磁悬浮列车产生的地面振动及其对周围环境的影响

磁悬浮列车是一种新型的交通运输工具,但目前关于磁悬浮运行时所产生的地面振动和其对周围环境的影响还未见报道。首次对这一问题进行了系统的现场测试,分析了磁悬浮列车产生的振动特性。与其它交通工具产生的地面振动比较,结果表明,磁悬浮运行时产生的地面振动远小于一般轮轨运输工具产生的地面振动;并且当列车运行速度达到较高值时也不会像高速铁路那样出现地面振动急剧增大的现象。     

摇杆式配气机构运动规律的计算分析

建立摇杆式配气机构运动规律的精确计算模型,给出了每一时刻下配气机构各部件的准确位置,具有较高的精度。根据该计算模型编制了摇杆式配气机构运动规律的计算程序,并运用该计算程序对G32柴油机摇杆式配气机构的运动规律进行了计算分析。     

Realization of anti-slip/skid re-adhesion control for electric commuter train based on disturbance observer

Recently, disturbance observer has been used in many system and industry applications. This paper focus on the fine motion control technology based on disturbance observer for electric commuter train. The improvement of adhesion characteristics is important in electric commuter train. We propose the anti-slip/skid re-adhesion control system based on disturbance observer and sensor-less vector control. The effectiveness of the proposed method is confirmed by the experiment based on the actual electric commuter train, which is Series 205-5000 of East Japan Railway Company. Moreover, in order to extend the anti-slip/skid re-adhesion control considering the bogie vibration phenomenon, we propose a new anti-slip re-adhesion control based on the high order disturbance observer considering the resonant frequency of bogie system. Copyright © 2009 Institute of Electrical Engineers of Japan. Published by John Wiley & Sons, Inc.     

A study on the dynamic performance of the 200km/h Korean tilting train by means of roller rig test

The dynamic performances of newly developed railway vehicles should be carefully verified step by step, from computer simulation through the laboratory-based roller rig test to the main line trial running test. The laboratory-based roller rig test is an effective and safe way to evaluate the dynamic characteristics such as high speed, ride comfort and dynamic behaviors. This experimental research was performed to evaluate the dynamic performances of the 200 km/h Korean tilting train, ‘Hanvit200’, by means of a full scale roller rig test. The newly developed tilting mechanism and stabilizer were included in the tilting bogie to satisfy both the conflicting requirements of higher stability and higher curving performance. This paper shows the roller rig test results and the effectiveness of tilting bogie design. Included are the roller rig test results of various kinds of conditions such as tare and fully laden load case, normal and failed case of important bogie components, linear and non-linear critical speed. This paper was presented at the 4th Asian Conference on Multibody Dynamics(ACMD2008), Jeju, Korea, August 20–23, 2008. Nam-Po Kim received a B.S. degree in Mechanical Engineering from Ajou University in 1985. He then went on to receive his M.S. and Ph.D. degrees from Ajou University in 1992 and 2008, respectively. Dr. Kim is currently a principal researcher at the department of vehicle dynamics and propulsion system at Korea Rail Road Research Institute in Uiwang, Korea. His research interests are in the area of railway vehicle dynamics, active control of running gear for railway vehicle and vehicle system engineering.     

Flow dynamics at the minimum starting condition of a supersonic diffuser to simulate a rocket’s high altitude performance on the ground

A numerical analysis was conducted to investigate and characterize the unsteadiness of the flow structure and oscillatory vacuum pressure inside of a supersonic diffuser equipped to simulate high-altitude rocket performance on the ground. A physical model including a rocket motor, vacuum chamber, and diffuser, which have axisymmetric configurations was employed. Emphasis was placed on investigating the physical phenomena of very complex and oscillatory flow evolutions in the diffuser operating very close to the starting condition, i.e. at a minimum starting condition, which is one of the major important parameters from a diffuser design point of view. This paper was recommended for publication in revised form by Associate Editor Jun Sang Park Hyo-Won Yeom received a B.S. degree in the department of Aerospace & Mechanical Engineering from Korea Aerospace University in 2007. He is currently a master candidate at the school of Aerospace & Mechanical Engi-neering at Korea Aerospace Uni-versity in Goyang-city, Korea. His research interests are in the area of numerical analysis for High-speed propulsion system. Sangkyu Yoon received a B.S. degree in the department of Aerospace & Mechanical Engineering from Korea Aerospace University in 2006 and M.S. degrees in the school of Aerospace & Mecha-nical Engineering from Korea Aerospace University in 2008. He currently works in Hanwha Corporation R&D Center. Hong-Gye Sung received a B.S. degree in the department of Aerospace Engineering from Inha University in 1984 and Ph.D. degree in Nuclear and Mechanical Engineering from The Pennsylvania State University in 1999. Dr. Sung has various research experiences in the fields of high-speed propulsion and rocket propulsion in Agency for Defense Development for 22 years (1984–2006). He is currently a professor at the School of Aerospace and Mechanical Engineering of Korea Aerospace University in Goyang, Korea. Dr. Sung’s research interests are in the area of propulsion, combustion, and its control.     

