Fastener failure critically threatens the safety and stability of high-speed railways. To systematically investigate the effects of fastener failure configuration and scale on the dynamic performance of vehicle and track systems, a rigid vehicle-flexible track coupled model was developed, integrating multibody dynamics and finite element theory. The results identify the vertical wheel-rail contact force and vertical rail displacement as sensitive indicators for both single-side and double-side fastener failure configurations. The safety limit is defined as 2 single-side or 2 pairs of double-side fasteners at speeds of 250 km/h and 300 km/h, which decreases to 2 single-side or 1 pair of double-side fasteners at 350 km/h. The influence zone exhibits directional asymmetry, extending further downstream than upstream, and single-side fastener failure produces a broader influence zone than double-side fastener failure. In the frequency domain, fastener failure downshifts the primary low-frequency peaks of the wheel-rail contact force PSD and amplifies the mid-to-high frequency components of the vertical rail acceleration PSD. These findings provide a theoretical basis for optimizing fastener system maintenance and developing vibration-based detection techniques.

ObjectiveThis study aims to investigate the coupling effect between inner and outer defects on fatigue crack initiation in high-speed train axles to ensure operational safety.MethodsFirstly, a multi-crystal finite element model was established at the mesoscopic scale based on crystal plasticity theory. Secondly, tensile and impact tests were conducted, and finite element simulations were utilized to analyze the stress field and structural deformation around these defects. Finally, the crack initiation location was predicted based on the characteristics of stress distribution and plastic strain energy density.ResultsThe findings indicate that the interaction between the two defects strengthens as the inner defect approaches the outer defect, significantly promoting crack initiation. Conversely, when the inner inclusion is located at the center of the model, the interaction is minimized, and external defects become the primary drivers of crack initiation.

The cloud manufacturing (CMfg) platform serves as a centralized hub for allocating and scheduling tasks to distributed resources. It features a concrete two-agent model that addresses real-world industrial needs: the first agent handles long-term flexible tasks, while the second agent manages urgent short-term tasks, both sharing a common due date. The second agent employs multitasking scheduling, which allows for the flexible suspension and switching of tasks. This paper addresses a novel scheduling problem aimed at minimizing the total weighted completion time of the first agent’s jobs while guaranteeing the second agent’s due date. For single-machine cases, a polynomial algorithm provides an efficient baseline; for parallel machines, an exact branch-and-price approach is developed, where the polynomial method informs the pricing problem and structural properties accelerate convergence. Computational results demonstrate significant improvements: the branch-and-price solves large-sized instances (up to 40 jobs) within 7200 s, outperforming CPLEX, which fails to find solutions for instances with more than 15 jobs. This approach is scalable for industrial cloud manufacturing applications, such as automotive parts production, and is capable of handling both design validation and quality inspection tasks.

In order to study the effect of coupling between inner and outer defects of high⁃speed train axle on fatigue crack initiation， a multi⁃crystal finite element model of high⁃speed train axle was established on mesoscopic scale based on crystal plasticity theory The stress field and structural deformation around the inner and outer defects of axle were analyzed by tensile and impact tests， and the effect of inner and outer defects coupling on fatigue crack initiation was investigated Based on the characteristics of stress distribution and plastic strain energy density distribution， the crack initiation location was predicted. The results show that the interaction between two defects was stronger when the inner defect was closer to the outer defect， and the crack initiation was promoted when the inner inclusion defect was at the center of the model， the interaction between the two defects was minimal， and the external defects were the main factors leading to crack initiation.

Brake disk friction wear is an important cause of disk brake failure in high-speed trains, and the circumferential spacing of the friction block is an important factor affecting the amount of brake disk wear. In order to study the influence of the circumferential spacing of friction blocks on the wear of brake disk, based on Archard wear model, a three-dimensional transient model of brake disk and brake pad is established by using ANSYS finite element simulation software. The wear volume and wear rate of brake disk friction surface under three different circumferential spacing of friction blocks during emergency braking of trains are simulated and calculated. The contact stress and temperature variation of the brake disk friction surface are analyzed, and the influence of different friction block circumferential spacing on the contact stress and temperature distribution of the brake disk is given. Finally, based on the response surface method, the circumferential spacing of friction blocks was optimized to obtain the value of the circumferential spacing of friction blocks that minimizes the wear of the friction surface of the brake disk. The results show that the target response value is minimum when the friction block circumferential spacing D1 = 2.018 mm, D2 = 2.02 mm, D3 = 3.896 mm, D4 = 2.005 mm, D5 = 3.982 mm, D6 = 2.034 mm, D7 = 2.018 mm, D8 = 2.039 mm, and D9 = 2.031 mm. The optimized brake disk wear volume was reduced by 0.4% and the wear rate was also reduced by 0.4%. This study is significant for reducing the brake disk wear volume and improving the brake pad friction block structure layout.

