高速列车转向架技术研究

高速铁路运营对转向架技术提出了更高要求,为能设计出性能更优越的动车组转向架,调查了中国高速动车组的线路条件、动车组的车轮踏面磨耗情况,分析轮轨匹配关系;动力学分析中考虑了转臂节点、抗蛇行减振器、空气弹簧等部件的非线性特性,橡胶、减振器等减振元件高低温变化条件下车辆参数的变化,电机弹性悬挂方式等,在实际轮轨匹配关系基础上建立了车辆系统动力学模型。动力学系统仿真选择了最优悬挂参数,结合部件台架测试对悬挂元件进行了工程化设计;为掌握转向架服役周期内关键部件可靠性,对运用动车组转向架进行了大量的动应力测试,系统分析了中国无砟轨道条件下转向架主要承载区域载荷随车辆运营周期、不同气候条件、不同线路条件下的变化趋势,建立了中国高速列车载荷谱体系。通过结构、悬挂、传动、制动、焊接、降噪、轮轨等系统集成,形成高速列车转向架技术体系。     

驱动工况下高速动车组蛇行失稳非线性度

基于信号的波内调制现象定义信号的非线性指标,并研究高速动车组在驱动工况下(驱动系统在直接转矩控制下)蛇行失稳的非线性特征。首先建立包括高速动车组的车辆动力学Simpack子模型和牵引传动系统的直接转矩控制Matlab/Simulink子模型在内的机械电气耦合联合仿真模型,然后计算动力学响应,最后基于黄变换计算列车在蛇行失稳状态下动力响应的非线性指标变化。仿真结果表明:若列车出现蛇行失稳,转向架和车体横向振动非线性指标会急剧增大;完全失稳情况下,车体横向加速度非线性度大于0.1,转向架横向位移非线性度大于0.3。     

高速列车车体振动特性分析

高速列车的振动特性直接影响旅客的乘坐舒适性,因而研究和评估高速列车运行中的振动特性具有现实意义。本文采用simpack软件建立车体模型,模拟高速列车线路正常运行情况,分析车体的振动特性。高速列车在线路实际运行情况下,测试车体的振动信号,分析车体实际振动特性。对比仿真分析结果和试验测试结果,评价高速列车的振动特性,为旅客舒适度改善提供依据。     

城际列车晃车机理试验研究

针对某在线运营的城际列车的晃车现象,实测整车不同位置处的振动信号,对比分析在晃车与非晃车时间段内车辆的运行平稳性、时频特征以及车辆不同部位的信号相干特征,据此初步了解车辆在晃车时的典型特征;进而基于ODS分析理论,掌握车辆晃动时的整体振动情况,并基于构架稳定性分析结果,发现并验证城际列车晃车的机理。结果表明,发生晃车时,车辆横向平稳性指标大于2.5,晃车主频在4 Hz左右,相干性分析表明车体晃动与转向架振动有直接关系;基于ODS分析结果发现晃车时转向架蛇行与车体摇头反相耦合,此时转向架的蛇行稳定性不足,该蛇行频率与基于实测轮轨匹配等效锥度所得的理论计算频率基本一致,因此车辆系统稳定性裕量不足,转向架在较高运行速度工况下接近蛇行失稳状态是晃车的主要原因。     

服役工况下高速动车组齿轮箱箱体振动特性分析

为探究某高速动车组齿轮箱箱体在服役工况下的振动特性,对齿轮箱开展线路跟踪服役试验,通过分析测试系统在齿轮箱箱体多路线工况下采集的数据,研究其所真实反映的齿轮箱箱体及轴箱在实际运营线路中的振动特性.结果表明:齿轮箱箱体的振动比轴箱的振动更易受到列车速度变化的影响,且箱体的振动加速度与列车运行速度变化趋势基本一致;试验动车...     

转向架构架工作模态及其对车下振动传递影响初探

为进一步了解运行过程中转向架构架的真实动态特性,对实际线路运行的某高速列车进行工作模态测试,获取构架响应点之间的互谱信号并进行模态参数识别。模态参数识别方法采用最小二乘复频域法。根据其识别结果,剔除由轴箱传至构架且引起构架显著峰值的虚假模态,获得构架真实工作模态参数。结合轴箱、车体外地板振动实测频谱,找到车体外地板显著振动频率来源,进而分析转向架工作模态对车体外地板振动显著峰值的影响。本文的相关实测结果为了解运行过程中转向架构架真实动力学行为、研究车体外地板振动显著频率的产生、传递机理提供依据;同时,测试及模态参数识别方法为车体运行部件工作模态试验提供参考。     

