轨道支撑失效对钢弹簧浮置板动力响应特性的影响

基于ANSYS软件建立钢弹簧浮置板轨道三维有限元分析模型,研究扣件和隔振器失效对地铁轨道交通列车—钢弹簧浮置板系统的动力响应影响。研究表明:当列车行驶在扣件和隔振器失效的钢弹簧浮置板轨道上,钢轨垂向位移、加速度和临近扣件支点反力变化显著,且随着失效扣件和隔振器数目增加变化越明显;失效扣件和隔振器的中心在浮置板端部比其在浮置板中部的影响大。     

一系螺旋弹簧动刚度对车辆-轨道耦合振动影响分析

建立准确表征一系悬挂轴箱螺旋弹簧波动特性的力学模型,运用动刚度矩阵法求解,研究其对悬挂系统隔振性能影响。结合基于格林函数法的车辆-轨道耦合动力学模型,引入弹簧刚度频变特性,对比分析考虑一系螺旋弹簧频变刚度前后车辆动力学性能之间的差异。结果表明,动刚度矩阵法可以精确求解螺旋弹簧随频率变化的动刚度特性,在一阶模态振动频率后弹簧刚度值呈现103等级的剧烈变化,该结果与有限元模型结果一致;一系螺旋弹簧的动态频率特性导致轮轨激励由车轮至构架的振动位移传递率提高到接近于1,而对车体的振动传递率提高到了10-3左右;在整车车辆-轨道动力学计算中,其对轮轨振动影响较小,但车体与构架出现了较高的高频振动能量峰值。包含一系悬挂动刚度的车辆模型更接近实际,为了降低车辆振动,应尽量提高一系螺旋弹簧自振频率并降低动刚度变化幅值。       

Formulation of equations of motion of finite element form for vehicle–track–bridge interaction system with two types of vehicle model

Vehicle, track and bridge are considered as an entire system in this paper. Two types of vertical vehicle model are described. One is a one foot mass–spring–damper system having two‐degree‐of‐freedom, and the other is four‐wheelset mass–spring–damper system with two‐layer suspension systems possessing 10‐degree‐of‐freedom. For the latter vehicle model, the eccentric load of car body is taken into account. The rails and the bridge deck are modelled as an elastic Bernoulli–Euler upper beam with finite length and a simply supported Bernoulli–Euler lower beam, respectively, while the elasticity and damping properties of the rail bed are represented by continuous springs and dampers. The dynamic contact forces between the moving vehicle and rails are considered as internal forces, so it is not necessary to calculate the internal forces for setting up the equations of motion of the vehicle–track–bridge interaction system. The two types of equations of motion of finite element form for the entire system are derived by means of the principle of a stationary value of total potential energy of dynamic system. The proposed method can set up directly the equations of motion for sophisticated system, and these equations can be solved by step‐by‐step integration method, to obtain simultaneously the dynamic responses of vehicle, of track and of bridge. Illustration examples are given. Copyright 2004 © John Wiley & Sons, Ltd.     

轮对振动和噪声的分析

以轮轨表面粗糙度为激励,利用车辆-轨道多刚体耦合振动模型计算轮轨作用力.利用有限元理论建立轮对的有限元分析模型,以轮轨作用力为激励进行轮对的振动频响分析.以振动响应分析结果作为边界条件,利用边界元理论建立轮对边界元声学分析模型,对轮对振动声学特性进行了计算分析.其结果与公认的模型和软件的计算结果相比具有较好的一致性,证明本文做法的正确性.     

基于动柔度法的轨道高架桥橡胶垫减振性能研究

为探讨下橡胶垫对桥梁减振效果,基于动柔度法建立车辆-轨道-桥梁耦合的垂向动力学模型,车辆考虑1/8轮对系统,只考虑一系弹簧阻尼计算车轮动柔度,钢轨看作无限长Timoshenko梁,桥梁简化为简支的Euler梁,扣件系统、橡胶垫用线性弹簧阻尼单元模拟,联合车轮动柔度、钢轨动柔度和线性接触动柔度计算频域轮轨力并施加到钢轨上,计算钢轨、道床板、桥梁的动力响应。采用振动加速度级、加速度级插入损失和Z振级插入损失评价橡胶垫的减振效果,结果表明,采用橡胶垫后钢轨振动响应略有增大,Z振级插入损失为–0.81 d B,道床板振动响应大幅增加,Z振级插入损失为–10.3 d B,桥梁的振动响应减小明显,Z振级插入损失为:15.6 d B,计算结果表明橡胶垫能有效的降低桥梁结构振动,相关的研究为桥梁的减振降噪提供了一定参考。     

