Wheel-rail Profiles Matching Design Considering Railway Track Parameters

The profile of wheel/rail has great concern with the vehicle running safety, the wheel/rail wear and the rolling contact fatigue between wheel and rail, due to its severer impact on the dynamic behavior of both the railway vehicle/track, and the wheel/rail rolling contact status. However, recent studies in this respect are mainly explored in reverse methods, where track parameters are predetermined and invariable during the optimizing process. This paper attempts to propose a wheel-rail profiles matching design method considering multi-parameter, through optimizing wheel/rail profile under different rail cants and track gauges, based on the existed optimization technology for the normal gap of wheel/rail. The method presented in this paper can also, compared with the prior reverse methods, be called ＂forward solution method＂ in which the riding comfort, wheel unloading rate and wheel/rail contact stress of the speed-up railway passenger car are calculated by means of a vehicle-track coupling dynamic model, with the range of the rail cant varying from 1/20 to 1/40 and the rail gauge from 1 433 mm to 1 441 mm. These results show that the distribution status of the pairs of contact points can be obviously improved and the contact stress can be reduced significantly; a great influence is exposed by the rail cant and track gauge on the dynamic behavior of the high speed passenger car, and an optimal vehicle dynamics behavior are obtained with the optimized wheel/rail profile when the rail cant is 1/30 and the track gauge is 1 435 mm. This research can provide important references for the investigation of the wheel-rail profiles matching design method considering multi-parameter.

Rotary-scaling fine-tuning (RSFT) method for optimizing railway wheel profiles and its application to a locomotive

The existing multi-objective wheel profile optimization methods mainly consist of three sub-modules:(1)wheel profile generation,(2)multi-body dynamics simulation,and(3)an optimization algorithm.For the first module,a comparably conservative rotary-scaling finetuning(RSFT)method,which introduces two design variables and an empirical formula,is proposed to fine-tune the traditional wheel profiles for improving their engineering applicability.For the second module,for the TRAXX locomotives serving on the Blankenburg–Rubeland line,an optimization function representing the relationship between the wheel profile and the wheel–rail wear number is established based on Kriging surrogate model(KSM).For the third module,a method combining the regression capability of KSM with the iterative computing power of particle swarm optimization(PSO)is proposed to quickly and reliably implement the task of optimizing wheel profiles.Finally,with the RSFT–KSM–PSO method,we propose two wear-resistant wheel profiles for the TRAXX locomotives serving on the Blankenburg–Rubeland line,namely S1002-S and S1002-M.The S1002-S profile minimizes the total wear number by 30%,while the S1002-M profile makes the wear distribution more uniform through a proper sacrifice of the tread wear number,and the total wear number is reduced by 21%.The quasi-static and hunting stability tests further demonstrate that the profile designed by the RSFT–KSM–PSO method is promising for practical engineering applications.

Simulation of wheel and rail profile wear:a review of numerical models

The development of numerical models able to compute the wheel and rail profile wear is essential to improve the scheduling of maintenance operations required to restore the original profile shapes.This work surveys the main numerical models in the literature for the evaluation of the uniform wear of wheel and rail profiles.The standard structure of these tools includes a multibody simulation of the wheel-track coupled dynamics and a wear module implementing an experimental wear law.Therefore,the models are classified according to the strategy adopted for the worn profile update,ranging from models performing a single computation to models based on an online communication between the dynamic and wear modules.Nevertheless,the most common strategy nowadays relies on an iteration of dynamic simulations in which the profiles are left unchanged,with co-simulation techniques often adopted to increase the computational performances.Work is still needed to improve the accuracy of the current models.New experimental campaigns should be carried out to obtain refined wear coefficients and models,while strategies for the evaluation of both longitudinal and transversal wear,also considering the effects of tread braking,should be implemented to obtain accurate damage models.

