Fatigue life analysis of wheels on guideway vehicle using multibody dynamics

A guideway vehicle is used in automobile, semiconductor and LCD manufacturing industries to transport products efficiently. Since the operating speed of the guideway vehicle should be increased for maximum productivity, the weight of the vehicle has to be reduced, and this weight reduction may cause a failure of a part in the system. Therefore, the estimation of the fatigue life of the parts becomes an important problem. In this study, the fatigue life of the wheels in the guideway vehicle is estimated using an S-N curve. To obtain the fatigue life of a part, the S-N curve, the dynamic stress time history applied to the part, and the material property of the part are required. The S-N curve of the driving wheel is obtained from the fatigue experiment on wheels. To obtain the material properties of the driving wheel, which is composed of aluminum with urethane coating, the result of a compression hardware test and static analysis of the wheel’s FE model are used. The dynamic stress time history influencing the driving wheel can be obtained from linear superposition of the dynamic load time history and the static stress. The dynamic load time history is estimated by multibody dynamic analysis, and the static stress is obtained by finite element analysis.     

Assessment of running safety of railway vehicles using multibody dynamics

An analysis model for multibody systems was developed to assess the running safety of the Saemaeul train passing through curves. Sensitivity analyses based on the variation of parameters related to derailments were conducted using this model and the ADAMS/Rail software package. These analyses showed that the derailment coefficient and the unload ratio of the right wheel were higher than that of the left wheel at low speed, but lower at high speed. The derailment coefficient and the unload ratio increased as the curve radius decreased. The derailment coefficient increased but there was no change in the unload ratio as the length of transition curves increased. The derailment coefficient and the unload rate increased in proportion to the increase in track cant.     

Synthetic analysis of flexible multibody system including a very flexible body

The progress in developing a dynamic analysis solver has different aspects of improvement in the sense of simulating the behavior of the parts. Among them, dynamics in flexible body and large deformable body have been an issue in recent decades. A modal coordinate formulation has been developed and used for analyzing the flexible body dynamics with a commercial dynamic solver, like in ADAMS. Flexible body dynamics using modal coordinates are reliable when the system’s deflection is relatively small, and generally its accuracy depends on how many relevant modes are used for the system. Conversely, to simulate the behavior of the large deflected body, absolute nodal coordinate formulation is derived and developed. The theory presents the mixed equations of motion, which consider both the absolute nodal coordinates and absolute cartesian orientation coordinates to simulate the large deflection. Its reliability is proved by many researches and experimental data. In this study, a dynamic solver which can handle the flexible bodies is developed. Three kinds of bodies, rigid, flexible and large deformable body, can be simulated. Its validity is verified by comparison with a commercial analysis program. For further studies, the constraints and force elements between different coordinates will be developed. Solving efficiency would be another major concern to be improved. This paper was presented at the 4th Asian Conference on Multibody Dynamics(ACMD2008), Jeju, Korea, August 20–23, 2008. Ji Won Yoon received B.S. and M.S. degrees in Mechanical Engineering from Ajou University in 2004 and 2006, respectively. Mr. Yoon is currently a Ph.D student at the School of Mechanical Engineering at Ajou University in Suwon, Korea. He is serving as an instructor for undergraduate students. Mr. Yoon’s research interests are in the area of multibody dynamics, flexible body dynamics, and fatigue analysis.     

Analysis of vehicle rollover using multibody dynamics

This study reports on the analysis of vehicle deformation due to rollover using multi-body dynamics which enables estimating motions of rigid bodies subjected to external forces. For the vehicle rollover analysis using the ADAMS, we have developed a FEA-based numerical vehicle model consisting of a rigid lower body and a deformable upper body. Here, comprehensive analysis of the static and dynamic roof strength resistance of a vehicle using our prediction model is described. We obtain the displacement of A-pillar top-end of a vehicle for each of the static and dynamic tests according to the FMVSS 216 protocol and the Controlled rollover impact system (CRIS) condition, respectively. The displacement of A-pillar top-end represents the roof intrusion causing injuries for passengers in the front seats, thereby evaluating the Strength to weight ratio (SWR) of a vehicle.

     

柔性多体系统动力学理论应用于轧制工业的综述

结合轧制工业的发展现状及柔性多体系统动力学的理论成果,从轧机设备的设计、改造、过程控制、系统特性、接触-碰撞问题的建模、轧制过程中多领域集成化、多体动力学软件的发展等几个方面阐述了将柔性多体系统动力学理论应用于轧制工业的可行性和必要性.     

