ZX—01镍磷合金化学镀工艺研究及应用

结合重型汽车典型令中件的特点，研究开发了一种性能优良的镍磷合金度工艺，采用正交试验法研究了镀液主要组分及主要工艺参数对镀层性能的影响规律，并对络合剂、缓冲剂和稳定剂进行了对比和筛选，优化最佳配方和工艺。该工艺操作简单，镀层综合性能优良，镀液稳定性好，寿命长，实际应用表明，ZX－01镍磷合金化学镀工艺完全可以用于生产，取代原来的电镀锌、电镀铬工艺。     

Carbody elastic vibrations of high-speed vehicles caused by bogie hunting instability

In particular locations of the high-speed track, the worn wheel profile matched up with the worn rail profile will lead to an extremely high-conicity wheel–rail contact. Consequently, the bogie hunting instability arises, which further results in the so-called carbody shaking phenomenon. In this paper, the carbody elastic vibrations of a high-speed vehicle in service are firstly introduced. Modal tests are conducted to identity the elastic modes of the carbody. The ride comfort and running safety indices for the tested vehicle are evaluated. The rigid–flexible coupling dynamic model for the high-speed passenger car is then developed by using the FE and MBS coupling approach. The rail profiles in those particular locations are measured and further integrated into the simulation model to reproduce the bogie hunting and carbody elastic vibrations. The effects of wheel and rail wear on the vehicle system response, e.g. wheelset bifurcation graph and carbody vibrations, are studied. Two improvement measures, including the wheel profile modification and rail grinding, are proposed to provide possible solutions. It is found that the wheel–rail contact conicity can be lowered by decreasing wheel flange thickness or grinding rail corner, which is expected to improve the bogie hunting stability under worn rail and worn wheel conditions. The carbody elastic vibrations caused by bogie hunting instability can be further restrained.     

Further study on the wheel–rail impact response induced by a single wheel flat: the coupling effect of strain rate and thermal stress

A comprehensive dynamic finite-element simulation method was proposed to study the wheel–rail impact response induced by a single wheel flat based on a 3-D rolling contact model, where the influences of the structural inertia, strain rate effect of wheel–rail materials and thermal stress due to the wheel–rail sliding friction were considered. Four different initial conditions (i.e. pure mechanical loading plus rate-independent, pure mechanical loading plus rate-dependent, thermo-mechanical loading plus rate-independent, and thermo-mechanical loading plus rate-dependent) were involved into explore the corresponding impact responses in term of the vertical impact force, von-Mises equivalent stress, equivalent plastic strain and shear stress. Influences of train speed, flat length and axle load on the flat-induced wheel–rail impact response were discussed, respectively. The results indicate that the maximum thermal stresses are occurred on the tread of the wheel and on the top surface of the middle rail; the strain rate hardening effect contributes to elevate the von-Mises equivalent stress and restrain the plastic deformation; and the initial thermal stress due to the sliding friction will aggravate the plastic deformation of wheel and rail. Besides, the wheel–rail impact responses (i.e. impact force, von-Mises equivalent stress, equivalent plastic strain, and XY shear stress) induced by a flat are sensitive to the train speed, flat length and axle load.     

车用增压直喷汽油机燃烧噪声试验研究

利用倒拖法对某车用涡轮增压缸内直喷汽油机空载加速和半载加速工况进行了燃烧噪声试验研究。联合发动机缸内燃气压力测试结果,通过分析气体动力载荷对其燃烧噪声的影响,进一步探讨燃烧噪声产生的根本原因。试验结果表明,在中低转速时,燃烧噪声随着发动机负荷的增加而增加,同时燃烧噪声对整机总声功率的贡献值也在随之增加。在较高转速时,燃烧噪声对整机总声功率的贡献值随着发动机负荷的增加变化不显著。就半载加速和空载加速工况时燃烧噪声的平均贡献值来看,空载加速时燃烧噪声对整机噪声的平均贡献值为22.2%,明显小于半载加速时的43.6%。随着发动机转速的提高,最大气缸压力及最大压力升高率总体变化趋势和燃烧噪声变化趋势一致,同时加速时最大气缸压力变化对燃烧噪声的影响更明显。     

