高速列车半主动悬挂可变刚度和阻尼减振器适应性研究

针对中国高速列车运行速度高、运营里程长、轮轨磨耗加剧,被动悬挂式抗蛇行减振器适应性较差,导致转向架抗蛇行稳定性能不足的情况,开展半主动悬挂抗蛇行减振器研究。首先,基于高速列车悬挂系统非线性和轮轨接触非线性特征,建立了高速列车模型、磁流变阻尼器模型、可变刚度和阻尼抗蛇行减振器模型;然后分析了抗蛇行刚度和阻尼参数对新轮轨和磨耗轮轨的车辆动力学性能的影响,并针对磨耗轮轨接触提出了半主动悬挂控制策略;最后,对比分析了被动悬挂和半主动悬挂车辆运行性能的差异。结果表明:通过采用半主动悬挂调整抗蛇行减振器的刚度和阻尼参数可大幅改善磨耗轮轨接触的车辆运行性能,保证构架不发生蛇行失稳,与采用被动悬挂抗蛇行减振器的车辆相比,车体横向加速度和构架横向加速度分别降低22.4%和16.0%。     

基于可变刚度抗蛇行减振器的车辆动力学性能研究

CRH3系列高速动车组在长期服役过程中偶有发生蛇行运动稳定性裕量不足的问题,车辆装配T60型抗蛇行减振器,在车轮磨耗末期易发生构架横向加速度报警问题,装配T70型抗蛇行减振器,则在新轮或车轮磨耗初期易发生“晃车”的问题。针对晃车和报警问题开展可变刚度抗蛇行减振器的仿真与试验研究,以满足车辆在不同轮轨接触状态下车辆的蛇行运动稳定性需求。动力学仿真表明,可变刚度抗蛇行减振器能有效兼顾解决“晃车”和“报警”问题;进一步分析可变刚度抗蛇行减振器与两种高速踏面的适应性,采用S1002CN踏面时车辆临界速度高于350 km/h,而采用LMB10踏面时仅为220 km/h,且S1002CN踏面对应的平稳性和舒适度指标都优于LMB10踏面。最后通过整车滚振台架试验对变刚度抗蛇行减振器性能进行了试验验证,结果表明该减振器可以兼顾轮轨低锥度和高锥度匹配状态,可使车辆均具有良好的动力学性能。     

高速动车组抗蛇行减振器参数优化研究

蛇行运动是轨道车辆的固有属性,随着高速铁路的发展,高速动车组稳定性问题越来越突出,抗蛇行减振器对于车辆稳定性具有重要影响,通过优化抗蛇行减振器参数可以有效提升高速动车组运行性能。本文建立高速动车组车辆动力学模型,利用超拉丁采样选取减振器设计参数,并采用 KSM 模型进行动力学响应分析,最后采用 NS?GA?Ⅱ算法对抗蛇行减振器参数进行优化,并对优化前后的动车组动力学性能进行对比。结果表明：优化后参数下,XP55 标准车轮临界速度提高 15.28%,达到 463.8 km/h, XP55 磨耗车轮临界速度提高 13.71%。优化后参数进一步提升了车体的平稳性和舒适度,轮轴横向力减小。同时优化后参数降低了新轮工况和磨耗车轮工况下的车体和转向架横向加速度幅值,抑制了车辆横向振动。分析了减振器参数优化对接触点位置和车轮磨耗指数的影响,优化后参数减小了车轮横向接触点横移,速度为 250 km/h 时,XP55 标准车轮磨耗指数减小 14.65%,XP55 磨耗车轮磨耗指数减小 15.8%。因此,抗蛇行减振器参数优化后可以有效提高车辆稳定性和运行性能。     

高铁车辆横向振动耦合机制及其减振技术对策

结合欧系车辆转向架技术创新特点,提出一种基于刚柔耦合仿真技术的车下质量橡胶吊挂优化设计方法。横向振动耦合机制是指以二系横向悬挂构成车体对走行部接口传递媒介的横向高频振动耦合机制,且具有抗蛇行高频阻抗、车体摇头大阻尼和"无纵梁无骨架"铝合金车体3大特殊性。因而整装车体下部1阶横向弯曲模态振动将对车体技术服役寿命30年造成十分严重的负面影响。对于车下质量橡胶吊挂来讲,比例阻尼是抑制车下质量横向振动的积极因素之一,而对中部地板横向加速度则具有极值特征,即比例阻尼取0.5%,其全频域(RMS)3σ最小。也应当注意到上述减振技术的局限性,即在走行部非常工况下,较大的车下质量存在横向耦合振动的可能性,进而造成自重楔紧失效。     