地铁列车运行引起的振动对精密仪器的影响研究

采用一种数值模型,并结合现场振动实测,对北京地铁4号线列车运行引起的振动对北京大学物理实验室内精密仪器的影响问题进行了研究,并对地铁4号线隧道内浮置板轨道的减振效果进行了探讨。该模型根据移动荷载作用下的动力响应解,把地铁列车运行引起的振动问题归结到计算频率-波数域内的传递函数和频域内移动轴荷载的问题上。传递函数采用三维周期性有限元-边界元耦合的数值模型来计算,移动轴荷载主要考虑为频域内轨道不平顺激励下的轮轨接触力。现场振动实测包括地铁列车与公交车单独引起的振动及两者的合振动测试。结果表明:浮置板轨道是一种有效的减振措施,在其工作频段内有显著的减振效果;在低频段,地铁列车单独引起的振动可能对精密仪器正常工作造成影响,公交车流单独引起的振动以及与地铁列车叠加的振动会对精密仪器的正常工作造成影响,仪器基座处应采取相应的隔振措施来减小这部分振动。     

Dynamic finite element modeling and fatigue damage analysis of thermite welds

Railway track comprises of continuous welded rail mounted with rail clips on sleepers integrated to a ballast track form system. Modeling the rail structure with thermite weld subjected to the complex dynamic loadings is a challenging problem. Fatigue failures at the head‐to‐web, web‐to‐foot, and foot regions of weld collar are investigated. In this paper, a combined method of multibody system dynamic analysis and dynamic finite element analysis was used. A train roll‐in experiment was conducted at a train depot test track to validate modeling results predicted at the strain gauge location. Three critical plane‐based multiaxial fatigue criterions incorporated with a smallest enclosing circle algorithm were implemented in Python code to study the fatigue behavior at weld collar. Parametric studies were also conducted to investigate the effects of track component materials, track curvature, and train velocity. This approach provides a method for predicting the failures of thermite welded joints in railway tracks.     

标准动车组用空气弹簧动力学建模与服役性能试验研究

空气弹簧作为我国动车组二系悬挂的关键部件,其性能直接影响到乘客的舒适性,甚至影响到行车安全。以我国最新研发的标准动车组上使用的510B型空气弹簧为研究对象,研究其服役前后性能的改变。分别建立了空气弹簧的有限元模型及气动力学模型,并对新空气弹簧和已经服役30万公里以上的510B型空气弹簧进行静态、动态的例行试验。通过对模型仿真数据与试验数据进行对比,结果表明:新空气弹簧模型动、静态的仿真的滞回曲线和试验所得的滞回曲线吻合较好,所建立的510B型空气弹簧模型能够很好的描述空气弹簧的动态特性;通过修改动力学模型的相关参数,能够很好的描述已经服役的空气弹簧的特性;能够初步的揭示510B型空气弹簧在服役后其垂向刚度及阻尼会有一定程度的增加,对研究空气弹簧老化以及其对整车动力学性能的影响具有一定的实际应用价值。     

考虑轨道弹性时机车轮对的纵向振动研究

在电机轴悬式机车-轨道垂向耦合动力学模型的基础上,考虑了机车的纵向运动自由度,通过对比牵引工况下考虑和不考虑轨道弹性时的轮轨作用力及轮对振动加速度,得到了轨道弹性变形对轮对轮轨切向力及其纵向振动的影响规律。研究结果表明,当轮轨界面无不平顺激扰时,考虑或忽略轨道结构的弹性对轮对牵引力的发挥及纵向振动影响不大;在不平顺激扰下,轨道结构参与轮轨间的耦合振动,由于轨道垂向的弹性及阻尼作用,轮轨垂向力特别是高频力得到缓冲及衰减,致使50Hz以上高频段的轮轨切向力及轮对纵向振动变的缓和,利于轮周牵引力的稳定发挥。总体上,分析模型中若不考虑轨道弹性会造成预测的轮轨切向力及轮对振动加速度偏大。     

高速铁路扣件弹条动力学分析

为了研究扣件弹条在高速列车动荷载作用下的振动特性,以我国高速铁路采用的Vossloh扣件弹条为研究对象,采用ABAQUS有限元软件建立详细的扣件系统有限元模型,基于非线性接触理论与车辆-轨道耦合动力学理论,研究弹条在安装过程中的受力及列车动荷载作用下的振动特性,并与现场实测结果进行了对比验证。结果表明:螺栓预压力施加到33kN时,弹条达到正常安装状态,此时弹条中圈环位移为20.3mm,弹条扣压力为13.8kN;考虑钢轨波磨情况下,弹条加速度和振动位移最大值分别约为3g、0.05mm,计算结果与实测结果在振动形态与幅值上均基本一致,弹条振动加速度与不考虑钢轨波磨下的结果相比约增大10倍,明显加剧了扣件弹条的振动,从而会加速弹条的疲劳损伤。     

Failure investigation and stress analysis of a longitudinal stringer of an automobile chassis

A failure analysis of a longitudinal stringer of a prototype vehicle has been carried out in this study. Failure took place at the bumpers fixation points of the vehicle suspension during durability tests. Crack was created and has grown causing fracture of the component. Stress analysis was performed using finite element method. A reinforcement model to solve the problem was proposed. Experimental quasi-static and durability tests were carried out and failures were no longer observed.     

