Theoretical research and experimental validation of quasi-static load spectra on bogie frame structures of high-speed trains

One of the major problems in structural fatigue life analysis is establishing structural load spectra under actual operating conditions.This study conducts theoretical research and experimental validation of quasi-static load spectra on bogie frame structures of high-speed trains.The quasistatic load series that corresponds to quasi-static deformation modes are identified according to the structural form and bearing conditions of high-speed train bogie frames.Moreover,a force-measuring frame is designed and manufactured based on the quasi-static load series.The load decoupling model of the quasi-static load series is then established via calibration tests.Quasi-static load–time histories,together with online tests and decoupling analysis,are obtained for the intermediate range of the Beijing—Shanghai dedicated passenger line.The damage consistency calibration of the quasi-static discrete load spectra is performed according to a damage consistency criterion and a genetic algorithm.The calibrated damage that corresponds with the quasi-static discrete load spectra satisfies the safety requirements of bogie frames.

Theoretical Research and Experimental Validation of Elastic Dynamic Load Spectra on Bogie Frame of High-speed Train

When a train runs at high speeds, the external exciting frequencies approach the natural frequencies of bogie critical components, thereby inducing strong elastic vibrations. The present international reliability test evaluation standard and design criteria of bogie frames are all based on the quasi-static deformation hypothesis. Structural fatigue damage generated by structural elastic vibrations has not yet been included. In this paper, theoretical research and experimental validation are done on elastic dynamic load spectra on bogie frame of high-speed train. The construction of the load series that correspond to elastic dynamic deformation modes is studied. The simplified form of the load series is obtained. A theory of simplified dynamic load–time histories is then deduced. Measured data from the Beijing–Shanghai Dedicated Passenger Line are introduced to derive the simplified dynamic load–time histories. The simplified dynamic discrete load spectra of bogie frame are established. Based on the damage consistency criterion and a genetic algorithm, damage consistency calibration of the simplified dynamic load spectra is finally performed. The computed result proves that the simplified load series is reasonable. The calibrated damage that corresponds to the elastic dynamic discrete load spectra can cover the actual damage at the operating conditions. The calibrated damage satisfies the safety requirement of damage consistency criterion for bogie frame. This research is helpful for investigating the standardized load spectra of bogie frame of high-speed train.

Methodology to Evaluate Fatigue Damage of High-Speed Train Welded Bogie Frames Based on On-Track Dynamic Stress Test Data

The current method of estimating the fatigue life of railway structures is to calculating the equivalent stress amplitude based on the measured stress data. However, the random of the measured data is not considered. In this paper, a new method was established to compute the equivalent stress amplitude to evaluate the fatigue damage based on the measurable randomness, since the equivalent stress is the key parameter for assessment of structure fatigue life and load derivation. The equivalent stress amplitude of a high-speed train welded bogie frame was found to obey normal distribution under uniform operation route that verified by on-track dynamic stress data, and the proposed model is, in effect, an improved version of the mathematical model used to calculate the equivalent stress amplitude. The data of a long-term, on-track dynamic stress test program was analyzed to find that the normal distribution parameters of equivalent stress amplitude values differ across different operation route. Thus, the fatigue damage of the high-speed train welded bogie frame can be evaluated by the proposed method if the running schedule of the train is known a priori. The results also showed that the equivalent stress amplitude of the region connected to the power system is more random than in other regions of the bogie frame.

Effect of Increasing Speed on Stress of Biaxial Bogie Frames

Increasing the trains’ speed has always been one of the goals of any railway industry and train manufacturers. Also, the influence of the train speed on bogie’s dynamics has an immense importance. Therefore, it is important to analyze the effect of train speed on the stress distribution in different parts of train structure. In this study the result of the increasing speed on the applied stresses of a biaxial bogie frame has been examined. For this purpose, a biaxial bogie frame has been modeled using finite element analysis. Static and dynamic forces applied on the bogie with biaxial frame have been obtained for different speeds and rail roughness. The Von Mises stresses are adopted as equivalent stresses in the strength calculation. The results show that maximum stress always has been induced in the bogie bowl also the increase in bogie’s speed has remarkable effect on the increment of applied stresses in the bogie frame.