Railway wheel profile fine-tuning system for profile recommendation

This paper develops a wheel profile fine-tuning system(WPFTS)that comprehensively considers the influence of wheel profile on wheel damage,vehicle stability,vehicle safety,and passenger comfort.WPFTS can recommend one or more optimized wheel profiles according to train operators’needs,e.g.,reducing wheel wear,mitigating the development of wheel out-of-roundness(OOR),improving the shape stability of the wheel profile.Specifically,WPFTS includes four modules:(I)a wheel profile generation module based on the rotary-scaling finetuning(RSFT)method;(II)a multi-objective generation module consisting of a rigid multi-body dynamics simulation(MBS)model,an analytical model,and a rigid–flexible MBS model,for generating 11 objectives related to wheel damage,vehicle stability,vehicle safety,and passenger comfort;(III)a weight assignment module consisting of an adaptive weight assignment strategy and a manual weight assignment strategy;and(IV)an optimization module based on radial basis function(RBF)and particle swarm optimization(PSO).Finally,three cases are introduced to show how WPTFS recommends a wheel profile according to train operators’needs.Among them,a wheel profile with high shape stability,a wheel profile for mitigating the development of wheel OOR,and a wheel profile considering hunting stability and derailment safety are developed,respectively.

Wheel Profile Optimization of Speed-up Freight Train Based on Multi-population Genetic Algorithm

The geometric shape of the wheel tread is mathematically expressed,and geometric parameters affecting the shape of the wheel were extracted as design variables.The vehicle dynamics simulation model was established based on the vehicle suspension parameters and track conditions of the actual operation,and the comprehensive dynamic parameters of the vehicle were taken as the design objectives.The matching performance of the wheel equivalent conicity with the vehicle and track parameters was discussed,and the best equivalent conicity was determined as the constraint condition of the optimization problem;a numerical calculation program is written to solve the optimization model based on a multi-population genetic algorithm.The results show that the algorithm has a fast calculation speed and good convergence.Compared with the LM profile,the two optimized profiles effectively reduce the wheelset acceleration and improve the lateral stability of the bogie and vehicle stability during straight running.Due to the optimized profile increases the equivalent conicity under larger lateral displacement of the wheelset,the lateral wheel-rail force,derailment coefficient,wheel load reduction rate,and wear index are reduced when the train passes through the curve line.This paper provides a feasible way to ensure the speed-up operation of a freight train.

Anode Simulation and Cathode Design for Electrolytic Dressing of Diamond Profile Wheel

The design methods of anode and cathode are proposed for precision profile grinding. Based on the electrolytic machining theory, electrolytic equilibrium condition and Faraday′s law of electrolysis are applied to establishing the mathematical model of profile diamond dressing process- es. A finite element method (FEM) program is developed to solve the inverse boundary problem of Laplace′s equation. Desired anode contour or cathode shape is determined by computing the distribution of electric potential layer by layer. Electrolytic machining experiment is carried out to verify the simulated anode shape. The research result shows that shape deviation between designed cathode and profile wheel increases with the value of angle between feed rate and the normal to anode surface. The shape of simulated anode is consistent with the contour of metal-bonded diamond profile wheel for a given cathode. Based on the anode contour, cathode shape can also be designed accurately.

Effects of Comprehensive Eccentricity of Involute Cam on Gear Profile Deviations

The manufacturing accuracy of ultra-precision master gears signifies the technological capability of the ultra-precision gear.Currently,there is little report about the manufacturing technologies of ultra-precision master gears at home and aboard.In order to meet the requirement of grinding ultra precision master gear,the gear grinder with flat-faced wheel Y7125 is chosen as the object machine tool and the geometric model of its precision generating part,the involute cam,is established.According to the structure of the involute cam,the effective working section and its adjustable range of the cam are determined,and the mathematical expressions of the effects of comprehensive eccentricity of the involute cam on gear profile deviations are derived.According to the primary harmonic trends of the deviation curve,it is shown that gear profile form and slope deviations in different work generating sections of the involute cam are different which the latter changes with the cam eccentricity obviously.Then,the issues of extreme values and methods of error compensation are studied and the conclusion that large adjustable range is benefit to search the optimal involute-cam section which is responding to the minimum gear profile deviations is obtained.A group of examples are calculated by choosing master gears with d=120 mm and m=2-6 mm and an involute cam with base diameter djcam =117 mm.And it is found that the maximum gear profile deviation counts for no more than 5% of the cam eccentricity after error compensation.A gear-grinding experiment on the master gear with m=2 mm is conducted by choosing different sections of the involute cam and the differences of gear profile deviations then the existence of the cam eccentricity are verified.The research discloses the rule of gear profile deviations caused by the comprehensive eccentricity of the involute cam and provides the theoretical guidance and the processing methods for grinding profile of the ultra precision master gear.

