Aluminum alloy and its welded joint are widely used in high-speed trains, which are subjected to complex fatigue loadings in service. The fatigue failure mechanisms and influential factors for Base Metals (BMs) and Welding Metals (WMs) subjected to low cycle (dwell) fatigue (R = 0) and (very) high cycle fatigue (R = -1) loads were investigated. The development of cumulative strain in tension-tension low cycle (dwell) fatigue was attributed to "cyclic ratcheting effect", which developed only when the applied maximum stress level is higher than the yield strength. In that condition, the cumulative strains continually developed and resulted in ductile fracture for BMs, but gradually converged to a finite value and resulted in fatigue fracture for WMs. Further, the dwell loading contributed to slowing down the development speed of cumulative strain and extending the fatigue life for BMs. Moreover, the welding processing reduced the (very) high cycle fatigue strengths and shortened the fatigue lives due to the introduction of welding defects, and a model replacing the nominal maximum stress by an equivalent one was proposed for modeling the impact of those defects on fatigue properties, which agrees with the S-N data.

The increasing number of train–moose collision accidents threatens train running safety. This study investigated the bullet train–moose collision process and explored the effect of parameters on the dynamic responses. The multibody (MB) model was developed and validated against real–world collisions and the validated finite element model. A parametric study including the moose size, train speed, moose velocity, moose offset, and impact angle was conducted using MADYMO software. The lateral and longitudinal displacements of the moose’s center of gravity (CG) were used to evaluate the crash safety. The results showed that the moose size significantly affects moose impact dynamics and kinematics. The velocity and the offset of the moose were positively correlated with the lateral displacement. However, there was an obvious nonlinear relationship between the train speed and the lateral displacement. With the increase in the collision speed, the front–end deformation weakens the obstacle removal effect of the front hatch. The landing spots of the small–sized moose were the most concentrated, which means greater risk of secondary collisions. This study provides practical help for improving the running safety of high–speed trains and protecting wild animals along railways.

Moose herd–train collisions represent one of the potential hazards that railway operations must contend with, making the assessment of passive train safety in such scenarios a crucial concern. This study analyzes the responses of bullet trains colliding with moose herds and investigates the influence of various factors under these conditions. To achieve this goal, a multibody (MB) model was developed using the MADYMO platform. The displacement of the moose’s center of gravity (CG) was employed to assess the safety boundaries, while the relative positions between the wheels and rails were used to evaluate the risk of derailment. The findings revealed that the collision forces exhibited multi-peak characteristics that were subsequently transmitted to the wheel–rail contact system, resulting in disturbances in the relative positions of the wheels and rails. However, these disturbances did not reach a level that would induce train derailment. Furthermore, larger moose herds exhibited higher throw heights, although these heights remained within safe limits and did not pose a threat to overhead lines. The primary safety risk in moose–train collisions stemmed from secondary collisions involving moose that had fallen onto the tracks and oncoming trains. This study offers valuable insights for enhancing the operational safety of high-speed trains and safeguarding wildlife along railway corridors.

Moose-vehicle collisions often cause broken glass, deformed roofs, and dented hoods, which makes the driving space invaded to a large extent and seriously threatens the life safety of occupants, and is an essential factor threatening traffic safety. However, there is currently a lack of moose numerical models that can be used to study moose-vehicle collision response. Based on actual body size data, this paper developed a moose numerical model that could be used for vehicle collision simulation of moose using MADYMO software, which could realize the representation of different physical signs of moose by the scaling method. The accident reconstruction was performed based on the video information of the Jeep-moose collision accident and the Volvo-moose dummy collision test. Comparing the kinematic response posture of the moose in the accident and simulation, the moose model and the scaling method were validated. This model is significant for the study of moose-vehicle collision response and the guidance of vehicle safety design.

