Investigation on influencing factors of wheel polygonization of a plateau high-speed EMU train

Purpose–This study aims to investigate the cause of high-order wheel polygonization in a plateau high-speed electric multiple unit(EMU)train.Design/methodology/approach–A series of field tests were conducted to measure the vibration accelerations of the axle box and bogie when the wheels of the EMU train passed through tracks with normal rail roughness after re-profiling.Additionally,the dynamic characteristics of the track,wheelset and bogie were also measured.These measurements provided insights into the mechanisms that lead to wheel polygonization.Findings–The results of the field tests indicate that wheel polygonal wear in theEMUtrain primarily exhibits 14–16 and 25–27 harmonic orders.The passing frequencies of wheel polygonization were approximately 283–323 Hz and 505–545 Hz,which closely match the dominated frequencies of axle box and bogie vibrations.These findings suggest that the fixed-frequency vibrations originate from the natural modes of the wheelset and bogie,which can be excited by wheel/rail irregularities.Originality/value–The study provides novel insights into the mechanisms of high-order wheel polygonization in plateau high-speed EMU trains.Futher,the results indicate that operating the EMU train on mixed lines at variable speeds could potentially mitigate high-order polygonal wear,providing practical value for improving the safety,performance and maintenance efficiency of high-speed EMU trains.

Research on fatigue evaluation method of high-speed train axle based on axle box acceleration

As a key safety component of the high-speed train, fatigue fracture of the axle would lead to major accidents such as derailment or overturning. The complexity of the axle dynamic stress test seriously enhances the difficulty of axle fatigue damage analysis. In this paper, the dynamic stress test of the high-speed train axle was carried out,the axle box acceleration was monitored on-track during the test, and the relationship between the axle stress spectrum and acceleration was analyzed on-track. The results show that the relationships between the axle equivalent stresses and the Root Mean Square(RMS) values of the axle box vertical acceleration and lateral acceleration exhibit a strong joint probability density distribution. The concept of the virtual surface density of wheel-rail contact is also proposed to realize the purpose of using axle box acceleration to deduce axle equivalent force. The results quantify the relationship between axle box acceleration and axle equivalent force, provide a new method for predicting the axle damage using the acceleration RMS values, and open up a new approach for structural health monitoring of high-speed train axles.

Analysis of the Temperature Characteristics of High-speed Train Bearings Based on a Dynamics Model and Thermal Network Method

High-speed trains often use temperature sensors to monitor the motion state of bearings.However,the temperature of bearings can be affected by factors such as weather and faults.Therefore,it is necessary to analyze in detail the relationship between the bearing temperature and influencing factors.In this study,a dynamics model of the axle box bearing of high-speed trains is established.The model can obtain the contact force between the rollers and raceway and its change law when the bearing contains outer-ring,inner-ring,and rolling-element faults.Based on the model,a thermal network method is introduced to study the temperature field distribution of the axle box bearings of high-speed trains.In this model,the heat generation,conduction,and dispersion of the isothermal nodes can be solved.The results show that the temperature of the contact point between the outer-ring raceway and rolling-elements is the highest.The relationships between the node temperature and the speed,fault type,and fault size are analyzed,finding that the higher the speed,the higher the node temperature.Under different fault types,the node temperature first increases and then decreases as the fault size increases.The effectiveness of the model is demonstrated using the actual temperature data of a high-speed train.This study proposes a thermal network model that can predict the temperature of each component of the bearings on a high-speed train under various speed and fault conditions.

高速动车组轴箱内置式转向架复合材料板弹簧技术研究及应用

针对轴箱内置式转向架一系悬挂结构横向空间尺寸相对较小的特点,为了保证高速动车组良好的动力学性能,文章设计、开发了新型的一系悬挂系统,采用了转臂定位+上置复合材料板弹簧结构,速度等级可达400km/h。对其进行了仿真分析和台架试验,并将其安装在试验转向架上进行了滚振试验和整车的线路动力学性能试验测试。结果表明,复合材料板弹簧强度和性能指标均达到了设计要求,为高速动车组的轻量化、全包覆减阻设计等提供了新的技术思路。

动车组自主化轴箱轴承台架试验研究

为解决自主化轴箱轴承台架试验运转初期温升高和跑合里程长的问题,基于温升机理及TB/T 3017.1—2016标准,通过控制变量设计了多个对比试验,系统分析了多个参数对自主化轴箱轴承台架试验初期轴承温升的影响趋势。研究结果表明:适当减小轴承注脂量、增大密封储脂空间均可有效降低自主化轴箱轴承台架试验初期的匀脂温度,显著缩短匀脂阶段的跑合里程。

