Study On Rail Grinding Profile For Small Radius Curved Track Of Metro Line

The construction and fast development of urban metro is playing a more and more important role in solving the problem of traffic jams.There are quite plenty of small radius curves in urban metro lines because of the limit by the geographical condition.The working conditions of small radius curves are more complex and special.When the metro vehicles running through the small radius curves,the wheel-sets attack angle gets bigger,the lateral force between wheel and rail increases a lot,the wear between the wheel flange and the rail side becomes more serious.What's more,the rail corrugations?oblique cracks and rail stripping are easier to arise and develop into a serious extent.So the application and maintenance of the rail on small radius curves are facing the most severe challenge.Whether the rail profile complies well with the wheel profile affects the wheel-rail contact geometry and contact mechanics characteristics directly,and then further decides metro vehicles' curve passage capacity.So one of the effective methods for improving the wheel-rail dynamic interaction on small radius curves is to carry out the research on optimal design of wheel-rail profiles.Nowadays,rail grinding is the primary way to realize the trims of rail profile.Reasonable optimization and design for the object grinding profile on small radius curves can effectively improve the wheel-rail matching performance.This paper puts forward an optimum design method for rail grinding profiles.Setting the objective wheel-set's rolling radius difference(RRD)as the optimization target,the method for designing the rail grinding profile is established based on the algorithm of wheel-rail contact relationship,the method for interpolating and fitting the rail profile by third NURBS and the complex method algorithm.And the corresponding MATLAB computation program is compiled.With reference to solving the problem of the lack of curve passage capacity,the severe wheel-rail dynamic interaction and serious wear of wheel and rail on small radius curves,the established method mentioned above is used to optimize the standard 60 kg/m rail and the worn-type rail profile.The comparative analysis of the contact geometry and contact mechanics characteristics before and after the design is carried out.The method established by this article provides a theoretical guidance towards the rail pre-grinding and the worn-type surface's repaired grinding on small radius curves of metro lines.It has significant engineer application values on the prevention of rail surface's abnormal wear and prolonging the rail replacement cycle.This paper's main work and conclusions are as follows:(1)First of all,this article describes the domestic and abroad researching status of wheel and rail profile optimization theories and methods.And then the rail grinding technology is summarized in detail.According to the research status quo,the researching idea,approach and technical route are put forward at last.(2)An optimum design method of rail grinding profile on small radius curves which sets wheel-sets' rolling radius difference(RRD)as the optimization goal is established.Based on the geometry characteristics of NURBS(Non-Uniform Rational B-Splines)and the De Boor algorithm for NURBS curve interpolation calculation,the cubic NURBS method for describing the rail profile is established.Based on the wheel-rail contact geometry relationship algorithm and complex method for solving nonlinear constraint optimization problem,the mathematic model of rail grinding profile's optimum design is established,then the corresponding MATLAB computation program is compiled.(3)The B-type vehicles' system dynamic model is built based on the multi-body dynamics software SIMPACK.The model can be used to simulate and analyze the vehicles' curve passage capacity before and after the rail is grinded.The indexes to assess the metro vehicles' curve passage dynamic performances includes the derailment coefficient,the rate of wheel load reduction,the wheel-sets lateral movement,the wheel-rail lateral force,the wheel-sets attack angle and the wheel-rail wear number,et al.(4)Using the optimum design method respectively to conduct the profile design for pre-grinding of the small radius curves' standard 60 kg/m rail and the corrective polishing of wear type rail.The results show that the optimized rail pre-grinding profile can slightly improve the contact status including wheel-rail contact geometry and mechanics characteristics and enhance metro vehicles' curve passage capacity,which conform with the goal of rail's pre-grinding.The designed target profile for corrective polishing of wear rail can significantly improve wheel-rail contact geometry and mechanics characteristics and enhance metro vehicles' curve passage capacity which has great significance for prolonging the rail's span life and improving the dynamic performances of vehicles on small radius curves.