复合材料车轮冲击试验仿真分析

根据轿车车轮冲击试验方法要求,建立复合材料车轮的冲击试验有限元模型,然后使用非线性有限元动力学分析软件LS-DYNA对复合材料车轮冲击过程进行了仿真分析,并获得了车轮上某些测量区域冲击应变的时间历程,并与结构相同的铝合金汽车车轮相同部位的应变进行了对比.结果表明,复合材料车轮应变比铝合金车轮小30%-40%,说明其抗冲击性能更优.     

正面25％偏置碰撞中车轮铰链失效的研究

在整车小偏置碰撞安全性能开发过程中,车轮作为主要承载构件,其与底盘连接铰链是否失效将影响车轮受力大小和变形模式,准确预测车轮铰链失效是碰撞安全性能前期开发的重要难点。针对该难点,本文中提出通过拉伸试验获取车轮与底盘连接铰链失效力并应用于仿真中,以准确模拟铰链失效的解决思路。首先,采用公开仿真模型,探究小偏置碰撞过程中车轮从车辆脱落对碰撞结果影响,通过仿真与数值计算相结合方法,分析车轮连接铰链各方向峰值力与碰撞能量相关性,确定铰链失效力测量范围。再针对采用与公开模型同型前悬架系统的某车型,设计出拉伸试验装置,以获取车轮与底盘连接铰链失效力,并应用于该量产车型的正向开发。结果表明:考虑车轮与底盘连接铰链失效力的准确仿真模型,能极大提高小偏置碰撞仿真精度,从而保障整车正向安全性能的开发。     

冲击荷载下预制装配式护栏的防撞性能分析

针对普通砼护栏无法解决车辆等冲击下损伤过大且碰撞发生时前车轮易卡死在护栏下的问题,提出新型有自复位功能的预制装配式防撞护栏,并通过有限元分析研究冲击荷载下装配式护栏的动力响应及能耗规律,分析不同冲击荷载及不同结构轴压比下护栏的防撞性能。结果表明,冲击发生时,该护栏呈现明显的瞬时碰撞和后期二次碰撞2个阶段,整个过程冲击力峰值持续时间较短,结构刚性位移较大且能量变化平缓;结构轴压比主要影响冲击时的后期二次碰撞阶段,较小的轴压比能增大结构的耗能能力并延缓二次碰撞发生时间;该护栏在冲击荷载下具有良好的防撞性能,且能满足快速绿色施工的要求。     

行人与汽车碰撞中颅骨骨折损伤机理的虚拟实验研究

采用汽车-行人多刚体动力学模型,模拟行人与汽车碰撞中人体的动态响应过程,并计算头部与风挡玻璃碰撞接触瞬间的方位、速度和角速度等运动参数;然后将这些参数输入到先前建立并验证了的行人头部有限元模型HBM-head中,模拟头部与风挡玻璃和A立柱的碰撞过程,并分析与损伤相关的生物力学参数.结果表明,结合多刚体动力学和有限元分析的虚拟实验技术可进行碰撞事故重建和损伤机理分析,模拟颅骨骨折,计算分析颅骨在冲击载荷下的应力,并确立骨折损伤与应力参数之间的内在关系,从而为降低行人头部损伤风险,改进轿车安全设计提供依据.     

摩托车铝车轮冲击试验方法讨论

摩托车在行驶过程中,铝合金车轮将承受多种交变载荷,尤其是碰到障碍物时,车轮需承受冲击载荷.国际上有3种冲击试验方法,我国的冲击试验方法标准采用国际标准中的坠落式单锤径向冲击试验法.现对该3类冲击试验方法的选用进行讨论.     

铝车轮冲击试验失效案例及其有限元分析

以一款6Jx15铝车轮为例,分别从时效过程和结构优化两方面对其13°冲击试验的失效机理进行了研究.并结合实际铝车轮的材料特性、热处理工艺和测试结果建立了以破坏应变为判定准则的有限元分析模型.利用该模型对铝车轮3种失效模式的改进措施进行了有限元分析及验证.     

