Effects Of Grinding Rotational Speed On Grinding Behaviors In Rail Grinding Based On Virtual Grinding Wheel Modeling

Rail grinding is a surface grinding material removal process by means of grinding wheel,and the interaction mechanism between the rail and grinding wheel is very complicated.Therefore,the studying on the material removal behaviors in the rail grinding process contributes to the selection of reasonable grinding parameters and grinding patterns,which improves the efficiency of grinding operations and the quality of grinding surface.In this study,a single grain grinding simulation model was established and single grain grinding process was simulated by means of smooth particle hydrodynamics method.According to the measurement results of real grinding wheel morphology,a virtual grinding wheel was built based on a virtual lattice method,which the abrasive grains are randomly distributed and height is normally distributed.Furthermore,a 3D finite element simulation model of rail grinding was established.The influence of different grinding parameters on grinding force,grinding removal amount,surface roughness,and surface morphology were simulated and explored.The rail grinding experiments were carried out using a rail grinding friction testing apparatus.By the comparison of simulation results and experiment results,the correctness of simulation model was verified.According to the wear forms,the process of fracture and rubbing of abrasive grains were simulated.The main conclusions are as follows:(1)When a single grain with different geometries grinds,the pyramidal grain gets the optimal grinding effect by means of analyzing the change of the cutting force and the deformation of the workpiece.The cutting force increases with an increase of cutting depth.The cutting force ratio decreases with the rake angle increasing when the abrasive grain with different rake angles is used.The simulation results have a good agreement with the theoretical value.The grinding debris after grinding is serrate,and the serration of the grinding debris is more obvious with the decrease of rake angle.(2)When the grinding rotational speed increases,the grinding force slightly decreases and the grinding removal amount obviously increases.The surface roughness decreases with the grinding rotational speed increasing,but increases with the grinding depth increasing.The grinding surface exhibits many ploughings and regional material uplifts.With an increase of grinding rotational speed,the ploughing phenomenon became slightly and the rail surface became smoothly.The simulation results are consistent with the experimental results,which verify the feasibility of simulating model for calculating the materials removal of rail grinding.(3)The fracture of abrasive grains is due to the contact stress being greater than the ultimate strength of the abrasive material.The crack appears when the contact stress increases to a certain extent.Then,the crack begins to expand and the contact stress fluctuates when the cracks of two dangerous zone expand.Finally,the contact stress gradually reduces at the later stage of crack growth.When the grain is rubbing,the material at the top of the grain falls off in the form of particles,and the grain top forms the worn flat.With the grinding speed and grinding depth increasing,the wear mass increases.The influence of grinding depth on the wear mass is more significant.