船体梁约束扭转极限承载力计算的简化逐步迭代法

船体梁约束扭转极限承载力计算由于问题复杂至今未有理论解，只能用非线性有限元方法计算，效率很低。论文通过对25块实船板格的非线性有限元分析，引入板的柔度系数，构建了加筋板格的剪切应力与应变关系，提出了船体梁约束扭转的变形和应力假设，构造了船体梁约束扭转的简化逐步迭代计算方法，编制了相应的计算程序。实船算例表明，所提出的剪应力与应变关系和约束扭转极限承载能力的计算方法与非线性有限元方法相比，具有较高的精度和效率，可应用于船舶与海洋平台结构以及各类薄壁梁约束扭转极限强度的计算。     

船体扭转强度分析

本文讨论了以有限元法和薄壁梁理论为基础的船体扭转强度分析方法。把船体横截面离散为薄膜和杆组成的有限元模型,使薄壁梁截面特性计算规格化。文中采用了C.F.Kollbrunner改进的薄壁梁扭转理论和K.Haslum提出的非棱柱薄壁梁的衔接条件。对突变截面公共面积、附属结构、扭转载荷以及扭转应力计算作了讨论。     

复杂薄壁剖面弯、剪、扭特性参数的有限元计算

集装箱船及其它大开口船舶的弯扭强度计算可合理地简化为复杂断面的薄壁梁计算。这种计算的第一步工作是计算剖面的弯、剪、扭特性,包括以下诸项内容:(1)剖面惯性主轴位置与方向,剖面抗弯惯性矩;(2)在横向剪力作用下剖面内剪流的分布以及有效抗剪面积;(3)剖面圣维南扭转常数,剖面翘曲坐标,剖面扇性矩与剪切中心位置。     

离心式叶轮计及二次流的三元流场计算方法

本文提出了在离心式压气机中基于流面理论的二次流场的修正的理论和计算方法。理论论证了S_1流面设有计及二次流的影响。然后根据剪切流理论,以S_1流面流场为基本流场,构筑了一个进行二次流修正的计算方法。本文在进行二次流修正的过程中,引进了二次涡的矢量势函数,并通过对其进行旋度运算,求出了相应的二次流速度分布。由于流面理论可以运用于各种流场条件,因此,可以认为本方法能够运用于“大剪切,大扰动”情况的计算,从而认为本方法具有广泛的适用性。     

船体薄壁梁的扭转刚度矩阵及其在弯矩分析中的应用

本文基于闭口薄壁杆件扭转时翘曲与扇性坐标间的普遍关系:ω=-θω,导出了薄壁梁约束扭转时的刚度矩阵,以及扭转与拉(压)、弯曲的组合刚度矩阵,并将此组合刚度矩阵用于船体梁的弯扭分析中,导出了通用的坐标转换矩阵。文中的结果比现有的结果更为合理并具有普遍性。推导中对闭口薄壁断面的双力矩概念还提出了一些补充的看法。     

船体弯扭耦合振动计算研究

基于Ｔｉｍｏｓｈｅｎｋｏ梁理论和Ｂｅｎｓｃｏｔｅｒ理论,建立了分析船体结构弯扭耦合振动的薄壁梁有限元模型。该模型能考虑翘曲和剪切变形的影响,能精确描述船体薄壁梁的纯弯状态和非均匀扭转,适用于任何形状的船体横剖面。重点讨论了翘曲位移协调问题,提出了新的船体不同剖面形式梁段间的翘曲位移协调方法。本文还讨论了船体薄壁梁计算模型的简化问题。数值算例证实了本文方法的正确性。     

船体薄壁梁弯扭耦合振动的流固耦合分析

采用耦合有限元,边界元法计算水中船体的弯扭耦合振动.文中用一维薄壁梁有限元模拟船体梁,在横剖面处用二维边界元方法计算结构表面卢压,推导出表征流体对振动特性影响的附加质量阵,编制了用流同耦合方法求解船体振动模态的程序.通过与采用ANSYS软件进行耦合场分析以及刘易斯方法得到的振动模念相比较,验证了文中方法的可行性和应用性.     