基于近似模型的高速列车头型多目标优化设计

为改善高速列车气动性能,建立一套高效的多目标气动优化设计方法,对流线型头型进行多目标气动优化设计。建立高速列车流线型头型三维参数化模型,并提取5个优化设计变量;为减少优化设计时间,利用最优拉丁超立方设计方法在优化设计空间中进行均匀采样,利用计算流体力学方法获得对应于各个采样点的气动载荷,利用Kriging代理模型构建优化设计变量和气动载荷之间的近似模型;利用多体系统动力学方法计算气动载荷作用下的高速列车轮重减载率;以气动阻力和轮重减载率为优化目标,利用多目标遗传算法NSGA-II对高速列车流线型头型进行多目标优化。优化设计变量和优化目标均呈现收敛的趋势,采用Kriging近似模型优化计算的Pareto前沿与采用CFD（Computational fluid dynamics,CFD）优化计算的Pareto前沿较为接近。优化后高速列车的气动阻力最多可降低3.27%,轮重减载率最多可降低1.44%,气动阻力最优的头型与轮重减载率最优的头型的主要差异在于中部辅助控制线的变化,前者向内凹,后者则向外凸。     

Preparation and printability of 24CrNiMo alloy steel powder for selective laser melting fabricating brake disc

Spherical 24CrNiMo alloy steel powder used for selective laser melting (SLM) fabricating high-speed train brake disc was prepared by the vacuum induction melting gas atomisation (VIGA) method. Powder morphology, particle size, flowability and microstructure were measured. Part properties fabricated by SLM were investigated via some modern analysis method. The experimental results showed that powder mean particle size D₅₀ was 75?μm, flowability was 16.69?s/50?g and apparent density was 4.71?g?cm^?3. 24CrNiMo alloy steel specimen microstructures prepared by SLM consisted of proeutectoid ferrite and granular bainite. Average microhardness was 346?HV, tensile strength was 1223?MPa, extensibility was 13.1% and the product of strength and elongation was 16.1?GPa%. 24CrNiMo alloy steel powder prepared by the VIGA method had good laser printability and huge potential application value for SLM-fabricated brake disc.     

基于非线性有限元接触理论行星齿轮副瞬态啮合特性研究

为了比较分析风电行星齿轮副啮合面和非啮面瞬态接触特性的差异,根据非线性有限元接触理论,建立了某风电增速用输入级传动机构NGW型行星轮系的非线性有限元模型,对行星齿轮副的瞬态啮合过程进行了动力学实验研究,获得了行星轮系构件齿廓不同啮合位置应力的时间历程曲线。研究表明啮合轮齿廓不同位置的应力具有相似的变化规律;与外啮合的行星齿轮轮廓应力相比,内啮合行星齿轮齿廓的应力较大。在此基础上,对比分析了风电行星齿轮副的关键工况参数对啮合面和非啮合面的瞬态接触的影响,为以改善行星齿轮啮合性能和可靠性为目标的动态优化设计方案确定提供有益的指导。     

超声冲击对SMA490BW钢焊接接头超高周疲劳性能的影响

采用超声冲击工艺对转向架用SMA490BW钢对接接头焊趾表面进行冲击处理,研究了超声冲击对接头超高周疲劳性能的影响。借助金相显微镜、SEM和TEM研究了冲击层金相组织、冲击前后焊趾处的形貌及表层金属晶粒细化程度。运用有限元软件计算焊接接头的应力分布,采用X射线应力仪对冲击前后焊趾表层的应力进行了测量和分析。结果表明,在5×10~6循环周次下,冲击态接头和焊态接头的疲劳强度分别为206 MPa和153 MPa,经冲击处理后疲劳强度提高了34.6%。在1×10~8循环周次下,冲击态接头的疲劳强度为195 MPa,与焊态接头的141 MPa相比提高了38.3%。在240 MPa的应力水平下,焊接接头经超声冲击处理后的疲劳寿命提高了7倍。经冲击处理的焊趾部位的应力集中系数下降了19.1%,其表面的残余拉应力得到消除,并转变为有益的残余压缩应力,焊趾表层组织得到明显细化,这3个方面均对提高焊接接头疲劳性能起到了积极贡献。     

采用单气门变升程工作模式的发动机经济性能仿真

基于全柔性化的电磁驱动配气技术,提出了单气门变升程工作模式;在考虑驱动机构驱动功耗的基础上对发动机进行了建模和仿真分析。研究结果表明：在发动机中低转速工况下,采用单气门变升程工作模式能够适度增大充气流速,减小泵气损失和配气机构驱动功耗,进而达到改善发动机燃油经济性的目的;且随着发动机转速和负荷的降低,改善幅度呈上升趋势,如发动机转速1000r/min、负荷率40%工况下单气门2.00mm升程运行模式有效燃油消耗率相比原型机减小了12.2%。