烧结机破碎齿耐磨堆焊层的金相分析

烧结机破碎辊的单(双)齿是承受高温冲击磨损的工件.本文对其堆焊层的金相组织、高温性能及抗磨性进行了测试与分析,采用高温金相、透射电镜、电子探针等检测手段,查明了堆焊层的组织构造.通过微区成分分析证实骨络状组织为 Fe4(Cr,Mo)2C型复合碳化物.文中还对自行研制的 L2型高温耐磨堆焊焊条堆焊层的组织性能进行了分析,证实其性能完全满足烧络机单(双)齿辊的技术要求.     

A local model for the simulation of two–dimensional spilling breaking waves

A numerical model for the simulation of two dimensional spilling breaking waves is described. It is derived from a previous model which, in turn, takes its underlying ideas from the Cointe and Tulin theory of steady breakers. With respect to the former model, the present one is local, i.e., the inception, extension, and geometry of the breakers are determined through the local shape of the water surface. The model has been implemented in a RANSE code, which was developed for the simulation of ship flows, through a modification in the boundary conditions. This yields a simple and effective way to reproduce the breakers influence on the underlying flow. The resulting code has been used to simulate the flow past a submerged hydrofoil. The numerical results are compared with those of the previous model and with the experimental data obtained by Duncan.     

海浪统计资料对船舶波浪弯矩设计值的影响

对船舶,特别是超规范船舶,进行结构的直接计算设计时,首先要知道波浪弯矩设计值。 要确切地做到这一点,设计人员应合理地选择船舶航行海域的海浪长期统计资料,然后根据船 舶的装载工况和实际可能达到的航速,借用线性理论或非线性理论进行波浪弯矩的长期预报 来确定设计值。本文就一艘大型集装箱船舶,按五个典型海域的海浪统计资料,对波浪弯矩及 波浪合成弯矩作了长期预报计算,并与 ＩＡＣＳ的统一纵强度要求ＵＲ—Ｓ１１的结果作了比较和 分析,给出了对船舶结构直接计算设计有指导意义的几点结论。     

基于马尔可夫链的极值波高预测

本文研究了由日最大波高系列估算设计极值波高时，相邻日最大波高间的相关性对极值预测的影响，从日最大波高系列遵从马尔可夫链的假定出发，考虑到国内外经常采用对数一正态分布的韦布尔分布拟合波高长期分布的现实，本文用解析法求解了对数一正态分布情况下的极值预测。同时，对解析法难以求解的非正态随机变量情况（如韦布尔分布），用计算机随机模拟方法求解其极值预测，用上述两种方法对北大西洋和北海有关日最大波高系列的预测     

改善小型高速艇总体性能的措施研究

结合某项产品的设计论证和船模试验,对小型高速艇的总体性能进行了研究,提出了减小船体阻力、改善耐波性和减小船体振动的若干措施。     

Transient design waves for green-water loading on bulk carriers

The wave surface profiles associated with extreme relative motion between a slender stationary vessel and the adjacent wave surface are investigated for long-crested head seas. The methodology is based upon an established statistical relationship for a Gaussian random process which indi-cates that in the vicinity of an extreme event the most probable shape of the time history approaches that of the autocorrelation function. Attention is given to the relative motion at a longitudinal position which is representative of the No. 1 hatch cover location on a bulk carrier. Second-order corrections to the wave surface profiles are used to provide estimates of nonlinear relative motions. It is shown that extreme relative motion at the hatch cover location is associated with the vessel encountering a steep-fronted wave with pronounced asymmetry in the horizontal and vertical directions. In order to evaluate the exceedence probabilities, it is hypothesized that the peaks of the nonlinear relative motions are closely correlated with the peaks of an underlying linear process. The overall methodology is applied to an investigation of relative motion exceedence probabilities for vessel lengths of 250 m and 300 m over a range of survival seastates. Received: July, 1999 / Accepted: November, 1999     

海堤前特殊地形对护面块体稳定性影响及对策

通过在波浪水槽内对海堤护面块体稳定性物理模型试验,发现在堤前存在特殊地形的条件下,波浪传播该区域后发生变形、破碎,形成的波能集中冲击范围内护脚人工块体,导致其失稳,进而使断面上整个护面块体向海侧滑移失稳。文章分析了块体失稳原因和影响因素,并从设计角度提出多种针对特殊地形下人工块体失稳的改善措施。     

基于希尔伯特变换的应力波波速估计的研究

研究基于希尔伯特变换的时间延迟估计方法及其算法,算法通过MATLAB语言编程实现。制作了4块混凝土板并在其上开展基于冲击反射法的双传感器波速测量实验,将互相关时延估计和希尔伯特变换时延估计应用到波速估计中,两者均能解决直接观察法中的人为误差的影响和噪声对测量精度的影响,取得比较满意的结果,希尔伯特变换时延估计得到的波速精度比互相关时延估计得到的波速估计精度更高。     

制挠工况下高铁大跨连续梁桥上无砟轨道受力研究

为探明高速铁路长联大跨度连续梁桥上CRTSII型板式无砟轨道制挠工况下受力特性,选取某高铁跨径(60+3×100+60)m的连续梁桥为工程实例,建立考虑梁轨各构件的空间有限元模型,计算分析单侧制挠工况下各层轨道结构纵向附加力分布规律;分析轨道关键结构参数变化对其纵向附加力影响规律,研究结果表明:在单侧制挠工况下,钢轨纵向附加力最大值出现位置随着加载区域的变化而变化,最大附加拉力及附加压力分别出现在加载区域后端点、前端点;轨道板和底座板纵向附加力分布趋势一致;3层轨道结构中,轨道板在制挠工况下纵向附加力最大;连续梁固定支座右侧300 m范围加载制动力为轨道结构相对最不利工况;道床板伸缩刚度以及滑动层摩擦因数对轨道结构附加力影响较大;CA砂浆层对轨道结构附加力影响较小;建议增大大跨连续梁两端无砟轨道结构强度,改进CRTSII无砟轨道CA砂浆层的设置。