Train–track coupled dynamics analysis:system spatial variation on geometry,physics and mechanics

This paper aims to clarify the influence of system spatial variability on train–track interaction from perspectives of stochastic analysis and statistics.Considering the spatial randomness of system properties in geometry,physics and mechanics,the primary work is therefore simulating the uncertainties realistically,representatively and efficiently.With regard to the track irregularity simulation,a model is newly developed to obtain random sample sets of track irregularities by transforming its power spectral density function into the equivalent track quality index for representation based on the discrete Parseval theorem,where the correlation between various types of track irregularities is accounted for.To statistically clarify the uncertainty of track properties in physics and mechanics in space,a model combining discrete element method and finite element method is developed to obtain the spatially varied track parametric characteristics,e.g.track stiffness and density,through which the highly expensive experiments in situ can be avoided.Finally a train–track stochastic analysis model is formulated by integrating the system uncertainties into the dynamics model.Numerical examples have validated the accuracy and efficiency of this model and illustrated the effects of system spatial variability on train–track vibrations comprehensively.

Lateral Stability Analysis of Heavy-Haul Vehicle on Curved Track Based on Wheel/Rail Coupled Dynamics

Being viewed from the standpoint of whole system, the hunting stability of a heavy-haul railway vehicle on a curved track is investigated in this paper. First, a model to simulate dynamic performance of the heavy-haul vehicle on the elastic track is developed. Secondly, the reason of the hunting motion is analyzed, and a bifurcation diagram for the vehicle on the curved track is put forward to simulate the nonlinear critical speed. Results show that the hunting motion of the heavy-haul vehicle will appear due to the larger conicity, the initial lateral shift and the wheelset angle of attack. With the hunting motion appearing, the lateral shift and force of the wheelset are changed sharply and periodically with a wave of circa 3.6 m. There is obvious difference in the bifurcation diagram between on a curved track and on a tangent track. Relative to the centerline of the track, each vehicle body on the curved track has two stable cycles. As for the curved track with a radius of 600 m and a superelevation of 55 mm, the nonlinear critical speed of the heavy-haul vehicle is 76.4 km/h.

Coupling Analysis of Moment of Inertia & Dynamic on Optoelectronic Tracking Turntable

With photoelectric tracking system as the research object,based on the theorem of moment of momentum and Euler dynamic equation,Nonlinear biaxial coupling dynamic model of tracking turntable is established.Effects of moment of inertia coupling,speed coupling and the dynamic coupling between tracking turntable shafts were studied,the analytical relation between them was given in theory.Verify the change trend of theoretical model.And it provides the theory reference and model base,for the future design of the high precision tracking controller And control parameter selection and optimization.In the end,specific measures are made for structure optimization.

A vertical coupling dynamic analysis method and engineering application of vehicle–track–substructure based on forced vibration

Purpose–This study aims to propose a vertical coupling dynamic analysis method of vehicle–track–substructure based on forced vibration and use this method to analyze the influence on the dynamic response of track and vehicle caused by local fastener failure.Design/methodology/approach–The track and substructure are decomposed into the rail subsystem and substructure subsystem,in which the rail subsystem is composed of two layers of nodes corresponding to the upper rail and the lower fastener.The rail is treated as a continuous beam with elastic discrete point supports,and spring-damping elements are used to simulate the constraints between rail and fastener.Forced displacement and forced velocity are used to deal with the effect of the substructure on the rail system,while the external load is used to deal with the reverse effect.The fastener failure is simulated with the methods that cancel the forced vibration transmission,namely take no account of the substructure–rail interaction at that position.Findings–The dynamic characteristics of the infrastructure with local diseases can be accurately calculated by using the proposed method.Local fastener failure will slightly affect the vibration of substructure and carbody,but it will significantly intensify the vibration response between wheel and rail.The maximum vertical displacement and the maximum vertical vibration acceleration of rail is 2.94 times and 2.97 times the normal value,respectively,under the train speed of 350 km$h
1.At the same time,the maximum wheel–rail force and wheel load reduction rate increase by 22.0 and 50.2%,respectively,from the normal value.Originality/value–This method can better reveal the local vibration conditions of the rail and easily simulate the influence of various defects on the dynamic response of the coupling system.