车辆与吊挂设备耦合作用垂向系统振动传递及平稳性研究

基于车辆-无砟轨道耦合系统垂向动力学模型,建立了由轨道不平顺到车体、转向架和各吊挂设备的振动加速度传递函数以及运行平稳性的传递函数,分析了吊挂设备与车体、转向架等主体部件间采用刚性与弹性两种吊挂方式下,车辆系统部件振动传递特性的差异。讨论了部件间连接刚度变化对各部件加速度传递特性以及车辆运行平稳性传递函数的影响,并通过对比给出了主体部件与吊挂设备间连接刚度的合理取值,研究了吊挂跨距的改变以及吊挂位置的偏置对于平稳性及部件加速度传递函数的影响。在考虑车体弯曲弹性振动下,分析了车体的抗弯刚度和结构阻尼比对平稳性传递函数的影响。结果表明:弹性吊挂能够优化车体和构架等主体部件的中、低频传递特性,吊挂跨距的增大使构架及车体吊挂位置处的传递函数增大;随速度的增加,前、后部平稳性指数的差异有所加大,车体抗弯刚度和结构阻尼比在常规范围内选取时,平稳性指数的变化并不十分显著。     

非稳态横风对货运动车组车体-集装器系统横向振动特性的影响

基于Cooper理论构建了平均速度20m/s的非稳态风谱及相应的侧风载荷和侧滚力矩载荷,并加载到货运动车组车体-集装器耦合模型中,分析了匀质集装器重心为其几何中心处,车体-集装器系统在风载激励和风载与轨道不平顺耦合激励作用下不同风速的横向加速度RMS值的变化规律,以及该系统在上述两种工况及武广轨道不平顺激励工况下的横向振动的频域特性。结果表明:货运动车组车体-集装器系统的横向振动加速度随风速的增加而增加;轨道不平顺激励与风载激励相互叠加后,可改变车体-集装器系统的横向振动时频域特征以及车体至集装器的横向振动传递特性;横风载荷对货运动车组车体-集装器系统的低频振动影响不容忽视。     

高速列车交会压力波特性分析

因动车组在高速交会时产生的瞬变交会压力波对车体侧壁变形、列车运行噪声及运行安全性都有不可忽视的影响,该文利用高速列车的实际测试数据,从3方面对高速列车在明线交汇和隧道交汇情况下的压力波进行深入分析:交会压力波的时-频特性,主要参数值及其与车速的关系,交会压力波对车体侧壁振动的激励作用。特别对压力波所产生的冲击响应谱进行深入分析,得到不同阻尼比下的频率响应。该文分析结果为进一步研究瞬变交会压力波对车体侧壁变形的影响、对列车运行噪声的贡献等提供新的参考依据。     

基于EMD的气动载荷作用下动车组横向振动提取研究

为研究高速动车明线会车时引起其横向振动的主要原因以及分析气动载荷对于动车组运行稳定性的影响,以线路实验采集的车体表面压力与列车振动数据为基础,利用EMD分解得到振动信号的各个本征模(IMF)分量;对分解后的IMF分量进行相关性分析,利用相关性原理来重构振动信号。重构信号即为气动载荷作用下的动车组横向振动。对比分析动车组在有气动载荷与无气动载荷下的横向稳定性。结果表明:明线会车时气动载荷引起的横向振动频率主要集中在低频段0.3~10 Hz内,动车组横向振动加速度及横向平稳性的影响比只考虑轨道不平顺时要明显增大,明线会车时气动载荷是引起列车横向振动的主要原因。     

Virtual multiple input multiple output in multiple high-altitude platform constellations

Multiple-input multiple-output (MIMO) technology, which makes use of the spatial dimension by utilising multiple antennas at the transmitter and receiver, has proved an efficient solution for providing higher data throughput and/or link reliability in wireless systems. In this study, the authors investigate a virtual MIMO (V-MIMO) technique, based on a constellation of multiple high-altitude platforms (HAPs), providing broadband wireless access to high-speed trains under predominantly line-of-sight (LOS) propagation conditions. They analyse the performance of transmit diversity based on space?time block coding (STBC), in particular Alamouti and extended Alamouti schemes, using fixed wide-lobe receive antennas, and compare it to the reference receive diversity scheme based on best HAP selection that requires highly directional and steerable antennas. Simulation results for different diversity schemes are based on the calculation of carrier to interference-plus-noise ratio (CINR) along representative railway lines in a realistic terrain configuration. The CINR levels obtained are mapped onto transmission modes specified by standards developed for two wireless systems operating at distinct frequency bands, the DVB-S2 assumed for operation in mm-wave bands and the IEEE 802.16e (mobile WiMAX) for operation at 3.5 GHz. Simulation results show that the use of transmit diversity schemes in a multiple HAP constellation decreases the link outage and also increases the average spectral efficiency, but requires a marked increase in transmit power, especially for the system operating in mm-wave bands.     

