波浪中船体梁后极限强度特性的实验评估(英文)

Experimental investigations into the collapse behavior of a box-shape hull girder subjected to extreme wave-induced loads are presented.The experiment was performed using a scaled model in a tank.In the middle of the scaled model,sacrificial specimens with circular pillar and trough shapes which respectively show different bending moment-displacement characteristics were mounted to compare the dynamic collapse characteristics of the hull girder in waves.The specimens were designed by using finite element(FE)-analysis.Prior to the tank tests,static four-point-bending tests were conducted to detect the load-carrying capacity of the hull girder.It was shown that the load-carrying capacity of a ship including reduction of the capacity after the ultimate strength can be reproduced experimentally by employing the trough type specimens.Tank tests using these specimens were performed under a focused wave in which the hull girder collapses under once and repetitive focused waves.It was shown from the multiple collapse tests that the increase rate of collapse becomes higher once the load-carrying capacity enters the reduction path while the increase rate is lower before reaching the ultimate strength.     

三维测量数据的钢结构虚拟装配过程仿真系统(英文)

The virtual erection simulation system was explained for a steel structure including ship and ocean plant blocks.The simulation system predicted the erection state to optimize any gap or overlap of blocks based on 3-D measurement data.The blocks were modified(cut) on the basis of the simulation result on the ground before erecting them by crane.The re-cutting process was not required and the blocks were erected into a mother ship speedily.Therefore,the erection time is reduced,increasing the dock turnover.     

迎浪规则波中波浪增阻和船体垂向运动的数值预报(英文)

The numerical prediction of added resistance and vertical ship motions of one ITTC (International Towing Tank Conference) S-175 containership in regular head waves by our own in-house unsteady RANS solver naoe-FOAM-SL JTU is presented in this paper. The development of the solver naoe-FOAM-SJTU is based on the open source CFD tool, OpenFOAM. Numerical analysis is focused on the added resistance and vertical ship motions (heave and pitch motions) with four very different wavelengths (0.8Lpp≤λ≤1.5Lpp) in regular head waves. Once the wavelength is near the length of the ship model, the responses of the resistance and ship motions become strongly influenced by nonlinear factors, as a result difficulties within simulations occur. In the paper, a comparison of the experimental results and the nonlinear strip theory was reviewed and based on the findings, the RANS simulations by the solver naoe-FOAM-SJTU were considered competent with the prediction of added resistance and vertical ship motions in a wide range of wave lengths.     

一种改进的海洋平台结构损伤诊断方法研究(英文)

In the exploitation of ocean oil and gas, many offshore structures may be damaged due to the severe environment, so an effective method of diagnosing structural damage is urgently needed to locate the damage and evaluate its severity. Genetic algorithms have become some of the most important global optimization tools and been widely used in many fields in recent years because of their simple operation and strong robustness. Based on the natural frequencies and mode shapes of the structure, the damage diagnosis of a jacket offshore platform is attributed to an optimization problem and studied by using a genetic algorithm. According to the principle that the structural stiffness of a certain direction can be greatly affected only when the brace bar in the corresponding direction is damaged, an improved objective function was proposed in this paper targeting measurement noise and the characteristics of modal identification for offshore platforms. This function can be used as fitness function of a genetic algorithm, and both numerical simulation and physical model test results show that the improved method may locate the structural damage and evaluate the severity of a jacket offshore platform satisfactorily while improving the robustness of evolutionary searching and the reliability of damage diagnosis.     

船模在简谐激励存在时的运行模态分析(英文)

A ship is operated under an extremely complex environment, and waves and winds are assumed to be the stochastic excitations. Moreover, the propeller, host and mechanical equipment can also induce the harmonic responses. In order to reduce structural vibration, it is important to obtain the modal parameters information of a ship. However, the traditional modal parameter identification methods are not suitable since the excitation information is difficult to obtain. Natural excitation technique-eigensystem realization algorithm (NExT-ERA) is an operational modal identification method which abstracts modal parameters only from the response signals, and it is based on the assumption that the input to the structure is pure white noise. Hence, it is necessary to study the influence of harmonic excitations while applying the NExT-ERA method to a ship structure. The results of this research paper indicate the practical experiences under ambient excitation, ship model experiments were successfully done in the modal parameters identification only when the harmonic frequencies were not too close to the modal frequencies.     

