Sensitivity analysis of suspension characteristics for Korean high speed train

The dynamic performance of railway vehicle is normally expressed as stability, safety and ride comfort, and is affected by mass properties, suspension characteristics, contact mechanism between a wheel and a rail, etc. This paper describes the procedure of sensitivity analysis between some of the suspension characteristics of the Korean high speed train (KHST) as the design variables and the dynamic performance as the response variables; and it analyzes the results of sensitivity characteristics for the design variables, comparing two different approximated approach processes known as the response surface model formulated in a polynomial equation and neural network model formulated in a processing code. Analyzing the suspension characteristics for KHST, the approximated method creating meta-models consisted of 29 design variables and 46 performance indexes, which are applied in this paper. The models were coded by using the correlation information between the design variables and the performance indexes made by the 66 times iterative simulations according to the design of experimental method. The table consists of the orthogonal array L32 and the D-Optimal design table. The results show that the proposed sensitivity analysis procedure is very efficient and simply applicable for a complex mechanical system such as railway vehicle system. Also they show that the two models applied in this paper have similar tendency in the view of the sensitivity order of the design variables. This paper was presented at the 4th Asian Conference on Multibody Dynamics(ACMD2008), Jeju, Korea, August 20–23, 2008. ChanKyoung Park received B.S., M.S., and Ph.D. degrees in Mechanical Engineering from Hanyang University in 1987, 1989, and 2004, respectively. Dr. Park is currently a Principal Researcher at the Korea Railroad Research Institute in Euwang, Korea. His research interests are in the area of high speed train dynamics and system engineering of trains.     

Cusp error reduction under high speed micro/meso- scale milling with ultrasonic vibration assistance

In the conventional use of vibration assisted machining, vibratory motion is mostly applied to the continuous machining processes such as turning where the cutting speed is much lower than the vibration speed. Even the recent articles on vibration assisted milling processes are also quite limited to low spindle speed less than 3k RPM. This study investigates vibration assistance that is applied to the workpiece in a high speed micro/meso-scale intermittent milling system where the cutting speed is much higher than the vibration speed. In addition to this, the vibration effect is analyzed considering feed and cross-feed directional application separately, which gives an idea of a right vibration assistance direction for surface quality improvement. To validate this, a one-directional ultrasonic vibration assisted milling system with ultrasonic frequency at 40 kHz and with amplitudes of a few microns is designed and its effect on the machined surface quality is investigated at high spindle RPMs over 15k. As a result, cusp heights are found to be reduced with ultrasonic vibratory motion of cutting edge in high cutting speed. Furthermore, the machined surface quality clearly tells that feed directional vibration assistance is able to generate better surface quality with reduced wavy burrs than cross-feed directional vibration assistance.     

超高速电梯轿厢横向振动控制方法

介绍了目前关于控制超高速电梯横向振动的方法。提出了考虑主被动控制的耦合性,采用多目标、系统级的集成设计方法,对主被动控制策略进行优化设计,可能是目前控制超高速电梯横向振动的研究方向。     

Optimization of secondary suspension of piecewise linear vibration isolation systems

A comprehensive optimal design solution is presented for piecewise-linear vibration isolation systems. First, primary suspension optimum parameters are established, followed by an investigation of jump-avoidance conditions for the secondary suspension. Within the no-jump zones, an optimal design solution is then obtained for the secondary system and overall results are discussed.Averaging method is employed to obtain an implicit function for frequency response of a bilinear system under steady-state conditions. This function is examined for jump-avoidance and a condition is derived which when met ensures that the undesirable phenomenon of ‘jump’ does not occur and the system response is functional and unique. Optimal stiffness and damping parameters for the primary suspension are extracted from a recently established work for passive linear vibration systems. For each point of the primary suspension optimal curve, jump-free zones are identified. Iterating this process, a boundary surface between no-jump (unique response) and jump (multiple-response) areas is established. Keeping optimal parameters for the primary suspension system fixed, the secondary suspension stiffness and damping parameters are varied inside the no-jump zones to explore optimum solutions for the secondary.The root mean square (RMS) of the absolute acceleration is minimized against the RMS of the relative displacement (η). It is observed that there is a certain band of parameters defined by primary damping, within which a valid frequency response can be obtained. An optimum numerical solution is sought within this band of parameters. Optimal solution curves are achieved for the secondary suspension. These can be used in conjunction with the optimal curve for the primary suspension to select design parameter values for the best possible vibration isolation performance in a given application.     