Numerical simulation of wheel wear evolution for heavy haul railway

The prediction of the wheel wear is a fundamental problem in heavy haul railway. A numerical methodology is introduced to simulate the wheel wear evolution of heavy haul freight car. The methodology includes the spatial coupling dynamics of vehicle and track, the three-dimensional rolling contact analysis of wheel-rail, the Specht's material wear model, and the strategy for reproducing the actual operation conditions of railway. The freight vehicle is treated as a full 3D rigid multi-body model. Every component is built detailedly and various contact interactions between parts are accurately simulated, taking into account the real clearances. The wheel-rail rolling contact calculation is carried out based on Hertz's theory and Kalker's FASTSIM algorithm. The track model is built based on field measurements. The material loss due to wear is evaluated according to the Specht's model in which the wear coefficient varies with the wear intensity. In order to exactly reproduce the actual operating conditions of railway,dynamic simulations are performed separately for all possible track conditions and running velocities in each iterative step.Dimensionless weight coefficients are introduced that determine the ratios of different cases and are obtained through site survey. For the wheel profile updating, an adaptive step strategy based on the wear depth is introduced, which can effectively improve the reliability and stability of numerical calculation. At last, the wear evolution laws are studied by the numerical model for different wheels of heavy haul freight vehicle running in curves. The results show that the wear of the front wheelset is more serious than that of the rear wheelset for one bogie, and the difference is more obvious for the outer wheels. The wear of the outer wheels is severer than that of the inner wheels. The wear of outer wheels mainly distributes near the flange and the root; while the wear of inner wheels mainly distributes around the nominal rolling circle. For the outer wheel of front wheelset of each bogie, the development of wear is gradually concentrated on the flange and the developing speed increases continually with the increase of traveled distance.

Parametric analysis of wheel wear in high-speed vehicles

In order to reduce the wheel profile wear of highspeed trains and extend the service life of wheels, a dynamic model for a high-speed vehicle was set up, in which the wheelset was regarded as flexible body, and the actual measured track irregularities and line conditions were considered. The wear depth of the wheel profile was calculated by the well-known Archard wear law. Through this model, the influence of the wheel profile, primary suspension stiffness, track gage, and rail cant on the wear of wheel profile were studied through multiple iterafive calculations. Numerical simulation results show that the type XP55 wheel profile has the smallest cumulative wear depth, and the type LM wheel profile has the largest wear depth. To reduce the wear of the wheel profile, the equivalent conicity of the wheel should not be too large or too small. On the other hand, a small primary vertical stiffness, a track gage around 1,435-1,438 mm, and a rail cant around 1：35-1：40 are beneficial for dynamic performance improvement and wheel wear alleviation.

Computer Aided Design of Grinding Wheel for Drill Flute Production

Twist drill flute profile design is necessary in order to determine the required grinding wheel profile for a flute production. An accurate drill flute profile design is generated for two-flute conical twist drills using analytical equations to generate a drill flute profile design needed for the production of twist drills with straight lips. The required grinding wheel profile for a flute production was expressed in digitized form as well as in terms of two curve-fitted circular arcs. The drill flute profile geometry can never be precisely generated when required grinding wheel profile is represented by two circular arcs and the generated flute profile is just a very good approximation of the design flute profile. A CAD （computer aided design） software has been developed using MATLAB to determine the required grinding wheel profile for generating a given drill flute profile design.