地铁钢轨波磨对轨道结构振动及减振特性影响

现场调查某地铁线路上普通短轨枕、先锋扣件和钢弹簧浮置板三种轨道的钢轨波磨特征,并分别进行振动测试,研究钢轨存在波磨时,三种轨道结构的振动特性及减振效果。结果表明:三种轨道结构都是内轨波磨明显,外轨表面不平顺幅值相比内轨都很小,可以忽略不计其影响;波磨主波长频率成分很容易在轨道各零部件(包括隧道壁)振动中激发出来,并且会引起较大幅值的振动;在4 Hz~200 Hz频率范围内,波磨激励下的减振型轨道依然具有良好的减振性能,但是与其最初设计用于的减振效果相比,有明显的下降;先锋扣件轨道短波长波磨会削减隧道壁在高频段的减振效果;钢弹簧浮置板轨道的波磨幅值显著,虽然对其隧道壁的减振效果影响不明显,但是会造成钢轨振动增加。     

基于悬架运动模型的传动轴空间动态运动分析和优化

为提高传动轴空间布置的合理性和适应性, 优化设计需要结合悬架的空间运动特性.从板簧汽车实际行驶的动态工况出发,对汽车板簧进行了运动学分析,建立基于悬架空间运动模型的传动轴运动模型,并提出了传动轴动态空间的优化目标,利用线性加权的方法,将多目标优化问题转化为单目标优化问题,选择小种群遗传算法作为优化算法.实例计算得到了平均当量夹角更小的传动布置方案,有效减小了振动和噪声.优化结果表明：基于板簧运动的传动轴空间动态设计,比传统的单一载荷下的优化设计更为合理,优化效率更高,并且优化结果的适应性更好.     

Moving element method for train‐track dynamics

This paper presents a new approach, called the moving element method, for the dynamic analysis of train‐track systems. By discretizing the rail beam on viscoelastic foundation into elements that ‘flow’ with the moving vehicle, the proposed method eliminates the need for keeping track of the vehicle position with respect to the track model. The governing equations are formulated in a co‐ordinate system travelling at a constant velocity, and a class of conceptual elements (as opposed to physical elements) are derived for the rail beams. In the numerical study, four cases of moving vehicle are presented taking into consideration the effects of moving load and rail corrugation. The method is shown to work for varying vehicle velocity and multiple contact points, and has several advantages over the finite element method. The numerical solutions compare favourably with the results obtained by alternative methods. Copyright © 2003 John Wiley & Sons, Ltd.     

运行列车对高层建筑结构的振动影响

建立了一种列车-轨道-路基解析分析模型,将钢轨视为竖直平面内支承在Winkler弹性基础上的一根连续的Euler-Bernoulli梁,考虑轮轨接触的影响,推导出单个轮对荷载对地基的作用力,通过迭加方式得到整列车对路基产生的动荷载;在此基础上,选取铁路线附近的某高层建筑,用有限元分析的方法计算了该高层建筑所受到的振动影响;研究了不同车速下不同距离建筑物中不同楼层的振动规律:振动随楼层高度增加具有不同程度增大的趋势;车速越大,建筑物的振动响应也越大;随着到轨道中心线距离的增加,建筑结构的振动逐渐减小。     

基于谱元法的车辆-轨道结构频域振动特性研究

基于谱元法建立车辆-轨道结构频域振动模型,其中轨道结构模拟为三层铁木辛柯梁,车辆部分考虑为整车模型,运用Lagrange方程实现车辆与轨道结构的耦合,并采用虚拟激励法将轨道不平顺模拟为虚拟荷载,通过求解车辆-轨道整体结构的谱元法方程,得到车辆-轨道结构在频域内的振动响应。结果表明:钢轨、轨道板和底座板的第一、二、四阶振动峰值分别由车体、转向架、车轮自振引起,其他振动峰值由轨道结构系统自振引起;钢轨、轨道板和底座板的振动能量分布在较宽的频率范围;在离开车辆一侧且距离端轮对2.5 m处,1～800 Hz内钢轨振动迅速衰减,当大于800 Hz时,钢轨振动衰减缓慢;在距离端轮对18 m处,25～1 171 Hz内钢轨振动衰减基本稳定;在距离端轮对20.5 m处,小于25 Hz时,钢轨振动随着离开端轮对距离的增加迅速衰减,当大于1 171 Hz时,钢轨振动则衰减较小。     