高速动车组变轨距转向架轮轴结构及联接设计

为实现高速动车组跨国互联互通要求,结合变轨距转向架总体设计方案,提出了高速动车组变轨距转向架关键技术之一的轮轴结构及其联接结构的设计方案。对能够实现车轮轴向滑动且传递扭矩的轮轴及联接结构组成进行了总体介绍,突破传统轮轴配合设计理念,采用在车轮与车轴之间增加滑动轴承和衬套、轮轴分别压装内外齿套结构实现车轮滑动及扭矩传递功能。对车轮、车轴的材料选型和结构设计进行了论述,选取成熟应用的轮轴材质,并设计出全新阶梯状轮毂结构。按照EN和UIC标准,对车轮和车轴进行了强度计算及分析,其静强度和疲劳强度均满足要求。同时为验证轮轴联接可靠性,按照GB/T17855—2017标准,对花键进行齿面接触强度、齿根弯曲强度、齿根剪切强度、齿面耐磨损能力及外花键扭转与弯曲强度计算,计算结果满足运用要求。

高速动车组轴箱轴承可靠性试验台动态加载系统设计研究

[目的]台架试验是研究高速动车组轴箱轴承性能的主要技术手段,而准确模拟轴箱轴承的实际运行载荷工况是获取真实、可靠的轴箱轴承性能数据的必要前提。合理设计轴箱轴承试验台,以模拟轴箱轴承高速重载的运转工况;设计径向加载机构和轴向加载机构控制策略,以满足加载系统控制精度和响应速度的要求。[方法]设计了一套高速动车组轴箱轴承可靠性试验台电液伺服动态加载系统。介绍了该系统中轴向加载系统和径向加载系统的结构组成及工作原理,并提出了一种模糊PID(比例-积分-微分)控制算法。搭建轴箱轴承可靠性分析试验台,进行加载性能测试和轴箱轴承可靠性测试试验,用以验证动态加载系统的合理性。[结果及结论]所设计的电液伺服动态加载系统能够满足轴箱轴承可靠性试验的加载要求;轴向加载响应时间为0.276 s,轴向加载稳态误差为0.339 kN,径向加载稳态误差为1.742 kN,满足EN 12082:2017标准要求。

动车组车轴新型防护涂层试验研究

涂层防护作为一种列车车轴防护方式,可以避免车轴运用中受到腐蚀或外物击打而产生损伤。既有车辆车轴采用底漆、面漆薄涂层防护结构存在一定损伤情况,然而采用过厚涂层防护也存在涂层附着力不足导致脱落问题。基于此,文章介绍了车轴涂层防护现有标准及动车组车轴新型防护涂层开发与试验过程,包括:确定涂层材料;根据多次冲击损伤试验确定涂层最小厚度;确定涂层结构;进行各项试验验证。试验结果表明,新型防护涂层符合标准规定。新型防护涂层在列车上进行了运用考核,考核结果表明,涂层状态总体正常。对个别存在涂层受击打损伤的车轴进行了进一步分析,说明了运用阶段对涂层进行及时维护的必要性。

高速动车组轮对压装参数对车轴结构设计的影响研究

通过有限元仿真分析的方法对比分析轮对压装过盈量、突悬量对轮对疲劳性能的影响,分析轮对压装参数对车轴结构强度的影响规律。结果表明:提高轮对压装的突悬量,有利于提高轮对部位的疲劳强度,但轴身的疲劳强度略有下降。随着过盈量的不断增大,轴身的疲劳强度有所下降,轮对部位的疲劳强度有所提高。整体而言,压装工艺参数对轮对疲劳强度的敏感程度高于轴身。车轴结构设计时需结合压装工艺参数综合权衡并考虑轮对和轴身的强度匹配关系,通过优化设计可以较好调整压装工艺参数数值,进而达到轮对和轴身强度优化匹配的目的。

Ni含量对动车组车轴钢组织和性能的影响

以我国自主设计研发的复兴号动车组车轴用国产钢为研究对象,设计不同Ni含量的车轴,对比分析不同Ni含量车轴钢的力学性能、金相组织和截面硬度。结果表明:车轴中高Ni含量的成分设计对车轴强度与冲击韧性均有较大提升,尤其是对低温冲击作用明显;从金相组织来看,车轴钢淬透性明显提升。基于轴坯中高Ni合金化成分设计开发出400 km/h动车组车轴样件,各项理化性能均优于标准要求。

CR-Fuxing high-speed EMU series

1Overview of the CR Fuxing high-speed EMUseries The independently developed CR(China Railways)Fuxing high-speed EMU(electric multiple unit)series by China currently comprises three speed-level product series:CR400,CR300,and CR200,as shown in Fig.1.The EMUs demonstrate adaptability to various geographical and climatic conditions,including high plateaus,extremely cold regions,strong wind and sandy environmental conditions,with a designed service life of 30 years.The 350 km/h speed level of the CR-Fuxing series primarily consists of two platforms,namely CR400AF and CR400BF,both of them are electric multiple units with distributed power.Each 8-car formation is configured with a 4M4T arrangement,divided into two traction units(Tc+M+Tp+M).

