防撞护栏最大动态变形量敏感性分析

碰撞参数在试验组织中会产生误差,为了解护栏最大动态变形量对碰撞参数的敏感程度,建立了车辆碰撞某金属梁柱式护栏有限元仿真模型,模型中考虑了碰撞过程中路基对护栏的影响,采用平均敏感度系数作为护栏敏感度的评判标准。结果表明,撞击速度是影响防撞护栏最大动态变形量的最敏感因素,该研究成果对制定碰撞试验误差范围具有指导意义。     

Flexible Bodies in Multibody System Codes

Multibody codes are'efficient tools to simulate nonlinear dynamic behaviour of rigid and flexible multibody systems undergoing large overall motions overlaid by small elastic deformation. This paper gives an overview of common approaches for the equations of motion of flexible body models and presents a general way to prepare the required data including geometric stiffening terms. In particularly, for the nodal approach the data are derived using standard results of a finite element analysis of the body. The computation of coefficient matrices describing the equations of motion is done outside the finite element code by matrix manipulations only. The data are stored in a standardised object-oriented structure. Consequently, the data set is independent of the formulation of the multibody system code.     

Flexible Bodies in Multibody System Codes

SUMMARY

Multibody codes are'efficient tools to simulate nonlinear dynamic behaviour of rigid and flexible multibody systems undergoing large overall motions overlaid by small elastic deformation. This paper gives an overview of common approaches for the equations of motion of flexible body models and presents a general way to prepare the required data including geometric stiffening terms. In particularly, for the nodal approach the data are derived using standard results of a finite element analysis of the body. The computation of coefficient matrices describing the equations of motion is done outside the finite element code by matrix manipulations only. The data are stored in a standardised object-oriented structure. Consequently, the data set is independent of the formulation of the multibody system code.     

罕遇地震作用下高速铁路桥墩动力响应分析

建立了列车荷载作用下高速铁路桥墩模型,将桥墩纳入高速铁路简支梁桥全桥体系中进行动力分析.采用弯矩-曲率关系计算程序以及有限元软件,对高速铁路桥墩进行弹塑性分析计算,分别计算了罕遇地震作用下不同车速和不同地震作用组合等工况下的桥梁的弹塑性地震响应。计算结果表明,随着车速的增加,桥梁的地震响应呈上升趋势,结构位移较大;罕遇地震作用下高铁桥梁墩底进入弹塑性状态,给出塑性铰长度数值计算结果,并与AASHTO规范对比验证。     

车辆动荷载下偏压深基坑支护结构受力变形分析

依托杭州某地铁车站偏压深基坑工程,基于PLAXIS有限元软件建立三维数值计算模型,分析车辆动荷载对基坑开挖变形影响。结果表明:随基坑开挖深度增加,基坑内竖向位移和墙体水平位移均呈现先增大后减小趋势;工程施工时,在开挖至第三层土体时需加大注意坑底竖向位移变化,防止基坑隆起过大影响施工;车辆动荷载对基坑影响深度有限,基坑开挖深度小于15 m时,车辆动荷载对基坑影响较大,应注意车辆荷载对土体稳定性和地连墙水平位移问题,宜采取相关保护措施。     

Prediction procedure for wear distribution of transient rolling tire

As a research method, finite element analysis (FEA) with ABAQUS can help researchers to study throughout the whole process of abnormal tire wear. For precise tread wear simulation, this paper introduces a tire finite element model building method. Then, the model is verified by comparing its simulation results with experiment data. Based on the verified model, tire high-speed rolling procedure is presented by combining steady-state transport analysis and dynamic analysis. To predict the wear distribution, micro tread wear calculation method is described. Finally, the wear prediction procedure of tread mesh evolving is introduced and tire polygonal wear pattern is simulated by this procedure.     