Damage Tolerance Assessment of a Brake Unit Bracket for High-Speed Railway Welded Bogie Frames

The brake unit bracket of a bogie frame is an important load-carrying component, particularly under emergency start/stop conditions. Conventional infinite/safe life approaches provide an over-conservative recommendation for the allowable strength and lifetime, which hinders the lightweight design of modern railway vehicles. In this study, to ensure the reliability and durability of a brake unit bracket, an attempt was made to integrate the nominal stress method and an advanced damage tolerance method. First, a complex bogie frame was modelled using solid elements instead of plate and beam elements. A hot spot stress region on the bracket was found under an eight-stage load spectrum obtained from the Wuhan–Guangzhou high-speed railway line. Based on the probability of foreign damage, a semi-elliptical surface crack was then assumed for residual life assessment. The results obtained by the cumulative damage and damage tolerance methods show that the brake unit bracket can operate for over 30 years. Moreover, even if a 2-mm depth crack exists, the brake unit bracket can be safely operated for more than 2.27 years, with the hope that the crack can be detected in subsequent maintenance procedures. Finally, an appropriate safety margin was suggested which provides a basis for the life prediction and durability assessment of brake unit brackets of high-speed railways.

常德高铁站房结构设计

常德高铁站是常益长正线线路上的重要站点,站房分为下部混凝土结构和上部钢屋盖。屋盖采用Γ形刚架作为主要支撑结构,一方面斜柱有效地增加了结构的抗侧刚度,另一方面也与桃花盛开的建筑意象相契合,其结构形式经历了立体三角形桁架、箱桁结合实腹梁、箱形实腹梁3轮方案的推敲演变。针对天窗区域连系桁架拱形下弦的矢高取值,采用Grasshopper+SAP2000联动程序进行自动化参数找形,得到结构受力性能和建筑空间效果均优的平衡点。通过ABAQUS壳单元模型与SAP2000杆单元模型的对比分析,验证了利用SAP2000截面设计器对变截面的异形截面构件分析的准确性,同时对Γ形刚架进行了弹塑性极限承载力分析,结果满足要求。Γ形刚架形态舒张有力,结构受力合理,实现了建筑与结构的完美结合。

新型中低速磁浮车辆动力学特性分析

针对一种速度160 km/h新型中低速磁浮悬浮架,文章运用SIMPACK多体动力学软件建立了车辆的动力学模型,分析了该悬浮架在直线以及曲线工况下的动力学特性。结果表明,直线运行工况下车辆速度可以达到160 km/h,悬浮间隙、车体振动加速度等指标均符合要求,但在120 km/h时车辆各项指标有所恶化,为减小车体共振影响,对车体振动加速度进行了频率分析并给出优化建议。在曲线工况下,车辆的导向力、空簧横向位移及滑台位移等指标均在正常范围。研究结果证明新型中低速磁浮车辆的动力学性能符合要求,相关动力学结果可为新型悬浮架后续研究及工程化提供数据支持。

高速精密数控轧辊磨床中心架液压润滑系统的设计及其优化

中心架作为轧辊磨床的重要部分之一,起着支承和卸荷的重要作用。文中以某型高速精密数控轧辊磨床为依据,设计了其中心架的液压润滑系统,基于AMESim软件建立该液压润滑系统模型并进行仿真计算,分析得出侧瓦和底瓦静压固定活塞直径、静压固定活塞杆径及调速阀设定流量对系统中静压腔油压特性具有显著影响。采用遗传算法对影响系统静压腔油压特性的3个参数进行优化,结果表明:优化后的中心架液压润滑系统中,静压腔油压稳定性得到了显著的改善,达到稳定状态的时间明显缩短,验证了优化方案的合理性,其结果可为轧辊磨床液压润滑系统的设计及优化研究提供理论依据。

大跨度高速铁路连续刚构桥转体施工监测与控制技术

为解决跨运营高速铁路连续刚构桥转体施工稳定性和安全性问题,以新建福州至厦门铁路西溪特大桥为研究对象,在分析新建高速铁路连续刚构桥与既有铁路线关系的基础上,提出“支架现浇+转体施工”的施工方案,并采用现场实测法研究转动称重关键参数。针对转体施工总体工艺,提出转动体系施工控制措施、转动平衡控制措施、转动牵引力及制动距离控制措施。研究结果表明,转动过程的平顺性验证了转动称重关键参数的准确性;在正常匀速转动阶段,梁体转动角速度变化平稳,平均转动角速度为1.12°/min,墩柱沿纵桥向和横桥向的姿态稳定;转动完成后轴线最大偏差为3.5mm,满足规范限值要求。