高速列车抗蛇行减振器作用机制与频变刚度应用研究EI北大核心CSCD

为了研究高速列车抗蛇行减振器作用机制进而对最优减振器参数选配提供理论指导,分析了减振器的频变特性和最优能量耗散条件,基于两类典型高速列车横向动力学模型对抗蛇行减振器参数进行多目标优化,及整车线性稳定性和模态能量分析,总结了抗蛇行减振器作用机制。得出结论如下:抗蛇行减振器不仅其阻尼对车辆蛇行能量起耗散作用,其刚度特性对车辆横向稳定性的影响更为显著,减振器刚度需随蛇行频率增加而增大;利用车体与转向架蛇行模态能量占比及其牵连作用说明抗蛇行减振器等效刚度作用机制,并根据最优能量耗散理论实现抗蛇行减振器串联刚度与阻尼的匹配。提出了应用频变刚度抗蛇行减振器的思路和结构方案,针对频变刚度曲线进行优化和车辆横向稳定性分析,结果表明,采用频变刚度抗蛇行减振器可显著改善极端轮轨接触状态下车辆横向稳定性,降低高速列车出现低频晃车和高频抖车现象的风险,对实现不同车轮踏面磨耗阶段车辆自适应稳定性起到积极作用。     

面向车辆平稳性的抗蛇行减振器结构参数多目标优化

高速动车组在运营过程中依赖抗蛇行减振器维持车体横向振动的平稳性,为提高不同工况下车辆运行平稳性,需要对抗蛇行减振器结构参数进行多目标优化.首先建立包含抗蛇行减振器液压数值模型与CRH3车辆动力学模型的UM-SIMULINK联合仿真模型,分析抗蛇行减振器结构参数对车辆平稳性的影响,随后基于车轮磨耗对轮轨接触几何的影响设计...     

服役条件下提速地铁车辆的横向运动稳定性研究EI北大核心CSCD

地铁提速是未来轨道交通发展的必然趋势,服役条件下的车轮磨损会导致车轮半径减小和等效锥度增大,容易造成车辆蛇行失稳。为了保持服役条件下提速地铁车辆的横向运动稳定性,通过调研获取了上海某线路地铁车辆的车轮磨损情况,建立了含抗蛇行减振器的地铁横向动力学模型,研究了车轮磨损对于地铁车辆横向运动稳定性的影响,对比服役条件下有无抗蛇行减振器的车辆临界速度,指明了安装抗蛇行减振器对于服役地铁提速的必要性。结果表明,服役条件下的地铁车辆车轮半径减小以及等效锥度增大会降低车辆的临界速度,增大蛇行运动幅值。通过安装抗蛇行减振器,能有效地解决地铁车辆车轮磨损以及提速带来的横向运动稳定性裕量不足的问题,同时也能避免地铁车辆在异常参数匹配下发生一次蛇行运动。论文工作对探究服役地铁车辆进一步提速以及车轮和钢轨的维护保养具有一定的参考价值。     

高速动车电机架悬参数对转向架动力学性能影响研究

为研究电机架悬参数对转向架动力学性能的影响,建立了等效到单轮对的2自由度横向简化模型和8自由度单转向架横向动力学模型,分析了在轮对横向激振下、在不同电机悬挂参数下,构架横移和电机相对构架横移的变化规律,最后研究了电机架悬参数对转向架稳定性的影响。计算结果表明:当电机横移频率接近且略小于转向架蛇行频率时,构架横移最小,线性临界速度最大,但是此时电机相对构架横移很大,此时电机相当于一个动力吸振器,把构架的振动转移到电机上来。电机横移阻尼比越小,构架横移越小,线性临界速度越高,但是电机相对构架横移越大。为了兼顾两者,电机横移阻尼可以适当取大一点。     

高铁运用经济速度与安全稳定裕度调控

高速晃车问题解决后京沪高铁安全运用已有1年多时间了。作为这次调控的跟踪研究,通过动态仿真、线路试验和构架动荷特征等多方面综合分析,可以确认抗蛇行软约束技术优越性,这是在中国高铁运用中首次自主进行安全稳定裕度调控的成功案例。面对高铁网络运用还必须认清目前存在的2个基本稳定问题：即转向架稳定裕度不充裕问题和高速列车稳定鲁棒性问题。这些稳定问题应当给予充分重视,因为功能元件性能持续稳定和结构部件疲劳安全是高铁网络运用的重要安全保障。转向架优配及其相应的经济速度是解决上述稳定问题的非常有效技术途径,其也体现了新一代高速转向架的3大稳定特征：即适度拓展速度空间系统优化构架动荷、有效抑制有害踏面磨耗的负面影响和更加强调高速列车稳定鲁棒性。     