Mortar void is the most prevalent disease in CRTS II ballastless slab track aggravating the service performance of vehicle and track structures. For determining a reliable mortar void limit, the influence of mortar void on the vehicle-track dynamics are analyzed through a refined rigid vehicle-flexible track coupled model, considering the randomness induced by track irregularity. Sensitivity analysis of mortar void are conducted taking into account train operation speeds and track irregularities measured from different railways. The findings suggest that when the train speeds are 250 km/h, 300 km/h and 350 km/h, respectively, mortar void length should be less than 0.98 m, 0.93 m and 0.81 m. Additionally, the impact of mortar void on the vehicle-track system dynamics becomes more pronounced as the amplitude of track irregularity decrease. This study provides a valuable insight for developing an effective maintenance plan for mortar void in CRTS II ballastless slab track.

为研究不同风向角下高速动车组的动力学性能,利用多体车辆动力学研究方法,对不同风向角下的某型动车组的车辆运行安全性进行仿真模拟分析.把气动载荷处理为时间函数,将其输入多体动力学软件,对动车组在风载作用下的动力学性能进行仿真分析.利用8节连挂动车组模型,分别分析各辆车在不同风向角下的运行安全性.分析发现:头车受风载的影响最为明显,在风速20 m/s、车速300 km/h下的工况相较于在风速25 m/s、车速200 km/h下的工况对列车运行安全性影响大.其中在风速20m/s、车速300 km/h下的工况105.风向角的风载对列车运行安全性影响最大.

为研究高速列车车轴疲劳裂纹萌生问题,基于滑移理论构建车轴钢材料体心立方晶体塑性本构方程,通过建立含缺陷的车轴试样晶体塑性有限元组合模型,从介观尺度研究了车轴钢材料上划痕缺陷位置的应力分布情况,并探索了缺陷位置微观变形演化规律.结果表明:模型缺陷位置应力呈梯度分布,相邻晶粒晶体取向的差异会造成应力集中,随着疲劳载荷的施加,累积塑性应变逐渐增强并形成较长的滑移带,这种较长滑移带会影响材料的疲劳行为,对疲劳裂纹的萌生起到诱导作用.

根据EA4T车轴钢疲劳试验,建立基于滑移理论的体心立方晶体塑性理论框架,从介观角度研究车轴钢材料内部夹杂物对疲劳裂纹萌生的影响.模拟材料内部CaS球状夹杂物和A12O3块状夹杂物附近应力分布规律.研究材料内部夹杂物对裂纹萌生寿命预测参数的影响,标定关键变量塑性应变能密度.以裂纹形成过程中能量的变化为切入点,研究不同夹杂物对裂纹萌生寿命的影响.结果表明:材料内部夹杂物缺陷形态以及弹性矩阵的差异是引起应力集中的主要诱因,对于EA4T车轴钢材料而言,Al2O3块状夹杂缺陷通常比CaS球状夹杂缺陷的对钢基体微观结构的破坏更严重,更容易萌生裂纹.

钢轨波磨是重载铁路上常见的一种病害,且波磨波长范围较广,为研究列车经过不同波长的波磨区段时轮轨垂向力变化情况,利用ABAQUS软件建立有限元模型,仿真计算不同工况条件下的重载线路轮轨垂向力响应.首先,结合重载铁路轴箱加速度的分析和现场复核,归纳钢轨波磨区段主要参数特征;接着,根据归纳的波磨特征建立有限元仿真模型并利用既有实测数据验证仿真结果的正确性;然后,利用控制变量法计算轮轨动力学在不同车辆轴重、运行速度、扣件刚度和弹簧阻尼参数下的影响特性.最后,通过比较不同波长下的轮轨垂向力发现,相同工况下,重载铁路短波长波磨区段能引起轮轨垂向力更大范围的幅值波动.因此,重载铁路产生钢轨波磨初期,为避免异常的轮轨力,要及时打磨.

