Analysis of lateral tyre friction dynamics1

The tyre friction model is a key part of the overall multi-body tyre dynamics model. The LuGre dynamic tyre friction model is analytically linearised for pure cornering conditions. The linearised model parameters are conveniently expressed as functions of static curve slope parameters. The linearised lateral force and self-aligning torque submodels are described by equivalent mechanical systems. The linearised model and equivalent system parameters are analysed for different slip angle and wheel centre speed operating points. An example of the application of linearised tyre friction model to tyre vibration analysis is presented as well.     

公路桥车桥耦合振动的隐式和显式分析方法研究

求解公路桥在车辆荷载作用下的振动响应,不仅能为设计提供参考,还可以为桥梁运营阶段的管理和养护提供依据。对比分析车桥耦合振动的隐式和显式分析方法,分别在Matlab自编程序和LS-DYNA有限元程序中建立隐式模型和显式模型,以一座简支空心板梁桥为算例,用两种分析方法分别求解该桥在移动车辆荷载作用下的振动响应,并将数值计算结果与实测结果对比,分析两种方法的合理性。研究结果表明,两种建模分析方法各有利弊,显式建模计算结果峰值偏大,综合考虑,建议采用隐式建模分析方法求解车桥耦合振动响应。     

A dynamic wheel–rail impact analysis of railway track under wheel flat by finite element analysis

Wheel–rail interaction is one of the most important research topics in railway engineering. It involves track impact response, track vibration and track safety. Track structure failures caused by wheel–rail impact forces can lead to significant economic loss for track owners through damage to rails and to the sleepers beneath. Wheel–rail impact forces occur because of imperfections in the wheels or rails such as wheel flats, irregular wheel profiles, rail corrugations and differences in the heights of rails connected at a welded joint. A wheel flat can cause a large dynamic impact force as well as a forced vibration with a high frequency, which can cause damage to the track structure. In the present work, a three-dimensional finite element (FE) model for the impact analysis induced by the wheel flat is developed by the use of the FE analysis (FEA) software package ANSYS and validated by another validated simulation. The effect of wheel flats on impact forces is thoroughly investigated. It is found that the presence of a wheel flat will significantly increase the dynamic impact force on both rail and sleeper. The impact force will monotonically increase with the size of wheel flats. The relationships between the impact force and the wheel flat size are explored from this FEA and they are important for track engineers to improve their understanding of the design and maintenance of the track system.     

Development and validation of a numerical model for predicting forklift truck tip-over

The aim of this paper is to present the dynamic behaviour modelling performed for a forklift truck and the validation of this model. The intention is to develop a permanent tool allowing both common and critical driving situations (especially that of lateral tip-over) to be simulated for this type of vehicle. The medium-term aim is to use this model as a tool to facilitate designing, training and preparing safety standards with a view to reducing the number of accidents related to this machine, which, on average, still cause nearly 10 deaths each year. This paper describes the forklift truck mechanical model and the tyre model. A Pacejka's lateral tyre model was used and integrated into the forklift truck model. The interacting forces and moments between the wheels and the ground are, therefore, computed at all times. Test bench-measured data, characteristic of the dynamic behaviour of several tyres, were used to identify the parameters of the Pacejka model. We studied the limits of this model adapted in this case to tyres with characteristics different from those of the car sector. Track testing was performed using a safe-test forklift truck. The purpose of these tests was to measure trajectory characteristics (velocity, position, acceleration and slip angle) and to compare them with model-based predictions, allowing validation of the robustness and accuracy of this model. Situations involving partial (up to 15°) tip-over were included. The quantities measured during testing were compared with the calculation results obtained for identical driving configurations. There was a close calculation/measurement correlation when performing a wide ‘J-turn’ (with and without tip-over) when following circular or slalom trajectories. The calculation/measurement correlation was less close when the forklift truck performed a sharp ‘J-turn’, for example. Model limits can be derived from the observations, data processing and calculations.     

直推自卸式垃圾车举升支座的优化设计

通常在设计直推自卸式垃圾车时,举升支座结构为安全起见均较为厚重,在结构布置上所占体积大且自重大。为此,应用ADAMS仿真分析软件建立举升机构的虚拟样机,对其添加约束、载荷、驱动,进行动力学仿真分析,得到举升支座的动力学仿真结果。再利用ANSYS有限元分析软件对其进行划分网格,定义受力条件,进行有限元分析,得出其应力应变与位移云图,并根据有限元分析结果对其进行优化设计。结果表明,优化后的举升支座强度满足要求,体积减小,成本得到降低。     

T式举升机构的设计和计算软件开发

介绍了T式举升机构的设计方法，通过对机构的分析，建立了举升机构的数学模型，在总结多年实践经验的基础上，运用计算机语言开发了一套专门用于T式自卸举升机构设计计算的辅助软件。本软件能快速计算出自卸举升机构各铰点在不同的举升角度下的坐标、受力大小及方向，并可运用EXCEL电子表格生成各点受力曲线和举升机构的总体参数。     

空气弹簧对重卡平顺性影响研究

为使重卡在平顺性方面满足国际或国家法规要求,利用专用软件,在建立有限元模型的基础上,通过计算机线性静态模拟计算分析,建立重卡有限元模型,进行动态模拟分析和数据分析,从重卡的平顺性出发,通过对安装空气弹簧重卡平顺性实验,然后建立重型卡车ADMAS/Car虚拟样机模型,针对空气弹簧在重卡上的平顺性能影响进行仿真和试验对比分析,并提出改进建议以达到设计目标。     

厢式载货汽车模型风洞试验技术的研究

风洞试验是进行汽车空气动力学研究的重要手段，介绍了试验数据系统，论述了用小型航空风洞进行厢式载货汽车模型试验时雷诺数，堵塞比，模拟地板等重要技术问题，给出厢式载货汽车改善气动阻力特性的试验结果。     

结构参数对鼓式制动器高频噪声的影响

本文在建立鼓式制动器高频噪声问题的结构闭环耦合计算模型的基础上，对某国产车的高频噪声问题进行了计算。分析中所用的制动底板，鼓和蹄的结构参数均取自实际结构。计算分析的结果表明：制动器所有部件的结构参数对制动高频噪声均有重要影响，过去仅把产生高频器材怕的原因归结为蹄与鼓间的参数匹配是不正确的。对计算结果的归纳表明：对制动器高频噪声起决定作用的是鼓子结构和包含有底板，蹄，分泵及油路操纵系统在内的ＰＳＰＯ     

基于能量法的连拱隧道钻爆施工对围岩损伤影响分析

以采用无导洞钻爆法施工的云南省武定至易门高速公路三台坡连拱隧道工程为依托，针对爆破施工对无导洞连拱隧道围岩造成损伤的问题，利用能量衰减公式推导隧道围岩振动速度衰减公式；采用FLAC^3D软件计算分析实际工程围岩振动速度以验证理论推导公式的准确性，并计算分析在爆破荷载作用下连拱隧道围岩、中墙的振动速度和振动位移的变化规律。研究结果表明：振动速度的理论计算结果和数值模拟结果之间的相对误差较小，说明基于理论推导得到的隧道围岩振动速度计算公式是可靠的；爆破过程中产生的能量以地震波的形式向外传播，当地震波传至地表仍未完全衰减时，未完全衰减的能量将以反射波的形式继续衰减；爆破施工过程中围岩振动速度和振动位移最大值均位于距掌子面6 m的已开挖区隧道拱顶围岩处，未支护情况下隧道拱顶8 m范围的围岩振动速度大于63.5 cm·s^-1，围岩处于损伤的状态，因此在爆破施工过程中应对已开挖区围岩进行预加固。