A simple finite element model for vibration analyses induced by moving vehicles

This study developed a simple finite element method combining the moving wheel element, spring–damper element, lumped mass and rigid link effect to simulate complicated vehicles. The advantages of this vehicle model are (1) the dynamic matrix equation is symmetric, (2) the theory and formulations are very simple and can be added to a standard dynamic finite element codes easily and (3) very complicated vehicle models can be assembled using the proposed elements as simple as the traditional finite element method. The Fryba's solution of a simply supported beam subjected to a moving two‐axle system was analysed to validate this finite element model. For a number of numerical simulations, the two solutions are almost identical, which means that the proposed finite element model of moving vehicles is considerably accurate. Field measurements were also used to validate this vehicle model through a very complicated finite element analysis, which indicates that the current moving vehicle model can be used to simulate complex problem with acceptable accuracy. Copyright © 2006 John Wiley & Sons, Ltd.     

Stress intensity factors evaluation for through-transverse crack in slab track system under vehicle dynamic load

The stress intensity factors (SIFs) for through-transverse crack in the China Railway Track System (CRTS II) slab track system under vehicle dynamic load are evaluated in this paper. A coupled dynamic model of a half-vehicle and the slab track is presented in which the half-vehicle is treated as a 18-degree-of-freedom multi-body system. The slab track is modeled as two continuous Bernoulli–Euler beams supported by a series of elastic rectangle plates on a viscoelastic foundation. The model is applied to calculate the vertical and lateral dynamic wheel–rail forces. A three-dimensional finite element model of the slab track system is then established in which the through-transverse crack at the bottom of concrete base is created by using extended finite element method (XFEM). The wheel–rail forces obtained by the vehicle-track dynamics calculation are utilized as the inputs to finite element model, and then the values of dynamic SIFs at the crack-tip are extracted from the XFEM solution by domain based interaction integral approach. The influences of subgrade modulus, crack length, crack angle, friction coefficient between cracked surfaces, and friction coefficient between faces of concrete base and subgrade on dynamic SIFs are investigated in detail. The analysis indicates that the subgrade modulus, crack length and crack angle have great effects on dynamic SIFs at the crack-tip, while both of the friction coefficients have negligible influences on variations of dynamic SIFs. Also the statistical characteristics of varying SIFs due to random wheel–rail forces are studied and results reveal that the distributions of dynamic SIFs follow an approximately Gaussian distribution with different mean values and standard deviations. The numerical results obtained are very useful in the maintenance of the slab track system.     

Design and failure modes of automotive suspension springs

This paper is a discussion about automotive suspension coil springs, their fundamental stress distribution, materials characteristic, manufacturing and common failures. An in depth discussion on the parameters influencing the quality of coil springs is also presented.

Following the trend of the auto industry to continuously achieve weight reduction, coil springs are not exempt. A consequence of the weight reduction effort is the need to employ spring materials with significantly larger stresses compared to similar designs decades ago. Utilizing a higher strength of steel possesses both advantages and disadvantages. The advantages include the freedom to design coil springs at higher levels of stress and more complex stresses. Disadvantages of employing materials with higher levels of stress come from the stresses themselves. A coil’s failure to perform its function properly can be more catastrophic than if the coil springs are used in lower stress. As the stress level is increased, material and manufacturing quality becomes more critical. Material cleanliness that was not a major issue decades ago now becomes significant. Decarburization that was not a major issue in the past now becomes essential.

To assure that a coil spring serves its design, failure analysis of broken coil springs is valuable both for the short and long term agenda of car manufacturer and parts suppliers. This paper discusses several case studies of suspension spring failures. The failures presented range from the very basic including insufficient load carrying capacity, raw material defects such as excessive inclusion levels, and manufacturing defects such as delayed quench cracking, to failures due to complex stress usage and chemically induced failure. FEA of stress distributions around typical failure initiation sites are also presented.     

高速铁路铰接式列车车桥系统动力响应分析

根据铰接式车辆结构和悬挂形式的特点,建立了铰接车辆单元模型,以现有通用软件为基础直接生成桥梁模型的质量、刚度矩阵,并以实测轨道不平顺为系统激励,求解车桥耦合动力相互作用问题;以欧洲布鲁塞尔-巴黎高速铁路线上的Thalys铰接式列车通过Antoing桥为例,分析了桥梁的动挠度、竖向和横向加速度等动力响应及运行车辆的振动加速度响应,并对铰接式列车的振动特性进行了初步的探讨;最后通过现场试验对分析模型和计算结果进行了验证。