Collisions between trains and moose that cross a track are common occurrences according to rail accident statistics. A moose lying on a track after a crash may increase the risk of train derailment. In addition, a moose thrown into the air during a collision may also hit and damage the panto-graph, which prevents a train from running. This paper developed a finite element (FE) model of moose and is aimed at investigating the train crash safety and moose motion trajectory in train -moose collisions for different moose crossing scenarios using the FE method. Material biome-chanics tests were conducted to obtain the mechanical property parameters of moose. Drop hammer impact tests were performed to validate the constitutive models of different moose segments. The whole moose FE model was verified against previous vehicle-moose crash tests. The numerical impact scenes of moose crossing the rail at different collision positions were established in LS-DYNA. The results showed that the impact force depends on the contact area between the train and the moose. A larger contact area corresponded to a larger impact force. The moose would be pushed away by the V-shaped locomotive and would not cause a derailment, and the height of the moose thrown into the air cannot reach the height of the pantograph, which would prevent damage to the pantograph of a bullet train.

为提高地铁列车耐撞性,降低碰撞姿态造成的二次损伤,提出一种控制列车碰撞姿态的辅助保护装置(抱轨装置).首先,设计抱轨装置的几何结构并定义抱轨装置的力学特性,采用动力学方法建立8编组地铁列车的碰撞模型;其次,结合实验验证仿真模型的准确性,研究抱轨装置对列车碰撞姿态的影响;再次,提出3种不同的抱轨装置安装方案,对比分析得到经济且有效的方案;最后,基于EN15227:2008标准对方案进行耐撞性评估,基于多目标遗传算法对抱轨装置的设计参数进行优化.研究结果表明:当钩状抱轨装置安装在车体质心正下方时,在满足控制列车碰撞姿态的要求的前提下,可以不占用车体太大的空间,满足EN15227:2008中耐撞性考核指标,是经济且有效的方案;当距离车体质心的纵向相对位移dinstall=10 000 mm,抱轨装置静止阶段距离x1=9.47 mm,抱轨装置线性阶段刚度k1=5 000 N/mm时,列车的车体和轮对的最大垂向抬升量最小,取到最优值,最大轮对位移抬升量dmax=13.87 mm,列车车体最大俯仰角θ =3.12°.

针对内燃机车燃油箱的振动疲劳寿命的计算问题,运用虚拟质量法对燃油箱油液进行模拟,并且在此基础上基于流固耦合对机车燃油箱进行频率响应分析,获得了机车燃油箱有限元模型的应力传递函数.随后,利用某疲劳分析软件对传递函数施加IEC 61373:1999 标准中的长寿命加速度功率谱密度(PSD)计算机车油箱的疲劳寿命.最后,通过计算对燃油箱结构进行优化处理,使得该型燃油箱能够在服役过程中满足使用要求.研究结果为机车燃油箱疲劳寿命的计算提供了参考,具有一定的参考意义与工程实践价值.

探寻运行速度和排障雪犁张角对动车组除雪特性的影响规律,是解决积雪环境下动车组运营效率及运行安全问题的关键举措.采用光滑粒子流体力学(SPH)方法模拟雪堆,构建动车组-雪堆-轨道耦合动力学仿真模型,研究运行速度40,80,120,160和180 km/h和张角60°,90°和120°对雪粒子运动状态和动车组排雪阻抗力、轮重减载率的影响.研究结果表明:积雪沿着雪犁外形向两侧推开,雪粒子运动呈抛物线状,飞雪轨迹均未遮挡司机室视野;排障雪犁张角为60°时,随着动车组运行速度从40 km/h增加到180 km/h,雪粒子距离地面最大垂向高度从1419 mm增加到4433 mm;纵向阻抗平台力从18.72 kN增加到260.28 kN,垂向阻抗力平台力从27.96 kN增加到300.64 kN,车辆-雪堆界面纵向和垂向阻抗力与速度呈现二次函数关系;轮轨关系方面,动车组头车一位端转向架2个轮对的轮重减载率分别从0.433和0.368增加到0.700和0.730,当速度超过120 km/h时,轮重减载率超过标准要求0.6;当运行速度为80 km/h时,随着排障雪犁张角从60°增加到120°,雪粒子距离地面最大垂向高度从2348 mm增加到4881 mm;纵向阻抗平台力从59.01 kN增加到92.91 kN;垂向阻抗平台力变化不大;张角的改变不影响动车组轮重减载率的变化.研究成果可为解决高寒地区应对暴雪等恶劣天气的动车组除雪运行问题和排障雪犁结构设计提供思路.