钢管混凝土提篮式拱桥动力特性及参数敏感性分析

以某大跨径钢管混凝土提篮式拱桥为研究对象,结合大型通用有限元程序,建立了3种基于不同假定的实桥空间有限元计算模型,利用子空间(Subspace)迭代法计算了该桥结构的自振频率和振型,并对3种模型的计算结果进行了对比分析;研究了拱肋内倾角、含钢率、钢管直径、混凝土弹性模量、横撑布置等结构参数对结构动力特性的影响。分析结果可为该类桥的动力设计提供参考依据。     

步行车辆运动弹性动力学分析

步行车辆在快速运动中,既有大刚体运动又有小弹性位移,且还有不连续的边界约束条件,是一个很复杂的动力学问题。本文用有限元方法建立了该系统的动力学模型,采用分段的直接积分法求解其弹性动力响应。     

Dynamic Interaction of Vehicles with Tracks and Roads

The principle problems of the new developing scientific field - dynamics of vehicles, tracks and roads - are defined. Basic theoretical models for the analysis of railway and road vehicles, tracks and roads and principle methods of their solution are shown. The dynamic interactions between vehicles and routes are emphasized and several basic equations are given to show the behaviour of their elements. The effect of some parameters, like speed, track or roads irregularities etc. is explained. The possibilities are described how to simplify the theoretical models to obtain a simple solution.     

Influence of the aerodynamic forces on the pantograph–catenary system for high-speed trains

Most of the high-speed trains in operation today have the electrical power supply delivered through the pantograph–catenary system. The understanding of the dynamics of this system is fundamental since it contributes to decrease the number of incidents related to these components, to reduce the maintenance and to improve interoperability. From the mechanical point of view, the most important feature of the pantograph–catenary system consists in the quality of the contact between the contact wire of the catenary and the contact strips of the pantograph. The catenary is represented by a finite element model, whereas the pantograph is described by a detailed multibody model, analysed through two independent codes in a co-simulation environment. A computational procedure ensuring the efficient communication between the multibody and finite element codes, through shared computer memory, and suitable contact force models were developed. The models presented here are contributions for the identification of the dynamic behaviour of the pantograph and of the interaction phenomena in the pantograph–catenary system of high-speed trains due to the action of aerodynamics forces. The wind forces are applied on the catenary by distributing them on the finite element mesh. Since the multibody formulation does not include explicitly the geometric information of the bodies, the wind field forces are applied to each body of the pantograph as time-dependent nonlinear external forces. These wind forces can be characterised either by using computational fluid dynamics or experimental testing in a wind tunnel. The proposed methodologies are demonstrated by the application to real operation scenarios for high-speed trains, with the purpose of defining service limitations based on train and wind speed combination.     

A Track-Wheel-Terrain Interaction Model for Dynamic Simulation of Tracked Vehicles

A mathematical model of track-wheel-terrain interaction is presented that supports the dynamic simulation of tracked vehicles. This model combines approximate and known constitutive laws for terrain response with a new representation for the track segment. The resulting track-wheel-terrain model allows the computation of the track tension and the normal and shear forces at the track-terrain interface as the track negotiates terrain of arbitrary profile. A key feature of this model is the uniform treatment of contact between the track and the roadwheels and the track and the terrain. Treating both contact problems in the same manner significantly simplifies the problem formulation and also reduces difficulties in computing points of track-wheel and track-terrain separation. The model takes the form of a two-point nonlinear boundary value problem that accounts for tension variations along the track (due to the non-uniformly distributed normal pressure and traction), track extensibility, and geometrically large (nonlinear) track deflections. Solutions are obtained using a finite element formulation. Both the model and the solution method are formulated for implementation within a multibody dynamics code for simulating full vehicles. Several examples illustrate the capabilities of the proposed model.     