氧化物夹杂对铝合金车轮抗冲击性能的影响分析

通过铝合金车轮在实车上的碰撞试验,结合铝合金车轮在内轮缘处的失效分析,以及铝合金车轮的生产实际状况,阐述氧化物夹杂的形成机理,以及氧化物夹杂对铝合金车轮抗冲击性能的影响。最后,通过阐述改进铸造模具、增加排气网络等相应的控制措施,来提高铝合金车轮在实车碰撞过程中的抗冲击性能。     

高速冲击下一种新型吸能部件的特性研究

为了研究一种新的多边形截面吸能部件的工程应用性,采用显式动力有限元方法模拟薄壁结构在轴向冲击下的屈曲,分别建立了圆形截面吸能部件、矩形截面吸能部件和新型吸能部件的有限元碰撞模型并在当前高速碰撞有限元分析中考虑材料的应变率效应.通过数值计算观察3种类型部件的变形模式和压皱力.数值计算的结果表明在重量相同、厚度相同以及长度相同的情况下,新型吸能部件与矩形截面吸能部件和圆形截面吸能部件相比在变形过程中吸收冲击能量的能力提高.     

基于ANSYS Workbench的赛车车轮疲劳仿真分析

赛车车轮是车辆承载的重要安全部件,行驶过程中,赛车车轮承受来自路面不同幅值、不同频率的激励除受垂直力外,还受因车辆起动、制动时扭矩的作用,转弯、冲击等来自多方向的不规则受力。高速旋转的车轮直接影响车辆的平稳性和操纵性。文章以Wonder7号铝合金车轮为研究对象,在CATIA中建立赛车车轮的三维模型,并导入到ANSYS Workbench软件中生成轮辋和轮辐的几何模型。根据计算极限工况下,对wonder7号车轮进行受力分析,并对车轮的受力载荷进行确定。建立车轮的有限元模型并进行有限元分析。为预测车轮的疲劳寿命,用Ansys中的Fatigue模块对车轮进行疲劳寿命分析,预测车轮疲劳破坏位置和使用寿命,对设计人员起了指导意义。     

非满载罐车罐体在追尾碰撞中变形失效研究

为了研究液罐车在碰撞中装载液体对罐体结构变形损伤的叠加作用,以客车与液罐车追尾碰撞为研究对象,运用Hypermesh建立两车追尾碰撞的有限元分析(Finite Element Analysis,FEA)模型,利用Fluent模拟碰撞后液体晃动过程,在考虑液体晃动冲击的前提下,计算模拟出两车在碰撞过程中的能量变化及罐体结构变形情况,分析了不同冲击载荷和加载工况下的罐体变形失效情况。结果表明,碰撞速度相同时,液体充装率k值越大,罐体的变形量越大,罐体破裂的临界碰撞速度与液体充装率k值呈正相关。液体晃动冲击对罐体变形失效的影响不太显著,液体晃动对罐体的冲击损伤远小于外部车辆带来的碰撞损伤。通过分析液体泄漏情况可知,充装率k值对液体泄漏速率有显著影响。     

车轮轮胎总成的路障冲击试验

轮毂的性能直接影响汽车的行驶安全和乘客的人身安全,车轮轮胎总成的路障冲击试验对轮毂的性能有了更高的要求。文章通过从SAEJ1981标准的总体要求、试验范围及冲击方式等方面的介绍提供了引导开发新的车轮轮胎总成路障冲击试验的背景信息,表明SAEJ1981标准能公正地评估车轮和轮胎总成的路障冲击试验,指出国内在车轮新品验证过程和周期性试验中也应增加该冲击试验项目,以充分保障产品的安全性。     

Further study on the wheel–rail impact response induced by a single wheel flat: the coupling effect of strain rate and thermal stress

A comprehensive dynamic finite-element simulation method was proposed to study the wheel–rail impact response induced by a single wheel flat based on a 3-D rolling contact model, where the influences of the structural inertia, strain rate effect of wheel–rail materials and thermal stress due to the wheel–rail sliding friction were considered. Four different initial conditions (i.e. pure mechanical loading plus rate-independent, pure mechanical loading plus rate-dependent, thermo-mechanical loading plus rate-independent, and thermo-mechanical loading plus rate-dependent) were involved into explore the corresponding impact responses in term of the vertical impact force, von-Mises equivalent stress, equivalent plastic strain and shear stress. Influences of train speed, flat length and axle load on the flat-induced wheel–rail impact response were discussed, respectively. The results indicate that the maximum thermal stresses are occurred on the tread of the wheel and on the top surface of the middle rail; the strain rate hardening effect contributes to elevate the von-Mises equivalent stress and restrain the plastic deformation; and the initial thermal stress due to the sliding friction will aggravate the plastic deformation of wheel and rail. Besides, the wheel–rail impact responses (i.e. impact force, von-Mises equivalent stress, equivalent plastic strain, and XY shear stress) induced by a flat are sensitive to the train speed, flat length and axle load.     

