跨座式单轨列车走行轮轮胎的不均匀磨损

为了优化跨座式单轨列车走行轮轮胎不均匀磨损性能，在运行工况分析基础上建立了走行轮轮胎有限元模型；结合走行轮磨损特性评价指标，建立了一套新的走行轮磨损间接评价方法，该方法以侧偏角和侧倾角为设计变量，通过探索走行轮轮胎侧偏角、侧倾角及其组合对走行轮轮胎磨损与不均匀磨损的影响对车辆二系悬挂参数进行优化，减轻走行轮轮胎磨损. 研究结果表明:优选前，转向架（以前转向架为例）中前、后排走行轮轮胎侧偏角分别为0.5°、0.3°、?0.4°、?0.2°；优选后，转向架中前、后走行轮轮胎侧偏角为0.2°、0.2°、?0.2°、?0.2°；车辆结构参数中二系悬挂横向刚度、垂向刚度对走行轮各轮胎不均匀磨损的影响较大，且选取合适的参数值在一定程度上能够减轻走行轮各轮胎不均匀磨损.      

我国城市轨道交通网络运营盈利能力的实证分析

为从财务可持续性角度探讨城市轨道交通网络盈亏平衡问题，本文建立了以票款净收入和运营成本为基础的网络运营盈亏平衡模型，定量分析票价率、客运强度、票价优惠策略等要素对运营企业盈利能力的影响。实证研究表明：我国不同城市票价率水平差异较大，多数城市体验了初期线网扩张带来的网络化运营红利；但随着网络进一步扩大到市区边缘或郊区，多数城市网络总规模超过300 km后，全网平均客流强度呈下降态势，企业盈利能力有所下降，政府补贴压力增加。由于城市轨道交通在解决通勤出行中的公益性定位，以及不同城市居民人均可支配收入水平和城市政府财政收入的差异，应进一步研究不同城市经济发展水平下票价水平、线网规模及技术制式、不同线路功能定位的关系，以提高轨道交通网络运营盈利能力，促进我国城市轨道交通行业的可持续发展。     

原太高速K706+547小桥加固设计

该小桥桥台发生整体沉降,通过对其成因进行了详细分析,并据此提出了两个加固方案,通过比较优缺点最终选用方案一为推荐方案;最后对加固后桥梁的承载能力进行了计算分析,确定该桥主梁的承载能力满足规范要求,显示该加固方案比较合理。     

120km/h地铁列车受电弓肘接部裂纹分析与改进

针对120 km/h地铁列车在运营过程中多次出现受电弓上框架肘接部位裂纹的现象,分析其故障原因,提出采用管对管焊接处加入加强筋板的改进方案。通过力学分析以及实践运用,验证了改进方案的有效性。     

路面基层级配碎石试验检测控制探讨

材料是构成公路建筑的核心要素,施工单位制定公路建造方案需考虑混合料的选用,通过材料试验判断其是否适用于公路建造。鉴于此,分析路面基层级配碎石试验检测的相关问题,并根据试验结果提出施工改良方案。     

Effects of Injection Timing on Transient Performance of A Regulated Two-Stage Turbocharged Diesel Engine with Turbine Bypass Valve

The object of this paper is to reduce soot emissions under typical 5s transient conditions of constant speed and increasing torque. And effects of fuel injection timing on combustion and emissions parameters were experimentally and numerically studied in a regulated two-stage turbocharged diesel engine with a turbine bypass valve (TBV). The test results indicated that: the smaller TBV opening could improve deterioration of smoke emissions and BSFC at medium and heavy loads. Afterward, the full-stage injection timing (FSIT) strategies (delaying injection timing during the entire transient process) could reduce soot and NO_X emissions simultaneously. However, when TBV opening became larger, smoke emissions and BSFC were deteriorated gradually. Moreover, the sectional-stage injection timing (SSIT) strategies (advancing injection timing from 10 % load to a preset load and delaying injection timing from the preset load to 100 % load) could markedly reduce soot emissions by 75.8 % with TBV opening 20 %; the degradation of fuel consumption could be effectively suppressed. Finally, coupling the SSIT strategies with the TBV control strategies could significantly improve the transient performance.     

High-frequency random vibration analysis of a high-speed vehicle–track system with the frequency-dependent dynamic properties of rail pads using a hybrid SEM–SM method

A hybrid Spectral Element Method (SEM)–Symplectic Method(SM) method for high-efficiency computation of the high-frequency random vibrations of a high-speed vehicle–track system with the frequency-dependent dynamic properties of rail pads is presented. First, the Williams-Landel-Ferry (WLF) formula and Fractional Derivative Zener (FDZ) model were, respectively, applied for prediction and representation of the frequency-dependent dynamic properties of Vossloh 300 rail pads frequently used in China's high-speed railway. Then, the proposed hybrid SEM–SM method was used to investigate the influence of the frequency-dependent dynamic performance of Vossloh 300 rail pads on the high-frequency random vibrations of high-speed vehicle–track systems at various train speeds or different levels of rail surface roughness. The experimental results indicate that the storage stiffness and loss factors of Vossloh 300 rail pad increase with the decrease in dynamic loads or the increase in preloads within 0.1–10,000?Hz at 20°C, and basically linearly increase with frequency in a logarithmic coordinate system. The results computed by the hybrid SEM–SM method demonstrate that the frequency-dependent viscous damping of Vossloh 300 rail pads, compared with its constant viscous damping and frequency-dependent stiffness, has a much more conspicuous influence on the medium-frequency (i.e. 20–63?Hz) random vibrations of car bodies and rail fasteners, and on the mid- (i.e. 20–63?Hz) and high-frequency (i.e. 630–1250?Hz) random vibrations of bogies, wheels and rails, especially with the increase in train speeds or the deterioration of rail surface roughness. The two sensitive frequency bands can also be validated by frequency response function (FRF) analysis of the proposed infinite rail–fastener model. The mid and high frequencies influenced by the frequency-dependent viscous damping of rail pads are exactly the dominant frequencies of ground vibration acceleration and wheel rolling noise caused by high-speed railways, respectively. Even though the existing time-domain (or frequency-domain) finite track models associated with the time-domain (or frequency-domain) fractional derivative viscoelastic (FDV) models of rail pads can also be used to reach the same conclusions, the hybrid SEM–SM method in which only one element is required to compute the high-order vibration modes of infinite rail is more appropriate for high-efficiency analysis of the high-frequency random vibrations of high-speed vehicle–track systems.