Mechanics analysis of a wheelchair robot with wheel-track coupling mechanism

A barrier-free wheelchair robot with a mechanism coupled by wheel and track is presen- ted in this paper. Using the wheelchair, the lower limb disabled persons could be more relaxed to take part in outdoor activities whether on flat ground or stairs and obstacles in the city. The wheel- track coupling mechanism is designed and the stability of the bodywork of the wheelchair robot on the stairs is analyzed. In order to obtain the stability of wheelchair robot when it climbs obstacles, centroid projection method is applied to analyze the static stability, stability margin is proposed to provide the stability under some dynamic forces, and the push rod rotation angle in terms of the guaranteed stability margin is given. Finally, the dynamic model of the wheelchair robot based on Lagrange equation is established, which can be a theoretical foundation for the wheelchair control system design.

GPU-Based Simulation of Dynamic Characteristics of Ballasted Railway Track with Coupled Discrete-Finite Element Method

Considering the interaction between a sleeper,ballast layer,and substructure,a three-dimensional coupled discrete-finite element method for a ballasted railway track is proposed in this study.Ballast granules with irregular shapes are constructed using a clump model using the discrete element method.Meanwhile,concrete sleepers,embankments,and foundations are modelled using 20-node hexahedron solid elements using the finite element method.To improve computational efficiency,a GPU-based(Graphics Processing Unit)parallel framework is applied in the discrete element simulation.Additionally,an algorithm containing contact search and transfer parameters at the contact interface of discrete particles and finite elements is developed in the GPU parallel environment accordingly.A benchmark case is selected to verify the accuracy of the coupling algorithm.The dynamic response of the ballasted rail track is analysed under different train speeds and loads.Meanwhile,the dynamic stress on the substructure surface obtained by the established DEM-FEM model is compared with the in situ experimental results.Finally,stress and displacement contours in the cross-section of the model are constructed to further visualise the response of the ballasted railway.This proposed coupling model can provide important insights into high-performance coupling algorithms and the dynamic characteristics of full scale ballasted rail tracks.

Characteristic analysis of mechanical thermal coupling model for bearing rotor system of high-speed train

Based on Newton’s second law and the thermal network method,a mechanical thermal coupling model of the bearing rotor system of high-speed trains is established to study the interaction between the bearing vibration and temperature.The influence of lubrication on the vibration and temperature characteristics of the system is considered in the model,and the real-time relationship between them is built up by using the transient temperature field model.After considering the lubrication,the bearing outer ring vibration acceleration and node temperature considering grease are lower,which shows the necessity of adding the lubrication model.The corresponding experiments for characteristics of vibration and temperature of the model are respectively conducted.In the envelope spectrum obtained from the simulation signal and the experimental signal,the frequency values corresponding to the peaks are close to the theoretical calculation results,and the error is very small.In the three stages of the temperature characteristic experiment,the node temperature change of the simulation model is consistent with the experiment.The good agreement between simulation and experiments proves the effectiveness of the model.By studying the influence of the bearing angular and fault size on the system node temperature,as well as the change law of bearing lubrication characteristics and temperature,it is found that the worse the working condition is,the higher the temperature is.When the ambient temperature is low,the viscosity of grease increases,and the oil film becomes thicker,which increases the sliding probability of the rolling element,thus affecting the normal operation of the bearing,which explains the phenomenon of frequent bearing faults of high-speed trains in the low-temperature area of Northeast China.Further analysis shows that faults often occur in the early stage of train operation in the low-temperature environment.

The effect of subgrade inhomogeneity induced by freeze-thaw on the dynamic response of track-subgrade system

The developed vertical coupling model of Vehicle-Track-Subgrade which considered subgrade layer vibration is present- ed. The equations of motion for the ballast, top and bottom subgrade layers are presented in detail. Through inputting different coefficients, the dynamic response of track-subgrade system in a seasonal frozen region in different seasons is obtained by the developed model and the uneven freeze-thaw action of subgrade soil is presented in this model. The ef- fect of subgrade inhomogeneity induced by uneven freeze-thaw on the dynamic response of track-subgrade system was studied and the conclusions are as follows. The force at the interface of ballast and top subgrade layer and the defor- mation of ballast induced by a passing train changed sharply at the stiffness mutation zone. The force and deformation decreased with increasing stiffness ratio with the same amplitude of irregularities as the excitation source. The force and deformation were larger with larger amplitudes of irregularities. There was an obvious effect of uneven deformation and stiffness of subgrade on the dynamic response of track-subgrade system.

