浮置板轨道结构对地铁车辆轨道耦合系统动力性能影响分析

以北京地铁6号线车辆为样本,研究了浮置板轨道对于车辆轨道耦合动力学模型的影响。建模时将浮置板轨道考虑成柔性体,用有限元实体单元建模,并利用模态叠加法进行求解。仿真后得出如下结论:与轨道不平顺引起的冲击相比,采用浮置板轨道后所产生的枕跨冲击、过渡冲击、轨道板冲击并不明显。车辆在浮置板轨道上行驶时,其竖向悬挂系统能够较好地降低轮轨的冲击力;轨道垫板刚度的主要影响是频率在60~150 Hz范围内的振动,对低频振动影响较小。随着轨道垫板刚度的变大,轮轨垂向力和轮重减载率逐渐变大,但其对轮轴横向力和脱轨系数影响很小,对车体振动几乎没有影响。轨道垫板刚度的主要影响是频率在10 Hz左右的轨道板的振动,对浮置板钢弹簧支承力的影响较小,即对路基的减振效果影响较小。     

轴系纵振对双层圆柱壳体水下声辐射的影响研究

采用有限元/边界元方法(FEM/BEM)对推进轴系纵振引起的双层圆柱壳水下辐射噪声特性进行研究.使用ANSYS有限元软件建立了流固耦合的有限元模型,计算了流-固耦合状态下结构振动位移响应.利用边界元技术对结构水下辐射噪声特性进行研究,并对推力轴承的布置位置和结构进行了改变,从而改变了激振力的大小及传递途径,对轴系纵振引起的结构水下辐射噪声起到了一定的改善.     

Effect of vertical and lateral coupling between tyre and road on vehicle rollover

The vehicle stability involves many aspects, such as the anti-rollover stability in extreme steering operations and the vehicle lateral stability in normal steering operations. The relationships between vehicle stabilities in extreme and normal circumstances obtain less attention according to the present research works. In this paper, the coupling interactions between vehicle anti-rollover and lateral stability, as well as the effect of road excitation, are taken into account on the vehicle rollover analysis. The results in this paper indicate that some parameters influence the different vehicle stabilities diversely or even contradictorily. And it has been found that there are contradictions between the vehicle rollover mitigation performance and the lateral stability. The direct cause for the contradiction is the lateral coupling between tyres and road. Tyres with high adhesion capacity imply that the vehicle possesses a high performance ability to keep driving direction, whereas the rollover risk of this vehicle increases due to the greater lateral force that tyres can provide. Furthermore, these contradictions are intensified indirectly by the vertical coupling between tyres and road. The excitation from road not only deteriorates the tyres’ adhesive condition, but also has a considerable effect on the rollover in some cases.     

Experimental and numerical investigation of the effect of rail corrugation on the behaviour of rail fastenings

This paper presents the results of a detailed investigation of the effects of rail corrugation on the dynamic behaviour of metro rail fastenings, obtained from extensive experiments conducted on site and from simulations of train–track dynamics. The results of tests conducted with a metro train operating on corrugated tracks are presented and discussed first. A three-dimensional (3D) model of the metro train and a slab track was developed using multi-body dynamics modelling and the finite element method to simulate the effect of rail corrugation on the dynamic behaviour of rail fastenings. In the model, the metro train is modelled as a multi-rigid body system, and the slab track is modelled as a discrete elastic support system consisting of two Timoshenko beams for the rails, a 3D solid finite element (FE) model for the slabs, periodic discrete viscoelastic elements for the rail fastenings that connect the rails to the slabs, and uniformly viscoelastic elements for the subgrade beneath the slabs. The proposed train–track model was used to investigate the effects of rail corrugation on the dynamic behaviour of the metro track system and fastenings. An FE model for the rail fastenings was also developed and was used to calculate the stresses in the clips, some of which rupture under the excitation of rail corrugation. The results of the field experiments and dynamics simulations provide an insight into the root causes of the fracture of the clips, and several remedies are suggested for mitigating strong vibrations and failure of metro rail fastening systems.     

变工况下的发动机连杆动态应力与疲劳损伤分析

以发动机曲柄连杆机构为研究对象,基于柔性多体动力学理论,建立了活塞、连杆、曲轴和飞轮的刚柔耦合动力学模型,分别计算了发动机稳态工况与变工况下的连杆应力,并对连杆危险节点的应力时间历程进行了雨流计数和疲劳损伤计算。结果表明,发动机在变工况运行时,连杆危险节点应力变化幅值相对稳态工况增大,加速了连杆的疲劳破坏。     

斜独塔混合梁斜拉桥风-汽车-桥梁系统耦合振动研究

针对公路汽车三维绕流特性显著的特点,按照准定常理论推导了适用于公路汽车的脉动风荷载表达式。将自然风、公路汽车、桥梁作为一个统一的相互作用系统,采用风-汽车-桥梁系统耦合振动分析模型,以某斜独塔混合梁斜拉桥为工程背景,研究侧风作用下汽车-桥梁耦合振动特性,并讨论了汽车-桥梁振动的影响因素。研究结果表明：由于桥梁和汽车的气动特性差异,桥梁的竖向抖振现象较横向抖振现象突出,而汽车的横向振动现象较竖向振动更明显。     

用十字万向联轴器实现可调多轴钻床

将十字万向联轴器的结构运用到多轴钻床上,实现可调多轴钻床,用于加工多种不同孔间距的零件及变形产品。     

膜片橡胶联轴器径向刚度特性分析研究

介绍了膜片橡胶联轴器的结构及工作特点,分析研究了橡胶块与两端膜片组之间不同的连接方式以及不同的橡胶块截面形状尺寸对该联轴器刚度特性尤其是径向刚度的影响,给出了改善该类联轴器刚度特性的途径。     

波浪作用下考虑桩土相互作用的桩柱响应*

以一离岸深水桩柱为例,依据JTJ 2132—1998《海港水文规范》的环境条件和环境荷载规范,对桩柱进行有限元离散。在海洋深水环境条件下考虑流固耦合效应,计算了在海洋极端规则波以及不规则波条件下桩柱的运动响应;为了进一步研究分析泥面以下土体对桩柱运动响应的影响,对比分析了在考虑桩土耦合相互作用下桩柱的响应与基岩面固结解下的响应;考虑到海洋地基为两相饱和土介质,对比了在不同简化阻抗处理下的运动响应结果。结果表明,桩土耦合相互作用对于波浪尤其是不规则波作用下的桩柱响应有很大影响,简化阻抗下的运动响应相比两相饱和地基阻抗处理论误差在10%左右,考虑桩土耦合效应对于工程设计具有指导意义和实用价值。     

基于J2EE架构的构件化集成

随着信息系统规模的不断扩大,软件变得更加复杂,系统面临可维护性降低、开发和调试周期长和重复开发的现象,如何降低系统的复杂性、开发和调试周期,提高软件的重用能力和系统的可维护性对信息系统至关重要。