城际列车晃车机理试验研究

针对某在线运营的城际列车的晃车现象,实测整车不同位置处的振动信号,对比分析在晃车与非晃车时间段内车辆的运行平稳性、时频特征以及车辆不同部位的信号相干特征,据此初步了解车辆在晃车时的典型特征;进而基于ODS分析理论,掌握车辆晃动时的整体振动情况,并基于构架稳定性分析结果,发现并验证城际列车晃车的机理。结果表明,发生晃车时,车辆横向平稳性指标大于2.5,晃车主频在4 Hz左右,相干性分析表明车体晃动与转向架振动有直接关系;基于ODS分析结果发现晃车时转向架蛇行与车体摇头反相耦合,此时转向架的蛇行稳定性不足,该蛇行频率与基于实测轮轨匹配等效锥度所得的理论计算频率基本一致,因此车辆系统稳定性裕量不足,转向架在较高运行速度工况下接近蛇行失稳状态是晃车的主要原因。     

Observation of glass transition upon cooling in Pd40Ni10Cu30P20 alloy by DSC

Two-stage cooling experiments were carried out in a differential scanning calorimeter for an untreated bulk amorphous alloy Pd₄₀Ni₁₀Cu₃₀P₂₀. The results showed that the critical cooling rate for glass formation for the alloy was about 50 K/min. The continuous cooling transformation (CCT) curve was constructed based on the cooling experimental results and the critical cooling rate for glass formation subsequently calculated is in excellent agreement. The present results are compared with previous reported results and effects on the critical cooling rate for glass formation are discussed.     

公路工程路堤临界填土高度一种计算方法研究

路堤临界填土高度是公路工程中一个非常重要的问题,填筑高度小于临界填土高度时,地基的变形和稳定能得到控制。依据极坐标表示的弗拉曼公式和统一强度理论,考虑中间主应力σ₂对地基承载力的影响,推导出土的静止侧压力系数K₀≠1条件下地基的临塑与临界荷载公式,提出路堤临界填土高度一种计算方法。结合算例,对中间主剪应力系数b和土的静止侧压力系数K₀取不同值时,临界荷载与路堤临界填土高度计算结果进行了对比分析,结果表明:基于统一强度理论得到的计算方法能确切地反映地基承载力的实质,使地基土体强度得到充分的发挥。     

Mechanical tests on the surface-coated Bi-2212 superconducting tapes

The strain dependence of the critical current of surface-coated Bi-2212 tapes is reported. Two methods are used in the measurements. The effect of bend strain on the critical current is obtained by a stepped cone apparatus. Peak stress or strain dependence of the critical current and the effect of the number of strain cycles on the critical current is also studied on multiple samples by employing a new in situ stress/strain device. The results show that the number of strain cycles does not significantly affect the critical current. Rather, the critical current of the tape depends only on the level of peak strain.     

纳米Al2O3对HMX临界起爆压力的影响

采用锰铜测压法和小隔板实验（SSGT）测试了纳米Al2O3对HMX临界起爆压力影响,对纳米Al2O3在混合炸药中的作用机理进行了探讨,混合炸药的配比HMX／纳米Al2O3为98 ：2,密度为90％理论密度。结果表明,与纯HMX相比,纳米Al2O3的间充作用使混合炸药的临界起爆压力升高,冲击波感度明显降低,并给出了HMX／纳米Al2O3（98 ：2）的临界起爆压力。     

Spare parts failure prediction of an automobile under criticality condition

Many studies on spare parts planning classified items based on the levels of importance using conventional approaches. Classification of spare parts based on the stated approach without considering failure value and/or its consequence may not withstand the test of time due to continuing technological advancement or environmental degradation. This study solved the stated problem by developing a system that is capable of dynamically determining critical equipment/spare parts based on failure rates using ABC analysis. In this analysis, all operable items were considered to be non-critical and they became critical when they approached failure time. These transitions were prompted by items’ failure conditional probability within the limits of 1, 2/3, 1/3 for highly critical, critical and less critical items, respectively. The most critical item(s) (A class) with highest failure value/consequence were sorted out based on specificity (one manufacturer’s item) and generality (many manufacturers’ item). Failure remedy was achieved by applying modified classical inventory model which considered heterogeneity in item failure. The stated conditions were integrated into a time series, linear regression model. The performance evaluation results showed that the new scheme was efficient in spare part failure criticality classification, consequence analysis and remedy. The practical implication of the findings indicated that the developed system could serve as a suitable alternative to the static classification style of the conventional approach in term of cost savings.     

Detecting and describing the inhomogeneity of critical current in practical long HTS tapes using contact-free method

The nondestructive and contact-free apparatus for measuring local critical current of long high temperature superconducting (HTS) tapes is presented. The local critical current of tape is acquired by using Hall probe array sensor to measure the remanent field after exposed to dc external magnetic field since the critical current is proportional to remanent field based on Bean critical state model. A detailed experiment on multifilamentary Bi2223/Ag tape is made to validate reproducibility, reliability, resolution, nondestructiveness and usefulness for manufacturer and user of tapes. The parameter COV (coefficient of critical current variation) is suggested for quantitatively describing the inhomogeneity and quality of practical long HTS tape based on Gaussian statistical analysis. The developed apparatus can detect HTS tape at velocity of 100 m/h with resolution smaller than 3 mm in liquid nitrogen.     