混凝土框架墩结构设计影响因素研究及对比评价

依托某高速铁路跨越漯舞铁路工程,对控制框架墩结构设计指标的多项影响因素进行系统分析,并对混凝土实心横梁和空心横梁结构设计的合理性、经济性及安全性进行对比评价。研究表明,框架墩结构对基础刚度、温度及沉降的影响较为敏感,除横梁跨中弯矩随基础刚度的增加而变小外,各截面内力均随各项影响因素指标的增大而大幅增加;在基础刚度、整体降温、基础沉降等对框架墩自身结构影响较大的因素作用下,两种横梁受力性能相当;从受力特性来说,两种横梁的刚度、强度设计指标相当,结构设计均较为合理;从经济性角度出发,空心横梁主要工程费用低4.3%,相对于实心横梁更经济;从安全性角度考虑,空心横梁能够有效避免现浇施工对既有运营铁路的影响,施工风险性更低。

高速铁路跨度250 m级连续刚构桥长波不平顺控制研究

连续刚构桥随着跨度增加,其收缩徐变、温度等引起的桥面变形随之增加,导致轨道长波不平顺加剧,进而可能对列车走行性产生不利影响。以一座试设计主跨250 m高速铁路连续刚构桥为研究对象,建立有限元模型,依据规范检算桥梁的强度和刚度,同时计算由于混凝土收缩徐变、温度效应等引起的桥面附加变形。采用“车-线-桥”动力仿真软件分析由于桥面附加变形导致的轨道长波不平顺对列车动力响应的影响。选用中点弦测法作为评价指标,通过相关性分析选出最优弦测长度,最后计算出最优弦长下连续刚构的桥面变形和等效不平顺限值。研究结果表明:横、竖向桥面附加变形均出现在桥梁的跨中截面;当附加变形增加到1.9倍,列车以速度350 km/h通过连续刚构时,车辆的竖向加速度首先达到限值1.3 m/s^(2);采用弦长为60 m的中点弦测法与车辆响应匹配性最好,适用于评价连续刚构的长波不平顺;连续刚构的桥面附加变形和等效不平顺60 m弦中点弦测值分别为7.2 mm和14.5 mm,对应限值建议分别为7 mm和14 mm。

高速电梯轿架启动工况的水平瞬态动力学分析

为探究高速电梯启动工况的水平瞬态动力学特性,以高速电梯轿架为研究对象,基于ANSYSWorkbench有限元软件仿真了轿架启动工况下的瞬态应力、瞬态变形和水平振动加速度,同时,对高速电梯轿架水平振动特性进行了实验验证。研究结果表明:高速电梯轿架上梁、下梁和直梁等三大关键部件满足强度、刚度要求,并且通过实验测得的水平振动加速度曲线变化区间与仿真分析所得水平振动特性的振动加速度曲线变化区间对比,两者基本一致,从而验证了仿真结果的正确性,为高速电梯运行过程中的舒适性研究提供了一定的借鉴。

高铁大跨双肢墩连续刚构桥减震系梁地震易损性分析

为了解地震作用下减震系梁对高铁大跨双肢墩连续刚构桥的减震效果,以某主跨180 m的山区高铁双肢墩连续刚构桥为背景,分别建立采用钢筋混凝土(RC)系梁、2种新型减震系梁(可屈服钢系梁与斜交筒式黏弹性阻尼器系梁)方案的全桥有限元模型,对比分析不同系梁方案下的结构损伤、桥面平顺性指标等。结果表明:2种新型减震系梁均不会在地震作用下出现负刚度,新型减震系梁方案较RC系梁方案能有效降低系梁和主墩的结构损伤概率,主墩最大压应变降低83.3%;但减震系梁对震后桥面平顺性指标无明显改善,需采用更具针对性的技术措施。

广州至湛江高速铁路引入广州枢纽方案研究

广州至湛江高速铁路利用广茂铁路通道,并采用双层框架结构设计引入城市中心车站,能够充分利用既有城市配套设施、更好地服务地方客流、最大程度减少征地拆迁,对构建广州枢纽总图“五主三辅”客站布局具有重要作用。本文结合广州枢纽既有及规划布局、城市空间布局等因素,从工程投资及运营时分、衔接线路及运输组织、运输质量、工程实施难度及对既有铁路运营干扰等方面,对广湛高速铁路多个引入广州站方案进行了综合分析比较,得出推荐意见,并对设计中创新采用的双层框架结构进行了介绍。希冀能为类似新建铁路项目引入城市中心的客运枢纽站提供借鉴和参考。

电动微卡高速抖动分析与控制

针对电动微卡高速抖动问题进行了分析,对高速抖动问题产生的机理及传递路径进行了阐述。同时就电动微卡高速抖动问题,从激励源到传递路径及响应点进行了排查分析,明确了产生抖动问题的原因是轮胎一阶不平衡激励引起前簧簧下系统振动,并与车架产生共振,进而引起驾驶室产生强迫振动。针对问题原因提出了控制轮胎的动平衡及端跳、径跳,减少激励源振动,以及通过提高轮胎刚度,提升簧下偏频的解决方案。从实际测试结果上看,效果明显,对实际工程问题的解决具有指导意义。

