| The complex and changing nature of metro lines,with a large proportion of small radius curves,leads to serious wheel-rail wear problems.The wheel-rail impact due to sudden changes in curvature in the transition section of gentle and circular curves can lead to differences in vehicle dynamic response and wheel-rail wear characteristics at different locations on the curve;at the same time,with the increase in wheel service mileage,wheel-rail contact characteristics change due to different degrees of wheel profile wear,which in turn affects vehicle operational performance.These factors complicate the strategy of controlling the friction coefficient at the wheel-rail interface,i.e.the friction coefficient at the wheel tread/rail top and wheel wheel flange/rail side contact areas becomes difficult.Therefore,the study of integrated friction coefficient optimisation at the wheel-rail interface at different positions of the curve on dynamic wheel profiles is of great significance for improving wheel-rail lubrication technology,reducing wheel-rail wear and improving vehicle dynamics.In this paper,according to the friction management problem of wheel-rail interface caused by different positions of small radius curve and dynamic wheel profile changes,the optimization method of integrated friction coefficient of metro small radius curve is studied.The vehicle-rail coupling dynamics model is established by the SIMPACK software,and six different positions are set for the small radius curve: straight line point,slow centre point 1,slow circle point,curved centre point,round slow point and slow centre point 2.A multi-objective optimization model based on the entropy-weighted TOPSIS method is established to study the optimal matching of the top/side friction coefficients at different locations and dynamic wheel profiles,which provides technical support for the refined lubrication control strategy for small-radius metro curves.The main content of this article is as follows:(1)Taking the different positions of curves as the entry point,a wheel-rail friction coefficient optimization method based on the different positions of curves is proposed.A simulation model of a B-type vehicle dynamics is established,and four radius curve working conditions,namely R300,R400,R500 and R600,are set up to analyse the corresponding changes in wheel-rail wear performance,rolling contact fatigue characteristics and curve safety at different positions of the curve when the friction coefficient is changed;a multi-objective optimization model is established by the entropy weight TOPSIS method,and the modified Elkins wear index,profile fatigue index and derailment coefficient are used as comprehensive performance evaluation indexes to optimize the friction coefficient at different positions of the curve.The multi-objective optimization model was established by the entropy weight TOPSIS method,and the modified Elkins wear index,profile fatigue index and derailment coefficient were used as comprehensive performance evaluation indexes to optimize the friction coefficients at different locations of the curve,so as to obtain the optimal friction coefficient interval and the dangerous friction coefficient range at different locations of the curve with different radii.The study shows that at R300 and R400 radii,the overall performance of the slow rounding and rounding points is poorer and the optimum friction coefficient range is narrower compared to other locations on the curve;as the radius of the curve increases,the overall performance of the slow rounding and rounding points improves and the optimum friction coefficient range tends to become wider.(2)The R300 curve is used as the research object,and a comprehensive friction coefficient evaluation method for the wheel-rail interface based on different positions of the curve is proposed.On the basis of the simulation model of metro dynamics,a wheel-rail interface integrated friction coefficient management model is introduced,63 matching conditions of top/sidewall friction coefficients are set,and the changes of wheel-rail wear performance,rolling contact fatigue characteristics and curve safety at different positions of the curve are analysed when the matching of top/sidewall friction coefficients changes;a multi-objective optimisation model is established by the entropy weight TOPSIS method,and the modified Elkins wear index,wheel pair punch angle,profile fatigue index and derailment coefficient are used as comprehensive performance evaluation indexes to optimize the wheel-rail interface friction coefficient at different locations of the curve,and to study the optimal top/side-rail friction coefficient matching strategies at different locations of small radius curves.The study shows that the optimum top/sidewall friction coefficients are different for different positions of the curve: 0.2/0.35 for gentle centre point 1,0.2/0.1 for gentle circle point,0.25/0.1 for curved centre point,0.2/0.2 for gentle circle point and 0.2/0.3for gentle centre point 2.(3)The wheel wear profile data of the two lines were measured at different operating mileage,and a comprehensive friction coefficient evaluation method based on the dynamic wheel profile was proposed for the wheel-rail interface.A simulation model of metro dynamics was established to analyse the wear performance,rolling contact fatigue characteristics and curve safety of the dynamic wheel profile under different top/sidewall friction coefficient matches;a multi-objective optimisation model was established by the entropy weight TOPSIS method,and the modified Elkins wear index,wheel pair punch angle,profile fatigue index and derailment coefficient were used as comprehensive performance evaluation indexes to analyse the best dynamic wheel profile based on The optimal top/sidewall friction coefficient matching strategy based on the dynamic wheel profile was analysed.The results show that due to the differences in wheel contact characteristics between wheel profiles,the optimum top/sidewall friction coefficients are different for different wheel profiles with different wear types and mileage: 0.3/0.1,0.25/0.1,0.2/0.1,0.25/0.1,0.25/0.1,0.25/0.1,0.25/0.1,0.25/0.1,0.25/0.1,0.25/0.1,0.25/0.1,0.25/0.1,0.25/0.1,0.25/0.1,0.25/0.1.The optimum top/sidewall friction coefficient matches are 0.2/0.15,0.2/0.3,0.2/0.35 and0.3/0.15 for 0 km,50,000 km,80,000 km and 140,000 km for treadwear wheels respectively. |
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