高速铁路客车振动特性试验研究

针对车辆线路跟踪试验所测得的各主要部件的三向振动加速度值,通过时域统计和频域分析方法提取数据的主要特征,探究轮轨激扰产生的振动能量从轴箱到构架、构架再到车体的传递关系。研究结果表明,由于车辆的一系悬挂系统刚度和阻尼比较大,其对于高频垂向振动有明显的隔振减震作用,但对于低频振动的隔振效果有限。二系悬挂系统对于低频振动则具有很好的隔振减震作用,很好地弥补了一系悬挂系统的不足之处,传递至车体的振动能量和幅值都明显成数量级衰减了。     

某型直升机大速度下的异常振动分析

某型直升机在大速度飞行时出现短时的抖动现象,采用传统傅立叶变换无法得到这一变化过程的详细信息。采用小波分析和修正的傅立叶级数展开算法对振动信号进行分析,结果显示采用该方法可以有效获取信号中的非稳态变化信息,并进一步分析得到大速度下激起的摆振后退型是直升机抖动的原因。     

Flexible vibration analysis for car body of high-speed EMU

The resonance of the flexible vibration of car body, which has not been detected before on a passenger coach, occurred recently on a high-speed Electric multi units (EMU) when the train was running at 300 km/h on Beijing-Shanghai line. In this investigation, the force transmission from track to car body via suspensions is elaborated first with possibly induced factors briefly discussed. Both the measurements and experiments in field and in laboratory were conducted to evaluate the resonances and the excitation as well as transmission. Moreover, a three-dimensional railroad vehicle model was built in a computational non-linear Multibody system (MBS) framework, in which the car body flexibility was modeled using Finite element (FE) method. The model was validated and shows good agreements with measurements. Furthermore, the measured wheel and rail profiles were used to analyze the wheel/rail interaction for both new and worn states. The effects of the wheel-rail contact conditions on stabilities, dynamics and riding comforts were also examined. Feasible solutions were promoted to avoid the resonance and following by validating tests. It shows that the high frequency excitation arises from the hunting motion of bogie that closes to the modals of the car body, leads to the resonance of the structure of the car.     

高速加工铣刀结构参数研究

针对高速加工过程中铣刀产生的振动进行了研究,利用有限元软件对不同结构铣刀模型进行了模态分析。分析表明:随铣刀齿数的增加,其固有频率越低,越易引起共振;相同齿数情况下,一阶和二阶铣刀固有频率接近,而之后的各阶固有频率相差很大;切削载荷对铣刀固有频率影响不大。     

高速高加速堆垛机速度控制曲线研究与优化

将以高速高加速堆垛机作为研究对象,采用动力学分析并利用叠加原理得到立柱动态挠曲变形公式,分析影响立柱变形的因素。提出一种新型速度曲线优化控制方案,当进行长距离作业,堆垛机速度可以到达最大设计速度时选择S型速度控制曲线,当运行短距离作业,堆垛机速度无法达到最大设计速度即需减速制动时选择三角函数型速度控制曲线。此方案使堆垛机速度加速度变化连续平滑,抑制立柱变形而产生摆动,提高堆垛机稳定性。     

降低车辆振动的悬架参数多体动力仿真分析和优化

针对悬架结构参数对由于路面不平而产生的车辆振动的影响,通过在多体动力学分析工具AD-AMS环境下,综合运用参数化设计、单变量和多变量的筛选实验以及正交实验优化方法,对建立的车辆1/4悬架模型作了分析和研究;最后以降低车轮最大振动加速度为优化指标,在极差分析结果的指导下,得出了实验约束范围内悬架参数最优解。研究结果表明,该优化方法有助于降低类似悬架等复杂系统的优化求解的难度,且优化效果明显。     

Optimization of suspension parameters to improve impact harshness of road vehicles

This paper illustrates the development and implementation of a parameter optimization methodology to improve impact harshness (IH) of road vehicles. A full ADAMS model of a small commercial vehicle is used as the IH test vehicle. The methodology involves the use of design of experiments methods together with response surface methodology. Significant design parameters affecting IH of the vehicle are first determined by the screening experiments. Once the critical parameters are identified, they are optimized to achieve improvement in the IH by constructing response surface. The optimization results indicate that the selected suspension parameters are capable of improving IH performance of the full vehicle ADAMS model by minimizing longitudinal and vertical acceleration responses. The results also show that considerable improvement can be obtained by using the proposed parameter optimization methodology.     

高速铣削下刀具进刀方式寻优研究

研究了高速铣削过程中切入角的变化对铣刀所受载荷的影响,在ANSYS软件中建模并进行了应力、应变分析,解决了型腔和外轮廓周铣刀轨最优的进刀方式选取,对高速铣削加工中切入角的寻优具有一定的指导性.     

