不同轮轨接触模型在车桥耦合振动中的比较

以工程实例为研究对象,建立了整车-整桥系统耦合振动数值分析模型。考虑车轮的跳轨和挤密情况,建立了单边弹簧-阻尼系统弹性轮轨接触模型。采用基于多体系统动力学和有限元法结合的联合仿真技术,计算了两种轮轨接触时动车组列车以不同车速通过大跨度连续桥梁的耦合振动响应。数值计算结果表明:两种轮轨接触模型的桥梁动力响应比较接近;列车的横向轮轨力、轮重减载率和脱轨系数相差较大,当速度为350km/h时,横向轮轨力增大了46.5%,轮重减载率增大了130.8%,脱轨系数增大了24.66%;用单边-弹簧阻尼系统弹性轮轨接触模型更符合实际。     

钢轨横向不均匀支撑刚度对钢轨波磨的影响

建立了钢轨波浪形磨损计算模型,模型中考虑车辆轨道垂向横向耦合动力学行为、轮轨三维滚动接触力学行为和轮轨材料摩擦磨损的循环相互作用关系. 发展了相应的计算程序,并用1: 1试验装置验证了理论模型. 详细分析了实际线路上由轨枕离散支撑导致的钢轨横向不均匀刚度和不同行车速度对曲线钢轨接触表面不均匀磨损的影响. 通过数值分析可知：(1)列车通过曲线钢轨时,轨枕离散支撑导致的钢轨横向不均匀刚度易引发曲线钢轨波磨的形成和发展;(2)这类钢轨波磨具有与轨枕间距几乎相等的波长和28~35mm的短波长,这个短波长不均匀磨损主要是由轮轨高频接触振动引起;(3)同一个转向架4个车轮作用下形成的钢轨波磨最大深度波谷的分布是不同的;(4)改变过车速度不能有效地抑制轨枕离散支撑导致的钢轨波磨形成和发展速度.     

Dynamical investigation of railway vehicles on a curved track

The main objective of this article is an examination of railway vehicle dynamics during motion along a curved track. Two main aspects are presented in the paper. First, two different methods used while investigating multi-rigid body systems such as railway vehicles are discussed, i.e. the quasi-statical (or kineto-statical) and dynamical approaches. Second, two practical problems dealing with vehicle motion along a curved track are investigated. The problems under consideration refer to vibrations as well as stability, examined via finding obtained with the author's software as a result of numerical simulation. The work has both a practical and a cognitive character. The aim of the investigations is firstly to indicate the limitations of quasi-statical (and kineto-statical) methods and secondly to study the problems which cannot be treated by these methods. Two specific problems of the type investigated using a dynamical approach are the influence of track geometrical irregularities on the evaluation of vehicle ride properties and limit cycle occurrence during vehicle curve negotiation. Due to the renewed interest in the rapid passenger railway, the investigations take into consideration curves of large radii introduced along railway routes for increased velocities. Furthermore, it is shown under which conditions the obtained results may have an important practical application. This concerns the influence of vehicle suspension parameters as well as conditions of motion (speed, superelevation, curve radius, transition curve existence) on limit cycle occurrence. The limited value of conclusions dealing with vehicle ride properties obtained while using quasi-statical (kineto-statical) methods is proved through quantitative analysis. The problem of the influence of geometrical irregularities on wheel-rail pair wear is also pointed out.     

On permanent long-wave distortions of a railway track due to the moving vehicle load

Summary  The paper presents a simple mathematical model which describes the evolution of the vertical profile of a railway track caused by the load arising from moving vehicles. Owing to the fact that the track ballast is not perfectly elastic, each passage of a train is accompanied by a residual deformation of the ballast. Being very small, these deformations, however, accumulate with time. It is shown that an initial imperfection in the vertical profile of the track will either grow or diminish after each passage. For given track and vehicle, the rate of growth is determined by the characteristic length of the imperfection and by the velocity of the vehicle. Received 3 February 2000; accepted for publication 19 July 2000     

摩擦自激振动引起摩擦面波状磨耗的试验研究

在销-盘摩擦磨损试验机上进行金属干摩擦试验,研究摩擦自激振动对盘试件磨痕表面轮廓的影响,采用激光位移传感器测量盘试件摩擦表面轮廓尺寸,用加速度传感器测量销试件的摩擦自激振动.试验结果表明：在干摩擦状态下,销-盘系统容易发生持续的摩擦自激振动,当摩擦时间达到一定数值后,盘试件的磨痕表面轮廓会出现明显的波浪形磨耗,波浪形磨损机理主要是疲劳磨损.分析表明波浪形磨耗的波长近似等于摩擦自激振动的周期与滑动速度的乘积,由此推断摩擦自激振动引起了摩擦表面的波浪形磨耗.     

