Research On Asymmetric Grinding Profile Of Rails In Sharp Curve Based On Freight Trains Dynamics

With the continuous development of rail transit in China,it is urgent to improve the transportation efficiency of freight trains to meet the increasing demand of freight.The capacity of the sharp curve of the trains is the key problem that affects freight trains transportation efficiency and ensures trains safety and speed.Rail grinding is a common line maintenance technology.Using rail grinding to repair the rail profile can remove the rail surface defects,so that the rail geometry profile can obtain good wheel-rail contact characteristics and trains dynamic performance.It is an effective measure to improve the curve capactity of trains,which has been paid much attention by many researchers.The target profile of rail grinding is the necessary premise of the entire grinding work,which directly affects the final grinding effect,and thus becomes the key to improve the curve capacity of the trains.This thesis studies the important issue of asymmetric grinding target profile design for sharp curve rails.The main research contents and results are as follows:(1)Based on the analysis of freight trains structure and its nonlinear system,the freight trains system dynamics model is established by the multi-body dynamics software Simpack.According to the speed-up requirements of freight trains,relevant trains dynamics performance evaluation indexes are given.The comparison of field test and simulation results verifies the correctness of the established dynamics model,which lays a foundation for the subsequent calculation of trains dynamics performance and the verification of the design effect of rail grinding target profile.(2)Based on the analysis of the principle of rail asymmetrical grinding and the geometric characteristics of rail profile of main railway lines in China,a design method for the target profile of rail asymmetrical grinding with sharp curve is proposed.In this method,by deriving the relations between the geometric parameters in the rail profile,the geometric parameters in the profile are used as design variables.The multiple objective function on both sharp curve trains dynamics performance and wheel/rail wear performance,combined with the characteristics of the rail grinding technology profile geometry set constraint conditions,established the sharp curve rail asymmetrical grinding target profile optimization model.An optimization model for the asymmetric grinding profile of rail on sharp curve is established,which is solved based on the differential evolution algorithm.This method is applicable for various steel rail profiles in China,and provides a simple and convenient way to improve the curve capacity of railway trains in small-and medium-radius curves.(3)The aforementioned asymmetric grinding profile design method of rails on sharp curve is applied to CN60 rail.Combined with field tests,reasonable design conditions are selected,and the target profile design for grinding on the sharp curve is carried out.The design results show that the method proposed in this thesis has the advantages of higher feasibility and better convergence of the algorithm,can obtain the ideal rail grinding target profile,and effectively improve the dynamic performance and wear performance of the trains when passing through the curve,and guarantee the wheel-rail contact stress is within the stability limit of the wheel-rail material,which meets the rail strength requirements.