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Numerical study of wheel–rail adhesion performance of new-concept high-speed trains with aerodynamic wings

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浙江大学学报(英文版)A辑:应用物理与工程 2023年第8期24卷 673-691页

作者： Yang CHEN Lin JING Tian LI Liang LING Kaiyun WANG State Key Laboratory of Traction Power Southwest Jiaotong UniversityChengdu 610011China

Wheel–rail adhesion is a complex tribological problem of wheel–rail rolling contact and is closely related to the operational safety of high-speed trains.A new design concept of high-speed trains was recently proposed with an expectation of a reduction of equivalent weight and total energy consumption by installing aerodynamic wings(aero-wings)on the roof,but it was accompanied by the disadvantage of deteriorating wheel–rail adhesion performance.In this study,a comprehensive multibody dynamics(MBD)model of the high-speed train with predesigned aero-wings is established using the commercial software SIMPACK,in which the real aerodynamic characteristics of the train are taken into account.The available adhesion and adhesion margin are employed to evaluate the wheel–rail adhesion performance.The influences of aero-wing lift,train speed,and contact conditions on the wheel–rail adhesion level are discussed.The results show that the load transfer caused by the action of aerodynamic load and braking torque was the main reason for the inconsistent adhesion condition of four wheelsets.The influences of aero-wing lift and train speed on the wheel–rail adhesion performance are coupled;the available adhesion of both motor car and trailer is negatively correlated with aero-wing lift and train speed under all contact conditions,while the variation law of adhesion margin with train speed shows differences under different contact conditions.When the wheel–rail interface was polluted by a‘third-body medium’such as water and oil,the wheel–rail adhesion performance was dramatically reduced and the wheelset tended to reach adhesion saturation and slide.However,track irregularity had little effect on the adhesion performance and could be ignored to save calculation time.These results are of positive significance for reducing the wheel idling or sliding phenomenon and to ensure the safe operation of high-speed trains with aero-wings.

关键词： High-speed train Wheel–rail adhesion Aerodynamic wing Multi-body dynamics(MBD)

Mesh excitations of spur gear considering strong correlation among tooth contact parameters,contact force,and tooth profile deviations

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中国科学:技术科学英文版 2023年第9期66卷 2500-2516页

作者： LI ZhengFa CHEN ZaiGang ZHAI WanMing State Key Laboratory of Traction Power Southwest Jiaotong UniversityChengdu 610031China

Gear mesh excitations are widely concerned in the dynamic studies of the gear transmission system.Meanwhile,intentional and unintentional tooth profile deviations often occur in gears.At present,the established calculation models of gear mesh excitations consider tooth profile deviations as displacement excitation.However,gear mesh excitations calculated by such models have reduced stability compared with the actual situation.Therefore,in this study,an improved analytical model of gear mesh excitations with tooth profile deviations is established.This established model considers tooth profile deviations,extended tooth contact,and the structure coupling effect of the gear body simultaneously.More importantly,the model considers the strong correlation among tooth contact parameters,contact force,and tooth profile deviations to better reflect the actual gear mesh.A calculation flowchart with a simple calculation method of contact forces is also proposed to calculate the gear mesh excitations.Finally,the effects of tooth profile deviations on gear mesh excitations are studied.The results show that the effects of tooth profile deviations on tooth contact position,the direction of contact force,and equivalent basic circle radii should be considered in the calculation of gear mesh excitations because of smaller system transmission errors,larger double-teeth meshing area,and slighter extended tooth contact.Tooth profile deviations also cause jumps in tooth contact position and time-varying mesh stiffness.Thus,our findings show that the proposed model can be used to calculate the gear mesh excitations more accurately when the tooth profile deviates greatly.

关键词： mesh stiffness extended tooth contact structural coupling effect tooth contact stability analysis

Crack Growth Rate Model Derived from Domain Knowledge-Guided Symbolic Regression

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Chinese Journal of Mechanical Engineering 2023年第3期36卷 286-301页

作者： Shuwei Zhou Bing Yang Shoune Xiao Guangwu Yang Tao Zhu State Key Laboratory of Traction Power Southwest Jiaotong UniversityChengdu 610031China

Machine learning(ML)has powerful nonlinear processing and multivariate learning capabilities,so it has been widely utilised in the fatigue field.However,most ML methods are inexplicable black-box models that are difficult to apply in engineering practice.Symbolic regression(SR)is an interpretable machine learning method for determining the optimal fitting equation for datasets.In this study,domain knowledge-guided SR was used to determine a new fatigue crack growth(FCG)rate model.Three terms of the variable subtree ofΔK,R-ratio,andΔK_(th)were obtained by analysing eight traditional semi-empirical FCG rate models.Based on the FCG rate test data from other literature,the SR model was constructed using Al-7055-T7511.It was subsequently extended to other alloys(Ti-10V-2Fe-3Al,Ti-6Al-4V,Cr-Mo-V,LC9cs,Al-6013-T651,and Al-2324-T3)using multiple linear regression.Compared with the three semi-empirical FCG rate models,the SR model yielded higher prediction accuracy.This result demonstrates the potential of domain knowledge-guided SR for building the FCG rate model.

