Mechanism Research Of Dry Grinding Of Railway Steel Under High Moving Speeds

The operation of railway vehicles under high speeds and heavy loads escalates the wear of rails, which has crucial effects on the safety and stability of the running vehicles and also the service life of rails. Regular repair operation on the rails is needed to ensure the normal service of rail, by removing various types of wear and fatigue related damages on the rails surfaces. Rail repairing operation is an important procedure to guarantee the safety and stability of railway systems, ensuring the normal functioning of the equipments and extending the service life of the whole system. In recent years, rail milling and grinding vehicle has become the main equipment for repairing and maintaining the rails. The grinding device on the vehicle is one of the key components, which directly determines the results of repair and maintenance operation. The rail milling and grinding system and also the grinding wheels are mainly imported from abroad, and not much research work on rail grinding technology has been conducted.In this thesis, experimental program has been developed and grinding wheels have been selected according to the operating conditions of the rail milling and grinding; The effects of grinding wheels and process parameters on grinding force, grinding temperature, specific grinding energy, surface roughness, surface appearance and surface residual stress, have been investigate. The main research includes:1) Grinding wheels were developed and custom-made, based on the investigation on the chemical and mechanical properties of grinding wheels currently used for rail grinding and also the rail material. The grinding ability, abrasive resistance and blockage of different grinding wheels were studied to choose the suitable for rail grinding.2) Considering the working parameters of rail milling and grinding train, process parameters were selected to conduct experiments with the selected wheels. Tests were carried out to further analyze the variation of grinding force, grinding temperature with the grinding parameters, and the effects of maximum undeformed chip thickness on grinding force and specific grinding energy. The forming mechanism of wear debris were analyzed. The experimental results show that, with the increase of grinding depth, the grinding forces and grinding temperature rise; with the increase of table speed, the grinding forces rise but the grinding temperature doesn ’t change significantly.3) By observing the morphological features of grinding surfaces and measuring the surface roughness and surface residual stress, the variation of th ese variables with the grinding parameters have been analysed. The grinding quality under different grinding parameters has been compared, which provide evidence for the selection of suitable grinding wheels and grinding parameters for rail grinding operation. The results show that, the chosen grinding wheels can meet the need of surface roughness requirement and the key influential factor on the ground surface roughness is the grit size of the abrasives. The residual stress status on the workpiece surface changes from compressive to tensile stress after grinding. Comprehensive understanding for the variation of grinding force, grinding temperature, surface residual stress and surface topography, is necessary, when setting the operating parameters for rail grinding.