Vehicle dynamics analysis of a heavy-duty commercial vehicle by using multibody simulation methods

In this paper, the computer-aided vehicle dynamics analysis of a 6?×?2 heavy-duty commercial vehicle is examined. For the analysis, Mechanical Simulation Corporation's TruckSim multibody dynamics simulation and SuspensionSim multibody statics simulation softwares are used. The aim of this study is to design and model the front suspension and tandem rear axle suspensions, compose the full-vehicle model representing the real-life vehicle, and examine the dynamic behavior of this model. The models related to the front and rear suspensions are prepared and solved in SuspensionSim and the solutions are imported thereafter to TruckSim. The full-vehicle model excluding the suspension system is formed by using TruckSim. The simulation scenarios, runs of which are made to observe the effects of different parameters concerning the dynamic behavior of the full-vehicle model, are also prepared in TruckSim environment.     

A continuous force model for the impact analysis of flexible multibody systems

A new continuous impact model applicable to multibody systems consisting of interconnected rigid and flexible bodies is presented. The continuous impulsive force that acts during the short-lived interval of impact is written in terms of the relative displacement and velocity of the impacting bodies. In the method developed in this paper, the material compliance and damping coefficients are determined from energy balance relations. In order to account for the kinematic constraints between the two impacting bodies and other bodies in the system, an effective mass compensation is proposed. Flexible bodies in the system are discretized using the finite element methods. The generalized impulsive forces associated with the system generalized coordinates are then derived using the virtual work and are written in terms of a coupled set of reference and modal elastic coordinates. Numerical examples are presented in order to demonstrate the feasibility of the mathematical model developed in this paper.     

Chute design of mackerel automatic grader using multibody dynamics

An automatic mackerel grader is a machine that automatically sorts mackerel according to size. The chute spreads the mackerel to allow the latter to enter each roller evenly. Sorting is simulated to confirm that the multibody dynamics model of the automatic grader correctly sorts the mackerel. This process is completed according to the shape of the chute to confirm the effect on performance. A new shape of the chute and the application are proposed and evaluated by a comparison with conventional chute shapes. RecurDyn, a multi-body dynamics program, is used for the sorting simulation. The contact parameters are defined by Hertzian contact theory using the material information of mackerel and C/S steel. A rigid-body mackerel model is used to express the behavior of mackerel. Sorting is simulated for each shape. The sorting accuracy and error of the new shape are compared with those of two existing shapes. The new shape shows a 0.29 mm sorting error and better sorting accuracy than the existing shapes.     

挠性剑杆织机机架固有频率分析及测试方法研究

目前困扰国内织机行业的主要问题就是如何经济地提高转速,而转速提高带来了振动、噪声过大问题。对织机主要部件机架的振动进行了固有频率的理论分析,给出了合理的测点布局与相应的测试方法,为减振提供了参考数据。     

车身扭转柔性对半挂汽车列车侧翻影响的仿真分析

首先建立牵引车和半挂车的刚性车身半挂汽车列车模型,然后考虑车身的扭转柔性,将牵引车和半挂车的簧载质量分为前、后两部分,并建立各部分相互作用的方程,从而建立柔性车身半挂汽车列车模型。在MATLAB软件中建立半挂汽车列车的仿真模型,以横向载荷转移率和悬架侧倾角为判断指标,在角阶跃转向工况和鱼钩转向工况下分别对刚性车身和柔性车身半挂汽车列车模型进行仿真。对比仿真结果可知,车身的扭转柔性对半挂汽车列车的侧翻有较大影响。     

Fizeau干涉仪主机的热稳定性设计与分析

搭建了光-机-热耦合模型,用于分析Fizeau干涉仪光机系统的热稳定性,并研究了该系统的计算流程、环境温度和系统光学质量的随机性、系统光学质量与环境温度的关系等.首先,根据实验室温控条件,建立环境温度的随机分布模型,进行了光-机-热耦合分析并计算不同温度下光机结构的热分布和结构变形;然后,通过Zernike多项式拟合透...     