当前浮式平台船体结构分析的方法与重点综述(英文)

浮式平台概念的选择及其结构设计是深水工程项目的关键环节之一.它决定了平台在波浪载荷作用下的动力学响应、立管在深水条件下的运动以及进行平台建造与安装的技术难度等.结构强度、结构的抗疲劳性能以及结构的整体和局部稳定性能是浮式平台设计必须重点考虑的三个主要方面.总结了当前浮式平台设计的主要方法和它的主要任务以及技术要求,着重分析了设计过程中的主要技术难点及重点;最后,讨论了浮式平台结构设计的潜在发展趋势.     

考虑内流和海床作用的柔性立管和钢悬链线立管非线性分析(英文)

Flexible risers and steel catenary risers often provide unique riser solutions for today’s deepwater field development. Accurate analysis of these slender structures, in which there are high-speed HP/HT internal flows, is critical to ensure personnel and asset safety. In this study, a special global coordinate-based FEM rod model was adopted to identify and quantify the effects of internal flow and hydrostatic pressure on both flexible and deepwater steel catenary risers, with emphasis on the latter. By incorporating internal flow induced forces into the model, it was found that the internal flow contributes a new term to the effective tension expression. For flexible risers in shallow water, internal flow and hydrostatic pressure made virtually no change to effective tension by merely altering the riser wall tension. In deep water the internal pressure wielded a dominant role in governing the riser effective tension and furthering the static configuration, while the effect of inflow velocity was negligible. With respect to the riser seabed interaction, both the seabed support and friction effect were considered, with the former modeled by a nonlinear quadratic spring, allowing for a consistent derivation of the tangent stiffness matrix. The presented application examples show that the nonlinear quadratic spring is, when using the catenary solution as an initial static profile, an efficient way to model the quasi-Winkler-type elastic seabed foundation in this finite element scheme.     

声传输进结构-声腔耦合舱室空间的主动控制策略和机理研究(英文)

An analytical study was presented on active control of sound transmission into a vibro-acoustic enclosure comprising two flexible plates. Two types of actuators were used, i.e. acoustic actuator and distributed lead zirconate titanate piezoelectric (PZT) actuator instead of point force actuator. Using the modal acoustic transfer impedance-mobility matrices, the excitation and interaction in the coupled sound transmission system can be described with clear physical significance. With the control system designed to globally reduce the sound field, different control system configurations were considered, including the structural actuator on the incident plate, actuator on the receiving plate, acoustic actuator on the cavity, and their combinations. The effectiveness and performance of the control strategy corresponding to each system configuration were compared and discussed. The role and control mechanism of each type of actuator were of particular interest. It was shown that the incident plate actuator is effective in controlling the cavity-dominated modes and the structural modes dominated by the incident plate and receiving plate. Two main control mechanisms are involved in this control configuration, i.e., modal suppressing and modal rearrangement. For control system configuration with only acoustic actuator in the enclosure, the mechanism involved in this arrangement is purely modal suppression. Desirable placements of structural actuators in terms of total potential energy reduction were also discussed.     

基于高精度近似模型的舰船线型优化

线型优化是船舶总体性能设计的重要内容,借助CFD软件开展船舶线型优化需要进行三维建模和复杂的网格划分,时效性有限。本文提出一种基于高精度近似模型的线型优化法,在CFD计算结果的基础上,通过构建神经网络近似模型,对线型优化结果进行预报。该方法不仅能够实现线型优化结果的快速预报,而且可以解决CFD离散优化随机性的难题,大大提高线型优化的效率。     

基于近似模型的海上发射船船型优化

基于耐径向基函数神经网络模型(RBF),以火箭承受弯矩为单目标优化函数,对双体发射船船型参数进行优化研究。选定对船型参数CB和L/B作为优化变量,利用Lackenby方法,对船型参数化建模,应用最优拉丁超立方方法(LHD)选取样本点,采用二次插值方法扩充样本点数据,建立双体船运动响应及阻力近似模型,利用多岛遗传算法(MIGA)搜索最优船型。结果表明优化后船型的火箭弯矩减小3.86%,从而为双体火箭发射船的设计及相关船型研究提供参考。     

方块码头安装偏差过大的计算分析及解决办法

依据安哥拉某重力式方块码头施工过程中发生的安装偏差超标的实例,根据海侧实测数据,利用静力计算、修正静力计算、有限元分析计算3个阶段的渐进过程分析偏差超标方块的受力情况,为后续工作的合理安排提供依据,在解决施工问题并保证进度方面具有普遍的参考意义。     