基于模流分析的动车组轴箱轴承工程塑料保持架注塑模具浇口数量方案分析

为了优化动车组轴箱轴承工程塑料保持架注塑模具的浇口数量,预设6种浇口数量方案,利用模流分析软件,对6种方案进行模拟分析,通过熔接线位置、注射时间、最大剪切速率、流动末端压力差和翘曲位移数据对比的模流分析结果,结合保持架结构和功能要求,选取最优浇口设计方案。通过该案例可以了解到浇口的数量和位置对塑料件质量的重要性。在产品设计前期利用模流分析软件进行模拟,可以提前预测设计方案的优劣,缩短产品设计开发周期,减少模具的报废率,提高产品的成型质量,从而降低研发成本。

Analysis of vibration and frequency transmission of high speed EMU with flexible model

When the operation speed of the high-speed train increases and the weight of the carbody becomes lighter,not only does the sensitivity of the wheel/rail contact get higher,but also the vibration frequency range of the vehicle system gets enlarged and more frequencies are transmitted from the wheelset to the carbody.It is important to investigate the vibration characteristics and the dynamic frequency transmission from the wheel/rail interface to the carbody of the high-speed electric multi-uint（EMU）.An elastic highspeed vehicle dynamics model is established in which the carbody,bogieframes,and wheelsets are all dealt with as flexible body.A rigid high-speed vehicle dynamics model is set up to compare with the simulation results of the elastic model.In the rigid vehicle model,the carbody,bogieframes and wheelsets are treated as rigid component while the suspension and structure parameters are the same as used in the elastic model.The dynamic characteristic of the elastic high speed vehicle is investigated in time and frequency domains and the di ff erence of the acceleration,frequency distribution and transmission of the two types of models are presented.The results show that the spectrum power density of the vehicle decreases from the wheelset to the carbody and the acceleration transmission ratio is approximately from 1%to 10%for each suspension system.The frequency of the wheelset rotation is evident in the vibration of the flexible model and is transmitted from the wheelset to the bogieframe and to thecarbody.The results of the flexible model are more reasonable than that of the rigid model.A field test data of the high speed train are presented to verify the simulation results.It shows that the simulation results are coincident with the field test data.

Effect of Nb addition on microstructure and mechanical properties of 25CrNiMoV(DZ2)steel for high-speed railway axles

The microstructure,precipitates and properties of 25CrNiMoV(DZ2)steel for high-speed railway axles with different Nb contents were investigated by means of optical microscopy,scanning electron microscopy,electron back-scattering diffraction,transmission electron microscopy and physicochemical phase analysis.The results show that the grain size of the original austenite of the test steels decreases from 20.5 to 14.2 and 10.8μm after adding 0.026 and 0.039 wt.%Nb to a 25CrNiMoV steel,respectively.Moreover,the block width of the tempered martensite in the test steels is refined from 1.91 to 1.72 and 1.60µm,respectively.MC-type precipitates in 25CrNiMoV steel are mainly VC,while(Nb,V)C gradually precipitates when Nb is microalloyed,and the amount of precipitates increases with increasing Nb content.Through strengthening mechanism analysis,it is found that grain refinement strengthening is the primary way to increase the strength.The improvement in the yield strength with increasing Nb content is attributed to a significant increase in precipitation strengthening,grain refinement strengthening and dislocation strengthening.

Improved fault location method for AT traction power network based on EMU load test

The autotransformer(AT)neutral current ratio method is widely used for fault location in the AT traction power network.With the development of high-speed electrified railways,a large number of data show that the relation between the AT neutral current ratio and the distance from the beginning of the fault AT section to the fault point(Q-L relation)is mostly nonlinear.Therefore,the linear Q-L relation in the traditional fault location method always leads to large errors.To solve this problem,a large number of load-related current data that can be used to describe the Q-L relation are obtained through the load test of the electric multiple unit(EMU).Thus,an improved fault location method based on the back propagation(BP)neural network is proposed in this paper.On this basis,a comparison between the improved method and the traditional method shows that the maximum absolute error and the average absolute error of the improved method are 0.651 km and 0.334 km lower than those of the traditional method,respectively,which demonstrates that the improved method can effectively eliminate the influence of nonlinear factors and greatly improve the accuracy of fault location for the AT traction power network.Finally,combined with a shortcircuit test,the accuracy of the improved method is verified.