Application of a Computational Tool to Study the Influence of Worn Wheels on Railway Vehicle Dynamics

The search for fast, reliable and cost effective means of transport that presents better energy efficiency and less impact on the environment has resulted in renewed interest and rapid development in railway technology. To improve its efficiency and competitiveness, modern trains are required to travel faster, with high levels of safety and comfort and with reduced Life Cycle Costs (LCC). These increasing demands for vehicle requirements imposed by railway operators and infrastructure companies include maintaining the top operational speeds of trainsets during their life cycle, having low LCC and being track friendly. This is a key issue in vehicle design and in train operation since it has a significant impact on the safety and comfort of railway systems and on the maintenance costs of vehicles and infrastructures. The purpose of this work is to analyze how the wear progression on the wheelsets affects the dynamic behavior of railways vehicles and its interaction with the track. For this purpose a vehicle, assembled with new and worn wheels, is studied in realistic operation scenarios. The influence of the wheel profile wear on the vehicle dynamic response is assessed here based on several indicators used by the railway industry. The running stability of the railway vehicles is also emphasized in this study.

轨底坡耦合车轮动态型面下地铁轮轨接触特性

为探究地铁车轮型面动态变化与轨底坡设置的关系,跟踪测试了运行里程5万、8万、14万公里车轮磨耗型面,研究轨底坡耦合车轮动态型面时的轮轨接触特性;以车辆动力学理论为依据,根据实测地铁车辆参数,建立了车辆系统动力学模型;基于轮轨接触几何关系和非赫兹滚动接触理论,建立了轮轨滚动接触计算模型;以轮轨接触点和接触位置、滚动圆半径差、接触角、等效锥度、蠕滑率、接触斑面积和最大接触压力作为轮轨接触几何和力学性能指标,分析轨底坡耦合车轮动态型面对轮轨接触特性的影响规律。结果表明:LM标准型面和5万公里车轮磨耗型面与1/20轨底坡匹配时轮轨接触点分布均匀;随着运行里程增加,车轮磨耗型面变化,轮轨接触恶化,轮对横移量4 mm下,8万和14万公里车轮磨耗型面与1/20轨底坡匹配时各指标出现断点。

小半径曲线上P75钢轨打磨廓形设计及应用研究

以国内某重载铁路R400 m曲线P75钢轨为研究对象,建立了轮轨接触模型和轮径差曲线描述模型,选取代表性车轮踏面和钢轨廓形,采用轮径差曲线逆向求解法优化了轮轨接触区域钢轨廓形,并依据打磨量最小化原则设计得到了曲线钢轨打磨廓形。建立了实测参数下的车辆-轨道多体动力学仿真模型,对比分析了实测廓形和设计廓形匹配下的动力学指标。按钢轨廓形设计要求,在该R400 m曲线上实施了钢轨打磨试验和轮轨动力学测试。研究结果表明,优化后轮径差曲线趋于平滑,车辆曲线通过能力得到提高,抗脱轨能力得到保持;轮轨关系得到显著改善、轮轨接触点交叉跳跃和集中问题得到缓解;轮轨横向力减小20%以上,脱轨系数减小16%以上,钢轨法向接触应力减小32%以上,轮轨蠕滑力减小26%以上;实施打磨后,轮轨横向力减小34%以上,脱轨系数减小35%以上,钢轨振动加速度减小35%以上;打磨后3个月轨面疲劳伤损未见明显发展,钢轨使用寿命由前一换轨周期的8个月延长至13.5个月。仿真分析和打磨试验验证了钢轨廓形设计方法在重载铁路小半径曲线的应用效果。

基于多目标函数的钢轨打磨廓形优选研究

针对CR400BF和CRH5动车组6~8 Hz主频车体抖动问题,从改善轮轨关系角度出发,分别建立车轮踏面和钢轨廓形样本库,通过确定目标函数和设置边界条件求解得到优选钢轨廓形。建立实参数车辆-轨道刚柔耦合动力学模型和轮轨接触弹塑性有限元模型,通过仿真分析对比优选钢轨廓形和60N廓形的等效锥度、动力学指标和轮轨接触应力。按优选钢轨廓形进行钢轨打磨试验,结果表明:优选钢轨廓形与磨耗车轮踏面匹配时轮轨关系改善,等效锥度小于上限值0.4;与不同磨耗车轮踏面匹配时,优选钢轨廓形动力学指标优于60N,且轮轨接触应力和打磨量均更小;按优选钢轨廓形进行钢轨打磨后,CR400BF、CRH5动车组舒适度、平稳性指标分别减小15.7%、13.1%以上,车体振动加速度主频消除。优选钢轨廓形可有效缓解CR400BF和CRH5动车组车体抖动,优选方法和实施流程可为相关问题研究提供参考。

