| In recent years,the speed and traffic volume of freight railway trains have been increasing year by year.As a key component,the heavy-haul wheels are more and more prone to various injuries such as tread wear and depression,rolling contact fatigue,surface abrasion and peeling,which need to be repaired by re-profiling.The selection of wheel repair parameters is in the stage of workers processing experience,and there is only one testing item about the surface integrity of wheel repair,while the surface integrity of wheel-rail machining directly affects the wheel-rail matching performance.In order to prolong the service life of freight line wheel and rail,improve the service performance of wheel and rail and provide the theory basis of re-profiling parameters,a kind of heavy-haul wheel material was chosen as the research object.Based on actual re-profiling condition of wheel,the experimental research on cutting performance and rolling contact wear of wheel material was carry out.The main tasks completed are as follows:(1)D840 heavy-haul wheel material which is widely used in freight railways is chosen as the research object.Based mechanical and physical performance test experiments,master the performance parameters of D840 wheel materials.On the basis of wheel material performance,select suitable turning tool combining with heavy duty wheel turning parameters,tool material and geometric parameters for the design of ordinary CNC lathe tool rod.(2)According to the actual re-profiling parameters of heavy-haul wheel,an experimental study was carried out on cutting force and cutting temperature of D840 wheels on a CNC lathe.The experimental results show that cutting force of D840 wheel material decreases with the increase of cutting speed,and increases with the increase of cutting depth and feed.The cutting tool temperature increases obviously with the increase of cutting speed,and the feed and cutting depth have less effect on the cutting tool temperature.(3)Experiment research on surface integrity of D840 wheel material was carried out to analyze the influence of cutting parameters on surface integrity after turning.The experimental results show that surface roughness,surface hardness,plastic deformation depth and surface residual compressive stress decrease with the increase of cutting speed,and increase with the increase of feed and cutting depth.Surface residual stress is compressive stress under different cutting parameters.When plastic deformation occurs on the surface of wheel material,the space between the pearlite laminates decreases.Thus the surface material strength and hardness increase.(4)The rolling contact wear experiment of D840 wheel and U71 Mn rail material after machining was carried out to analyze the influence of surface integrity on the friction and wear performance of wheel-rail material.The experimental results show that the friction coefficient increases with the increase of wheel-rail material surface roughness.Surface roughness and surface hardness after wheel material turning have comprehensive influence on the wear volume,surface wear morphology,plastic deformation layer and hardness of wheel-rail material.Increasing the wheel material surface roughness and surface hardness materials appropriately can improve the wheel and rail friction and wear performance. |
