Honeycomb sandwich structure has been widely used in lightweight and impact protection of rail vehicle structures due to its excellent mechanical properties. In this paper, the plastic deformation, failure response and energy absorption characteristics of honeycomb sandwich panels for rail vehicles under repeated impact loads were studied. The three-point bending tests and low-speed impact tests of honeycomb sandwich panels were carried out, and a three-dimensional numerical model considering the detailed structure of the honeycomb core and the failure of the adhesive layer was established. The model can reasonably simulate honeycomb sandwich panels' stiffness, strength, and structural failure. The effects of impact times and impact angle on the performance indexes of the honeycomb sandwich panel were studied. The results show that when the impact energy is the same, the impact times will affect the energy absorption distribution of honeycomb sandwich panels. With the increase in impact times, the panel's absorption energy decreases, the core's absorption energy increases, and the total absorption energy decreases. For multiple impact conditions, with the increase of impact times, the single energy absorption of the upper panel and core decreases, and the single energy absorption of the lower panel increases. When the impact energy is the same, the rise in impact angle will increase the damage to the honeycomb sandwich panel, and the energy absorption of each part will increase. In addition, the influence of impact times on the energy absorption efficiency of honeycomb sandwich panels is related to the impact angle.

[Objective] Currently, the CAC (cutting-type anti-climber) faces the issue of excessively high initial peak cutting force, leading to cutting tool detachment or fracture and finally the anti-climber failure. Moreover, the existing double-cutting type anti-climbers are prone to the accumulation of internal chips within the pipe. Therefore, the study on new CAC for urban rail transit vehicles is necessary. [Method] First, a CAC finite element model is established. The simulation results of CAC cutting force and collision energy absorption are compared with the experimental results in relevant literature to verify the accuracy of the finite element model simulation method. The working principles of the honeycomb composite CAC and the improved internal-external double CAC are introduced. The cutting performance of two new CAC devices is analyzed through finite element model simulation calculations. [Result & Conclusion] Setting an induction groove at the position where the CAC initial peak force occurs can effectively reduce the peak force. The depth of the induction groove should not be less than the cutting depth for optimal results. But excessive width of the induction groove increases the secondary peak force and causes significant fluctuations in cutting force after the cutting tool passes through the induction groove. In comparison with the conventional drawer-type honeycomb anti-climbers, the honeycomb composite CAC not only exhibits excellent energy absorption capacity, but also allows for component replacement, making them reusable. The new internal and external double CAC can smoothly discharge the chips from the pipe, thereby avoiding the chip accumulation. Compared to a single CAC, the new internal-external double CAC demonstrates superior energy absorption performance.

为研究不同结构参数对质量相同、强度不同的两种铝蜂窝夹芯板低速动态冲击响应的影响,建立了铝蜂窝夹芯板受半球型落锤低速冲击的数值模型,并将有限元计算结果与试验结果进行对比,检验了模型的可靠性.在此基础上,对比研究了不同上下铝板厚度和不同蜂窝芯壁厚对两种铝蜂窝夹芯板在低速冲击下吸能效果的影响.结果表明:在质量相同的情况下,强度小、高度大的夹芯板在低速冲击下力-位移曲线更易出现双峰模式,增加蜂窝芯壁厚或是上下铝板厚度都会使第一次的峰值力增加,第二次峰值力降低;强度小、高度大的夹芯板蜂窝芯在低速冲击中吸能占比更多,强度大、高度小的则是上层铝板吸收的能量更多,前者的质量、体积比吸能更高;铝蜂窝夹芯板质量比吸能和体积比吸能与壁厚边长比、板厚芯高比均呈幂次关系.

为研究某型地铁车辆蜂窝式防爬器的吸能特性,根据轨道车辆耐撞性标准,对其吸能区域的结构进行合理设计,进而研究了不同薄壁壳厚度和蜂窝厚度下蜂窝式防爬器的吸能特性.利用四次多项式响应面代理模型拟合出其压缩力效率,并运用多岛遗传算法对其压缩力效率最大值进行寻优.结果表明:多级蜂窝式防爬器的比吸能和压缩力效率都明显优于相同质量下的单级蜂窝式防爬器和圆管式防爬器;薄壁壳壁厚对多级蜂窝式防爬器的撞击力影响较铝蜂窝壁厚更为显著;通过使用四次多项式响应面法和多岛遗传算法在设计空间中寻找到其最优的壁厚组合,压缩力效率比优化前提高了6.03％,相较圆管式防爬器提高了60.96％;该防爬器在压缩力效率和比吸能方面具有明显优势,应用于地铁车辆的吸能防爬环节将发挥其重要的作用.