粗粒度金刚石砂轮的放电赋能磨削修整试验研究

针对粗粒度金刚石砂轮磨粒出刃形貌难以控制的问题,提出了放电赋能磨削修整技术,旨在实现出刃磨粒的等齐性。系统研究了该复合修整技术的材料去除机理,建立脉冲放电传热数值模型,以金刚石热软化深度作为磨削深度,最大限度发挥放电赋能磨削的修整优势。探究了机床运动参数(待修砂轮转速、刀具轮转速、进给速度、磨削深度)对砂轮修整精度和刀具轮损耗深度的影响规律,并优化了工艺参数以实现粗粒度砂轮的高效高精修整。磨粒粒度为180目的金刚石砂轮修整后轮廓误差PV值为11.97μm。修整砂轮表面形貌检测结果表明,放电赋能磨削修整可将磨粒部分去除,使得砂轮表面磨粒具有较好的等齐性。磨削的碳化硅陶瓷工件表面粗糙度达412 nm,表明了修整砂轮具有优异的磨削性能。

等效锥度非线性研究及其在踏面设计中的应用

为研究等效锥度非线性特性对车辆系统动力学和磨耗性能的影响,提出可以用于踏面优化设计的非线性特性建议指标。通过对轮轨关系进行细致推导,应用踏面逆向设计快速递推算法,得到具有不同等效锥度非线性特性的踏面,对不同踏面的轮轨关系进行分析。建立车辆系统动力学模型和基于Archard理论的磨耗预测模型,对不同非线性特性踏面的临界速度、横向平稳性、磨耗性能进行对比分析。研究结果表明:非线性因子值过高或过低都会导致临界速度下降,但该指标过高对临界速度影响更大,最大降幅可达20%;等效锥度非线性特性还会影响到踏面的磨耗发展,踏面的初始非线性因子越高,名义等效锥度在磨耗过程中的增长越慢,对延长车轮服役周期是有利的。综合动力学性能及磨耗性能,建议高速列车踏面的非线性因子应取尽可能接近于0的负值。在这一结论的指导下,对S1002CN踏面进行优化设计,得到名义等效锥度为0.1,等效锥度非线性因子为0.013(与S1002CN持平)、-0.002的优化踏面S1002CN_opt1、S1002CN_opt2,优化踏面S1002CN_opt2与S1002CN相比临界速度和横向平稳性有所优化,同时磨耗性能也有所提升。S1002CN_opt2与S1002CN_opt1之间的等效锥度非线性关系在动力学性能及磨耗性能中的表现证明以等效锥度非线性因子限值指导踏面进行优化设计的可行性,研究结果可为踏面设计及轮轨关系研究提供参考。

均载组合式小轮径货车转向架车轮型面优化设计研究

小轮径转向架技术是驼背运输车辆的关键技术,小轮径低地板驮背车车轮型面磨耗问题严重,对其动力学性能造成严重影响,为了进一步提升其服役性能,对小轮径低地板驮背车车轮型面进行优化设计。首先建立小轮径低地板驮背车动力学模型,然后利用轮径差反向设计方法对车轮型面进行优化,最后利用车辆动力学模型对优化后型面的车辆动力学性能和磨耗特性进行验证分析。结果表明,优化后型面进一步降低了车轮等效锥度,同时减小了轮轨法向接触应力。通过对比优化前后动力学特性,优化后车轮型面有效提升了空重车状态下的临界速度,空车临界速度较LM踏面提高23.3%,重车临界速度较LM踏面增大17.54%。同时优化后型面有效提升了车辆的平稳性和曲线通过性能,最后利用车轮磨耗模型计算了直线段和曲线段的车轮磨耗,优化后曲线外侧车轮磨耗最大深度减小54.8%,曲线内侧车轮磨耗最大深度减小48.13%,型面优化可以有效减小小轮径低地板驮背车直线段和曲线段的车轮磨耗,为抑制车轮磨耗,提升服役性能具有重要作用。