Steady-state analysis of multibody systems with reference to vehicle dynamics

This paper presents a systematic methodology and formulation for determining the steady-state response of multibody systems. The equations of motion for a general multibody system are described in terms of a set of relative joint accelerations. Then, the differential equations of motion are converted to a set of algebraic equations for the steady-state response. These equations are derived based upon a set of conditions that must exist for the steady state. The application of this formulation in determining the steady-state response of a vehicle moving in a circular path is shown. The multibody model of the vehicle for two- or four-wheel steering is presented. The results of the steady-state simulation are compared with those obtained from a transient dynamic analysis.     

Ride dynamics mathematical model for a single station representation of tracked vehicle

Tracked vehicles are exposed to severe ride environment due to dynamic terrain-vehicle interactions. Hence it is essential to understand the vibration levels transmitted to the vehicle, as it negotiates different types of terrains at different speeds. The present study is focused on the development of single station representation of tracked vehicles with trailing arm hydro-gas suspension systems, simulating the ride dynamics. The kinematics of hydro-gas suspension system have been derived in order to determine the non-linear stiffness characteristics at various charging pressures. Then, incorporating the actual suspension kinematics, non-linear governing equations of motion have been derived for the sprung and unsprung masses and solved by coding in Matlab. Effect of suspension non-linear dynamics on the single station ride vibrations have been analyzed and validated with a multi-body dynamics model developed using MSC.ADAMS. The above mathematical models would help in estimating the ride vibration levels of the tracked vehicle, negotiating different types of terrains at various speeds and also enable the designers to fine-tune the suspension characteristics such that the ride vibrations are within acceptable limits. The mathematical ride model would also assist in development of non-linear ride vibration model of full tracked vehicle and estimate the sprung mass dynamics.     

基于逆虚拟激励法的垂向轨道不平顺功率谱识别

提出一种识别轨道垂向不平顺功率谱的新方法.采用定点激励的垂向车辆-板式轨道耦合动力学模型.车辆简化为多刚体模型,板式轨道考虑为3层梁模型,并通过线性轮轨力耦合车辆模型和轨道模型.以轴箱加速度作为测量对象,采用逆虚拟激励法识别垂向轨道不平顺的功率谱,并研究了测量误差和车辆运行速度对垂向轨道不平顺的识别精度的影响.数值结果表明,本文方法能够较为准确地识别垂向轨道不平顺功率谱,为列车运行环境载荷识别与评估提供了新的途径.     

Interface damage and its effect on vibrations of slab track under temperature and vehicle dynamic loads

This paper presents a three-dimensional finite element model to investigate the interface damage occurred between prefabricated slab and CA (cement asphalt) mortar layer in the China Railway Track System (CRTS-II) slab track system. In the finite element model, a cohesive zone model with a non-linear constitutive law is introduced and utilized to model the damage, cracking and delamination at the interface. Combining with the temperature field database obtained from the three-dimensional transient heat transfer analysis, the interface damage evolution as a result of temperature change is analyzed. A three-dimensional coupled dynamic model of a vehicle and the slab track is then established to calculate the varying rail-supporting forces which are utilized as the inputs to the finite element model. The non-linearities of the wheel–rail contact geometry, the wheel–rail normal contact force and the wheel–rail tangential creep force are taken into account in the model. Setting the maximum interface damaged state calculated under temperature change as the initial condition, the interface damage evolution and its influence on the dynamic response of the slab track are investigated under the joint action of the temperature change and vehicle dynamic load. The analysis indicates that the proposed model is capable of predicting the initiation and propagation of cracks at the interface. The prefabricated slab presents lateral warping, resulting in severe interface damage on both the sides of the slab track along the longitudinal direction during temperature drop process, while the interface damage level does not change significantly under vehicle dynamic loads. The interface damage has great effects on the dynamic responses of the slab track.     

两种型面轮轨滚动接触蠕滑率和摩擦功

采用数值分析方法详细分析了2种型面轮对与轨道在滚动接触过程中的接触几何、蠕滑率和摩擦功。在摩擦功分析计算中利用了Kalker三维弹性体非赫兹滚动接触理论,并考虑了轮轨的结构变形的影响。分析计算表明,在轮对运动相同的情况下,磨耗型轮对与轨道之间的蠕滑率和摩擦功与锥型轮对轨道之间的蠕滑率和摩擦功相差甚大。数值分析结果表明,现行铁路中正在推广使用的磨耗型轮对并不能减少轮轨接触表面之间的磨损,磨损型车轮的型面与钢轨尺寸的匹配还有待进一步改进。     

Effect of an innovative vertical vibro-tracked vehicle on soil compaction

The aim of this paper is to compare a new vertical vibro-compaction machine, carried by a tracked vehicle of total weight 10.9 kN, with compactors using centrifugal, vertical and horizontal oscillators at the exciting force of 9.8 kN and at a frequency of 16 Hz. These were tested experimentally on a thick lift of decomposed weathered granite sandy soil. It was observed that the final amount of sinkage of the terrain surface using the vertical vibro-tracked vehicle was the greatest. The final distribution of dry density was almost uniform in depth and the values were the largest of all other maximum dry densities for centrifugal and horizontal vibro-tracked vehicles. As a result, the vertical vibro-tracked vehicle was verified theoretically from the analysis of the stress and the acceleration propagation to be an excellent and impressive new compaction machine for compacting thick lifts of soil stratum.     