On the overriding issue of train front end collision in rail vehicle dynamics

A three-dimensional dynamic model of crashed vehicles coupled with moving tracks is developed to research the dynamic behaviour of the train front end collision on tangent tracks. The three-dimensional dynamic model consists of a crashed vehicle model, moving track models, a simple wheel–rail contact model, a velocity-based coupler model and the model of energy absorption and anti-climbing devices. The vector method dealing with the nonlinear wheel–rail geometry is put forward in the paper. The developed model is applicable in the scope that central collisions occur on tangent tracks at low speeds. The examples of the vehicle impacting with a rigid wall and the train front end collision are carried out to obtain the dynamic responses of vehicles. The overriding issue is studied on the basis of the wheel rise in train collisions. The results show that the second bogie of the first colliding vehicle possesses the maximal wheel rise. The wheel rise increases with the increase of vehicles. However, the number of vehicles has tiny influence on the overriding in train collisions at low speeds. On the contrary, the impact speed has significant influence on the overriding in train collisions. The wheel rise increases rapidly if the impact speed is close to the critical speed of overriding. The large wheel rise is principally generated by the great coupler force related to the rigid impact in the axial direction.     

New approach for performing failure analysis of fuel cell-powered vehicles

Safety of hybrid-electric and fuel cell vehicles is a critical aspect of these new technologies, since any accident exposing occupants of such vehicles to unconventional hazards may result in significant setbacks to successful market penetration. Fuel cell and hybrid-electric drive systems are complex, and it is essential to perform a thorough analysis to determine critical failure conditions. There are several safety concerns for routine operation of such systems, particularly for hydrogen-fueled vehicles. A modified Failure Modes and Effect Analysis (FMEA) has been developed, along with a Criticality Analysis (CrA), to identify potentially hazardous conditions for crash and non-crash situations. A mathematical model of fuel cell operation has been developed and used here in conjunction with the FMEA. Component failures during the event modes are simulated using vehicle models developed with Matlab Simulink tools. Six simulation models were created using the software. In addition, a preliminary finite element model of a fuel cell vehicle, using a Ford Taurus (91′) model year sedan, has been developed and implemented. This finite element model is used as a demonstration of the crash simulation of the vehicle.     

多梁式小箱梁桥沿纵向有效宽度的动力识别方法

与传统的有效宽度计算方法不同,在整桥的动力分析结果和弹性支承连续梁法荷载横向分布理论的基础上,通过假定弹性支承连续梁法动力分析模型的面内1阶转动频率与整桥1阶扭转频率相等,提出了一种多梁式小箱梁桥沿纵向有效宽度的动力识别方法。然后利用该方法识别得到的有效宽度计算各主梁的横向分布影响线及横向弯矩,并与空间有限元模型的计算结果进行了对比,结果表明该法具有很高的精度,为此类问题的研究提供了一种新的思路。     

车用结构胶有限元模型方法的分析与比较

随着车用结构胶技术的进步,其性能不仅可以满足大量新型复合材料的连接工艺要求,而且可以弥补在汽车碰撞过程中点焊连接工艺应力集中的缺陷,因此开展对车用结构胶的研究十分必要。文章从有限元方法分析的角度,在总结国内外有关结构胶有限元模型的前提下,综合模型的理论基础、模型计算时间、模型仿真结果与试验的比较等因素,评价各模型特点,结合整车碰撞有限元模拟的要求,论证得出一维模型方法更适用于整车碰撞模拟。     

路面不平度对低路堤动应力的影响研究

基于正弦函数变化的路面不平度和两自由度的四分之一车辆模型,推导出车辆随机动荷载计算公式,研究路面不平度对车辆荷载作用下低路堤动力响应的影响规律。建立车-路耦合三维动力有限元模型,计算分析6种工况下不同路面不平度时车辆随机动荷载作用下低路堤的动应力,得出低路堤动应力均随路面不平度值的增加而增大,且与车辆附加动荷载系数m近似为线性关系;提出不同路面不平度时车辆随机动荷载作用下低路堤动应力计算模型,并对比有限元模型得到的低路堤动应力与应力计算模型得到的低路堤动应力。