Dynamic Response of Elastic Sleeper Ballasted Track on Bridge

A vehicle-track-bridge coupling dynamics model was built based on the theory of vehicle-track coupling dynamics. Using this model, a comparison was made between the dynamic response of an elastic sleeper ballasted track and a common sleeper ballasted track on bridge under the same working conditions. The results show that laying elastic sleepers on the bridge could solve the problem of large track stiffness caused by a thin ballast thickness, and improve the dynamic response of the bridge. This is beneficial to train operation safety and riding comfort.

Distribution characteristics and influencing factors of the frequency-domain response of a vehicle–track vertical coupled system

Employing theory on vehicle-track coupled dynamics, the equation of motion of a vehicle-track vertical coupled system was established by combining frequency analysis and symplectic mathematics. The frequency response of the vehicle-track vertical coupled system was calculated under the excitation of the German low-interfer- ence spectrum, and the effects of the vehicle speed, vehicle suspension parameters, and track support parameters on the frequency response of the coupled system were studied. Results show that, under the excitation of the German low- interference spectrum, the vertical vibration of the car body is mainly concentrated in the low-frequency band, while that of the bogie has a wide frequency distribution, being strong from several Hertz to dozens of Hertz. The vertical vibrations of the wheel-rail force, wheelset, and track structure mainly occur at a frequency of dozens of Hertz. In general, the vertical vibration of the vehicle-track coupled system increases with vehicle speed, and the vertical vibrations of the car body and bogie obviously shift to higher frequency. Increasing the vehicle suspension stiffness increases the low- frequency vibrations of the vehicle system and track struc- ture. With an increase in vehicle suspension damping, the low-frequency vibrations of the car body and bogie and the vibrations of the wheel-rail vertical force and track structure decrease at 50-80 Hz, while the mid-frequency and high- frequency vibrations of the car body and bogie increase. Similarly, an increase in track stiffness amplifies the vertical vibrations of the wheel-rail force and track structure, while an increase in track damping effectively reduces the vertical vibrations of the wheel-rail vertical force and track structure.

9号道岔区铺设减振垫浮置板的行车安全性及舒适性研究

地铁道岔区在基本轨、尖轨处以及道岔钢轨接头处存在大量钢轨不连续地段,轮轨相互作用强烈,轨道系统振动明显,减振垫浮置板轨道作为一种高等减振措施已应用于地铁线路道岔区。为探究减振垫浮置板应用于9号道岔的适用性,并作为减振地段与普通无砟轨道的过渡段的可行性,以某地铁高架9号道岔为研究对象,建立桥上道岔三维有限元模型,仿真分析地铁B型车在120 km/h直向过岔和30 km/h侧向过岔的情况下,列车的行车安全性、舒适性以及轨下结构形变。对比在9号单开道岔区域设置的2种刚度过渡方式的优劣及其减振效果,较为系统地论证了在9号道岔区域铺设减振垫浮置板的可行性。研究结果表明:1)列车通过铺设减振垫浮置板的9号道岔区域时,浮置板位移极值出现在转辙区域和心轨区域,最大位移出现在尖轨位置,可增大尖轨处单板橡胶垫支承刚度,以保证轨道结构变形均匀;2)列车逆向侧向通过设置过渡段的减振垫浮置板道岔区时,2级过渡方式的车体最大垂向加速度、最大横向加速度、最大脱轨系数、最大轮重减载率、轨道刚度变化率以及减振效果等指标均优于1级过渡方式;3)在道岔区铺设减振垫浮置板,列车直向和侧向通过时的行车安全性和舒适性均能满足相关评价指标,且2级过渡方式更优。研究结果可为后续道岔区减振设计研究提供一定的理论参考。