接触应力对轮轨材料滚动摩擦磨损性能影响

利用MMS-2A型微机控制摩擦磨损试验机研究了接触应力对轮轨材料的滚动摩擦磨损性能影响.结果表明：随接触应力的增加,滚动摩擦系数呈增加趋势,车轮和钢轨试样磨损加剧;相同接触应力水平下,车轮试样磨损量大于钢轨试样,表面损伤严重;随接触应力的增加,车轮试样表面从犁沟且轻微剥落向严重剥落损伤转变,钢轨试样表面损伤主要表现为犁沟效应并伴随有剥落现象,但相比车轮试样的剥离损伤要轻微.     

干-水态下圆形硌伤对钢轨材料滚动接触疲劳特性影响

采用布氏硬度仪在钢轨试样表面制得不同尺寸的圆形硌伤,利用MMS-2A型微机控制摩擦磨损试验机研究了未硌伤和硌伤钢轨的表面硬度、磨损量及滚动接触疲劳损伤特性.结果表明:与未硌伤钢轨相比,硌伤钢轨的表面硬度和磨损量都有所增加;随硌伤尺寸增加,钢轨磨损量与硬度随之增大.较小尺寸的硌伤坑(1.6 mm)有助于减轻硌伤处疲劳裂纹的产生,硌伤坑超过临界值(2.0 mm)则会加重硌伤区附近疲劳裂纹的萌生并导致支裂纹和垂向裂纹的出现.未硌伤钢轨疲劳裂纹以沿晶扩展为主,大尺寸硌伤钢轨试样的疲劳裂纹呈现穿晶扩展现象.     

The motion of viscous liquid column with finite length in a vertical straight capillary tube

This paper deals with the motion of viscous liquid column with finite length and two free surfaces in a vertical straight capillary tube. It is assumed that fluid is Newtonian. Linearizing the boundary conditions, analytic expressions in the form of infinite series have been obtained for velocity, piessure and free surface at low Reynolds number. The numerical calculation is carried out for a set of cylinder’s length of water and blood. It has been revealed that there are considerable circulating currents at the upper and lower meniscuses. Its maximum velocity is about 57% of the average velocity of the mainstream. Iner-tial effect is also studied in this paper. Using the time-dependent method in finite difference techniques, numerical solution of the corresponding nonlinear equation at Re<24.5 is computed. Comparing it with analytic exact solution at low Reynolds number shows that inertial effect is negligible provided Re<24.5.     

Response of railway track system on poroelastic half-space soil medium subjected to a moving train load

Based on the dynamic poroelastic theory of Biot, dynamic responses of a track system and poroelastic half-space soil medium subjected to moving train passages are investigated by the substructure method. The whole system is divided into two separately formulated substructures, the track and the ground, and the rail is described by introducing the Green function for an infinitely long Euler beam subjected to the action of moving axle loads of the train and the reactions of the sleeper. Sleepers are represented by a continuous mass and the effect of the ballast is considered by introducing the Cosserat model for granular medium. Using the double Fourier transform, the governing equations of motion are then solved analytically in the frequency-wave-number domain. The time domain responses are evaluated by the inverse Fourier transform computation for a certain train speed. Computed results show that the shape of the rail displacements of the elastic and poroelastic soil medium are in good agreement with each other of the low train velocity, but the result of the poroelastic soil medium is significantly different to that of the elastic soil medium for the high train velocity which is higher than Rayleigh-wave speed in the soil. The influence of the soil intrinsic permeability on soil responses is discussed with great care in both time domain and frequency domain. The dynamic responses of the soil medium are considerably affected by the fluid phase as well as the load velocity.     