柔性机器人动力学分析与控制策略综述

综述了柔性机器人动力学分析和控制等相关问题,对柔性机器人动力学分析中变形场的离散化、建模方法、近似分析等问题进行了系统分析。详细介绍了被动控制、PID控制、模糊控制、神经网络控制、自适应控制、鲁棒控制、变结构控制、奇异摄动控制和非线性控制等在柔性机器人控制中的应用情况。指出了在柔性机器人动力学建模和控制中应解决的问题,这对包括柔性机器人在内的多柔体系统动力学建模与控制问题的研究有一定的促进作用。     

基于多体动力学仿真的履带车辆转向性能分析

以多体系统动力学理论和方法为基础,基于RecurDyn软件建立高速履带车辆多体动力学模型及路面模型,对履带车辆在硬、软两种地面的高速转向过程进行动力学仿真和对比分析。重点分析车辆在转向过程中履带预张紧力、转向半径和路面工况这3方面因素对转向特性的影响。研究结果表明:履带车辆高速转向时,软地面转向性差,易发生车辆侧翻、脱轮等现象;车辆以20 km/h的速度,转向半径r>B/2软地转向时,两侧履带滑移(滑转)现象不明显,转向稳定性最好,当选取车重力的10%(20 kN)作为预张紧力时,履带动态张紧力波动变化小,车辆转向角加速度没有出现幅值突变,转向平稳。     

多体动力学的三轮摩托车动态特性研究

为了获得三轮摩托车人-车系统在振动载荷下的各项动态特性指标,基于多体动力学理论,对整个系统的固有频率、模态振型、加速特性和制动特性进行研究,得到系统在各状态下的性能指标,并对研究结果进行评价,为整车开发和优化设计提供了参考指标。     

造船龙门起重机主梁结构件的疲劳试验与分析

以580吨级造船龙门起重机主梁结构为研究对象,通过设计结构试件进行疲劳试验,获得试件在不同应力水平下的疲劳寿命循环次数,同时观测试件的裂纹形成、扩展现象。最后,根据试验结果拟合出的S-N曲线,对照选取标准中的S-N曲线,为结构疲劳分析提供试验依据。     

液压镦锻机下横梁结构的静态有限元分析

在对某液压机下横梁结构特点研究的基础上,以有限元软件ANSYS为工具,选用实体单元建立下横梁结构的有限元模型,并对模型进行了整体静态有限元分析,揭示下横梁结构的应力和应变的分布规律,获得了受力及变形危险点的位置,为其进行结构改进提供了重要的依据。     

柔性机器人动力学分析与振动控制研究综述

综述了柔性机器人动力学分析与振动控制的研究现状，对变形的描述、变形场的离散化、建模方法、近似分析减振结构设计及关节作动系统控制律设计等关键问题进行了详细阐述。     

中小型燃气轮机试验台主设备基架的有限元分析

针对中小型燃气轮机试验台主设备基架结构设计可行性和螺栓连接结合面钢化模型适用范围等问题,对不带箱装体燃气轮机机组、带箱装体燃气轮机机组以及水力测功器机组载重状态下基架结构动力学特性等方面进行了有限元分析,对机组载重状态以及螺栓连接结合面的处理方法进行了归纳,提出了将质量单元法应用到机组载重状态的模拟中以及将弹簧单元法和钢化模型技术应用到螺栓连接结合面的模拟中。研究结果表明,两种螺栓连接结合面处理方法下,不带/带箱装体燃气轮机基架的模态计算结果最大偏差为2.85%,水力测功器基架的结果最小偏差为19.2%;同时,主设备基架的结构动力学分析结果验证了其结构设计满足使用要求,进而为试验的安全运行提供保障。     

应用预应力张拉器修复桥式起重机主梁

我厂是铁道部直属大型企业 ,担负着铁路客车制造的繁重任务。生产中我厂有各种规格、吨位的起重机近 10 0台 ,其中铸钢分厂的一台 10ｔ× 2 2 5ｍ双梁抓斗桥式起重机与一台 2 0 / 5ｔ× 2 2 5ｍ双梁桥式起重机均已使用 2 0多年。修复前这两台起重机存在大车运行不稳 ,大车轮啃轨 ,小车爬坡、溜车等问题。经检测 ,从主梁原始上拱计算 ,传动梁下挠 37 5ｍｍ ,导电梁下挠 30 5ｍｍ ,主梁旁弯 5～ 11 5ｍｍ不等。由于存在上述问题 ,严重影响了车间的安全生产。1999年 8～ 10月我们分别两次与江西省洪海经济技术公司的国家科技成果重点推…     

望远镜主转动框架设计分析方法

利用有限元方法，完成对望远镜主转动框架的结构静力分析和模态分析。并利用有限元中建立刚性区和坐标变换等方法进行了简化模型。阐述了基于有限元分析的结构模型的建立及简化处理过程，利用ANSYS软件完成了静力及模态分析计算，通过分析的结果为工程实际提供参考和建议，为主转动框架的分析提供了一种新的思路。