车辆-轨道系统动力极值预测及可靠度计算

为从车辆-轨道系统的动力极值预测及其可靠度计算角度分析车辆系统行车安全、衡量系统可靠程度,基于车辆-轨道耦合动力学及概率理论,提出一种车轨系统动力极值预测及可靠度评估方法。首先,基于轨道不平顺概率模型,采用轨道不平顺累计概率谱确定具有不同激振能量的随机不平顺序列;依据离散Parseval定理,建立轨道不平顺时域序列和功率谱间的对应关系;将轨道不平顺概率模型与车辆-轨道耦合动力学模型相结合,从随机动力计算中提取车辆-轨道的动力极值及可靠度信息;随后利用车辆-轨道耦合动力模型及二维插值算子,根据谱线能量关系实现动力极值预测;此外,基于此系统激励输入与响应输出间的概率等效性,导出了动力极值的可靠度计算式。以实测的轨道不平顺和车体加速度数据及4种类型不平顺在不同累计概率下的谱组合计算得出的轮轨横向力和钢轨垂向位移的计算结果为样本,与预测结果进行对比。研究结果表明:计算时程的分布趋势基本与实测时程一致,动力极值预测结果与实际的动力计算结果较为接近。由于轨道不平顺随机性的存在使得车辆-轨道系统的动力响应存在随机离散及方差特征,但通过轨道不平顺的幅频及能量特性预测车辆-轨道系统的动力极值的方法是较为可行的。

列车荷载作用下CRTS Ⅲ型板式无砟轨道层间离缝水力特性研究

在雨水充沛或排水不畅地区,积水会造成无砟轨道层间离缝扩展显著加速。针对含层间离缝的CRTS Ⅲ型板式无砟轨道的水力特性问题,建立列车荷载与水耦合作用下的CRTS Ⅲ型板式无砟轨道-离缝积水双向瞬态流固耦合计算模型,揭示无砟轨道层间离缝内动水压力和水流速度的分布及其峰值的变化规律,并分析列车轴重、行车速度、离缝形态及积水深度对动水压力和水流速度的影响。研究结果表明:随着列车的趋近与远离,层间离缝内固定点处的动水压力与水流速度呈周期性的正负交替变化;动水压力沿着离缝出口方向逐渐减小,其峰值发生在离缝尖端处,而水流速度沿着离缝出口方向逐渐增大,其峰值发生在离缝出口处;动水压力与水流速度峰值随列车轴重增加而线性增大,轴重每增加1 t,动水压力和水流速度峰值分别增加2.850 kPa、0.085 m/s;动水压力峰值与车速呈二次方增大关系,而在车速小于300 km/h时水流速度峰值与车速基本上呈线性关系,超过该车速后流速增长趋势较之前更大;动水压力、水流速度峰值与离缝开口量呈反比关系;动水压力与水流速度峰值都随着离缝深度和离缝积水深度增加而显著增大,且两者都与离缝深度呈3次多项式增大关系,与离缝积水深度呈2次方增大关系。研究结果可为CRTS Ⅲ型板式无砟轨道在列车荷载与水耦合作用下的层间离缝扩展分析以及养护维修工作提供依据和参考。

基于结构振动响应的长型浮置板轨道隔振器失效检测方法

目前钢弹簧浮置板轨道的隔振器失效判别主要依赖于人工巡检或视觉成像系统,但此类方法效率低、检测滞后且成本高昂。本文提出了一种自动化的检测方法,该方法利用残差学习思想和卷积神经网络基本理论构建数据分类器,并通过列车动荷载作用下的结构动力响应对现役某常见的长型浮置板轨道进行隔振器失效的检测识别。首先,基于车-轨垂向耦合动力学建立考虑隔振器不同服役状态的地铁车辆-浮置板轨道垂向耦合动力学仿真分析模型,进而生成多种运营工况下的数据集,用于网络的训练和性能测试;其次,进一步研究了传感器布置方式对网络检测性能的影响,以决定适宜的传感器布置方案;最后,在实际地铁线路中开展试验,对所提出的方法进行了验证。结果表明:通过对传感器布置位置进行优化,深度残差网络模型的检测准确性显著提升;合理设置传感器的数量也可以提高本文方法的检测性能;此外,通过适当选取传感器布置方案,本文提出的基于深度残差网络的隔振器失效检测方法在仿真数据中实现了98.99%的准确度,并在试验数据中实现了96.33%的准确度。该方法具有较高的可行性和应用潜力,可为地铁浮置板隔振器智能运维提供参考,并有望在未来用于隔振器失效的自动化检测。