考虑主动时滞的汽车悬架系统控制特性研究

以汽车悬架系统为研究对象,采用理论和试验相结合的方法对考虑主动时滞的悬架系统控制特性进行分析。首先建立含时滞悬架系统动力学模型,分析系统的控制稳定性。理论和仿真结果均表明,采用传统二次型最优控制律不能保证含时滞系统的稳定性。系统时滞量存在稳定区间,时滞超出稳定区间时系统将失稳发散;为了保证控制系统的稳定性,采用状态变换法设计了含时滞系统的主动控制律,计算表明,该控制律可以保证系统稳定性。研究还发现,时滞量的变化会使系统振动幅值产生较大改变,为此在控制系统中引入主动时滞,研究主动时滞对系统振动特性的影响,计算表明,合理的主动时滞可以降低系统振动幅值;为验证结果的正确性,搭建了悬架时滞主动控制试验平台,通过对相同工况下仿真结果与试验结果进行对比,发现两者具有较好的一致性;而由于悬架受到的路面激励具有随机性,采用含时滞系统的主动控制律对路面随机激励下的悬架系统进行控制分析,发现当主动时滞为0.04 s时,车身加速度均方根值比无主动时滞降低了39.4%,说明主动时滞对悬架控制的有效性。本文研究对时滞主动控制的理论研究具有重要的促进作用。     

Effects of vertical exciting force of a tracked vehicle on the dynamic compaction of a high lifted decomposed granite

The main purpose of this paper is to evaluate the effects of a jumping action of a tracked vehicle mounted with a vertical oscillator on vibro-compaction of a high lifted decomposed granite. A vibro-compaction test was executed using a model tracked vehicle of 4.9 kN weight under a condition of frequency of 16 Hz and load ratio of maximum vertical exciting force to vehicle weight of 0.2–2.0. As a result, it was observed that both the amount of sinkage of terrain surface and the dry density of soil increased hyperbolically with increment of the load ratio and the dry density distribution with depth became uniform for the whole depth of the soil stratum. It was confirmed that the volume shrinkage of soil was succeeded by the propagation of acceleration to deep stratum due to the jumping action and the dilatancy phenomenon due to an alternative shear stress. The optimum load ratio obtaining a maximum dry density at the frequency of 16 Hz was judged to be 2.0 within this experiment. In the application of these test results to an actual prototype tracked vehicle of 39.2 kN weight, it was estimated that the degree of compaction of a high lifted soil stratum of 90 cm became over 90% at the load ratio of 2.0.     

Effect of the contact-line dynamics on the natural oscillations of a cylindrical droplet

The natural oscillations of a cylindrical droplet of an inviscid liquid surrounded by a different liquid and bounded in the axial direction by solid planes are studied. The motion of the contact line is described using an effective boundary condition. The dependence of the frequency and damping ratio on the capillary parameter is found. It is shown that the fundamental frequency of the translation mode vanishes beginning from a certain value of the capillary parameter. Depending on the ratio of the radial and axial dimensions of the droplet, the fundamental frequency of the axisymmetric mode and modes higher than the translation mode can vanish in a certain range of the capillary parameter. This dependence of the natural oscillation frequencies on the problem parameters allows one to determine the capillary parameter. __________ Translated from Prikladnaya Mekhanika i Tekhnicheskaya Fizika, Vol. 48, No. 5, pp. 78–86, September–October, 2007.     

Large eddy simulation on the unsteady aerodynamic response of a road vehicle in transient crosswinds

A large eddy simulation method based on a fully unstructured finite volume method was developed, and the unsteady aerodynamic response of a road vehicle subjected to transient crosswinds was investigated. First, the method was validated for a 1/20-scale wind-tunnel model in a static aerodynamic condition; this showed that the surface pressure distributions as well as the aerodynamic forces and moments were in good agreement with wind-tunnel data. Second, the method was applied to two transient crosswind situations: a sinusoidal perturbation representing the typical length scale of atmospheric turbulence and a stepwise crosswind velocity corresponding to wind gusts. Typical transient responses of the aerodynamic forces and moments such as phase shifting and undershooting or overshooting were observed, and their dependence on the frequency and amplitude of the input perturbation is discussed. Thus, the utility and validity of the large eddy simulation was demonstrated in the context that such transient aerodynamic forces are difficult to measure using a conventional wind tunnel.     

基于振动监测的静载荷滑动轴承接触摩擦故障诊断实验研究

采用静载荷滑动轴承试验台模拟轴颈-轴承从液体润滑状态逐步向干摩擦状态过渡时的接触摩擦故障的发生和发展过程,进而利用振动信号诊断滑动轴承的接触摩擦故障;通过对特征参数进行归一化处理得到无量纲特征参数,进而通过无量纲特征参数的适当数学组合得到无量纲诊断准则,并探讨了无量纲诊断准则的适用性.结果表明:利用所得到的无量纲诊断准则进行轴颈-轴承接触摩擦故障诊断时无须建立用于模式识别的标准模,可实现快捷方便的故障诊断;无量纲诊断准则对工况不敏感,而对故障更敏感,适用于可变工况下滑动轴承的故障诊断,且诊断成本较低.