磨削圆柱螺旋槽的砂轮轮廓及位姿快速计算方法

在立铣刀螺旋槽的数控磨削过程中,砂轮的安装位姿对螺旋槽的前角、芯径、槽宽等截形参数影响显著,进而影响刀具的切削性能。精确、高效求解砂轮位姿是螺旋槽磨削工艺的首要任务,目前大多采用迭代的优化计算方法,但存在计算模型的精度与效率不足的问题。基于此对模型进行分析研究,采用一种优化计算新方法,根据芯径形成机理,通过接触原理对砂轮与工件的相对位姿进行运动变换,得到能够预先保证芯径的位姿参数表达式,降低了位姿参数变量维度,从而提高计算效率;同时推导了前角、槽宽的解析表达式,以此为约束,采用数值优化算法可精确计算出砂轮位姿参数。通过仿真与磨削试验对算法进行验证。结果表明,所提算法可以较精确地计算出砂轮位姿参数,相比于预先设计值误差较小,且计算效率比迭代法高,具有较高的工程实用性。

基于多目标优化策略的曲线钢轨非对称打磨设计

铁路曲线钢轨打磨一直是养护维修工作的重点之一,虽然钢轨的磨损不可避免,但适当打磨型面能有效减缓磨损。为了降低打磨去除量,改善轮轨接触性能,提高铁路系统的安全性和经济性,提出一种基于多目标协方差矩阵自适应优化策略(MO-CMA-ES)的曲线段打磨型面设计方法。首先,通过主成分分析方法(PCA),从钢轨磨耗型面中选取代表性的磨耗型面作为初始种群。接着,采用NURBS曲线拟合算法对这些型面进行曲线拟合,以建立参数化模型。随后,使用MOCMA-ES算法进行多目标优化,其中目标函数包括降低打磨去除量、轮重减载率和轮轴横向力。根据每个型面在不同目标函数下的适应度值,进行种群的进化与连续迭代,直到满足终止条件,即适应度函数值不再显著变化。最后,从最终的种群中选取目标适应度值最小的子代个体作为最优解。优化结果显示,优化型面降低了45.3%的打磨去除量,同时内外轨轨顶的打磨下降高度分别降低了0.84 mm和0.23 mm。静态轮轨接触方面,优化后的轮轨接触点分布更加均匀,且轨距角过渡区域的跳跃现象得到改善。动力学性能方面,优化型面降低了列车车体的横向加速度和轮轨横向力。此外,有效减小了轮对的横向位移,并微幅降低了轮轨最大接触应力。研究结果为曲线钢轨打磨提供了一种智能化的设计方法与参考。

动车组车轮薄轮缘旋修廓形轮缘强度分析

面对工程中最小轮缘厚度多依据经验确定的现状,利用ANSYS建立了考虑CR400AF型动车组车轮薄轮缘旋修廓形的三维轮轨静态接触有限元模型,钢轨选用CN60,轮径取极小值850 mm,轮轨载荷取自UIC 510-2020标准。分析了不同横移、载荷下的轮轨接触状态,对比了22.0、26.0、32.9 mm这3种典型轮缘厚度下轮辋和轮缘内应力分布。重点分析设计廓形接触和磨耗后共形接触条件下,轮缘贴靠和道岔通过时轮缘内部应力场分布特征,及其最大应力的幅值和发生位置,总结了特征应力随轮缘厚度的变化规律。以车轮360 MPa的许用应力作为评判准则,发现工程中采用的轮缘最薄22.0 mm的车轮轮缘强度有保障。提出了薄轮缘车轮安全评估的接触分析策略,为未来最小轮缘厚度研究奠定了基础,也为现行薄轮缘车轮的运营提供了关键服役应力信息。