关键词： Fatigue crack growth rate Stress intensity factor range Threshold stress intensity factor range R-ratio Symbolic regression Machine learning

Bogie active stability simulation and scale rig test based on frame lateral vibration control

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Journal of Zhejiang University-Science A(Applied Physics & Engineering) 2023年第7期24卷 625-636页

作者： Yadong SONG Hu LI Jun CHENG Yuan YAO State Key Laboratory of Traction Power Southwest Jiaotong UniversityChengdu 610031China

This paper puts forward a high-speed train bogie active stability method,based on frame lateral vibration control,for improving the stability and critical speed of railway vehicles at high speeds.Two inertial actuators apply active control forces to the front and rear end beams of the bogie frame.A scale model of bogie lateral dynamics is established,as well as the state space equation of the control system.Also,the multi-objective optimization is used to construct state feedback parameters,which take hunting stability and control effort into account.Furthermore,the effects of time-delay in the control system and suspension parameters on bogie hunting stability are studied.The dynamic behaviors and the stability mechanism of the bogie control system are analyzed.Finally,a 1:5 scale test rig is used to conduct a bogie active stability experiment.The results reveal that active control of frame lateral vibration can effectively improve the bogie system's hunting stability margin at high speeds,but time-delay in the control system cannot be ignored.

关键词： Railway vehicle Bogie Active stability Scale test rig Time-delay

Improved analytical model for mesh stiffness calculation of cracked helical gear considering interactions between neighboring teeth

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Science China(Technological Sciences) 2023年第3期66卷 706-720页

作者： NING JieYu CHEN ZaiGang ZHAI WanMing State Key Laboratory of Traction Power Southwest Jiaotong UniversityChengdu 610031China

As one of the most typical fault forms of the helical gear,the crack will change the dynamic excitation and further affect the dynamic behaviors of the transmission systems.Due to the complicated structure of the helical gears,the coupling effect between the neighboring loaded teeth is usually ignored in the mesh stiffness calculation,making it considerably overestimated especially in the case of the crack fault.An improved mesh stiffness calculation method of helical gear with spatial crack is proposed to make up this gap.The interactions between the loaded neighboring teeth induced by the gear body flexibility were considered to improve the calculation accuracy and applicability.Besides,the load distribution law for the engaged cracked tooth along the tooth width and profile can be obtained.The results indicated that the mesh stiffness of the multi-tooth engagement calculation using this model could be further improved compared with the traditional methods.Finally,the effects of the helix angle,crack depth,and crack propagation length on the mesh stiffness and load distribution were investigated using the proposed method.

关键词： mesh stiffness helical gear structural coupling effect slice method spatial crack

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基于蛇行运动根轨迹的转向架振动特性研究

Acta Mechanica Sinica 2022年第2期38卷 165-180,I0005页

作者：关庆华杜星温泽峰梁树林池茂儒 State Key Laboratory of Traction Power Southwest Jiaotong UniversityChengdu 610031China

转向架蛇行运动的振动性态蕴含着主导铁道车辆动力学行为的关键信息,其中各个模态的特征值反映了其振动阻尼比和固有频率.本文着眼于转向架蛇行运动的根轨迹,从刚性转向架开始,扩展到具有一系悬挂的柔性转向架.对于刚性转向架,推导并验... 详细信息

转向架蛇行运动的振动性态蕴含着主导铁道车辆动力学行为的关键信息,其中各个模态的特征值反映了其振动阻尼比和固有频率.本文着眼于转向架蛇行运动的根轨迹,从刚性转向架开始,扩展到具有一系悬挂的柔性转向架.对于刚性转向架,推导并验证了蛇行运动特征值、临界速度及对应蛇行频率的解析公式.对于柔性转向架,通过数值方法求解根轨迹.研究表明,在任何速度下,自由状态的刚性转向架和自由轮对均是动力学不稳定的;转向架临界速度随等效锥度、轨距、轮对和构架惯性参数的下降以及轴距和轮径的增大而提高;一系悬挂刚度和等效锥度是影响临界速度的关键参数,在车辆系统设计中应进行综合优化;阻尼系数及蠕滑系数变化对临界速度的影响可忽略.电机悬挂对转向架根轨迹和临界速度影响显著,不当的电机悬挂设计以及电机刚性架悬均会降低转向架临界速度;通过电机悬挂来提高临界速度只有在满足电机-构架-轮对系统的低阶固有频率与蛇行频率相等或接近时才能实现.对于电机悬挂设计而言,需要特别注意,一是要避开临界速度以下的低阻尼比区,二是系统参数的变化不应导致临界速度的急剧下降.本文旨在通过解析的或经过数值计算的根轨迹来表征转向架蛇行运动的振动性态,所总结的转向架蛇行运动关键参数影响规律和电机悬挂设计原则,可为采用新结构、新材料以及先进控制和监控系统的现代轨道车辆稳定性设计提供参考.

