Three-dimensional vortex-induced vibrations of a circular cylinder predicted using a wake oscillator model

This paper reports a numerical study based on a wake oscillator model, to determine the three-dimensional vortex-induced vibration (VIV) responses on a flexible cylinder with pinned-pinned boundary conditions subjected to a uniform flow. Four different aspect ratios have been selected for the study. The coupling equations of the structural oscillator models and wake oscillator models in both the cross-flow (CF) and in-line (IL) directions have been solved using a standard central difference method of the second order. The structural displacement, structural frequency, response wave pattern, response trajectory, and lift force coefficient, for four aspect ratios, have been compared. The numerical results establish that, for a small aspect ratio, the CF displacements have absolute standing wave behaviors without travelling wave behaviors, and the IL displacements have dominant standing wave behaviors with slight travelling wave behaviors. Further, the VIV trajectory is repeatable and displays figure-eight shapes. However, for a large aspect ratio, the CF displacements display identical characteristics with the IL displacements for a small aspect ratio, and the IL displacements for a large aspect ratio are simultaneously dominated by standing and travelling wave behaviors. Moreover, the VIV trajectory is apparently aperiodic and shows chaotic shapes.     

水深对抛石强夯影响的模型试验研究

通过模型试验,探讨水深对重锤夯击抛石后夯沉率及抛石应力的影响,以及有、无水情况下抛石夯击夯沉率和抛石应力随落距的变化关系。试验研究成果表明：水面与抛石面齐平的情况与有水的夯击效果相近,为缩比尺模型试验中消除边界效应及水深影响提供了理论依据。     

移动非均布荷载作用下的沥青路面动力响应分析

为更准确地模拟沥青路面实际的受力状态,基于弹性层状理论,借助大型有限元分析软件ANSYS,建立了沥青路面三维有限元粘弹性模型,并对其施加非均布垂直和切向摩擦行为的共同影响,分析车辆在匀速行驶时,沥青路面在不同载重车辆荷载作用下的动力响应。结果表明,纵向最大拉应力位于基层层底,纵向最大压应力位于沥青面层。超载显著增加了各层结构应力,加速了路面结构的破坏。路面设计时应提高上层材料的抗压强度。     

基于容差模型的发动机悬置系统稳健优化设计

应用稳健优化设计理论,考虑设计变量的不确定性对结果的影响,建立稳健优化模型。以发动机悬置系统能量解耦为目标,用Pareto遗传算法对系统的刚度参数进行稳健优化,并将优化结果运用Monte Carlo方法进行分析.结果表明,优化方法可以有效提高悬置系统的稳健性。     

Rice公式外推桥梁荷载效应

在当今,如何对桥梁进行合理评估已成为桥梁工作者的一个重要课题。而在桥梁评估过程中,科研工作者往往需要定量描述评估周期内某座桥梁的交通车辆荷载大小,一般用荷载效应描述。就此根据动态称重系统实测的107国道路段交通荷载数据产生的模拟车流对评估周期内荷载效应极值的计算方法进行了初步研究,以各种跨径简支梁为例,利用Rice外推理论外推各个观测周期的荷载效应极值,并以此作为建立评估荷载模型的基础。     

浅析新能源汽车发展现状及发展趋势

以新能源汽车发展现状和发展趋势为主线,详细介绍了当前各类新能源汽车的技术特点,并在此基础上系统地分析了未来新能源汽车的发展前景。最后,在权衡目前的技术状态和未来新技术的可行性后,分析了汽车工业发展的趋势。     

光纤光栅传感器在钢桥面铺装长期监测中的应用

钢桥面板在车辆荷载作用下,容易产生较大的局部变形。国内对于桥面铺装应力应变分析多采用有限元,实桥长期监测仍然处于空白阶段。该文依托桃浦路蕴藻浜大桥项目,对实桥监测过程中的传感器布设进行了研究。从不同结构、不同用途传感器选取方面入手,对传感器的埋设方案,安装方法进行详细介绍,为以后工程中传感器使用提供了借鉴。     

浅谈关于泵站节能的一些措施

该文根据泵站的实际特点,阐述了泵站节能所采取的一些措施,可供同行参考。     

Stability enhancement and fuel economy of the 4-wheel-drive hybrid electric vehicles by optimal tyre force distribution

In this paper, vehicle stability control and fuel economy for a 4-wheel-drive hybrid vehicle are investigated. The integrated controller is designed within three layers. The first layer determines the total yaw moment and total lateral force made by using an optimal controller method to follow the desired dynamic behaviour of a vehicle. The second layer determines optimum tyre force distribution in order to optimise tyre usage and find out how the tyres should share longitudinal and lateral forces to achieve a target vehicle response under the assumption that all four wheels can be independently steered, driven, and braked. In the third layer, the active steering, wheel slip, and electrical motor torque controllers are designed. In the front axle, internal combustion engine (ICE) is coupled to an electric motor (EM). The control strategy has to determine the power distribution between ICE and EM to minimise fuel consumption and allowing the vehicle to be charge sustaining. Finally, simulations performed in MATLAB/SIMULINK environment show that the proposed structure could enhance the vehicle stability and fuel economy in different manoeuvres.     

SBS改性沥青热储存稳定性评价

采用8种成品SBS改性沥青,根据《公路工程沥青及沥青混合料试验规程》(JTJ 052-2000)中T0661的方法,分别对其进行热储存离析试验;并且采用AR-2000型动态剪切流变仪对不同品牌的成品SBS改性沥青及热储存离析试验上、下部试样进行动态剪切试验,以获取SBS改性沥青动态力学温度谱。试验表明,仅以离析试验上下部软化点差值小于2.5℃来评价SBS改性沥青储存稳定性是不全面的,SBS改性沥青在储存中会产生软化点的升高或衰减,这些同样会导致沥青的使用性能的不稳定性。在温度扫描下损耗因子tanδ是否出现平台区,即是否形成空间网络结构与SBS改性沥青的储存动力稳定性的好坏没有必然的联系。