颗粒增强铝基复合材料的差分扫描热分析

利用差分扫描分析研究了利用Ａｌ－ＴｉＯ２－Ｂ２Ｏ３系统制备Ａｌ２Ｏ３和ＴｉＢ２颗粒增强金属基复合材料的原位反应过程，用Ｘ射线衍射分析了反应过程中的相应，实验结果表明，在较低的扫描速率下，当ＴｉＯ２和Ｂ２Ｏ３的克分子比为１时，ＴｉＢ２和α－Ａｌ２Ｏ３在８００℃－９００℃之间形成，而加热和冷却过程中采用低扫描速率有利于揭示原位反应的细节，加入过量ＴｉＯ２和Ｂ２Ｏ３导致了钛或硼的铝化物在冷却过程中的析出     

空调硬卧车内人体热舒适性研究

针对目前空调硬卧车内气流分布不均匀,不同铺位的乘客对车厢内的热舒适感差别较大这一现状,采用计算流体动力学对空调硬卧车内流场和温度场进行了数值模拟,研究了空调硬卧车内空气流动速度和温度分布规律及热舒适评价指标PMV和人体吹风感指标PD分布状况。研究结果对于改变目前车厢内上、中、下铺气流分布不均的现状,改善车厢内人体热舒适环境提供了理论依据。     

FPSO船典型节点疲劳强度分析

本文对浮式生产储油轮(FPSO)肋骨框架局部结构的节点进行了疲劳强度分析和计算。使用通用的有限元分析软件——ANSYS，对一个典型的局部结构节点建立了计算模型并进行参数分析。该局部结构为舷侧纵桁与腹板的连接节点。大量的调查实践证明，此处是疲劳损伤的高发区。文中选取了挪威科技大学建立的一个试验模型作为参考依据，采用美国船级社的计算规范对局部结构的两个热点应力区的疲劳强度进行了估算，并将计算结果与试验模型的结果进行了比较。结果表明：合理的补板以及腹板开口的尺寸可以提高该局部结构的疲劳寿命；疲劳损伤的定义需要根据疲劳失效后果加以确定从而给出基于风险的最佳检测和维修计划。     

高速动力车转向架焊接构架优化设计

以高速动力车转向架焊接构架的质量为目标函数,以16Mn钢母材和焊缝的疲劳强度为约束条件,根据UIC615-4所规定的构架强度试验载荷,对高速动力车转向架焊接构架进行结构优化,提出了降低结构弯曲和扭转刚度的设计方法,以提高轻量化焊接构架的疲劳强度。优化方案构架的最大等效应力较原方案降低15.33%,结构刚度和应力分布趋于均匀,构架疲劳强度满足设计要求。     

冷芯盒法砂芯的高温力学性能

本研究发现了冷芯盒法砂芯的较特殊的高温强度变化规律:温度刚开始升高时,砂芯强度下降;温度上升到约200℃之后,强度又开始上升,而温度上升到约400℃之后,强度一直下降。在200℃下的试样与在常温和400℃下的试样相比,随着应变的增加,应力增加较慢,产生较小的形变后试样就破坏。预先在180℃下对砂芯进行热处理,可提高砂芯的高温承载能力。     

Influence of the track quality and of the properties of the wheel–rail rolling contact on vehicle dynamics

This work describes an analytical approach to determine what degree of accuracy is required in the definition of the rail vehicle models used for dynamic simulations. This way it would be possible to know in advance how the results of simulations may be altered due to the existence of errors in the creation of rolling stock models, whilst also identifying their critical parameters. This would make it possible to maximise the time available to enhance dynamic analysis and focus efforts on factors that are strictly necessary. In particular, the parameters related both to the track quality and to the rolling contact were considered in this study. With this aim, a sensitivity analysis was performed to assess their influence on the vehicle dynamic behaviour. To do this, 72 dynamic simulations were performed modifying, one at a time, the track quality, the wheel–rail friction coefficient and the equivalent conicity of both new and worn wheels. Three values were assigned to each parameter, and two wear states were considered for each type of wheel, one for new wheels and another one for reprofiled wheels. After processing the results of these simulations, it was concluded that all the parameters considered show very high influence, though the friction coefficient shows the highest influence. Therefore, it is recommended to undertake any future simulation job with measured track geometry and track irregularities, measured wheel profiles and normative values of the wheel–rail friction coefficient.     

高速机车牵引齿轮强度的试验研究

对美国和国产要车牵引齿轮进行了强度试验分析，认为只要适当优选材料和工艺，国产机车牵引齿轮要以取代美国的牵引齿轮。     

钢桥面板弧形切口疲劳裂纹切割修复与优化

对正交异性钢桥面板的弧形切口进行疲劳修复时，切割孔形的优劣决定了疲劳修复效果。以检查到较多弧形切口疲劳病害的钢桥面板为研究对象，采用有限元和结构力流法分析了弧形切口处应力集中的原因。结合4种修复方案对切割孔形的圆弧半径、直线长度和倾角进行参数优化，得到了切割孔形对峰值应力的影响规律。依托钢桥面板弧形切口疲劳裂纹切割、修复工程，选择切割前、后的弧形切口开展试验研究。采用试验车进行纵向和横向移动加载，测试了2片横隔板弧形切口断面和侧面的应力分布规律和轮载位置-应力变化关系，并采用修正名义应力法近似评估其疲劳寿命。研究结果表明：轮载产生的力流通过U肋以剪应力的形式传递给横隔板，力流扩散中遇到弧形切口的阻碍，导致切口处力流高度密集；弧形切口开孔尺寸宜小，开孔半径宜大，避免阻碍力流传递路径；弧形切口优化后，其峰值应力降低58.4%，考虑横向概率分布的等效应力降低55.2%；因增大弧形切口的开孔而削弱截面面积，导致横隔板的平均压应力稍有增大；基于有限元计算和试验测试的峰值应力进行疲劳寿命预测，修复前的疲劳寿命分别为3.8年和7.2年，修复后的寿命分别为58.5年和184.4年，说明此切割修复方法具有良好的加固效果。     

钢轨踏面斜裂纹伤损原因及对策的研究

广深准高速铁路全长139km。对准高速区段和非准高速区段曲线上钢轨进行探伤检查,发现在44个曲线,37km长的范围内存在踏面斜裂纹,斜裂纹主要发生在上下行上股钢轨,斜裂纹呈成段、非连续、跳跃式分布。踏面斜裂纹及断口的宏观形貌和理化检验与分析表明,踏面斜裂纹伤损属于滚动接触疲劳裂纹伤损类型。研究认为:钢轨性能、线路状况、车辆性能及运行速度、车轮踏面形状等是产生斜裂纹的主要原因。提高钢轨的接触疲劳强度,在曲线上使用微合金淬火钢轨,研究和改善轮轨接触方式,加强轨道的养护维修,合理地进行预防性打磨和校正性打磨是解决钢轨踏面斜裂纹伤损的主要措施。     

Fatigue of jack-ups: Simplifying calculations

Simplification of calculations for fatigue of jack-ups is essential in order to understand the primary influences and the uncertainties involved. Considerable simplification is possible for jack-ups because calculations for fatigue are dominated by the few worst loading conditions, while the large number of lesser conditions can be ignored. The dominating conditions are likely to be — during operations, the resonant sway and surge motions at the natural period of the structure; and during towage, the 1 or 2 days of maximum roll and pitch motions. Examples for both situations examine loading conditions and demonstrate simplified calculations.