大型客滚船舱段屈曲和疲劳强度直接计算

[目的]客滚船是一种高技术、高附加值的船型。由于其结构的特殊性,目前各国船级社还未形成统一的有关客滚船屈曲和疲劳强度的计算规范。[方法]在充分分析客滚船结构特点的基础上,基于项目组自主研发的软件,依照挪威船级社(DNV)的客滚船屈服强度直接计算规范,并参考中国船级社(CCS)有关其他船型的相关规范,对某大型客滚船舱段进行屈曲强度、高级屈曲、热点疲劳3方面的直接计算,并详细介绍直接计算前处理设定方法,[结果]结果表明,目标舱段的屈曲强度、高级屈曲强度及疲劳强度的直接计算结果全部满足规范值。[结论]研究结果对大型客滚船的相关结构分析具有一定的参考价值。     

双向受压裂纹板剩余极限强度分析北大核心CSCD

[目的]船舶在航行过程中船底板等船体结构除了受到纵向弯曲应力以及舷侧外板传递的横向水压力载荷影响外,还因焊接及应力集中容易产生裂纹,使船体结构的承载能力降低。为此,[方法]通过数值计算,研究双向受压载荷作用下含中心裂纹船体板的剩余极限强度。首先,提出计算含裂纹船体板剩余极限强度的参数化函数模型;然后,计算和分析影响其强度的因素,如裂纹长度、倾角和船体板细长比、长宽比以及横纵载荷比,并提出倾斜裂纹的有效投影长度参数;最后,基于计算结果,拟合得到双向受压载荷作用下含中心裂纹船体板的剩余极限强度计算公式。[结果]结果表明,运用计算公式得到的结果具有较高的精度,[结论]可用于对实船上含中心裂纹船底板纵向极限承载能力的计算分析。     

船体极限强度试验小比尺相似模型研究

基于薄壁梁理论推导了总纵极限强度试验的相似模型设计应该满足的条件,然后选取小相似比尺满足某实验室的加载条件,分别设计出某集装箱船的双层模型和单层模型.通过对三段形式模型的非线性有限元分析,验证实船与模型的中拱、中垂极限强度的相似性.相对而言,总纵极限强度试验更适合选用单层模型.     

基于实船观测的北极东北航线窗口期海冰冰情研究

随着全球气候变暖,北极海冰覆盖范围的日趋减小使得北极航道的夏季通航性不断提高.与通过苏伊士运河的传统航线相比,北极东北航道可以节省欧洲和亚洲之间近三分之一的航行距离.然而,北极海冰不可避免地为北极航运带来极大的挑战.为此,在2018年夏季窗口期期间在中远"天佑号"东北航道航行过程中对航线冰情开展了走航观测.通过船载摄像机对航道中的海冰视频图像进行采集,并通过图像处理软件对海冰密集度进行提取.数据显示,窗口航道中海冰类型主要为低密集度的碎冰且部分碎冰内部夹杂着冰脊,其中平均密集度为17.8％,而最高值可达80％.此外,将视频数据与遥感数据进行对比分析,结果表明卫星遥感数据在低密集度(0-0.2)时存在一定的低估,而在较高密集度下则偏向高估.     

水下爆炸载荷下舰船结构的多目标优化

水面舰船对轻量化和抗爆性能均有特殊的需求，而这两个目标此消彼长的关系又使得实现它们的途径相互矛盾。为找到能同时提高轻量化和抗爆性能的满意解，建立以板厚为变量的多目标优化模型。在优化过程中，通过参数化建模技术实现建模的自动化，数值模拟采用船体三舱段有限元模型，使用ABAQus／ExPLIcIT求解器进行非线性有限元分析，并在优化流程中引入实验设计和近似模型进行响应预报，在此基础上，还通过NSGA—II遗传算法进行多目标优化，得到优解。通过对优化后的船舯舱段与优化前的进行对比分析，发现重量和抗爆性能这两个目标分别有0．46％和22．51％的改进，实现了轻量化和抗爆性能的双向提升。     

铝合金夹心板结构极限承载能力有限元分析

随着新材料及新型结构的不断出现,以往的线性理论已不能满足现代工程设计的需要.本文利用MSC.NASTRAN的弧长法对一种新型铝合金夹心板结构进行了极限承载能力有限元分析,跟踪出了其屈曲平衡路径以及破坏模式.为验证有限元模拟的准确性,对结构进行了静载强度模型试验.研究结果表明,计算结果与试验符合较好.     

Influence of unidirectional tensile external-loading on electromagnetic property of the perforated frequency selective surface illuminated by electromagnetic wave incident at arbitrary angles

That whether unidirectional tension changes the influence of incident angle on FSS's(frequency selective surface) electromagnetic(EM) property and whether incident angle changes the effect of unidirectional intension on FSS's EM property is researched.The pattern and magnitude of these changes are revealed.Firstly,the analyses for the mechanism of unidirectional tension's influence and the mechanism of the coupling between the influences of unidirectional tension and incident angle are conducted.Then,accord...     

Containership structural design and optimization based on knowledge-based engineering and Gaussian process

Knowledge-based engineering （KBE） has made success in automobile and molding design industry, and it is introduced into the ship structural design in this paper. From the implementation of KBE, the deterministic design solutions for both rules design method （RDM） and interpolation design method （IDM） are generated. The corresponding finite element model is generated. Gaussian process （GP） is then employed to build the surrogate model for finite element analysis, in order to increase efficiency and maintain accuracy at the same time, and the multi-modal adaptive importance sampling method is adopted to calculate the corresponding structural reliability. An example is given to validate the proposed method. Finally, the reliabilities of the structures＇ strength caused by uncertainty lying in water corrosion, static and wave moments are calculated, and the ship structures are optimized to resist the water corrosion by multi-island genetic algorithm. Deterministic design results from the RDM and IDM are compared with each separate robust design result. The proposed method shows great efficiency and accuracy.     

Influence of excitation frequency on slosh-induced impact pressures of liquefied natural gas tanks

Liquid sloshing phenomena in No. 2 tank of 140 km³ liquefied natural gas (LNG) carriers have been studied numerically and experimentally. The scale of the model tank was selected as 1/55.9. Roll and pitch motions were tested. For measuring impact pressures, seventeen pressure sensors were installed on the tank model. A large number of excitation frequencies and filling heights were investigated. The experimental results showed that when the frequency of tank motion is close to the natural frequency of fluid inside the tank, large impact pressures may be caused. Resonance frequencies and maximum impact pressures of different filling height were presented. Among all the experimental situations, the maximum impact pressure always occurs at the place near 70% height of tank where should be especially concerned. A computational fluid dynamics (CFD) model was developed to simulate the sloshing in the tank. The model was based on the Reynolds-averaged Navier-Stokes (RANS) equations, with a standard κ-ɛ turbulence model. The volume of fluid (VOF) method was used to predict free surface elevations. Dynamic mesh technique was used to update the volume mesh. Computations for pressure time histories and peak pressures were compared to experimental results. Good agreement was observed.     

直角域内的结构声辐射特性研究

直角空间域的边界特性影响内部结构的声辐射特性.文章通过引入保角映射取得不同边界特性下直角空间域内声边界元法的格林函数,以此导出相应的声辐射方程.并以脉动球声源的声辐射为例,进行数值分析并对比了直角空间域的边界特性、频率和与边界的距离对声功率和声辐射指向性的影响.