基于FKM标准的转向架构架疲劳强度评估

随着车辆速度的提升及振动程度的加剧,转向架焊接部位极易发生疲劳破坏,因此选用较为科学的疲劳评估标准非常重要。文章以某高速动车组拖车转向架构架为例,综合UIC 515-4和EN 13749标准要求进行超常载荷和模拟运营载荷等工况分析,依据分析结果选取疲劳评估点,并分别应用FKM标准和修正的Goodman-Smith曲线进行疲劳强度评估和对比分析。结果表明:FKM标准可应用于轨道车辆各结构的疲劳强度评估,且评估过程更为科学合理,评估结果更为保守可靠。

铁路跨线人行天桥力学性能测试

铁路跨线人行天桥的定期检测和安全评估,是保证其结构安全应用的必要手段。为增进安全评估准确度,采用模型仿真与静动载试验相结合的全过程评估方法,对包神线新建东胜人行天桥工程进行安全性评估。结果表明:桥梁弦杆应变、挠度与荷载呈线性相关,在卸除荷载后,残余应变与最大应变之比≤20%,残余变形与最大变形之比≤20%,且应变测点及挠度测点实测数据均小于理论计算值;该桥前三阶的实测频率均大于理论数值,并且高阶次误差较小,该桥的实际结构刚度大于理论刚度,满足规范设计的承载力设计要求。

甘沟河特大桥关键施工技术研究

为解决大跨度连续钢构桥挂篮悬臂施工时的桥梁线型控制和挂篮稳定性问题,依托炉红山至慈利高速公路TJ1标甘沟河特大桥项目,运用连续钢构桥梁线性控制系统对挂篮悬浇施工线形控制进行监测,并运用数值模拟手段对施工阶段挂篮主构架进行受力和变形计算。研究结果表明,挂篮悬浇施工时,17号墩上部连续钢构桥线性大致呈单峰“抛物线”型,经过实际数据采集后,现场梁段的位移与理论值呈现不同程度的偏差,位移偏差范围为–0.956~0.954mm,控制在1.0mm的误差范围内,表明基于连续钢构桥梁线性控制系统的施工控制技术可起到了良好的变形控制效果;挂篮悬臂浇筑阶段,挂篮三角形主构架的前点竖向位移为7mm<20mm,其变形满足要求;主构架杆件的最大应力是49.7MPa<205MPa,其应力满足要求。

非匀速条件下车辆底盘超近距成像测量方法

针对车辆非匀速条件下轴距视觉测量及轴型识别所面临的超近距、大幅面、低畸变成像及视觉测量问题,提出一种适用于非匀速条件下的车辆底盘结构超近距成像测量方法。利用鱼眼相机采集运动车辆底盘的超广角图像序列,通过一种改进的多采样点圆拟合方法实现图像感兴趣区域的提取。建立三维等距成像模型对鱼眼图像进行畸变校正。针对车辆非匀速行驶带来的视频帧重叠度差异,采用基于图像内容的重叠度分析技术,实现了多步分层的关键帧提取,有效避免了车速不稳定对车辆底盘结构测量的影响。现场实验结果表明:该方法可在非匀速条件下,以20~50 cm的成像距离获得清晰、低畸变的完整车辆底盘图像,车辆轴距测量误差均值约为5%。

高速铁路钢轨波磨激扰下动车组转向架振动特性

以一高速线路波磨区段轴箱、构架、车体垂向振动加速度为研究对象,基于时域分析、频域分析、时频分析以及统计分析方法,研究了高速铁路钢轨波磨激扰下动车组轴箱-构架-车体的振动传递机理,总结了垂向振动传递规律和构架振动特点,提出了基于自适应噪声的完备总体经验模态分解(Complete Ensemble Empirical Mode Decomposition with Adaptive Noise,CEEMDAN)和平滑伪WignerVille分布(Smoothed Pseudo Wigner-Ville Distribution,SPWVD)的时频分析方法 CEEMDAN-SPWVD。利用车辆动态响应系统测试数据进行了实例分析,并进行了现场复核验证。结果表明:波磨区段构架最大振动幅值约为非波磨区段的1.88倍,且波磨区段500~600 Hz频带的总均方根加速度占全频带范围内的总均方根加速度的65.12%,远大于非波磨区段的占比(4.56%);本文提出的CEEMDAN-SPWVD方法能够有效识别波磨区段,理论推算的波磨波长与现场实测波长接近。