摘要: 车轴遭受异物冲击缺陷存在多种形式,其中棱角冲击对车轴疲劳性能影响较大,会加速车轴的失效。为研究棱角冲击缺陷对车轴疲劳极限的影响,针对30NiCrMoV12车轴钢,采用软件模拟与疲劳试验相结合的方法,借助ABAQUS对冲击缺陷区域进行应力场分析,对预制好的缺陷车轴试样进行疲劳试验,依据试验结果采用近似欧文单侧公差极限法拟合各试样组疲劳P-S-N曲线,得到相应的疲劳极限。根据各试样组的疲劳试验结果预测全尺寸车轴疲劳极限。考虑冲击缺陷深度的分散性,对缺陷深度和全尺寸车轴疲劳极限两参数进行拟合。最后基于EI-HADDAD公式,建立含棱角冲击缺陷的30NiCrMoV12车轴钢的多变量疲劳极限预测模型。采用该模型能够快速预估含不同尺寸棱角缺陷的全尺寸车轴疲劳极限。

通过车辆系统刚柔耦合多体动力学与有限元模型联合仿真分析高速列车运行过程中车轮多边形和钢轨波磨对螺栓松动的影响,采用ABAQUS建立轴箱体、轴箱盖和带精细螺纹的轴箱螺栓三维有限元模型,将动力学计算得到轴箱振动加速度谱导入有限元模型,计算轴箱螺栓危险点最大等效应力和螺纹张紧力,得到不同工况对螺栓松动影响的定性分析结果.结果表明,车轮多边形的和钢轨波磨对轴箱端盖螺栓垂向振动加速度影响最为明显,车轮多边形和钢轨波磨是影响轴箱松动的主要原因.

基于Archard磨损理论,以磨损率计算公式的修正指数(压力指数m和速度指数n)作为研究磨损和摩擦应力的响应参数,利用ANSYS有限元软件,建立制动盘-闸片简化模型;通过Box-Behnken试验设计方法和最小二乘法,拟合出影响Archard磨损模型修正指数的目标函数响应面模型,对轨道列车盘形制动磨损行为进行非线性分析,并约束制动盘接触应力和摩擦应力,制定修正指数优化原则;分析制动初速度和压力对制动盘磨损的影响.结果表明:速度指数n对列车磨损值影响较大,模型优化后的最优修正指数为压力指数m=0.97、速度指数n=0.96,基本满足磨粒磨损试验理论值m=n=1;施加不同的制动压力和制动初速度时,制动盘表面摩擦应力和磨损深度在摩擦半径处呈周向递减,制动初速度对制动盘摩擦应力影响不大;当制动盘在较大制动压力作用下时,盘面出现严重挤压,摩擦应力随之增大.

The impact defects on the surface of the axles of high-speed trains may cause hidden dangers to the safe operation of the trains. In order to study the influence of different shape defects on axle fatigue limit, the method of combining finite element simulation and fatigue test is adopted. According to the statistics of the foreign object damage impact defect of the axle in the workshop, impact defects were prefabricated on the axle specimen surface, stress analysis of the impact defect area was carried out, and then the more dangerous defect shape was obtained. Fatigue tests were carried out on prefabricated axle specimens. The P-S-N curves of each specimen group were fitted by the approximate Owen one-side tolerance limit method. In line with the fatigue test results of samples, considering the factors such as axle surface mass coefficient, size effect coefficient and load type, to ensure the security of the train operation, fatigue strength safety factor Sσ is introduced to establish a full-size axle fatigue prediction mathematical model. The fatigue limit of full-size axle with impact defects was predicted and the accuracy of the model was proved. Finally, on the basis of the defect shape, the modified EI Haddad model was used to fit the two-parameter theoretical model of defect depth and full-size axle fatigue limit, the standards were combined for safety assessment.

随着我国高速列车速度的不断提高,尤其是长大坡道的存在,使得制动盘的应用环境更加恶劣.由于制动摩擦产生的热量使得制动盘温度快速升高,如果散热不及时,会形成高的热应力,从而导致热疲劳裂纹的产生.因此,高效的制动盘散热问题显得尤其重要.目前,制动盘的散热设计主要采用改变散热筋结构形式,这样的散热效果有一定的局限性.为了进一步降低制动盘的制动温度和热应力,根据相变储热原理,设计制动盘散热结构,通过连续两次紧急制动使得制动盘温度上升.应用有限元分析软件对不同的相变储热材料进行散热分析,得到三种制动盘的温度场和应力场.结果表明,具有相变储热材料的制动盘能够明显降低制动过程中制动盘的最高温度,同时降低了制动盘的温度梯度,从而使得制动盘受到的热应力有所降低,在一定程度上预防了热疲劳裂纹的产生.