采用混合面和滑动网格模型对艇体流场数值分析比较

借助CFD软件,对螺旋桨／艇体相互作用的流场进行了数值模拟。采用了混合面模型和滑移网格模型分别对螺旋桨,艇体流场的整体进行计算,揭示了螺旋桨和艇体之间相互作用的内在规律。     

基于遗传算法的最小阻力船型优化设计

遗传算法是一种全局最优化算法,它能够克服传统优化方法的缺点和不足,从而获得全局最优解。因此,为了获得阻力性能更好的优良船型,将遗传算法进行适当改进并用于船型优化中,进行最小阻力船型优化设计,以非线性兴波阻力理论(Rankine源法)为基础,利用遗传算法并结合CAD技术进行船型优化设计。在优化过程中,把总阻力作为目标函数,设计变量取船型修改函数的参数,确保排水量为基本约束条件下,对船体前半体型线进行优化研究。选取某高速巡逻艇作为初始船型进行优化计算,获得的最优船型总阻力降低了13.1%,兴波阻力降低了21.7%,表明遗传算法用于船体线型优化设计是行之有效的。     

基于SolidWorks的AUV耐压舱体设计与校核

自主式水下航行器的耐压和密封是非常关键的两方面,基于SolidWorks软件对324型AUV耐压舱体进行了设计与仿真校核。综合考虑薄膜理论和不连续效应,根据NSGA-Ⅱ算法实现多目标优化,确定出直舱和封头的基本尺寸,利用美国海军试验水槽公式和稳定条件进行初步验证,以保证强度和稳定性。根据得出的几何尺寸在SolidWorks里完成三维建模,并在Simulation模块中完成数值模拟仿真,最终对舱体进行实际耐压试验,将结果和理论计算、软件仿真进行对比。针对直舱段舱体不同尺寸和材料进行了三维建模和数值仿真,得出相应结论。     

Modeling and analysis of panel hull block assembly system through timed colored Petri net

To implement efficient production control, this paper provides a timed colored Petri net (timed CPN) approach to performance modeling, real-timed dispatching and simulation of Panel hull block assembly system (PHBAS). The definition of Petri net is extended to accord with the real-world PHBAS’s organization, and the modeling method for hull flow production is provided in order to simplify modeling program. Using modeling and analyzing method, the dynamic characteristics of the system can be emulated and quantitatively calculated and work control tactics can be optimized. For the double bottom hull block shipbuilding system in a recently built shipyard in China, the simulation model with timed CPN was described and the system parameters and optimal task sequence which has the minimum operation time were obtained for a scheduling case.     

虚拟装配中基于层次包围盒的空间快速验证

[目的]针对现有虚拟装配与维修中可移动空间计算的算法精度、效率较低,甚至缺少算法的问题,结合舰船虚拟装配、维修的实际需求,提出一种能够快速、准确计算零部件在移动空间中碰撞验证的算法.[方法]首先,以层次包围盒与三角面片相交检测算法为基础,改进层次包围盒与三角面片在移动空间中进行变换的方法;然后,根据二分法与递增法求得干...     

基于克里金模型的潜水器耐压舱结构优化

本文研究Kriging建模和序贯加点相结合的方法,用于解决目标函数或者约束函数无法显式表达下的优化问题。在加点准则中为了避免出现龙格现象,改进了加点优化时步长要求,在优化过程中融入多种群遗传算法提高了序贯加点值的计算准确性。计算结果表明,改进后的加点准则在存在多区域或者多个极值点的情况下均可快速搜索到最优点位置。建立了载人潜水器载人舱以重量为优化目标,以强度要求为约束的球壳厚度优化模型,采用此方法在初始选取5个样本取样,序贯加点6个样本点,计算得到球壳的最优厚度值为50.5569 mm,可有效指导设计工作。     

基于SVM的液压设备仿真模型的故障诊断

阐述了SVM算法在液压系统的故障诊断领域中的应用及其诊断效果.以全液压克令吊模型为研究对象,将克令吊模型的回转回路作为一个独立系统,使用功率键合图方法建立其数学模型,并用Matlab中的Simulink对模型进行计算机仿真,对回转回路选择不同的参数进行流量的特性仿真,运用支持向量机理论依据流量值的特性对回转回路进行故障分类,得到了令人满意的故障分类正确率.