随着轨道车辆轻量化设计需求日益突出,拓扑优化技术正加速应用于车辆关键局部结构高性能轻量化设计并取得较显著减重成果,但受限于制造要求和较大的计算规模,整车级车体结构拓扑优化已为轨道车辆设计阶段的难点之一.论文针对某不锈钢地铁车体结构设计需求,基于移动可变形组件法(Moving Morphable Com-ponent,MMC),开展显式拓扑优化框架下的整车级车体结构优化设计.依据EN 12663标准工况及车体设计空间,建立了地铁车体结构MMC拓扑优化数学模型,给出了相应的拓扑优化设计流程,搭建了地铁车体结构显示拓扑优化算法平台.按照设计流程,基于灵敏度的驱动,以车体结构的整体刚度作为设计目标,同时设置质量约束,通过调控组件移动、旋转和变形,实现对整车级车体结构的拓扑优化研究,确定了车体拓扑构型.基于MMC方法,可有效降低优化过程中的计算量,直接获取较为清晰的不锈钢地铁车体结构整车级传力路径,论文数值算例验证了该算法的优势.

In this paper, a series of static/dynamic tensile tests are performed for glass fiber reinforced plastic (GFRP) composites. Using the combination of high-speed photography and digital image correlation (DIC) technology, true stress–strain curves in different directions and strain rates are obtained. We also obtained the dynamic failure strain of the material in different directions, which are used to accurately describe the dynamic tensile and failure behavior of the material. The experimental results show that there is a stiffness change point N in three directions under different strain rate (10 −3 s −1 , 10 s −1 , 100 s −1 ) tensile conditions. The stiffness before and after N point is recorded as E initial and E changed respectively. The values of E changed in weft direction and warp direction are about 30% to 50% of E initial , while E changed in tilt direction is only about 10% of E initial . The fiber has the highest strength in the weft direction and the tilt direction has the lowest strength. With the combination of high-speed photography and DIC technology, the dynamic failure parameters of different directions under the strain rate of 100 s −1 are obtained. The dynamic failure strains in three directions are 0.245, 0.373 and 0.341, respectively. The parameters are verified by impact three-point bending test. These works can more accurately describe the dynamic mechanical behavior of glass fiber reinforced plastic (GFRP) composites and provide reference for the design of GFRP structures.

为了保证低成本、短周期,采用仿真与试验相结合的方法对某蒙皮蜂窝式整体式吸能装置展开设计;针对吸能装置设计指标,基于单个蒙皮蜂窝式整体吸能装置压缩、两个相同蒙皮蜂窝式整体吸能装置对压等工况,通过有限元仿真分析方法进行结构尺寸、蜂窝强度等参数迭代优化,确定设计参数,并试制全尺寸样件开展同工况静压试验,试验结果显示:仿真结果与试验结果一致,说明建模方法可靠,可用于防爬器前期设计;蒙皮蜂窝式整体吸能装置主要性能参数满足相应技术指标要求.

地铁是城市公共交通重要部分,碰撞事故一旦发生,将会造成巨大伤亡.本文建立车厢-乘员-扶手耦合三维多刚体动力学模型与头-地板耦合三维有限元模型,基于生物力学指标,研究3种基本工况下不同站姿地铁乘员头部损伤,旨在探究乘员姿态对头部损伤影响规律.结果表明:1)头部损伤生物力学指标最大值均基本集中在脑干处与颅脑顶端,可以判断发生脑损伤;2)地铁站立乘员抬头角度、面向方向对头部损伤影响较大,脚部竖跨角度对头部损伤结果有一定影响,而脚步横跨角度对头部损伤结果影响不大;3)地铁站立乘员保持头部弯曲角度45°、面向地铁行驶方向、脚步竖跨角度0°姿态,将在地铁碰撞事故中面临更严重脑损伤风险.

