Research On Wear Mechanism And Characteristics Of Abrasive Belt Used For Rail Grinding

Rails are easy to suffer various rail surface defeats due to the variable load repeatedly applied by the train wheelset.The most effective way to clean such defeats is rail grinding.How to improve the grinding efficiency to solve the contradiction between short time and large amount of grinding work has become an important issue in the field of rail maintenance.In recent years,with the continuous development of abrasive belt manufacturing technology,an efficient rail grinding technology based on abrasive belt grinding is gradually applied to engineering with its advantages of high material removal efficiency,cold grinding,elastic contact.However,compared with the common grinding wheel,the abrasive belt only has single layer abrasive material,and the number of available abrasive is limited by the size of abrasive belt,resulting in low service life,which hinders the further development and application of rail abrasive belt grinding technology.Therefore,this paper took the wear of rail grinding abrasive belts as the research theme,and studied the wear mechanism and characteristics of rail grinding abrasive belt including the wear modes,critical conditions and wear mechanism,so as to scientifically formulate the grinding modes and process parameters,exploit the grinding ability of the abrasive belts,and realize the efficient engineering application of the abrasive belts in rail grinding.Firstly,according to the “efficiency first” maintenance characteristics and the macro material removal characteristics of abrasive belt under constant load grinding,the service life of abrasive belts under rail grinding condition was defined.Based on the service life of abrasive belts,the reasonable ground rail surface roughness was taken as the constraint condition to carry out the abrasive belts selection experiments.The whole service life of abrasive belt wear experiments was carried out,and three typical wear modes of abrasive belt,namely fracture,abrasion and pull-off,were found out under the condition of rail grinding.Then,the characteristics and wear mechanism of typical wear modes were explored.Based on the "abrasive belt embedding" method,the internal microstructure of different wear modes was studied.It was found that the layered structure in the abrasion grits,and the essential of the abrasion was the material peeling caused by paramorph transformation.In order to accurately evaluate the material consumption of abrasion grit,based on the wear rate,combined with hard conical grits grinding characteristics,a wear model of abrasion grit was established,followed by verification experiment.The stress around pores inside the grit was transformed into the stress of the internal elliptical pores of the brittle materials.The stress equation around the pores was established and solved to obtain the characteristics of the internal crack.Combining with the external crack development of the grit found based on Rankine criterion,the formation of the multi-peak structure after fracture was obtained.The stress model of the grit’s root was established,according to the static equilibrium condition,and the factors influencing the pull-off of the grit were revealed.Next,the occurrence condition of wear and the critical conditions of various wear modes were proposed.The 3D contact problem between the elastic contact wheel and the rail was transformed into a 2D plane problem between the elastic circle and the rigid circle,and the deformation of the contact wheel was solved.Combined with the geometric distance of the contact wheel,the deformation of contact wheel and the protrusion height of the grits,the critical condition of wear was established and verified by the finite element method.On this basis,the critical condition between fracture and abrasion was abstracted as the internal crack development of brittle material.The critical condition of crack development was corresponded to the critical condition of grits fracture and abrasion.The indentation test and high-speed friction tests were carried to verify the critical conditions of different wear modes under static and dynamic conditions respectively,and the wear mechanism diagrams were obtained with the wear volume in the experiments.Finally,the abrasive belt wear model was established and the wear characeteristics of abrasive belt were studied.Wear characterization parameters were abstracted from multi-grit system to quantify the wear of abrasive belt.Imitating the electrostatic grits planting process by applying random vibration method,the polyhedral grits were distributed evenly on the surface of the abrasive belt to achieve the virtual abrasive belt surface.What’s more,according to abrasive material loss caused by different wear modes and the transformation of different wear modes,the virtual abrasive belt surface was updated,and the abrasive belt wear model was obtained and verified.The wear characteristcs and wear process of abrasive belt was studied by applying the wear model.