钢桥面板纵肋顶板焊缝疲劳裂纹扩展的关键影响因素

正交异性钢桥面板疲劳问题突出，纵肋与顶板焊缝处是其关键疲劳易损部位，研究该部位疲劳裂纹的扩展过程并确定关键影响因素及其效应，有助于深刻理解其疲劳损伤机理。建立正交异性钢桥面板疲劳试验节段模型的有限元分析模型，将纵肋与顶板焊缝焊根处的疲劳裂纹近似为半椭圆形裂纹，基于断裂力学实现其扩展全过程的三维数值模拟。在此基础上研究初始裂纹的纵向位置和初始裂纹形状对疲劳裂纹扩展过程的影响，阐明扩展过程中的疲劳裂纹的形状变化，以及疲劳裂纹关键部位应力强度因子幅值的变化规律。研究表明：对于典型的正交异性钢桥面板纵肋与顶板焊缝，在纵向一段范围内，初始裂纹的纵向位置对裂纹扩展的影响不大；初始裂纹形状对裂纹扩展的影响主要体现在裂纹扩展的初始阶段，经过一段时间的扩展之后，不同形状的初始裂纹将演变为相对稳定的形状；持续一段时间后，裂纹将逐渐变得较为扁长；疲劳裂纹在深度方向上扩展超过约顶板厚度一半时，最深点的扩展速率将会减慢；深度相同的裂纹，形状越扁长时越倾向于向深度方向扩展，越不扁长时越倾向于向长度方向扩展。     

Driver fatigue: a vision-based approach to automatic diagnosis

In this paper, we describe a system that locates and tracks the eyes of a driver. The purpose of such a system is to perform detection of driver fatigue. By mounting a small camera inside the car, we can monitor the face of the driver and look for eye movements which indicate that the driver is no longer in condition to drive. In such a case, a warning signal should be issued. This paper describes how to find and track the eyes. We also describe a method that can determine if the eyes are open or closed. The primary criterion for this system is that it must be highly non-intrusive. The system must also operate regardless of the texture and the color of the face. It must also be able to handle changing conditions such as changes in light, shadows, reflections, etc. Initial experimental results are very promising even when the driver moves his/her head in a way such that the camera does not have a frontal view of the driver’s face.     

The perception of Bus Rapid Transit: a passenger survey from Beijing Southern Axis BRT Line 1

Bus Rapid Transit (BRT) has emerged as a cost-effective transport system for urban mobility. As a relatively new form of Mass Transit, its ability to provide a high-quality transport service and potential to stimulate land development remain largely unexplored. This study intends to investigate the public attitude towards BRT services, as well as respondents’ perception of living near BRT stations, using the Beijing Southern Axis BRT system as a case study. A data-set of responses to 525 questionnaires were assembled and analysed using a combination of statistical techniques. The results show that BRT has gained great popularity among passengers, and brought about a positive impact on the attractiveness of residential property. The data identify that the majority of passengers are work-related commuters and use BRT more than once a day. The captive users have a higher satisfaction than choice users with respect to reliability, comfort & cleanliness and overall satisfaction with the BRT service. It is argued that the BRT has significantly improved the attractiveness of residential property along the BRT corridor.     

跨径对水泥混凝土桥面铺装力学性能影响的数值分析

水泥混凝土桥面铺装力学计算分析中,桥梁跨径对铺装层力学响应有重要影响。文章针对跨径长短对桥面铺装力学性能指标的影响展开研究,为桥面铺装力学计算中模型的简化提供理论依据。     

海洋工程用钢疲劳寿命与CTOD值关系的研究

通过对钻井平台上所用高强钢EQ70进行了韧度和疲劳性能的试验研究,得出了反映其韧度指标的裂纹尖端张开位移(CTOD)值和不同交变载荷下疲劳寿命值呈近似的线性关系.在应力幅值ΔP一定的情况下,疲劳寿命值N随着CTOD值的增大而增大,并且在高应力幅的时候,对数疲劳寿命和CTOD值有比较好的线性关系,最后还从微观意义上解释了产生这种关系的原因.     

Roll- and pitch-plane coupled hydro-pneumatic suspension

Passive fluidically coupled suspensions have been considered to offer a promising alternative solution to the challenging design of a vehicle suspension system. A theoretical foundation, however, has not been established for fluidically coupled suspension to facilitate its broad applications to various vehicles. The first part of this study investigates the fundamental issues related to feasibility and properties of the passive, full-vehicle interconnected, hydro-pneumatic suspension configurations using both analytical and simulation techniques. Layouts of various interconnected suspension configurations are illustrated based on two novel hydro-pneumatic suspension strut designs, both of which provide a compact design with a considerably large effective working area. A simplified measure, vehicle property index, is proposed to permit a preliminary evaluation of different interconnected suspension configurations using qualitative scaling of the bounce-, roll-, pitch- and warp-mode stiffness properties. Analytical formulations for the properties of unconnected and three selected X-coupled suspension configurations are derived, and simulation results are obtained to illustrate their relative stiffness and damping properties in the bounce, roll, pitch and warp modes. The superior design flexibility feature of the interconnected hydro-pneumatic suspension is also discussed through sensitivity analysis of a design parameter, namely the annular piston area of the strut. The results demonstrate that a full-vehicle interconnected hydro-pneumatic suspension could provide enhanced roll- and pitch-mode stiffness and damping, while retaining the soft bounce- and warp-mode properties. Such an interconnected suspension thus offers considerable potential in realising enhanced decoupling among the different suspension modes.     

粘层强度车辙疲劳试验研究

目前的粘层强度试验不能反映粘层的真实强度,鉴于此,先采用车辙仪碾压模拟道路实际运行环境,然后用拉拔、剪切试验测定车辙碾压后粘层的实际强度,并与车辙疲劳前粘层的强度进行对比。试验证明：该方法能真实地反映粘层强度,较目前常用的试验方法更为科学。     

大型开敞式深水码头导管架结构管节点的疲劳分析

结合大连新港新建30万吨级(兼靠45万t)进口原油码头工程,以导管架结构为研究对象,阐述该结构管节点的疲劳计算方法,并计算开敞式码头导管架结构中管节点的疲劳寿命.结果表明管节点的疲劳寿命满足相应规范的要求,可为实际工程设计提供参考.     

考虑疲劳强度和减轻质量的转向架构架设计

用有限元法对各种载荷工况下的转向架构架进行了疲劳分析,利用人工神经网络和遗传算法最大程度地减轻了转向架构架的质量.     

机车车轴疲劳问题分析与对策

通过对机车车轴常见故障及车轴的疲劳问题进行探讨,对车轴的疲劳裂纹、疲劳强度进行分析,提出了在机车车轴设计,材料、工艺选择以及运用维护中应采取的对策。