动车组用中间车钩缓冲吸能装置主要由气液缓冲器和压溃管组成,为研究其工作场景中动态吸能特性,采用两辆台车与中间车钩连挂,撞向刚性墙进行冲击实验,台车冲击速度分别为7.19、18.7和25.7 km/h 3种工况.冲击作用下,气液缓冲器阻抗力具有明显的动态特性,最大压缩行程的阻抗力随冲击速度提升而增高,可达1500 kN,远高于其静压实验最大阻抗力800 kN;而压溃管动态阻抗力与静压结果基本一致为1500 kN;冲击速度为18.7和25.7 km/h,气液缓冲器压缩行程达到30 mm时,阻抗力达1200 kN,压溃管被触发压溃,气液缓冲器与压溃管同时进入压缩状态,一起压缩变形.

通过对高速动车组端部吸能系统进行冲击试验和碰撞仿真分析,对该吸能系统的车钩安装座结构进行了优化设计,并验证了优化结构车钩安装座的抗冲击性能满足设计要求.

根据快速货运动车组铝合金车体结构特点,简化车体几何模型,建立相应的有限元模型.基于车体静强度计算标准,确定8种车体结构静强度的计算工况,在这些计算工况作用下,计算车体结构的静强度,计算在最大垂直载荷作用下车体结构刚度,以及车体结构模态,计算结果表明快速货运动车组车体结构的刚度、静强度和模态均满足车体结构设计要求.

In this study, we focus on the dynamic failure property of A6N01S-T5 aluminum alloy use for high-speed trains. The method of split Hopkinson tensile bar (SHTB) and three-dimensional (3D) digital image correlation (DIC) was put forward to find the dynamic mechanical properties and dynamic failure strain of A6N01S-T5 aluminum alloy, and on the basis of this, Johnson–Cook model constitutive parameters and dynamic failure strain parameters were obtained through a series of static and dynamic tests. An important character of this method was that the sandwich structure from the true high-speed train was used in penetration test, followed by the numerical calculation of the same working condition using LS-DYNA. Then we compare the experimental results with simulation results mentioned above in terms of failure morphology in structure and the bullet speed throughout the entire process to verify the accuracy of the parameter. The experimental results provide a data basis for the crash simulation model of high-speed trains, in turn to optimize the structural design and whole efficiency.

通过试验结果校准并验证了薄壁方管的仿真有限元模型,然后基于仿真分析对薄壁方管在偏置载荷下的吸能性能进行了研究.研究结果表明,对选定的薄壁方管,在一定偏置距离下,薄壁方管的吸能性能和变形模式基本不受影响,当偏置距离达到一定值时,薄壁方管将发生整体倾覆失稳,且吸能性能急剧下降.此外,诱导结构的存在会降低薄壁方管吸能过程的稳定性,使得倾覆失效提前发生.

Selective laser melting (SLM) is a mature method in the fabrication of structures bearing static loading and small strains; however, structures experiencing large deformation under impact loading remains an issue. In this paper, the author fabricates a 316L stainless steel thin-walled circular tube with preset internal circumferential rectangular groove defects using the SLM method. MTS compression and Split Hopkinson Pressure Bar tests are performed to judge the material behavior of SLM printed 316L stainless steel, and Johnson-Cook constitutive model parameters are fitted from the results. The crushing behavior of the SLM printed tube is studied experimentally and numerically via the drop hammer test and the finite element analysis. There are two stages of the crushing process of the tube as the results show: the buckling stage and the splitting stage. The internal grooves have effects on controlling the initial buckling position and fracture position during the buckling stage. The double buckling-splitting crushing mode in one simple structure, provides a new energy absorption approach for engineering application.

利用结构非线性有限元计算程序LS-DYNA,对具有相同截面积,但不同形式的铝合金薄壁元件进行轴向低速冲击仿真计算,分析各种元件的吸能特性,获得一种适用于轨道车辆前端大吸能量要求的吸能元件.

在按照欧标EN15227评价轨道车辆的耐撞性能时,需对碰撞仿真过程中轮轨间的垂向位移做出准确的判定.基于HYPERMESH和LS-DYNA仿真软件的工程应用,以提高模拟精度与计算效率为目标,提出了一种有效模拟转向架实际结构、转向架与车体间连接关系以及轮对与轨道间接触关系的仿真方法.最后以某列10节编组轨道客车以25 km/h速度对撞为例,进行仿真验证,结果表明:该转向架模拟方法是较为准确且有效可行的.