客车车身试验模态分析及其在车身定型中的应用

试验模态分析了解结构动特性的重要工具，介绍了客车车身的试验模态分析结果，并与国外同类型车身模态试验结果进行了对比分析，通过对比分析，对某客车车身提出了相应的改进措施，并评价了改进后车身的动态性能，使该型客车车身在短时间内定型。     

Traditional neighborhoods and commuting in the San Francisco Bay area

Neo-traditional designs, proponents argue, reduce dependency on the automobile and provide attractive environments for walking, bicycling, and transit riding. This paper explores the extent to which this proposition holds for seven traditional neighborhoods in the San Francisco Bay Area that evolved around early streetcar services. Matched-pair comparisons of modal shares and trip generation rates for work trips are made between these neighborhoods and newer auto-oriented suburbs, controlling for the effects of income and, to a lesser extent, existing bus service levels. Pedestrian/bicycle modal shares and trip rates tended to be considerably higher, in some cases five time as high, in transit-oriented than in the paired auto-oriented neighborhood. Transit neighborhoods also averaged around 70 more daily transit work trips per 1,000 households than auto-oriented neighborhoods, though trip rates varied considerably among neighborhood pairs. Higher residential densities were also found to have a proportionately greater impact on transit commuting in transit-oriented than in auto-oriented neighborhoods. The paper concludes that in order to yield significant transportation benefits, neo-traditional development must be coordinated with larger regional planning efforts and public policy initiatives to reduce automobile dependency.     

某缸盖结构有限元模型的动力修改

简要介绍了用模态分析结果修改结构有限元模型的“设计参数修改法” ,以某大功率柴油机的缸盖为例进行了验证。计算和分析结果表明 ,利用设计参数修改法修改后的有限元模型能够比较准确地反映结构的动态特性。     

基于声固耦合非线性系统的汽车车内噪声计算研究

采用具有线性和非线性连接子结构的自由界面模态综合法，建立整车系统声固耦合非线性动力学模型。用该模型对发动机激励产生的车内噪声进行数值仿真，并通过试验对仿真结果进行验证。     

复合材料覆盖件及其模具曲面逆向工程造型

利用径向基函数（RBF）神经网络优异的非线性逼近能力，将流线型玻璃钢覆盖件样件外形数据、加工余量、变形数据作为神经网络输入，在神经网络的输出上可以分别得到覆盖件曲面和模具曲面离散数据点。再通过神经网络的输出数据对曲面进行造型。通过在复杂曲面模具造型上的实际应用，证明该方法能够实现产品和工艺装备的并行设计，缩短产品研制周期，提高了设计和生产效率。     

客车车内噪声控制中的有限元模态分析方法

车内噪声中的结构噪声是由车身结构振动与车内空腔声场的耦合产生的,传统的振动模态分析方法在针对车内噪声控制时由于没有考虑这种耦合特性而存在很大的局限性。在介绍结构—声场耦合模态分析方法的原理基础上,计算出了客车的结构、空腔和声固耦合的各阶模态频率和振型,据此分析了产生车内低频噪声的原因,并提出了具体的车身结构修改意见。     

Observer-based clutch disengagement control during gear shift process of automated manual transmission

A clutch disengagement strategy is proposed for the shift control of automated manual transmissions. The control strategy is based on a drive shaft torque observer. With the estimated drive shaft torque, the clutch can be disengaged as fast as possible without large driveline oscillations, which contributes to the reduction of total shift time and shift shock. The proposed control strategy is tested on a complete powertrain simulation model. It is verified that the system is robust to the variations of driving conditions, such as vehicle mass and road grade. It is also demonstrated that the revised system with switched gain can provide satisfactory performance even under large estimation error of the engine torque.     

超大跨度双跨钢桁梁悬索桥动力特性分析和模态试验

以跨径布置460 m+1480 m+491 m的一座双跨钢桁梁悬索桥结构为工程背景,充分考虑结构几何非线性效应、大位移非线性效应等因素的影响,建立了算例桥梁的MIDAS空间有限元分析模型,对基本动力特性进行了仿真分析和结构振动试验测试;对成桥结构进行动力特征参数测试,并与理论计算值进行了对比分析,该桥实测动力特征参数与对应理论计算值基本吻合,且测试值大于理论计算值,这表明成桥结构实测刚度大于理论设计目标值。     

Influence of polygonal wear of railway wheels on the wheel set axle stress

The coupled vehicle/track dynamic model with the flexible wheel set was developed to investigate the effects of polygonal wear on the dynamic stresses of the wheel set axle. In the model, the railway vehicle was modelled by the rigid multibody dynamics. The wheel set was established by the finite element method to analyse the high-frequency oscillation and dynamic stress of wheel set axle induced by the polygonal wear based on the modal stress recovery method. The slab track model was taken into account in which the rail was described by the Timoshenko beam and the three-dimensional solid finite element was employed to establish the concrete slab. Furthermore, the modal superposition method was adopted to calculate the dynamic response of the track. The wheel/rail normal forces and the tangent forces were, respectively, determined by the Hertz nonlinear contact theory and the Shen–Hedrick–Elkins model. Using the coupled vehicle/track dynamic model, the dynamic stresses of wheel set axle with consideration of the ideal polygonal wear and measured polygonal wear were investigated. The results show that the amplitude of wheel/rail normal forces and the dynamic stress of wheel set axle increase as the vehicle speeds rise. Moreover, the impact loads induced by the polygonal wear could excite the resonance of wheel set axle. In the resonance region, the amplitude of the dynamic stress for the wheel set axle would increase considerably comparing with the normal conditions.     

环境激励下自升式海洋平台损伤诊断

为探究适用于海洋平台结构的有效损伤诊断方法,针对某自升式平台的比例模型开展环境激励下损伤诊断试验研究。分别采用频域法中的增强频域分解法和时域法中的随机子空间法处理测试数据,提取前三阶的固有频率、振型和阻尼比等模态参数,并结合频率和振型识别结果计算节点柔度矩阵。通过分析平台模型模态参数和节点柔度矩阵的变化率,识别预先设置的结构损伤。试验结果表明,两种模态识别方法均能有效识别环境激励下的平台模型模态参数,其中利用固有频率变化率能够有效判断结构是否产生损伤,利用振型和柔度矩阵的变化率能够实现损伤的准确定位。