Force Path Analysis of Ballasted Jointless Bridge Turnout

The action between bridge and ballasted jointless turnout on bridge is reversible. To locate the force path between them, the model of a jointless turnout on a 4×32 m continuous beam were calculated and analyzed. Also analyzed were factors of influence, such as: temperature increment, longitudinal pier stiffness, ballast resistances, and turnout and bridge layouts.     

压路机复杂形状偏心块的激振力计算

在振动压路机的设计中,从结构方面考虑,经常出现具有复杂形状的偏心块结构。本文给出了其激振力计算的一般方法和公式,具有普遍适用性。     

Design of a forced control system for a dynamic road simulator using QFT

This paper presents the road simulator control technology for reproducing a road input signal to implement real road data. The simulator consists of a hydraulic pump, a servo valve, a hydraulic actuator and its control equipment. QFT (Quantitative Control Theory) is utilized to control the simulator effectively. The control system illustrates a tracking performance of the closed-loop controller with a low order transfer function G(s) and a pre-filter F(s) for a parametric uncertainty model. A force controller is designed to communicate the control signal between the simulator and digital controller. Tracking specification is satisfied with upper and lower bound tolerances on the steep response of the system to the reference signal. The efficacy of the QFT force controller is verified through the numerical simulation in which combined dynamics and actuation of the hydraulic servo system are tested. The simulation results show that the proposed control technique works well under an uncertain hydraulic plant system. The conventional software (Labview) is used to make up for the real controller on a real-time basis, and the experimental works show that the proposed algorithm works well for a single road simulator.     

Prediction of interior noise by excitation force of the powertrain based on hybrid transfer path analysis

In the early design stage of a vehicle, simulation of interior noise is useful for assessment and enhancement of the noise, vibration and harshness (NVH) performance. Traditional transfer path analysis (TPA) technology cannot simulate interior noise since it uses an experimental method. In order to solve this problem, hybrid TPA is employed in this paper. Hybrid TPA uses simulated excitation force as the input force, which excites the flexible body of a car at the mount points, while traditional TPA uses the measured force. This simulated force is obtained by numerical analysis of the finite element (FE) model of a powertrain. Interior noise is predicted by multiplying the simulated force by the vibro-acoustic transfer function (VATF) of the vehicle. The VATF is the acoustic response in the compartment of a car to the input force at the mount point of the powertrain in the flexible car body. The trend of the predicted interior noise based on the hybrid TPA corresponds very well to the measured interior noise, with some difference due to not only experimental error and simulation error, but also the effect of the airborne path.     

悬挂式多波束水动力分析

多波束主要用于考察海底地貌,保证良好的水动力性能可以更有利于多波束的工作。波浪中舰船产生的纵摇和垂荡是影响多波束水动力性能的主要因素。多波束所受的合力主要是由波浪中舰船垂荡和纵摇所产生的耦合垂向加速度引起的。采用势流理论计算舰船水动力系数,进一步采用STF二维切片理论对舰船耐波性进行预报。多波束升力的计算要考虑波浪和纵摇的攻角,合力与升力、重力以及浮力的差值即为多波束与船体间的作用力。多波束的水动力周期性变化,变化周期同舰船摇荡周期相同。     

水下微结构功能表面设计及减阻特性研究

研究表明,当物体表面存在微结构时,可以减小阻力,降低能源消耗。本文设计M形和V形两种微结构,使用SST k-ω湍流模型,分析微结构的减阻机理及影响微结构减阻的因素。将V形微结构应用于水下航行器模型,探讨湍流状态下外流域的减阻率和流场变化。结果表明微结构能够减缓湍流猝发过程,降低湍流猝发强度,改善边界层的流态;当微结构夹角为60o、高度小于0.04mm时具有较好减阻作用;V形微结构在水下航行器模型中的减阻率达到1.77%,且减阻率随布置面积增加而增大。     

环境因素对战时野战机场开设影响的模糊分析

分析了野战机场环境对后勤保障影响的问题。以场务保障为例,提出了影响飞行场务保障实施的因素集,从量化角度运用模糊相似优先比决策法对几个野战机场方案对场务保障实施影响情况进行了排序。在直观地看出各个野战机场方案对场务保障支持情况基础上,说明了各个方案中影响场务保障因素的利弊,从而可以针对各个方案有的放矢地制定未来应急场务保障预案,实现场务保障快速、高效的目标。经推广研究,可以得出野战机场选址对空军后勤保障的影响,增强制定战时后勤保障预案的针对性。     

大跨度铁路钢桁梁斜拉桥带水平K撑桥面系传力特性

在列车制动力等纵向力及竖向荷载作用下的空间变形均会导致钢桁梁桥面系存在复杂的纵向受力和传力,针对大跨度铁路钢桁梁斜拉桥带水平K撑内密肋桥面系,基于解析公式推导、有限元仿真分析研究其受力特性和桥面构件的纵向传力比。在此基础上,基于应力等效准则制作1∶4的试验模型,进行最不利工况下加载试验,研究该桥面系的实际受力和传力特性。结果表明:纵向传力解析式显示,K撑与横梁的纵向传力比仅与结构参数相关,为0.69~2.76的定值,能传递40.83%~73.40%的总纵向力,K撑面积、横梁外伸长度是影响纵向传力比的主要参数;由全桥杆系有限元模型分析的内力结果计算的纵向传力占比介于61.09%~72.53%之间,由局部有限元模型分析的应力结果计算的纵向传力占比介于57.45%~86.60%之间,试验模型实测应力计算的纵向传力占比介于58.16%~87.95%之间,不同方法计算的纵向传力占比存在一定误差,其原因主要源于理论简化、计算模拟及测试误差,但均能反映纵向传力比的基本范围。可见,K撑构件能够有效传递纵向力,降低横梁面外弯矩,改善桥面系结构受力。     

两相流相互作用下的船模微气泡减阻性能数值仿真

基于两相流理论,对集装箱船船模进行微气泡减阻性能数值仿真研究。分析船模在不同喷气口位置、流体含气率、不同喷射速度和角度下的流场分布和减阻效果。结果表明：当流体微气泡含量过高时,会增大船体摩擦阻力,流体含气率为10%~20%时,有较好的减阻效果,喷气口位置在距离球鼻艏后缘约三分之一船长附近具有较高的空气覆盖率,喷气口喷气方向垂直向下所产生的减阻效果比喷气方向偏向船侧效果要好,且船速较高时可允许较高含气率流体注入流场并增大减阻效果。