OBRABOTKAMETALLOV TECHNOLOGY Vol. 24 No. 3 2022 applicability. Also the technology of passive grinding of rails is relatively new and is characterized by a small amount of research in this area, and as a result, a limited number of publications, which is confi rmed in the works. Thus, purpose of the studies presented in this paper was to conduct a comparative theoretical analysis of the two methods passive grinding of rails using the HSG and STU methods from the standpoint of the effectiveness of its application in the machining of rails. Theoretical research The effi ciency of the rail grinding process is determined, fi rst of all, by the productivity of the machining process, which in turn is determined by the speed of linear motion of the abrasive tool (the speed of the rail grinding train) and the removal of metal from the surface of the rail. In order to compare the two grinding methods, it is assumed that two grinding trains travel at the same speed. Then the key parameter for assessing effectiveness will be the removal of metal during processing. Here metal removal implies an analogue of the processing allowance, which differs in that, due to the lack of rigidity of the technological system, the amount of metal layer to be removed is determined not by the adjusting size of the technological equipment but by the force of pressing the grinding wheel to the rail [17]. Based on the theory of single grit cutting [18–20], the metal layer to be removed during grinding is determined by the depth of the scratch marks formed by the abrasive grit and by its quantity. In turn, the depth of the scratch marks is determined by the pressing force of the grinding wheel to the surface being processed, and its number is determined by the speed of rotation of the grinding wheel. Thus, the potential productivity of the “passive” grinding methods will be determined by the increasing speed of rotation of a grinding wheel and its torque. Together, these two parameters determine the possible cutting power. In view of the foregoing, in order to determine productivity, a kinematic and force analysis of the two grinding methods was carried out. The following assumptions were made: 1. During the analysis, idealized conditions for the interaction of the grinding wheel with the rail were taken. 2. The movement of the grinding train transmits a force to the grinding wheel through the rail. That is, the impact of the rail on the grinding wheel is considered. 3. The interaction of the grinding wheel with the rail at the point of contact on its periphery is analyzed. At this point, there is a force effect from the movement of the grinding train. 4. The metal cutting coeffi cient is taken as the coeffi cient of friction. The analysis does not take into account the area of interaction of the grinding wheel with the rail. a b Fig. 6. Passive grinding method by STU: a – grinding schematic diagram of; b – formation of eccentricity diagram
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