轮轨摩擦系数对低地板轻轨动力响应及车轮磨耗的影响

为了确保低地板轻轨车辆安全且平稳地运行,以某轻轨线路为依托,利用多体动力学软件UM(Universal Mechanism)建立了低地板轻轨车辆-轨道耦合动力学模型。选用LM磨耗型车轮踏面以及R50标准钢轨,以美国六级不平顺轨道谱作为线路激扰。基于Hertz及Kalker简化理论、Archard模型,进行不同摩擦系数共5个工况下车辆动力响应以及车轮磨耗变化规律的仿真分析。在此基础上进一步分析了4个不同运行里程阶段对应共96组车轮磨耗型面下轻轨车辆安全性指标的变化规律。研究了4个不同运行里程阶段对应的不同车轮磨耗型面下车辆过曲线时安全性指标随摩擦系数的变化情况。结果表明:脱轨系数、轮轴横向力、轮轨横向力、车体横向加速度受摩擦系数的影响较为显著,而轮重减载率、车体垂向加速度对摩擦系数的改变并不敏感。车轮磨耗深度随里程和摩擦系数的增加而增大,且相同工况下独立旋转车轮的磨耗情况更加严重。在车辆运行40000 km后,其轮轨横向力、轮轴横向力、脱轨系数整体呈现随里程增加而增大的规律,而轮重减载率基本不受运行里程的影响。在不同摩擦系数及运行里程的叠加影响下,轮轨横向力、轮轴横向力、脱轨系数的峰值出现的位置不同,而轮重减载率却始终处于较为稳定的状态。

面向虚拟连挂的城轨列车群组追踪运行仿真研究

城市轨道交通是解决城市交通拥堵问题最强有效的绿色交通方式,其高峰期客流激增且客流时空分布不均,而面向虚拟连挂的城轨列车动态灵活编组和群组追踪运行能有效满足复杂多变的城轨运营需求。本文剖析面向虚拟连挂的城轨列车群组追踪运行过程,给出虚拟连挂列车群组最小安全追踪距离计算公式;以单列标准车长的线路路段为一个元胞单元,设计速度及位移更新规则,构建基于元胞自动机的城轨列车群组追踪运行仿真模型;以某市地铁2号线为背景,多角度仿真刻画面向虚拟连挂的城轨列车群组追踪运行性能。仿真结果表明:面向虚拟连挂的城轨列车群组追踪运行模型能有效缩短列车最小安全追踪间隔时间,城轨线路通过能力较移动闭塞制式提高78.4%;头车延迟引起的后续列车晚点总数量及总晚点时间更小,呈现出更佳的抗干扰性与恢复性能,且宜采用小编组列车实现虚拟连挂;动态混合编组的城轨列车群组追踪运行性能最佳,单一小编组的次之,大编组列车群宜在小编组列车群前面运行;城轨列车群组旅行速度总体上与平均站间距呈正相关;当列车发车间隔大于延迟时间时,平均站间距对列车群组的延迟影响不敏感,相反,则影响较为显著。研究结论能够为面向虚拟连挂的城轨列车群组追踪运行决策提供技术支撑。

400 km/h高速铁路典型路基段风致行车安全研究

以某设计速度400 km/h的高速铁路4种典型路基段结构为研究对象,采用风车路耦合动力分析方法,运用ANSYS和多体动力学软件SIMPACK分别建立路基和列车模型,分析CRH380动车组在环境风速20~40m/s区间工况,以速度400 km/h通过时车辆的动力响应。根据评价准则提出风致行车安全控制指标。结果表明:车体横向加速度反映列车横风稳定性,可以作为风致行车安全的控制指标;脱轨系数随着风速增大而增大,在风速不超过40 m/s条件下,均未达到上限值0.8;4#路基段可以承受的环境风速最大,风致行车安全的效果最好;背风侧的车辆响应指标均明显好于迎风侧,对于横风影响下的动力仿真分析,应将迎风侧作为主要研究对象。

