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151.
J. De Arizon O. Verlinden P. Dehombreux 《Vehicle System Dynamics: International Journal of Vehicle Mechanics and Mobility》2007,45(9):849-866
One of the most important maintenance costs in tramway transport comes from wear of wheel profiles. In the highly competitive railway market, the prediction of wear is then a major concern of the constructors. In this article, we present and compare four models well adapted to tramway conditions, involving contacts on the rolling tread and on the flange with very different sliding and pressure conditions. Moreover, all models can be implemented from the natural outputs of the railway simulation packages classically used in industry for the dynamics design of the vehicles. The first one, proposed by Jendel, is based on the well-known Archard's wear model. Enblom continues Jendel's approach by taking into account the contribution of wheel deformation on the sliding velocity. The last two models, developed by Zobory, and Pearce and Sherratt, determine the wear from the energy dissipation in the contact area. The models are first compared on a theoretical basis and, for that purpose, are rewritten in a common form. Two cases are distinguished: mild wear as arising on the rolling tread and severe wear as arising on the flange. The models are also compared in the practical case of an urban transport vehicle running on circular tracks with different curve radii. Although the models show equivalent trends according to the theoretical study, important discrepancies appear between estimated wear depths. All models are actually dependent on experimental coefficients and it is likely that they were estimated in different conditions. On the other hand, a reasonable agreement can be found in some particular conditions. As an example, Zobory's, Enblom's and Jendel's models are very close to each other in severe wear conditions. This work shows that a general and reliable model could probably be developed from all positive aspects of the existing ones. 相似文献
152.
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154.
隧道用混凝土耐久性问题 总被引:2,自引:0,他引:2
隧道中混凝土常受到侵蚀性地下水的侵蚀面破坏,分析了侵蚀的原因和机理,提出了提高隧道混凝土耐久性的措施。 相似文献
155.
选用40例成人尸头标本,在手术显微镜下对鞍区周围结构进行了观察。为经额和经蝶两种垂体手术径路提供了有关解剖学依据。主要结果如下:1.视交叉位置,82.5%属正常型,7.5%属后置型,均为经额径路的适应型。但前置型(10%)则不适应于经额径路施术;2.测量了两侧视神经颅内段内侧缘间距及夹角。间距及夹角越小,经额径路越难施行;3.两侧颈内动脉间距以平前床突平面处最窄;4.观察了各海绵间窦。出现率基底窦为100%,前间窦为75%,下间窦为40%后间窦为33.3%。在前、下间窦较大的个体施行经蝶径路可能出现困难。 相似文献
156.
碳纤维布加固钢筋混凝土梁挠度的一种计算方法 总被引:1,自引:0,他引:1
本文研究了碳纤维布加固性能,利用钢筋混凝土结构设计中的梁理论,推导并验算了粘贴碳纤维布加固钢筋混凝土梁挠度的计算公式方法,分析了影响碳纤维布加固钢筋混凝土梁挠度值大小的因素。 相似文献
157.
有软弱夹层岩体边坡的稳定性评价 总被引:11,自引:0,他引:11
对发育多个规则软弱夹层的岩体边坡稳定性评价方法进行了探讨。在塑性极限分析的基础上,采用机动位移法,提出可以用能量系数作为稳定性评价的标准,并推导了相应公式。通过川藏公路上一个典型滑坡实例的稳定性分析,与极限平衡法进行了对比,证明了本方法的可行性。 相似文献
158.
随着STCW 新公约的生效和实施,航海教育改革在世界范围展开。本文从航海教育模式和院校管理体制两个视角比较研究国内外航海教育的经验和特点,阐述中国航海教育改革的必要性和迫切性 相似文献
159.
Safety in density (SID) potentially explains the safety in numbers (SIN) phenomenon by positing that ‘the SIN effect can be reproduced simply through encouraging behaviour that leads to the formation of higher-density cyclist groups’. The study further explores this hypothesis using event-based exposure, queues and groups of road users. Using three different definitions of encounters between road users, these were manually counted at signalized intersections, and their relationship to traffic volume was assessed. Based only on the frontmost motor vehicle in a queue and one cyclist among the several passing in front of that vehicle, the results show a less than linear relationship between meetings and traffic volume. An increase in the number of cyclists entails a general increase in cyclists passing in front of each motor vehicle, and an increase in motor vehicles increases queue lengths. However, crash data from the Swedish accident database (STRADA) show that it is exceedingly rare for multiple cyclists to be injured in the same crash. Together with results from a crash-encounter model, this suggests that the SID hypothesis may help to explain SIN 相似文献
160.
D.?Savitski V.?IvanovEmail author B.?Shyrokau T.?Pütz J.?De?Smet J.?Theunissen 《International Journal of Automotive Technology》2016,17(2):327-338
Functions of anti-lock braking for full electric vehicles (EV) with individually controlled wheel drive can be realized through conventional brake system actuating friction brakes and regenerative brake system actuating electric motors. To analyze advantages and limitations of both variants of anti-lock braking systems (ABS), the presented study introduces results of experimental investigations obtained from proving ground tests of all-wheel drive EV. The brake performance is assessed for three different configurations: hydraulic ABS; regenerative ABS only on the front axle; blended hydraulic and regenerative ABS on the front axle and hydraulic ABS on the rear axle. The hydraulic ABS is based on a rule-based controller, and the continuous regenerative ABS uses the gain-scheduled proportional-integral direct slip control with feedforward and feedback control parts. The results of tests on low-friction road surface demonstrated that all the ABS configurations guarantee considerable reduction of the brake distance compared to the vehicle without ABS. In addition, braking manoeuvres with the regenerative ABS are characterized by accurate tracking of the reference wheel slip that results in less oscillatory time profile of the vehicle deceleration and, as consequence, in better driving comfort. The results of the presented experimental investigations can be used in the process of selection of ABS architecture for upcoming generations of full electric vehicles with individual wheel drive. 相似文献