大开口船弯扭耦合振动分析

本文探讨了用计及剪切和翘曲影响的薄壁梁有限元方法来计算大开口船弯扭耦合振动的特性,导出了抗扭箱对增加船体扭转附加刚度的计算公式,并作了数值计算和实验研究。按本文方法编制的计算程序,除能进行弯扭耦合振动分析外,还能计算垂向或水平扳动以及扭转振动。     

水下爆炸二次脉动压力下舰船抗爆性能研究

将船体梁视为两端自由的Timoshenko梁,在借用二维切片法和水弹性方法的基础上,计算船体染在水下爆炸二次脉动压力下的响应特性。同时,还建立了在考虑水面效应和气泡运动时舰船受到二次脉动压力的计算模型。最后,分析了浮筏式减振装置在水下爆炸二次脉动压力下船用设备的减振抗冲性能。     

HCSR舱段模型中端部梁剖面属性对扭转变形的影响

针对HCSR强度计算中为合理考虑模型之外的构件对模型端面的弹性约束,须在三舱段模型两端施加端部约束梁的规定,分析端部约束梁对于三舱段模型的扭转变形的影响,采用数值试验的方法,进行了端部约束梁的剖面属性对于其扭转变形的敏感性分析。     

船体梁扭转极限承载能力的有限元分析

在船体梁扭转极限承载能力的有限元计算中,对于比较大而且形状复杂的结构,需要采用足够多的单元数来模拟其真实的破坏模态,因而会耗费大量的CPU计算时间和硬盘空间,并且往往因为单元数太多而使数值计算变得不现实.本文采用弹塑性有限元对箱形薄壁梁进行了一系列扭转屈曲数值计算,分析了不同参数对箱形薄壁梁极限扭矩的影响,根据计算结果提出了一个修正粗糙网格有限元计算结果的修正系数,采用此修正系数可以在数值计算中节省大量的CPU计算时间和硬盘空间.     

用准定常升力线理论预报螺旋桨在非均匀流场中的性能

本文应用准定常升力线理论预报船用螺旋桨的性能,建立了适合中型计算机的程序。通过四个桨模的敞水试验和性能计算结果比较表明,对于计算螺旋桨的推力与转矩系数,只要应用升力线理论加上简单的粘性经验修正及升力面影响修正,不必作边界层计算即可得到比较满意的结果。伴流场中单个叶片推力与转矩脉动计算表明,用升力线作计算时,伴流产生的水流弯曲对推力、转矩脉动有较明显的影响,对推力偏心度则影响不大,计算所得的推力、转矩脉动可供计算主机扭振及轴系振动的外力作参考。     

Experimental and numerical investigations of the ultimate torsional strength of an ultra large container ship

Structures of ultra large container ships (ULCS) are characterized by large deck openings and low torsional rigidity. It is essential to comprehensively figure out their collapse behaviors under pure torsion with both model experiments and numerical simulations, making an evaluation of their ultimate torsional strength. In this paper, a similar scale model of a 10,000TEU container ship has been designed and manufactured first, in which both geometric similarity and strength similarity are taken into account. Next the collapse behaviors of the test model are detailedly illustrated with both experimentally and numerically obtained results. Then discussions on warping or shear buckling deformations involved in the collapse process of the structure are conducted with extended numerical simulations. Finally, the ultimate torsional strength of the true ship is evaluated according to the similarity theory. Results show that it is the yielding and shear buckling of the side shells that causes the failure of the hull girder under pure torsion. Further nonlinear finite element analysis demonstrates that it may either have warping or shear buckling deformations in the torsional collapse process of the hull girder with a large deck opening, depending on the local rigidity distribution of side shells, which has a significant effect on the ultimate torsional strength of the hull girder.     

Hydroelasticity of large container ships

The importance of hydroelastic analysis of large and flexible container ships of today is pointed out for structure design. A methodology for investigation of this challenging phenomenon is drawn up and a mathematical model is worked out. It includes the definition of ship geometry, mass parameters, structure stiffness, and combines ship hydrostatics, hydrodynamics, wave load, ship motion and vibrations. The modal superposition method is employed. Based on the presented theory, a computer program is developed and applied for hydroelastic analysis of a large container ship. The transfer functions for heave, pitch, roll, vertical and horizontal bending and torsion are presented. Rigid body and elastic responses are correlated.     

