Numerical analysis of the dynamic interaction between wheel set and turnout crossing using the explicit finite element method

A three-dimensional (3-D) explicit dynamic finite element (FE) model is developed to simulate the impact of the wheel on the crossing nose. The model consists of a wheel set moving over the turnout crossing. Realistic wheel, wing rail and crossing geometries have been used in the model. Using this model the dynamic responses of the system such as the contact forces between the wheel and the crossing, crossing nose displacements and accelerations, stresses in rail material as well as in sleepers and ballast can be obtained. Detailed analysis of the wheel set and crossing interaction using the local contact stress state in the rail is possible as well, which provides a good basis for prediction of the long-term behaviour of the crossing (fatigue analysis). In order to tune and validate the FE model field measurements conducted on several turnouts in the railway network in the Netherlands are used here. The parametric study including variations of the crossing nose geometries performed here demonstrates the capabilities of the developed model. The results of the validation and parametric study are presented and discussed.     

Influence of wheel and rail profile shape on the initiation of rolling contact fatigue cracks at high axle loads

The influence of wheel and rail profile shape features on the initiation of rolling contact fatigue (RCF) cracks is evaluated based on the results of multi-body vehicle dynamics simulations. The damage index and surface fatigue index are used as two damage parameters to assess the influence of the different features. The damage parameters showed good agreement to one another and to in-field observations. The wheel and rail profile shape features showed a correlation to the predicted RCF damage. The RCF damage proved to be most sensitive to the position of hollow wear and thus bogie tracking. RCF initiation and crack growth can be reduced by eliminating unwanted shape features through maintenance and design and by improving bogie tracking.     

高压共轨喷油器压力波动与针阀响应解耦分析

多次喷射过程中,不同喷射之间的相互影响导致循环喷油量的控制难度增大。建立了高压共轨系统的AMESim仿真模型,通过数值仿真和试验测试相结合的方法,揭示了喷油器内部压力波动和针阀开启阶段动作响应的强耦合作用是导致主喷油量随喷射间隔波动的根本原因,当主喷油量基准值为60．0 mm3时,其波动量最大可达3．6 mm3。建立了共轨系统的无阻尼 L C液力系统模型,通过对模型的分析,针对强耦合作用提出了减小喷油器内部油道长径比和盛油槽容积的解耦方法。对解耦方法的仿真试验验证表明,采用解耦方法后压力波动和针阀响应的耦合程度降低53％。     

差异化公交发展策略研究

以深圳市龙岗区为例,根据龙岗土地利用现状和规划,结合公共交通发展态势、需求分布和公交系统规划布局,划分不同类型的公交发展区域,提出差异化公交发展策略,并以实例加以说明。     

浅析Caterpillar公司HEUI共轨燃油喷射系统

随着越来越严格的排放法规的出台和微电子技术的迅猛发展,柴油机的电子控制技术也取得了长足的进步。尤其是高压共轨燃油喷射系统以其精确的控制、可靠的性能、具有故障自诊断功能和通用性较强等优点得到了广泛的应用。本文以卡特彼勒（Caterpillar）公司的HEUI系统为例进行阐述。     

城市公交系统的时间可靠度研究

针对城市公共交通系统的行车时间和行车问隙易受影响的特点,以整个公交出行链为落脚点,从出行者的角度对公交的运行时间和乘客的在站等车时间进行了研究,建立了公交的运行时间可靠度、等候时间可靠度模型.以北京市为例,对晚高峰的公交时间可靠度进行了计算和分析,结果表明北京市的公交时间可靠度为中等水平.     

钢轨侧面磨耗因子

木文基于轮轨滑动和钢轨侧磨机理,推导出了钢轨一次磨耗量同轮轨横向力、冲角等的关系式, 给出了各种情况下建议采用的磨耗因子,引用了有关试验结果验证了部分理论推导。      

键图模拟在轮轨动力学研究中的应用

本文应用键图法模拟机车车辆的动态特性。文中建立了轮轨蠕滑力、自由轮对和两轴车的健图模型,并给出了部分数值计算的结果。从初次将键图法引入车辆动力学的经验来看,健图模拟具有简明、快速和便于研究参数等优点。值得加以推广应用。      

轮轨塑性变形与安定状态的关系研究

运用弹塑性理论分析了轮、轨接触工况时的塑性变形,提出了轮轨材料在弹塑性状态下安定极限值的概念,并依此进行了轮轨接触计算,预测了轮轨廓形的塑性变形值。     

便秘患者胃肠通过时间测定及意义

为提高对功能性便秘的认识并观察便秘患者胃肠通过时间的特点,对３５例便秘患者通过口服不透Ｘ线的标志物用Ｘ线法测定了胃肠通过时间,结果便秘患者５０％ 全胃肠、口 回盲、右半结肠、左半结肠、乙状结肠直肠通过时间分别是（６７２０±１４．６９）ｈ、（８．４２±１．６１）ｈ、（１７．９２±２．５１）ｈ、（１７．９０±４８５）ｈ 及（２２．１４±８００）ｈ。３５ 例便秘患者根据其５０％ 胃肠通过时间而被分为正常传输型和慢传输型,后者又根据通过延长主要部位而分为右半结肠无力型、左半结肠无力型、出口梗阻型和全结肠无力型。结肠分段通过时间的测定对于肠道排空延迟的定位十分重要,用胃肠通过时间延长来诊断便秘更为可信