用于高速转轴径向振动检测的光纤传感技术

采用光纤测量技术实现航空叶轮泵高速转轴径向振动的检测,对检测系统的工作原理做了详细介绍。设计了新型的光纤测头,提出相应的补偿方案,并对补偿机理进行了详细的分析。对测试系统的特性进行了研究,得出位移特性调制函数表达式,给出了仿真曲线。理论计算和仿真分析表明, 该测试系统能有效地消除因光源光强波动、光纤弯曲损耗、表面反射率等因素对输出特性的影响,可以在叶轮泵内部电磁干扰严重和高温等恶劣环境下实现对高速转轴径向振动的检测。实验测试结果表明,随着转轴转速由1 000 r/min提高到10 000 r/min,径向振动幅值单调增加,这与实际情况相符合。     

动车组电机吊架多目标可靠性优化设计

为提高高速动车组电机吊架的承载能力,考虑几何参数的随机性,将响应面法和多目标遗传算法相结合对其进行可靠性优化设计.首先,对电机吊架进行静强度和位移灵敏度分析,找出设计变量;其次,对设计变量进行中心组合试验设计,根据试验设计点来拟合静强度和位移的多项式响应面模型;然后,将几何参数的随机性转化为可靠度,运用最小二乘法拟合可靠度函数方程作为约束条件;最后,运用多目标遗传算法对电机吊架进行可靠性优化设计.研究结果表明:响应面法与结构可靠性优化方法相结合,可以简化求解过程,提高优化结果的可靠度.     

淬硬钢高速铣削参数优化试验研究

采用正交试验法对切削力和粗糙度两个试验指标进行优化,最后采用综合平衡法确定出一组最优方案。经验证满足加工要求,达到了试验目的。     

非公路车辆座椅悬架振动的动力学分析

非公路车辆工作条件恶劣,座椅振动具有低频高强度的特点。将座椅简化为由浮动机座驱动的单自由度系统,依此分析了非公路车辆座椅的振动动力学特点,结果表明在底座低频振动区,座椅和激励振动的振幅和相位基本一致,振幅随阻尼增大而增大;在高频振动区,座椅振幅小于激振振幅,振幅随阻尼增大而减小。使用磁流变阻尼器等半主动减振器进行减振时,低频区应采用高阻尼,高频区应采用低阻尼。     

Effects of macro-parameters on vibration and radiation noise for high speed wheel gear transmission in electric vehicles

Considering flexible shafts, a coupled dynamic model for the gear transmission system of wheel reducer used in electric vehicle was developed. By combining the acoustics finite element modal for housing in Virtual Lab and the coupled dynamic model for gear transmission system, a simulation method was proposed for the prediction of the radiation noise for the wheel reducer. Then, the effects of different macro geometry gear parameters including pressure angle and helical angle on the dynamic response and radiation noise were investigated under the rated working condition. Results show that the peak-peak value of the transmission error dramatically falls in the starting zone, followed by an upward trend with the increase of the pressure angle for the low speed stage gear pair. The minimum transmission error and vibration acceleration occur when the pressure angle is 17°. The increase of the pressure angle does not affect the sound pressure level at the field point obviously. The design case with 17° pressure angle shows the optimum radiation noise level, which is 4.41dB less than the original model. Compared to the pressure angle, the helix angle has a major influence on the transmission error, vibration acceleration and acoustic radiation noise. With the increase of the helix angle, the time-varying transmission error curve becomes more smooth with a lower peak-peak value. Besides, the increase of helix angle results in lowering the varying and fluctuating trend of both vibration acceleration and acoustic radiation noise. The design case with 24° helix angle shows the prime radiation noise level, which is 7 dB less than the original scheme.     

先导式高速开关阀的优化设计与动态仿真

针对一种主阀为滑阀结构的先导式大流量高速开关阀控制腔面积的优化设计问题,首先对主阀芯进行了动力学分析,得到先导阀与主阀之间参数匹配的优化目标函数,依据该目标函数对一个具体的先导式大流量高速开关阀的控制腔面积进行优化设计。为验证理论优化的结果,基于AMESIM平台建立了该先导式大流量高速开关阀的精确仿真模型,通过动态仿真对控制腔面积进行优化,所得结果与理论分析优化的结果基本一致。研究结果表明,主阀芯换向时间与控制腔面积之间为非单调关系,存在一最佳控制腔面积使主阀换向时间最短。     

Effect of test parameters on large particle high speed slurry erosion testing

Abstract

A high speed slurry-pot wear tester was developed for close-to-reality heavy-duty wear testing of materials used in mineral applications. The samples are attached on four levels in a pin mill configuration. The tester and the developed sample rotation test method deliver reproducible results. This study focuses on the effects of testing parameters in large particle slurry testing. Parameters such as the speed, particle size and slurry concentration were varied. The effect of test duration was also examined. Round steel samples and slurry of water and granite gravel were used for testing. The test parameter variations were 4 to 10 mm for particle size, up to 23 wt-% for concentration and up to 20 m s^?1 for the sample tip speed. The relationships between the parameters are discussed. The kinetic energy of the large abrasive particles is also considered. Wear surfaces studied with optical and electron microscopy are also presented and discussed.