船体扭转强度可靠性分析

本文用随机迁移矩阵法结合改进的一阶二次矩法,计算船体扭转强度的可靠性指数,计算结果表明,该方法有较高的计算效率,所需计算机内存小,方法收敛性好。     

An advanced theory of thin-walled girders with application to ship vibrations

The paper presents an outline of the advanced theory of thin-walled girders. The improvement includes shear influence on torsion as an extension of shear influence on bending. The analogy between bending and torsion is recognized and pointed out throughout the paper. Complete differential equations of coupled flexural and torsional vibrations for a prismatic girder are derived. In addition, the 8 d.o.f. beam finite element, utilizing the energy approach, is constituted with stiffness and mass matrices, and load vectors. The paper describes determining of geometrical properties of multi-cell open cross-sections by employing the strip element method. Numerical procedures for vibration analyses are outlined. Furthermore, dry natural vibrations of a VLCS (Very Large Container Ship) are analysed by 1D FEM model as a prerogative for hydroelastic analyses of these relatively flexible vessels. Influence of transverse bulkheads is taken into account by increasing torsional stiffness of the ship hull proportionally to their deformation energies. Validation of 1D FEM model is checked by correlation analysis with the vibration response of the fine 3D FEM model.     

双壳驳模型的结构设计及约束扭转试验研究

本文从双壳驳模型结构设计、扭转试验技术两方面作了系统介绍。 在指导畸变模型设计的理论上,提出了两个独立的几何参数L、t的概念,基本解决了这类模型所必然存在的构件厚度与其它几何尺度不能取同一相似倍数的问题,从而使模型试验结果对实船进行相关预报成为可能。 在约束扭转试验技术方面,设计中采用了双滑轮悬吊支承,油顶-滑轮自平闭式加载系统,百分表随动臂架变形测量装置等,形成一套新的弯、扭组合测试技术,与国外类似试验相比,模型的边界条件更为合理。 本文结论对于箱形结构模型是适用的;所介绍的试验技术对于集装箱船、双体船、工程船和海洋平台等大比例尺模型试验具有一定的参考价值。     

舰船轴系扭振计算的传递矩阵法及三维图形系统

该文论述了轴系扭振计算的复数形式传递矩阵法和系统的累积传递矩阵方程,根据系统边界条件推导了自由和强迫扭振计算方法,并以Matlab为编程工具实现了相应的CAD及三维图形系统。实例验算证明了其有效性和工程应用价值。     

大开口船舶扭转强度及结构加强方式研究

文章介绍了大开口船舶扭转强度的薄壁杆件理论计算,以120 TEU内河集装箱船为例,详细计算了该船的扭转强度及弯扭合成应力;并对120 TEU集装箱船结构加强方式进行了研究,从中找出较佳的抗扭结构加强方式,得到一些具有工程应用价值的结论.     

基于Morabito方法的滑行艇喷雾详细研究的计算机程序开发(英文)

Recently, Morabito(2010) has studied the water spray phenomena in planing hulls and presented new analytical equations. However, these equations have not been used for detailed parametric studies of water spray around planing hulls. In this paper, a straight forward analysis is conducted to apply these analytical equations for finding the spray geometry profile by developing a computer program based on presented computational process. The obtained results of the developed computer program are compared against existing data in the literature and favorable accuracy is achieved. Parametric studies have been conducted for different physical parameters. Positions of spray apex are computed and three dimensional profiles of spray are examined. It is concluded that spray height increases by an increase in the speed coefficient or the deadrise angle. Ultimately, a computational process is added to Savitsky's method and variations of spray apex are computed for different velocities. It is shown that vertical, lateral, and longitudinal positions of spray increase as the craft speed increases. On the other hand, two new angles are defined in top view and it is concluded that they have direct relation with the trim angle. However, they show inverse relation with the deadrise angle.