钢弹簧失能下车辆-浮置板轨道耦合系统动力特性研究

在列车荷载作用下浮置板轨道会发生钢弹簧失能,为研究此问题对车辆-浮置板轨道系统动力特性的影响,基于车辆-轨道动力学理论,建立车辆-浮置板轨道耦合动力学模型,研究不同钢弹簧失能数量、位置、组合形式对车辆-浮置板轨道系统动力响应的影响。结果表明:当钢弹簧失能数量相同时,同一块浮置板的振动响应板中位置大于板端位置;钢弹簧失能1个时,板中位置钢轨、浮置板位移最大值分别比板端位置大0.49 mm和0.22 mm,加速度有效值分别比板端位置大13.34%和21.42%;单侧连续失能钢弹簧数量≥2个时,列车荷载作用下钢轨和浮置板垂向位移最大值均分别超出《浮置板轨道技术规范》规定的限值4 mm和3 mm;车体在频域上的振动响应主要集中在10 Hz内,钢弹簧失能会导致车体振动响应在频域上增大;单侧钢弹簧失能2个比双侧失能2个的钢轨位移最大值、加速度有效值分别增大17.75%、2.22%,比正常状态下钢轨位移、加速度分别增大37.08%,10.84%。钢弹簧失能增加了系统的振动响应,影响减振效果,应注意及时检修。

宽频式钢轨动力吸振器对波磨的影响分析

为了解决某地铁钢弹簧浮置板轨道曲线段钢轨波磨问题,首先对钢轨波磨进行了现场测试,其次依据波磨特征进行宽频式钢轨动力吸振器(wide-frequency tuned mass damper,WTMD)的精准调频和研制。然后将WTMD的质量、刚度和阻尼等参数输入到建立的车辆-WTMD-钢弹簧浮置板耦合动力学模型。模型中浮置板和基础考虑为柔性体,轮轨接触采用多点非赫兹接触的Kik-Piotrowski模型求解。以美国5级谱叠加现场实测的波磨不平顺谱作为激励,运用有限元软件ANSYS和多体动力学仿真软件UM进行联合耦合动力学分析,逐次迭代优化WTMD参数。同时,将有无WTMD的仿真分析得到的钢轨振动加速度和现场实测数据进行对比,研究了WTMD对钢轨振动的影响。最后进行了有无WTMD的钢轨振动总振级、钢轨振动衰减率和3次波磨跟踪测试,研究了WTMD对钢轨振动、钢轨振动衰减率和波磨发展的影响。研究表明:设计的WTMD前3阶振动主频分别为518、700、759 Hz,与车辆通过波磨频率(520~830 Hz)一致;仿真和实测的钢轨振动加速度数据吻合较好,安装WTMD后钢轨振动加速度均方根值由200 g降低为20 g,减振效果为8.1 dB;WTMD可以提高钢轨的垂向和横向振动衰减率,抑制钢轨的垂向和横向pinned-pinned共振;3次波磨跟踪测试发现,WTMD安装后,钢轨波磨发展缓慢,无肉眼可见的波磨。通过以上的仿真和试验都验证了WTMD可以有效地抑制钢轨波磨。

高速铁路铺设CRTS Ⅲ型板式无砟轨道地段的路基冻胀限值

我国冻土地区高速铁路分布广泛,路基冻胀对高速铁路无砟轨道结构损伤影响较为突出,危害行车安全。但是目前尚未建立针对铺设CRTS Ⅲ型板式无砟轨道地段的路基冻胀控制限值。本文基于车辆-轨道耦合动力学理论和混凝土塑性损伤理论,考虑混凝土结构损伤和车轨相互作用,建立车辆-无砟轨道-冻胀路基静动力分析模型,分析路基冻胀对CRTS Ⅲ型板式无砟轨道结构的损伤和车辆动力性能指标的影响。综合静、动力控制指标,提出一种针对冻胀变形的分级控制限值;分别考虑轨道结构层间离缝和结构损伤、钢轨垂向动位移、乘车舒适性和行车安全性等多项控制指标,将路基冻胀限值划分为5个区域。研究结果表明:路基冻胀作用于轨道板中部时损伤和离缝量出现极值;结构损伤和车辆动力学响应均随波长减小和波峰增大而呈增大趋势,且均对波长的影响更为敏感。可以根据不同分区的冻胀限值保障车辆运营安全,为冻土区无砟轨道养护维修提供参考。