Moments of multiple scattering

We present an analytical technique that solves exactly, and in closed form, for the first and second moments of the spatial and angular positions of photon distributions in a multiple-scattering medium. The analysis leads to simple analytic expressions for these moments, both conditioned on the number of scatterings and summed over all scattering events. The conventional results for small-angle forward scattering, and for the diffusion regime, are recovered in the appropriate limiting cases.     

Vibrations of multiple delaminated beams

The free vibrations of beams with two enveloping delaminations have been solved analytically without resorting to numerical approximation. The multiple delaminated beam is analyzed as several interconnected Euler–Bernoulli beams. The differential stretching and the bending–extension coupling are considered in the formulation. The influence of the sizes and locations of the delaminations on the primary and secondary frequencies and mode shapes of a beam are investigated. For clamped–clamped beams, the primary frequency shows a high sensitivity for the long delamination but a low sensitivity for the second short delamination, while for the secondary frequency, the sensitivity is high for both delaminations. For cantilever beams, the primary and secondary frequencies show a high sensitivity for the long delamination but low sensitivity for the second short delamination. Results are compared with the analytical and experimental data reported in the literature to verify the validity of the present model.     

The theory of multiple peeling

In this paper we derive the theory of multiple peeling, extending the pioneering energy-based single peeling theory of Kendall, including large deformations and pre-stretching. We can thus treat a complex system of films, adhering over a substrate and having a common hinge where the pulling force is applied. Two case studies are investigated: the asymmetric V-shape double peeling and the symmetric cone-shape configuration with N peeling tapes, both requiring the solution of six nonlinear coupled equations (instead of the one needed in the simpler single peeling problem). Remarkable implications emerge: (1) for moderate deformations, the critical strain of a tape is identical to that of the single peeling; (2) an optimal peeling angle, at which adhesion is maximal, is discovered; (3) an additional optimization, even for hierarchical structures, is introduced by imposing the delamination force equal to the intrinsic fracture of the tape. Also, the length of the peeling process zone is calculated, suggesting different optimal values for flaw-tolerant peeling at different angles. Applications to gecko adhesion, for which the flaw-tolerant peeling is demonstrated, and spider silk anchors, that we are going to discuss in details in subsequent papers, are envisioned (including a new pre-stretching mechanism for adhesion control) and suggested by the evidence of a smart mechanism capable of maximizing adhesion simply by increasing the applied tension.     

Quantity discount decisions under conditions of multiple items,multiple suppliers and resource limitations

This research considers quantity discount procedures under conditions of multiple items, resource limitations and multiple suppliers. This is a very complex problem that has not yet been addressed in the literature. In this paper we offer an efficient heuristic programming procedure for evaluating alternative discount schedules. Moreover we use an example problem to test the suggested procedure. The results offer several encouraging findings for managers facing this impressive problem.     

Mechanics of composites of multiple scales

This paper uses the method of multiple scales for heterogeneous media to derive the constitutive equations on the meso- and macro-scales for composite materials consisting of fibers and a matrix material. We have deduced the general theory for problems of three scales. The subscale solutions are obtained by numerical or analytical methods.     

The multiple mixing chamber

This paper deals with the multiple mixing chamber in which He³, circulating in a dilution refrigerator, is diluted in steps.The double mixing chamber in the stationary and in the dynamic state is described and the important design features are given. The triple mixing chamber is also discussed. A comparison is made between the performance of dilution refrigerators operating with a single mixing chamber and with a double mixing chamber.     

Automated multiple failure FMEA

Failure mode and effects analysis (FMEA) is typically performed by a team of engineers working together. In general, they will only consider single point failures in a system. Consideration of all possible combinations of failures is impractical for all but the simplest example systems. Even if the task of producing the FMEA report for the full multiple failure scenario were automated, it would still be impractical for the engineers to read, understand and act on all of the results.This paper shows how approximate failure rates for components can be used to select the most likely combinations of failures for automated investigation using simulation. The important information can be automatically identified from the resulting report, making it practical for engineers to study and act on the results. The strategy described in the paper has been applied to a range of electrical subsystems, and the results have confirmed that the strategy described here works well for realistically complex systems.