目的:不锈钢蜂窝具有较大的额定吸能容量,可以作为车辆端部的吸能材料,现已应用于车辆防爬器的吸能区,因此需研究应变率效应对不锈钢蜂窝动态冲击性能的影响.方法:以304不锈钢为基体材料,建立了不锈钢蜂窝异面压缩数值模型.采用两种不同规格的不锈钢蜂窝进行仿真建模,并结合不锈钢蜂窝的准静态压缩试验,验证模型的有效性.基于不锈钢蜂窝有限元模型,分析应变率效应对不锈钢蜂窝结构压溃应力、吸能和不锈钢蜂窝变形模式的影响.结果 及结论:304不锈钢材料具有明显的应变率强化效应;考虑应变率效应的压溃应力-位移曲线较为光滑,与文献中的试验所得的曲线更接近;考虑应变率效应后,不锈钢蜂窝的峰值压溃应力和平均压溃应力明显增大,最大压缩位移和理想吸能效率有所减少;304不锈钢材料的应变率效应会使蜂窝结构形成塑性铰所需的应变增大,进而影响其变形模式.

为研究某型地铁车辆的铝蜂窝防爬器的吸能防爬特性,利用非线性有限元数值模拟方法,建立了可靠的等效铝蜂窝防爬器有限元模型.通过对不同结构参数铝蜂窝防爬器的吸能特性研究,对该防爬器进行了优化设计,并将优化后的防爬器用于整车,模拟了 6编组地铁车辆在速度为25 km/h时的对撞工况.仿真结果表明,增加薄壁壳壁厚将使碰撞初始峰值力大幅度增加,碰撞力的波动也随之增大;在多个铝蜂窝块之间插入隔板串联组合使用,将极大地提高蜂窝块的吸能效果;在薄壁壳上开诱导孔是诱导防爬器稳定有序变形的手段之一,但是诱导孔数量过多反而对吸能造成不利影响.通过整车碰撞模拟,以欧洲铁路标准EN 15227:2020的相关要求对其进行评判,证明了该防爬器具有良好的吸能和防爬性能,为铝蜂窝防爬器在地铁车辆上的应用提供了理论依据.

针对我国200 km/h城际动车组车轮发生的I类滚动接触疲劳,对16列动车组及4个不同半径曲线轨道进行轮轨状态现场观测.基于多体动力学软件SIMPACK和损伤函数模型,建立车轮滚动接触疲劳预测模型,系统分析城际动车组的车轮I类疲劳损伤.研究结果表明:早期时动车组不调头运行,Ⅰ类疲劳在运行(6～9)万km即出现,集中在左侧车轮,其疲劳区最初位于名义滚动圆外侧5～15 mm处,之后略有扩大并向踏面外侧移动;曲线通过时的低轨侧轮轨相互作用是导致I类疲劳的根本原因,当半径R大于400 m时,预测的疲劳寿命随半径的增加而增加;所运行线路上小半径曲线(R≤450 m)全为左曲线,导致早期不调头Ⅰ类疲劳集中在左轮,定期调头后,两侧车轮交替承受疲劳载荷;现场中轮轨廓形演化和轨底坡误差等是Ⅰ类疲劳区扩大和向外侧移动的直接原因.

对国内某A型地铁发生于单侧车轮轮缘根部的2类滚动接触疲劳,开展现场调研.调研发现,疲劳集中出现在轮缘厚度更大的动车左轮上.基于SIMPACK建立车辆动力学模型,并利用损伤函数预测了车轮疲劳的萌生.研究结果表明:由踏面磨耗导致的轮缘厚度增加,大大提高了轮缘根部与曲线高轨轨距角接触的可能性,且增加了轮轨蠕滑率/力,是所调研地铁萌生2类疲劳的根本原因.更详细分析显示,线路R≤400 m的曲线全为左曲线的事实,导致左轮的踏面磨耗更大,形成的非对称磨耗进而使得车轮在通过半径较小的右曲线时,非导向轮对的左轮更易萌生上述2类疲劳.牵引力会加剧非对称磨耗,所以动车车轮的疲劳更严重.初步模拟显示,可以通过增加轮缘磨耗来治理上述2类疲劳损伤.