车用LNG行情受国三柴油车“禁令”提振

<正>工信部近日公告,定于2014年12月31日废止适用于国家第三阶段汽车排放标准(简称国三)柴油车产品《公告》,2015年1月1日起国三柴油车产品将不得销售。受去年7月以来全国范围内非居民天然气提价影响,LNG价格整体上扬,导致车用LNG的经济性有所下降。业内人士认为,国三柴油车"禁令"将加速柴油升级换代,一定程度上使车用LNG的经济性和替代效益再次凸显。不过,受天然气价格上涨预期的影响,短期内车用LNG的发展仍需政策扶持。     

摩托车轻合金车轮径向冲击试验数据分析

摩托车轻合金车轮质量的好坏直接关系到摩托车骑乘者的人身安全,而摩托车轻合金车轮的径向冲击试验结果直接反映了车轮质量的优劣。通过对车轮径向冲击试验数据进行分析,以对车轮额定载荷的设定提出建议,希望摩托车整车企业及车轮生产企业合理设计轻合金车轮的额定载荷。     

汽车操纵稳定性的中间位置转向试验

操纵稳定性中间位置转向试验最初是由美国德尔福公司制定的，是汽车在高速行驶条件下操纵性和稳定性的重要评价方法。通过试验的原始数据可以绘制出转向盘转角与侧向加速度、转向盘力矩与侧向加速度、转向盘力矩与转向盘转角等多条特性曲线，以作为不同的评价指标。以CAll41载货汽车作为实例分析，发现该车转向干摩擦偏大，转向刚度偏低，高速行驶时的非线性路感不够理想。     

The role of the contact geometry in wheel–rail impact due to wheel flats: Part II

A classification of wheel flats according to the different stages of their growth is given, along with the characteristic features of the dynamic wheel–rail interaction for each category. Mathematical expressions and frequency spectra of the corresponding wheel mass trajectories are derived. Difference is made between the subcritical and the transcritical speed regime. A criterion is derived for contact loss for worn flats. Simulations show that the dynamic wheel–rail interaction is governed by the track stiffness for low train speeds or long flat lengths; for high speeds and/or short flat lengths the interaction is governed by the inertial properties of the wheel and the rail. For a given flat geometry, nonlinearities in the relationship between the impact magnitude and the train speed occur in the stiffness-dominated speed domain, whereas this relationship is approximately linear in the inertia-governed domain. In the latter domain, the impact magnitude is found to be linearly dependent upon the maximum trajectorial curvature or inversely linearly dependent on the minimum circumferential wheel tread curvature. The above relationships are valid for the subcritical speed regime, in which no contact loss occurs. Different contributions from the literature are compared with respect to the established relationship between impact magnitude and speed. Significant differences are found, due to insufficiently defined parameters and conditions. Conditions are derived for a consistent application of the so-called equivalent rail indentation in experiments with wheel flats, and the indirect strain registration method for measuring dynamic wheel–rail contact forces is reviewed.     

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.     

An investigation on wheel/rail impact dynamics with a three-dimensional flat model

Wheel flat is one kind of railway train wheelset defects. It has great influence on wheel/rail dynamics and damages. In most of the presented studies, wheel/rail impact velocity or rolling radius variation of the wheel because of flat spot was taken into account to study the wheel/rail impact dynamics. In this paper, a three-dimensional wheel flat model considering the length, width and depth of the flat spot is established. Including the wheel rotation and wheel/rail contact geometry, a high-speed vehicle–rail coupling system dynamics model is developed to investigate the effect of the wheel flat on the wheel/rail dynamics. With time integration method of the models, the impact dynamics of the wheel/rail system with three types of flat width and five kinds of flat length are obtained. The results show that the width, the length of the wheel flat and the width/length ratio have a great influence on the wheel/rail impact dynamics. The wheel/rail impact dynamics of the flat with large width is more severe than with small width as the flat length is fixed. When a flat spot occurs, the permissible length of the wheel defect, needless to action, is 25?mm in maximum. The speed safety domain with three kinds of flat width/length ratio of a vehicle is obtained according to the wheel/rail vertical force limitation.