinding depths for single stone, and the results caused by sequence grinding of multi-stones.Since the rail grinding is carried out on the running condition of the rail grinding vehicle, the dynamic features of railway vehicle running behavior will affect the grinding contacts between the grinding stone and the rail. Such influences can change the grinding positions or grinding depths of the grinding stone, which further change the grinding results. As such, a vertical dynamic model is firstly built which can analyze the vertical influences caused by the vertical running behaviors of the rail grinding vehicle.Subsequently, a three-dimensional model of rail grinding vehicle is built to analyze the lateral displacements of wheelsets. Then the lateral and vertical infulences on the grinding stone caused by the lateral displacements are analyzed. To get closer to the actual grinding conditions, the impacts from the dynamic running behavior to the grinding performances of the grinding stone are ultimately obtained and then used to modify the grinding behavior of the grinding stones.