Study On Static Contact Theory Of Rail Grinding Using Abrasive Belt Considering Various Factors

It is internationally recognized that rail grinding is by far the most frequently used and most effective railroad line maintenance technology,while with the extension of domestic railroad mileage,rail grinding is facing increasingly severe challenges.As a brand new technology of rail damage prevention and repair,rail grinding using abrasive belt is gradually applied by the advantages of grinding efficiency,grinding quality,safety,economy,eco-friendliness and so on.Being the core element of rail grinding using abrasive belt,the contact problem affects material removal,grinding temperature rise,residual stress,and acts as a direct determinant of grinding efficiency and quality.However,the current research simplifies the rail surface as a cylindrical surface to analyze the contact behavior between the grinding head system and the rail surface during grinding.Also,there is a lack of in-depth research on the influencing mechanism of contact wheel parameters,grinding process parameters and rail surface profile on contact behavior,which limits the engineering application of abrasive belt grinding technology in railroad line maintenance to some extent.Therefore,the author takes discontinuous curvature of rail head section profile arc,different contact wheel parameters and different grinding process parameters as well as other various factors into consideration in this thesis,and carrys out a deep study on the static contact theory of rail grinding using abrasive belt.The main research content of this thesis is as follows.Based on the geometric relationship,this thesis analyzes the contact behavior of contact wheel and rail surface in rail grinding using abrasive belt,constructs the coordinate system of rail grinding using abrasive belt,establishes the equation of rail profile and contact wheel profile under this coordinate system,and solves the mathematical analytic equation of both profiles so as to develop an accurate calculation method to determine the position of grinding contact point.The MATLAB program is also used to analyze the variation patterns of the grinding angle with the coordinates of rail surface.In addition,the contact stress problem for the case of discontinuous curvature of the rail head cross-section profile in rail grinding using abrasive belt was studied.The actual contact deformation between the contact wheel and the rail is replaced by the geometric interference of the two contours,and the rail section is sliced,for each slice the Hertz line contact theory is used to calculate its load and contact stress.A “slice model” is further constructed to calculate the contact patch size and the maximum contact stress at the transition point of the arc section with different radii of curvature in the contact area.Given the relevant parameters,the author carried out the calculation and analysis of specific cases and conducted tests on the contact problem between contact wheel and rail using the contact hydrostatic test bench to verify the accuracy and validity of above established theoretical model.Moreover,on the basis of finite element method and using ABAQUS CAE software,this thesis calculates and analyzes the effect of contact wheel parameters(contact wheel radius of curvature,rubber layer thickness ratio,rubber layer hardness),grinding process parameters(grinding force,grinding angle)and rail profile category(GB60/60 N and CRH3 profile)on the contact stress in the process of rail grinding using abrasive belt,and obtain the contact spot distribution map and contact parameter curve.Finally,a finite element model of point defects on rail surface is established to analyze the effects of pore and inclusions on the contact behavior during rail grinding using abrasive belt.