大功率柴油机相继增压技术研究综述

随着大功率柴油机不断向高增压、高功率密度、宽转速范围以及低排放的方向发展,发动机与增压系统的匹配矛盾愈发突出,特别是在低速低负荷的工况范围内。而相继增压技术可使增压系统与发动机在较宽泛的运行范围内达到良好的匹配,被认为是改善高增压柴油机性能的最成熟的技术措施。因此,重点阐述了相继增压技术的工作原理、国内外的应用情况以及研究现状与发展趋势。     

基于直接刚度法的弹性地基深梁单元

为研究弹性地基深梁的受力及变形性能,根据双参数弹性地基模型和Timoshenko深梁模型的基本方程,建立了弹性地基深梁挠度控制方程,求得了挠度方程全解,并给出了弹性地基深梁梁轴转角、截面弯曲转角及剪切角的表达式;结合节点位移条件,得到了位移系数;根据节点力方程建立了刚度平衡方程,给出了弹性地基深梁的刚度矩阵方程及均布荷载的等效节点力向量。在此基础上,分别计算了均布荷载、跨中集中力、两端集中力、两端集中力矩等荷载工况下的节点位移,求得弹性地基深梁挠度曲线,验证了本文给出的刚度矩阵方程及等效节点力向量的合理性及适用性。     

大断面越江电力管廊隧道管片接头力学行为研究

为了探究盾构隧道管片接头力学性能,基于苏通GIL综合管廊隧道工程,采用有限元软件ANSYS建立用三维精细化数值模型对其接头力学参数和破坏过程进行计算和分析,并采用试验方法对接头力学行为进行分析,将试验结果与数值计算结果进行对比分析。结果表明:接头竖向位移、接头转角和接头抗弯刚度与接头内力关系曲线具有明显的分段线性或非线性特征,其中接头竖向位移和接头抗弯刚度与弯矩的关系曲线可以分为两段,接头转角与弯矩的关系曲线可以分为3段;轴力对管片接头的各项力学参数均有不同程度的影响;正弯矩接头的破坏始于外弧面混凝土压溃;试验得到的接头力学参数和数值计算结果均呈现出相同的变化规律,验证了数值计算的可信度。     

40t轴重68kg/m钢轨18号道岔设计

提出了适用于40 t轴重铁路18号道岔的设计原则与技术指标。新型重载铁路道岔采用68 kg/m钢轨制造,道岔全长69 m,前长31 729 mm,后长37 971 mm。平面线型采用相离量24 mm、半径1 100 m的单圆曲线,仿真分析显示该线型动力学性能良好,曲线尖轨具有较好的耐磨性能;尖轨采用60AT1钢轨制造,曲线尖轨为"直曲组合型",直线段长度7 276 mm,直曲尖轨采用刨切基本轨加厚尖轨技术。辙叉采用可动心轨辙叉,翼轨采用TY钢轨、心轨采用60AT1钢轨制造,直向不设护轨,侧向增设一段护轨,用于保护叉跟尖轨的薄弱断面;尖轨、长心轨、翼轨通过锻压与68 kg/m钢轨顺接。     

基于大客流的北京地铁网络化运营风险研究

客流冲击对北京地铁网络化运营安全的影响日益突出。通过统计分析北京地铁各线路日常运营的客流量数据,总结北京地铁运营网络的客流规律和大客流冲击地铁线网结构产生的运营风险特点。结合风险管理的相关理论,构建地铁网络化运营风险评价指标体系和多层次模糊综合评价模型。实证研究部分以北京地铁客流量较大的1号线为评价对象,计算该条线路上22个车站的风险值,风险值大小能够反映出不同站点对地铁网络化运营风险大小的影响程度。其中国贸站、大望路站风险值达到0.7以上(属于高风险),需要作为运营风险管理的关键站点,以期为今后进行地铁网络化运营关键站点风险管控研究提供参考思路。     

我国铁路货车技术标准的现状及发展建议

介绍目前我国铁路货车技术标准的现状,阐述存在的主要问题。与国外先进技术标准进行对比分析,提出今后我国铁路货车技术标准的发展建议。