车轴是高铁车辆走行部重要的部件之一，其在服役过程中产生的裂纹会严重影响车辆运行的安全性。目前还未实现实时在线检测，现场检修时采用超声和磁粉方法存在检测效率低、操作复杂等问题。直流电位降（Direct current potential drop,DCPD）检测方法可靠方便，能够克服上述问题。基于DCPD检测原理，建立裂纹检测数学模型，结合稳定直流电场的Laplace方程，运用ABAQUS建立带裂纹的全尺寸车轴三维有限元模型，对一系列带不同深度半椭圆裂纹的车轴进行仿真。分析裂纹区域电位降信号，研究全尺寸高铁车轴电位降与裂纹深度的关系，并绘制电位降随裂纹深度变化的校准曲线，讨论影响校准曲线的相关因素，发现裂纹面相对于轴线的偏转角度和探针的相对位置均会影响校准曲线选择。该研究结果为高铁车轴裂纹的实时检测提供了实现思路和方法。

目前,高速列车制动闸片剩余厚度采用人工方法测量,耗时费力,成本较高.闸片与制动盘的贴合情况也难以判断,影响了制动安全性.为了解决此问题,通过对高速列车转向架基础制动结构空间、实际工况的充分考虑,基于阿贝原则,考虑测量误差补偿,结合现场运用环境,采用光电与机械方法相结合,并考虑数据测量精度,应用模块化设计的理念,建立了合理的检测模型并进行了误差分析,验证了模型的可行性.

：With the construction of high-speed railways in the central and western regions of China, the problems caused by long ramps have become increasingly prominent.If the electric brake fails when driving on a long slope, pure air braking will be adopted.The continuous braking caused by the long slope will cause the thermal load of the brake disc of the EMU to rise sharply.Due to the slow aging of heat dissipation, the temperature of the brake disc is too high, and at the same time, a larger temperature gradient is generated, which leads to the generation of thermal fatigue cracks in the brake disc.In order to solve the problem of increasing the heat transfer efficiency and cooling of the brake disc under the long ramp working condition, based on the long ramp working condition of the LanXin line, a new type of aluminum-embedded steel structure brake disc was designed and finite element analysis software was adopted.The simulation calculation of aluminum-embedded steel structure brake disc and all-steel brake disc is carried out, and the temperature field and thermal stress distribution are obtained.The results show that when pure air braking is used on long ramps, the aluminum-embedded steel brake discs can significantly reduce the temperature and temperature gradient of the brake disc surface while achieving lighter weight, and alleviate thermal fatigue problems caused by braking on long ramps.

It is well known that due to the mechanical properties of Inconel 718, it is difficult to cut Inconel 718 with conventional machining techniques and can cause inconsistencies between EDM machined Inconel 718. The high melting point of the Inconel 718 requires a large amount of discharge energy to melt, and the low thermal conductivity reduces the use of a large amount of discharge energy. At the same time, the deionization of the liquid is incomplete because the temperature rises rapidly after a series of pulse discharges. In this way, the final result may increase and cause arc pulses to be generated, resulting in unstable processing. In order to solve this problem, the expected value of machining state is used to balance machining stability and machining efficiency for the first time. Then, an adaptive clearance servo voltage control system is built, in which the clearance servo voltage is adjusted, so that the machining state can follow the expected value of the machining state in the machining process. In this way, the current problem can be solved, and the practical experiment verifies the value and practicability of the proposition in the future.

高速列车车轴表面的缺陷会给列车的安全运行带来隐患.据统计,冲击压痕与划痕在车轴表面缺陷中占据了较大比例.为研究冲击压痕与划痕对车轴的疲劳极限造成的影响,采用有限元仿真与疲劳试验相结合的方法.首先借助Abaqus有限元软件,分析预制缺陷后形成的残余应力场及施加外载荷后产生的叠加应力场,查看仿真结果中的高应力区域与试验中的裂纹源位置的吻合程度;随后根据试验结果拟合疲劳S-N曲线,分析各缺陷对车轴疲劳极限的影响,并采用残差平方和分析各缺陷在试样破坏过程中的影响权重;最后根据试样的试验结果预测全尺寸车轴疲劳极限.研究发现,相同条件下划痕对车轴的疲劳极限影响更大;若轴身表面出现类似缺陷,会威胁到列车的运行安全.