Dynamic Train-Track Interaction: Variability Attributable to Scatter in the Track Properties

A numerical method to simulate vertical dynamic interaction between a rolling train and a railway track has been used to investigate the influence of stochastic properties of the track structure. A perturbation technique has been used to investigate the influence of the scatter in selected track properties. The train-track interaction problem has been numerically solved by use of an extended state-space vector approach in conjunction with a complex modal superposition for the whole track structure. All numerical simulations have been carried out in the time-domain with a moving mass model. Properties such as rail pad stiffness, ballast stiffness, dynamic ballast-subgrade mass and sleeper spacing have been studied. To obtain sufficient statistical information from track structures, full-scale measurements in the field and laboratory measurements have been carried out. The influence of scatter in the track properties on the maximum contact force between the rail and the wheel, the maximum magnitude of the vertical wheelset acceleration, and the maximum sleeper displacement have been studied. Mean values and standard deviations of these quantities have been calculated. The effects of the variation of the investigated track properties are discussed.     

面向现代造船条件的船体类模块分段定义

为了使造船企业走出靠简单扩大再生产提高生产效率的误区,提出船体类模块分段的概念,以模块制造理论为基础,以模块化制造思想为指导,在不改变现有非标准船舶的船体结构和非标准生产能力配置的前提下,对船体分段进行几何结构和制造工艺等方面的相似性分析,确定船体类模块分段标准。     

船舶水平纵向浮船坞下水分析

通过采用有限元法求解船舶下水过程中的墩木反力变化过程,进而得出浮船坞压载水调节方案。为了进一步检验该模型的可靠性,根据计算模型编写计算程序对50000吨级散货船的水平纵向浮船坞下水过程进行计算模拟,实际结果表明该模型能满足船舶水平纵向浮船坞下水受力分析的精度要求。     

浮船坞固定装置导柱的修理解析

文章介绍了某船厂的浮船坞的固定装置,即上下游方位的导柱遭到了一次强对流大风的破坏而引起了严重的损伤,该船厂紧急进行了抢修,这是一次具有挑战性的修理,结果比较成功。文章配合不同修理阶段的图片和具体数据对修理过程详细地加以分析和解释。     

港珠澳大桥岛隧工程钢圆筒制造技术

根据港珠澳大桥岛隧工程人工岛护壁钢圆筒直径大、高度高、壁厚薄、体积庞大但径向刚度差的结构特点,结合生产场地条件,确定了钢圆筒上、下分成两段,单段筒体采用垂直分块法分成六片板单元在车间制造,再到外场吊装合拢的总体工艺方案,并分析了制作工艺难点及对策措施。详细介绍了钢圆筒板单元制作,外场拼装焊接,上下段对接合拢,宽榫槽制作安装和转运装船工艺,对今后类似超大直径钢圆筒的制作具有较高的借鉴意义。     

WD/WP气缸体铸造工艺的持续优化

文章分析了WD/WP气缸体的铸造工艺,指出该汽缸体铸件存在主要质量问题,结合本厂实际生产条件,提出了行之有效的解决办法。结果显示,铸件的质量明显提高。     

造船分段无余量合拢挂装工艺初探

造船分段无余量合拢挂装工艺,把待合拢分段挂装在已经完成的分段上,使挂件、支撑件承载60％至70％待合拢分段的重量,消除了90％以上因吊装产生的弹性变形,实现了造船分段无余量合拢.该工艺比传统工艺提高工效1倍以上,使造船在坞合拢时间缩短53天,使年出船艘数增加30％,并较大的降低了生产成本.     

基于PSO-BP神经网络的船体分段任务包工时定额模型

为解决船体分段任务包工时定额的计算过度依赖线性公式而忽略工时定额与工艺参数之间的非线性关系的问题,提高工时定额计算的效率和精确度,将PSO-BP神经网络技术应用到船体分段任务包工时定额中。通过对影响船体分段中间产品额定工时的工艺参数进行分析,建立多输入单输出的PSO-BP神经网络模型,并应用实际数据对PSO-BP神经网络进行训练,测试仿真结果与实际值之间的误差在允许范围内。验证结果表明,采用PSO-BP神经网络建立船体分段任务包工时定额模型,能对任务包作业工时进行准确预测。