Kritische Einflußgrössen für die Spannungsrißkorrosion von 18Cr10Ni-Stahl in Chloridlösungen und Hochtemperaturwasser

Critical Values of Influencing Parameters for the Stress Corrosion Cracking Behaviour of 18 Cr 10 Ni Austenitic Stainless Steels in Chloride Solutions and in High Temperature Aqueous Environments. In the Critical systems “material/corrosive environment” stress corrosion cracking can only occur when the stress exceeds a critical value (“classical” systems of SCC) or the strain rate lies within a critical range (“non-classical” systems of SCC). The terms “classical” and “non-classical” refer to the test methods used to investigate SCC phenomena. Furthermore, some system parameters must exceed certain critical values to cause SCC. Such system parameters are mainly the electrode potential, temperature, and the concentration of specific corrosive species present in the environment. With the critical systems “austenitic chromium-nickel-steel/aqueous chloride solution” the crack path is exclusively transgranular provided the material is properly solution annealed and free from harmful precipitations. The current knowledge about critical values of system parameters is outlined. Above all, it is shown by open circuit experiments that with the critical system “304 SS/boiling 42 MgCl₂”, a threshold stress for SCC exists at very low stress levels of about 50 N/mm². This low threshold stress can only be found when residual compressive or tensile stresses are completely avoided in the uniaxially loaded tensile test specimens used for the experiments. In isothermal exposure tests using U-bend specimens and involving a triple phase boundary 304 SS/aggressive environment (CaCl₂ solutions of various concentrations)/air, a critical temperature was found below which no SCC occurs. The critical temperature does not depend on the chloride concentration over a broad range between 1 and 100 g/l chloride ions and is between 40 and 45°C. This critical temperature is somewhat lower than that found with ground flat specimens in diluted NaCl solution (0.1 g/l chloride ions). The system parameters potential and temperature influence each other, and their critical values depend furthermore on the chemical composition, i.e. on the chemical resistant properties the steels tested. In high temperature, high pressure aqueous environments (250 to 300°C), SCC with transgranular or intergranular crack path occurs in the solution annealed and/or sensitized condition of the steel. In the sensitized material, ISCC takes place at strain levels exceeding the hot yield strength at the operating temperature and above a critical electrode potential. Hence the oxygen content of the environment has a decisive effect on the ocurrence of ISCC in sensitized 304 SS.     

短纤维橡胶复合材料临界长径比数学模型研究

概述了短纤维复合材料临界长径比数学模型的研究进展, 基于短纤维橡胶基复合材料的结构-应力传递特点和Cox 剪滞法推导了其临界长径比数学模式, 并由此进行了讨论。结果表明,推导的模型能够较好地适合短纤维橡胶复合材料的特性, 与以往的模型相比, 它能全面地反映结构因素对复合材料中短纤维临界长径比的影响。     

Experimental Investigations on the Critical Current of the Jointed Bi-2223/Ag HTS Tapes

This paper summarizes the experimental investigations on the critical current of two jointed Bi-2223/Ag superconducting tapes connected by Sn63Ag2Pb solder. Different lap lengths of contact surface were studied. The joint resistance was measured to be in the range of 0.059??0.76????, and the critical current of the jointed Bi-2223/Ag HTS tapes was measured with different charging rates using standard four-point-method in a zero-applied magnetic field applying 1 ??V/cm criterion. The experimental results showed that the longer the lap length was, the smaller the joint resistance was and the nearer the critical current approached that of Bi-2223/Ag superconducting short-sample. On the other hand, the critical current decreased with the increasing of the charging rate.     

碳纳米管增强型功能梯度板的屈曲预测

基于一种新的修正偶应力理论,建立了碳纳米管（CNTs）增强型功能梯度板（CNTs/FGP）的屈曲模型。基于最小势能原理和一阶剪切变形理论,推导了该种板模型的平衡微分方程和相应的边界条件,并以四边简支方板的屈曲问题为例,讨论了材料尺度参数、CNTs的体积分数及4种不同CNTs分布形式对CNTs/FGP临界屈曲载荷的影响。结果表明：采用本文模型预测的CNTs/FGP的临界屈曲载荷总是大于传统宏观理论的预测结果,两种理论结果间的差距随着板几何尺寸的减小而逐渐增大;CNTs体积分数的少量增加,即可使板的临界屈曲载荷有明显的提升;CNTs的不同分布形式对临界屈曲载荷有显著的影响,在工程设计中应予以关注。