Optimization Design Of Railhead Profiles On Curve Tracks Of Heavy Haul Railway

With the development of the railway transportation industry,in order to meet the stable growth of transportation capacity,heavy haul railway will inevitably increase the axle load and transport density.But it will inevitably intensify the interaction between wheel and rail,and accelerate the wheel/rail wear.There are so many small or medium-radius curves in heavy haul lines.While improving the efficiency of railway transportation,the phenomenon of high rail side wear and low rail crushed fat edge are particularly prominent,which seriously affects the vehicle’s running safety and rail life,increasing maintenance cost of railway transportation.A reasonable wheel-rail matching relationship can improve the wheel-rail contact geometry,vehicle running stability and curve negotiation performance,also can reduce wheel and rail damage.Carrying out wheel-rail profile optimization is one of the effective means to improve the wheel-rail relationship and inhibit the development of rail diseases.Therefore,this thesis conducts wheel-rail investigation and analysis for heavy haul railway curve line,and establishes a multi-objective optimization method for heavy haul railway curve line based on genetic algorithm and analytic hierarchy process.Finally,an optimal profile was obtained by using this method,and its adaptability of different running speeds,different track parameters and vehicle parameters were researched.In this thesis,the main work and conclusions are as follows:(1)The heavy haul railway curve line is investigated on site,and the characteristics of rail side wear and crushed fat edge of heavy haul railway curve line were mastered.Through the comparison of the dynamic characteristics and static contact geometry between the measured rail profile and the standard rail profile,it is clear that the main purpose of rail profile design for heavy haul railway curve line is to reduce wheel/rail wear and wheel/rail contact stress.(2)A multi-objective optimization model based on the combination of vehicle-track dynamics model and analytic hierarchy process was established.In this model,the improved NURBS curve is used to realize the parametric description of the asymmetric rail profile,and the dynamic performance evaluation specification is used as the constraint.The genetic algorithm is used to obtain the globally optimal asymmetric rail profile.(3)The rail profile optimization method of heavy haul railway curve line is carried out with the aim of minimizing wheel/rail wear,minimizing contact stress,and minimizing wheel/rail wear and contact stress.The results show that the single-objective optimization strategy will cause the performance of other indicators to deteriorate,and the multi-objective optimization strategy is the best.For example,the wheel/rail wear and wheel/rail contact stress are reduced by 12% and 22% respectively after the multi-objective optimization,and the effect is significant.(4)According to the optimized rail profile,the adaptability of running speed,track parameters and vehicle parameters are analyzed.The results show that the optimized design profile is effectively improved in most cases compared to the measured profile and the standard profile in terms of dynamic characteristics and wheel-rail contact geometry.