关键词：临界速度蛇行运动一系悬挂柔性转向架等效锥度车辆系统根轨迹轮径

A numerical study on tread wear and fatigue damage of railway wheels subjected to anti-slip control

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Friction 2023年第8期11卷 1470-1492页

作者： Yunfan YANG Liang LING Jiacheng WANG Wanming ZHAI State Key Laboratory of Traction Power Southwest Jiaotong UniversityChengdu 610031China

Tread wear and rolling contact fatigue (RCF) damage propagated on railway wheels are the two extremely important focal points as they can tremendously deteriorate wheel/rail interactions and hunting stability and destroy wheel surface materials, and subsequently, cut down the lifetime of the wheels. The on-board anti-slip controllers are of essence aiming to hold back the striking slipping of the powered wheelsets under low-adhesion wheel/rail conditions. This paper intends to investigate the impact of anti-slip control on wheel tread wear and fatigue damage under diverse wheel/rail friction conditions. To this end, a prediction model for wheel wear and fatigue damage evolution on account of a comprehensive vehicle–track interaction model is extended, where the wheel/rail non-Hertzian contact algorithm is used. Furthermore, the effect of frictional wear on the fatigue damage at wheel surface is considered. The simulation results indicate that the wheel/rail contact is full-slip under the low-adhesion conditions with braking effort. The wear amount under the low-adhesion conditions is observably higher than that under the dry condition. It is further suggested that the wheel tread is prone to suffering more serious wear and fatigue damage issues with a higher anti-slip control threshold compared to that with a lower one.

关键词： anti-slip control wheel/rail non-Hertzian contact adhesion condition wheel tread wear fatigue damage

Improved Dynamics Model of Locomotive traction Motor with Elasticity of Rotor Shaft and Supporting Bearings

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Chinese Journal of Mechanical Engineering 2022年第5期35卷 333-350页

作者： Yuqing Liu Zaigang Chen Jieyu Ning Kaiyun Wang Wanming Zhai State Key Laboratory of Traction Power Southwest Jiaotong UniversityChengdu 610031China

The locomotive traction motor is described as a rotor-bearing system coupling the kinetic equations of the traction shaft and its support bearings with the determination of their elastic deformations in this study.Under the effect of excitations induced by the dynamic rotor eccentric distance and time-varying mesh stiffness,the elastic structure deformations of the shaft and support bearings are formulated in the vibration environment of the locomotive.In addition,the nonlinear contact forces between the components of the rolling bearing,the lubricating oil film,and radial clearance are comprehensively considered in this study.The results indicate that the elastic deformations of the shaft and bearings can change the dynamic responses of the traction motor and its support bearings.There are large differences between the ranges of the rotor motion calculated by the rigid and the flexible traction motor models when the intensified wheel-rail interaction is considered.With the increase of the rotor eccentricity,the results underscore the role of the elasticity of traction shaft and support bearings in dynamic researches of the traction motor.The critical value of the initial eccentric distance for the rub-impact phenomenon decreases from 1.23 mm to 1.15 mm considering the flexible effect of the shaft and bearings.This dynamics model of the traction motor can provide more accurate and reasonable simulation results for correlational dynamic researches.

关键词： traction motor Bearing Gear mesh Vehicle-track coupled dynamics

Step-by-Step Numerical Prediction of Aerodynamic Noise Generated by High Speed Trains

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Chinese Journal of Mechanical Engineering 2022年第2期35卷 251-264页

作者： Tian Li Deng Qin Ning Zhou Weihua Zhang State Key Laboratory of Traction Power Southwest Jiaotong UniversityChengdu 610031China

In this paper,the unsteady flow around a high-speed train is numerically simulated by detached eddy simulation method(DES),and the far-field noise is predicted using the Ffowcs Williams-Hawkings(FW-H)acoustic model.The reliability of the numerical calculation is verified by wind tunnel experiments.The superposition relationship between the far-field radiated noise of the local aerodynamic noise sources of the high-speed train and the whole noise source is analyzed.Since the aerodynamic noise of high-speed trains is derived from its different components,a stepwise calculation method is proposed to predict the aerodynamic noise of high-speed trains.The results show that the local noise sources of high-speed trains and the whole noise source conform to the principle of sound source energy superposition.Using the head,middle and tail cars of the high-speed train as noise sources,different numerical models are established to obtain the far-field radiated noise of each aerodynamic noise source.The far-field total noise of high-speed trains is predicted using sound source superposition.A step-by-step calculation of each local aerodynamic noise source is used to obtain the superimposed value of the far-field noise.This is consistent with the far-field noise of the whole train model’s aerodynamic noise.The averaged sound pressure level of the far-field longitudinal noise measurement points differs by 1.92 dBA.The step-by-step numerical prediction method of aerodynamic noise of high-speed trains can provide a reference for the numerical prediction of aerodynamic noise generated by long marshalling high-speed trains.

关键词： High-speed train Aerodynamic noise Sound source superposition Numerical prediction