| Metro rail transit gains its popularity for its advantages of high efficiency,punctuality,environmental friendliness and less land occupation.Due to the constraints of urban planning and development,the proportion of sharp curves in metro lines is often large.It leads to a larger wheelset lateral displacement and attack angle when vehicles negotiate a sharp curve,which will aggravate the wheel flange wear and rail side wear,thus shorten the service life of wheel and rail and increase the cost of operation and maintenance.Reasonable wheel-rail matching can not only ensure sufficient running stability and curve negotiation performance,but also ensure uniform wheel-rail contact point distribution and lower contact stress,avoiding the inhomogeneous wear and fatigue damage at wheel-rail interface.Therefore,wheel/rail profile optimization is one of the effective means to improve wheel-rail matching relationship and reduce wheel flange and rail side wear.In view of the serious wheel flange wear of a B-type metro vehicle in China,this dissertation makes a detailed analysis of the causes by means of field investigation and numerical simulation,and optimizes the wheel profile based on the rolling radius difference.The new wheel profile is then verified through numerical simulation.The main work and conclusions are as follows:(1)The domestic and foreign researches on wheel flange wear and wheel/rail profile optimization are reviewed and summarized.The significance of wheel profile optimization for reducing wheel flange wear is clarified,and the entry point,means and technical route of this dissertation are proposed.(2)The wheel and rail wear of a certain B-type metro is measured on site.Investigations and analysis are made on wheel flange wear,rail side wear and rail cant,etc.It is found that serious wheel flange wear occurs at the initial stage of the metro train operation.There is also obvious rail side wear on the gauge corner of outer rail in sharp curves.(3)The causes of flange wear on investigated metro wheels are analyzed in detail,based on wheel-rail contact characteristics,vehicle dynamics performance and wheel wear prediction.The results show that the main reason for wheel flange wear is the improper matching of wheel and rail.The insufficient rolling radius difference at a larger wheelset displacement leads to the poor curve negotiation performance.The larger rail cant and the large proportion of sharp curves also contribute to the wheel flange wear.(4)Combining the wheel-rail contact geometry algorithm and Complex algorithm,an optimization method of reverse solution for wheel profile based on rolling radius difference is established.The corresponding MATLAB numerical program is compiled.The numerical results show that the optimized profile is superior to the original S1002 profile adopted by the metro vehicles in wheel-rail contact geometry,static mechanical characteristics,running stability,curve negotiation performance and wheel wear evolution characteristics at 1/20 and 1/40 rail cant.The flange thickness loss can be reduced by 78.9% at 100,000 km running distance,which means it can reduce wheel flange wear effectively. |
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