基于平均自相关和优化VMD的轴箱轴承故障诊断

针对动车组运行过程中轴箱轴承振动加速度信号非平稳特性以及较大的背景噪声导致故障特征难以提取的问题,提出一种平均自相关结合参数优化变分模态分解(variational mode decomposition,简称VMD)的轴箱轴承故障诊断方法。首先,利用平均自相关对原始信号进行降噪,增强故障周期性冲击信息;其次,以故障特征频率能量比相反数为适应度函数,利用哈里斯鹰优化算法(Harris hawks optimization,简称HHO)优化VMD的模态分量数和二次惩罚系数,实现对降噪信号的自适应分解并提取出最佳模态分量;最后,计算其平方包络谱进行故障诊断分析。仿真和试验结果表明:该方法能够有效地降低背景噪声的影响,稳定地提取出周期性故障冲击成分,实现轴箱轴承故障的准确诊断。

动车组轴箱及定位装置故障模式分析及风险评估

动车组转向架的检修质量直接关乎行车安全,轴箱及定位装置作为转向架重点部件,为提高其检修品质,对轴箱装置的可靠性进行分解,并根据实车故障数据分析制定了轴箱及定位装置故障先验模式,再结合三维仿真分析和实车数据完善了轴箱装置故障后验模式,同时推导了其故障风险顺序数(RPN)的计算权重,设计了计算方法,将实车故障数据按故障模式和RPN进行归纳整理,得出轴箱及定位装置不同种类故障的针对性检修方法,对指导优化轴箱装置的维修策略,提高其检修品质有着积极的促进作用。

CRH2动车组轮对与轴箱弹簧的强度分析

高速列车运行超过蛇行稳定性临界速度时会出现安全隐患。为了解决这一隐患需对CRH2型动车组转向架进行数学建模。首先通过对轴箱体的简化处理及受力分析,在Pro/E软件中整体建模,并导入到Mechanica模块;然后对CRH2车轴建立刚性节点和弹性节点;最后进行静强度分析。结果表明,简化后的CRH2型转向架模型在临界速度上较初始模型有了一些改善,并且各个动力学参数均满足行业标准要求。

考虑车轮多边形演化的动车组轴箱轴承载荷及寿命分析

以某型250 km/h级动车组为研究对象,考虑轴箱轴承的时变刚度特性、轮对轴箱与轨道的柔性,建立了轴承-车辆-轨道刚柔耦合动力学模型,研究了实测车轮多边形演化下轴承滚道载荷与疲劳寿命的发展规律,揭示了车轮多边形对轴承载荷的影响机理。结果表明,随着运营里程的增加,车轮多边形磨耗幅值总体上不断增大,导致轴箱轴承外滚道接触载荷最大值与8和9号滚道的接触载荷标准差均呈现增长趋势;轴承每千米的损伤值也会不断增大,最高可达1.4×10^(-7),额定寿命则会不断减少;车轮经过镟修后,外滚道最大接触载荷降低了14%,9号滚道载荷标准差降低了56%,轴承每千米的损伤值降低了39%,故及时镟轮可以明显改善滚道载荷环境,延长轴承寿命。此外,当车轮多边形通过频率与钢轨局部弯曲模态产生耦合后,轴承载荷会更加恶劣。因此,针对该型动车组,在运行1.5×10^(5)km后,应适当增加车轮不平顺的检测频次,并重点关注14,15,25和26阶多边形磨耗幅值。

内轴箱悬挂高速动车组转向架抗倾覆稳定性研究

内轴箱转向架由于轴箱悬挂内置大幅度降低了车体的抗侧滚刚度,影响其运行性能。为提高其抗倾覆性能,内轴箱转向架通常采取安装抗侧滚扭杆和提高一系悬挂垂向刚度的措施。文章提出了一种抗倾覆装置,以提高内轴箱悬挂高速动车组转向架抗倾覆稳定性。该装置由2条互不连通的回路组成,安装在轮对轴箱和构架之间。在分析抗倾覆装置的基本原理、刚度特性和车辆动力学模型之后,利用MATLAB/Simulink软件,联合AMESim和SIMPACK软件进行联合仿真,得到车辆在不同速度条件下通过大半径曲线时的动力学性能和动态包络线。结果表明,采用抗倾覆装置可以在保证车辆运行稳定性的条件下大幅提高车体的抗侧滚能力,在车辆脱轨系数和轮轴横向力等安全性指标方面有着更优异的表现,同时有着较小的动态包络线。