车轮多边形磨耗统计规律及关键影响因素分析

针对列车车轮多边形磨耗问题广泛存在于轨道交通运输领域,会导致车辆/轨道系统产生高频的振动冲击,严重影响车辆和轨道系统零部件的使用寿命,危及行车安全这一问题,调查了大量车轮的多边形磨耗情况并进行统计分析,掌握了高速列车车轮多边形磨耗问题的现状和特点。以18～20阶多边形磨耗车辆为例,通过理论研究和试验分析(试验分析包括车辆系统振动特性测试和转向架模态特性测试),对车轮多边形磨耗的根本原因及诱导因素进行研究。研究发现,轮轨系统在580 Hz频率附近存在固有模态是导致车辆发生18～20阶多边形磨耗的根本原因,轮轨表面的各种不平顺能激发或者加剧轮轨系统在580 Hz频率附近的模态共振,从而诱发车轮多边形磨耗的产生。该结果可为高速列车车轮多边形磨耗问题的防止和进一步研究提供参考。     

Experimental investigation on the plasma morphology of ablative pulsed plasma thruster with tongue-shaped and flared electrodes

Ablative pulsed plasma thrusters(APPTs) are considered as an attractive propulsion option for station-keeping and drag makeup purposes for mass-and power-limited satellites. In order to understand the physical mechanism of APPTs, high-speed camera and optical emission spectroscopy are utilized to investigate the plasma characteristics including the spatial distribution and composition between the electrodes. The plume images and spectra at different times and positions are experimentally recorded, and the spatial distribution, composition, and trajectory of plasmas can be concluded through analyzing them. With the increase of the distance from the ablation surface, two clusters of plasmas near the anode and cathode meet downstream,and the species and density of plasmas tend to be uniform.     

列车贮藏方式对生猪肉原料新鲜度的影响研究

探究夏季高温期某铁路局集团公司旅客列车贮藏条件下生猪肉原料的品质变化,为改善餐车生猪肉保存及取用方式、保障旅客列车食品安全提供可靠依据。在实验室条件下模拟该列车餐车实际条件下生猪肉贮藏及取用方式:将生猪肉分别在4℃(冷藏)和-10℃(冷冻)两种条件下贮藏,再解冻,使用,再贮藏。通过猪肉的色泽、气味、组织状态感官指标以及挥发性盐基氮(TVB-N)、硫化氢、球蛋白沉淀理化指标的变化为依据,来评价猪肉的新鲜度。结果表明:夏季高温期间,该铁路局集团公司列车生猪肉原料,在4℃冷藏贮存条件下,有2d保质期,在-10℃冷冻贮藏条件下,10d内猪肉品质能够保持新鲜,满足铁路运输的时限要求。该铁路公司列车贮藏和使用生猪肉符合规范,用肉时限在保质期范围内,能够保证全年时段肉质新鲜安全。为保障铁路旅客的食品安全,生猪肉原料应贮存在制冷效果良好的冷冻冰箱内,取用肉类置于冷藏保存的,应在2d内使用完毕。     

基于S变换的高速列车小幅蛇行识别方法

针对现有的高速列车监测方法没有考虑高速列车振动信号的非平稳特性,从而使得列车出现蛇形失稳现象的问题，提出一种采用S变换的方法对高速列车转向架信号进行处理，进而提取高速列车运行特征。采用最小二乘支持向量机（LS-SVM）对特征进行训练和识别，结果证明，基于S变换的特征提取方法的识别准确率达到了100%，优于基于小波变换的特征提取方法，从而可以及时预测高速列车的运行状态，保障列车的运行安全。     

Wear and Tribological Performance of Different Ceramic Tools in Dry High Speed Machining of Ni-Co-Cr Precipitation Hardenable Aerospace Superalloy

Tool wear is an important machinability criterion. To reduce total machining costs, this study demonstrates the wear and tribological performance of four ceramic tools in dry high-speed turning of Ni-Co-Cr precipitation hardenable superalloy (Inconel 100). Wear of the tool materials and the structural and phase transformations at the tool–chip interface were investigated. Results obtained reveal that SiAlON ceramic outperformed other ceramic tool materials at different cutting speeds due to the formation of a large amount of mullite tribofilms on the tool face, which serve as a thermal barrier layer. Alumina ceramic with the addition of ZrO₂ can be recommended for machining Inconel 100 at speeds above 150 m/min due to its ability to form thermal barrier ZrO₂ tribofilms, which decrease the coefficient of friction at the tool–chip interface. Mixed alumina and an alumina matrix reinforced with SiC_w were found to be unsuitable for machining age-hardened Inconel 100 superalloy.     

高铁土建工程质量安全治理探讨

为进一步提升高铁土建工程源头质量安全治理能力,本文通过对高铁土建工程质量安全治理现状和源头质量隐患进行系统梳理,按照从宏观到微观、从前到后的原则依次从标准规范、工程建设及政府监管层面展开分析,针对性提出了标准规范、质量管控、人员素质、技术保障、信用体系五方面的治理措施。文中创造性提出从标准规范层面和质量安全信用体系构建的治理建议。     

接触器触头系统振动机理分析及算法优化

为了解决合闸过程中动、静触头接触引起的振动弹跳问题.本文建立了接触系统的二自由度运动微分方程,并利用遗传算法对交流接触器吸合过程进行优化,同时通过高速摄影实验对接触弹跳的全过程进行了观察和分析.结果表明:理论与实验结果高度一致,铁心在触头分离前发生碰撞,进一步加剧触头弹跳;铁芯弹跳再次碰撞时,触头的弹跳不受影响;在接触器运行过程中,动铁芯的运动会引起系统轻微振动;采用遗传算法优化的接触器触头弹跳时间和最大振幅均减小.研究结果为进一步控制和减小接触弹跳提供了理论依据.     

Electric characteristic and cavitation bubble dynamics using underwater pulsed discharge

Underwater pulsed discharge is widely applied in medicine, machining, and material modification. The induced cavitation bubble and subsequent cavitation collapse are considered the major motivations behind these applications. This paper presents an underwater pulsed discharge system. The experimental setup is established to induce and investigate the cavitation bubble assisted with a high-speed camera. Three aspects, including the characteristic of the discharge with different applied voltages and conductivities, the evolution of the cavitation bubble profile, and the energy efficiency of cavitation bubble inducing, are investigated, respectively. Especially, the mechanism of pre-discharge time delay in the low field intensity case is explained using the Joule heat effect. The results show the validity of the underwater pulsed discharger and experimental setup. The present underwater pulsed discharger is proved to be a simple, portable, and easy-to-implement device for the investigation of cavitation bubble dynamics.     

槽波地震勘探技术在瓦斯富集区探测中的应用研究

为查清糯东煤矿11705工作面内部煤厚变化，并圈出工作面瓦斯治理高风险区域，为工作面安全高效生产提供指导，采用槽波地震透射法对11705工作面进行探测。联合槽波速度解释与能量解释两种方法，辨析透射槽波的质量，将质量差的槽波射线分别绘制在平面图上，采用射线交汇的方法划分工作面的开采风险分布区域。探测成果与实验室中解吸法的瓦斯测定成果进行了对比，结果表明，煤与瓦斯突出矿井槽波速度与瓦斯富集区存在一定相关性，在槽波高速区、波速急剧变化带或高低速相间分布区，瓦斯含量可能较高；被四周高速区所包围的低速区域瓦斯含量较高。上述结论为国内同类型矿井瓦斯富集区探测提供了借鉴。