基于BP神经网络的加筋板动力极限强度预测方法

船舶在航行过程中常受到动力载荷的作用,因此有必要对船体结构的动力极限强度预测方法进行研究。本文首先通过与现有试验结果对比,验证了本文有限元计算方法的正确性。随后通过数值计算,得到828组几何与材料参数不同的船体加筋板模型在不同加载速度下的动力极限强度。而后,以板柔度系数、加筋梁柱柔度系数、材料屈服强度为主要输入参数,构建3层BP神经网络,预测加筋板动力极限强度。所得神经网络均方差及相关系数分别达到0.000 47与0.99。将训练的神经网络应用于实船加筋板,与有限元计算结果对比,最大误差仅6.4%,证明该BP神经网络能较好预测实船结构动力极限强度。     

含初始变形船体加筋板有效宽度及剩余极限强度研究

为了评估舰船结构损伤后的剩余强度,对船体加筋板出现初始几何变形后,参与总纵强度的有效宽度和加筋板剩余极限强度进行研究。将加筋板受到垂直于平面压力后的变形,作为其初始几何变形,改变变形的方向和大小,利用有限元软件Ansys对加筋板结构进行线性和非线性分析。定义了板有效宽度计算方法,对不同变形方向和变形幅值时板的有效宽度和加筋板的极限强度进行对比分析,并拟合得到了计算板有效宽度和加筋板极限强度的经验公式。结果表明,初始几何变形会削弱加筋板结构的强度。在对损伤后船体结构强度进行分析和校核时,提出的经验公式可以直接用来计算板的有效宽度和加筋板的极限强度。     

含裂纹加筋板在压缩载荷下的剩余极限强度试验研究

在老龄化引起的船舶结构安全性问题中,裂纹损伤是结构强度衰减的一个重要因素。文章采用逐步加载法对含裂纹损伤的加筋板压缩剩余极限强度进行试验研究。设计六种典型的穿透裂纹损伤加筋板,对损伤试件进行轴向压缩试验。通过改变裂纹尺寸、位置及倾角参数并根据试验观测结果,探讨了不同裂纹参数下加筋板的屈曲破坏特点和对剩余极限强度影响。试验结果表明,不同的裂纹长度以及裂纹位置改变加筋板结构承载力的分布,影响结构应力应变场,进而改变其失效崩溃模式;倾角为45°的裂纹相对于垂直于加筋的裂纹对加筋板结构的剩余极限强度影响较小,此外初始缺陷对结构的剩余极限强度的影响也不容忽视。     

Patran的PCL语言在板格和加筋板极限强度计算中的运用

用Fortran编写程序生成Patran的.ses文件,可将任意指定的初始挠度施加到要计算分析极限强度的光板和加筋板结构模型中去.具体分析6块光板和4块加筋板结构的极限强度,计算结果表明,该方法可以模拟任意复杂的变形形式,从而更加准确地计算和评估加筋板结构的极限强度.     

极地小型邮轮加筋板结构冗余度试验研究

以极地小型邮轮加筋板结构为研究对象,设计并制作典型加筋板缩比模型,开展完整结构和损伤结构的轴向压缩极限强度试验研究,揭示完整结构和损伤结构下,主甲板板架结构的极限承载能力和屈曲失效模式,并基于全船结构强度有限元方法,计算主甲板板架完整结构和损伤结构的应力,进行了主甲板板架结构冗余度评估。研究发现：轴向压缩载荷作用下,单独一根加强筋出现局部损伤会小幅度降低加筋板结构的极限承载能力;加筋板完整结构和损伤结构屈曲破坏模式均为加强筋率先破坏引起整个板架结构屈曲破坏;单独一根加强筋的损伤不会引起极地小型邮轮加筋板结构的连续性垮塌,具有良好的结构冗余。研究结果对极地小型邮轮结构设计和冗余度研究具有一定参考价值。     

含凹陷损伤FPSB典型加筋板剩余极限强度研究

本文选取一型FPSB典型加筋板结构,在考虑初始缺陷的情况下采用非线性元法,通过对比研究,选定了(1/2 1 1/2)的加筋板模型以及合适的边界条件、网格尺寸。分别研究了三种不同凹陷形状对加筋板极限强度的影响,选定了以弧形凹坑为主要研究对象的凹陷形式。分别研究了凹陷损伤加筋板随凹痕深度、凹痕长度、凹痕宽度、凹痕位置变化时结构在单轴受压情况下的极限强度变化情况。本文的计算结果可对此型FPSB加筋板结构在凹陷损伤后的极限强度评估提供一定的参考。     

组合压载下金属折叠式夹层板的后屈曲极限强度分析

金属夹层板以优异的力学性能已应用于实船。本文根据与加筋板重量相当原则,设计一种金属折叠式夹层板结构,考虑其应用于舰船甲板的受力特性,采用非线性有限元方法,研究夹层板结构在不同组合载荷作用下的非线性后屈曲极限强度。首先通过与经验公式及相关结果对比验证了本文数值仿真方法和技术的可行性和准确性;然后建立双向面内受压和垂向载荷作用下的金属折叠式夹层板结构数值模型,基于屈曲特征值确定屈曲极限强度分析的初始缺陷;考虑结构初始缺陷,计算得到夹层板结构的后屈曲极限强度;对金属折叠式夹层板在不同组合载荷作用下的横向、纵向后屈曲极限承载能力进行计算分析;并与传统加筋结构对比,结果显示本文设计的金属折叠式夹层板结构具有更优异的稳定性和极限承载力,结果对金属夹层板的应用与强度设计提供参考。     

具有初始缺陷的船体加筋板结构在复杂受力状态下的极限强度研究

采用非线性有限元法对带有初始变形缺陷及受轴向、侧向压力同时作用的复杂受力状态下结构的极限承载力进行研究。通过Smith模型试验并与共同规范给出的逐步破坏计算方法比较,验证了有限元方法的准确性;以基于共同规范设计的典型AFRAMAX型双壳油船为研究对象,对多个加筋板模型的比较分析表明,单个双跨加筋板模型(1/2+1/2)可很好地用于结构的极限强度分析。该模型能模拟横向构件对结构纵向强度的影响,且纵向边界条件的设置可以体现多个加筋板结构间的相互影响。在此基础上,对具有初始缺陷且在轴向和侧向压力同时作用下的复杂受力状态下的加筋板结构的极限强度进行分析,并与共同规范法的结果进行比较,表明结构的初始变形缺陷及侧向压力将明显降低其极限承载力,而共同规范极限强度计算法的结果因没有考虑结构的工艺缺陷及真实加载工况而偏于危险。     

考虑腐蚀损伤的双体船连接桥结构极限强度分析

为了解腐蚀损伤对双体船连接结构桥极限强度的影响,采用有限元分析方法,通过数值模拟,计算分析考虑腐蚀情况下铝质双体船连接桥结构的极限强度,建立评估含有点蚀损伤的船体板格结构和加筋板结构极限强度的工程化方法,实船分析结果表明：腐蚀体积是影响板格及加筋板结构极限强度的重要因素,且当腐蚀体积较小时,连接桥区域结构存在不满足极限强度要求的情况。     

切线模量理论的内涵和用途的扩展

借助弹性力学中的应变能定理扩展了切线模量理论的内涵,给出了相应的平衡状态参数图及其数学表达式,并以此为基础,提出了非线性屈曲临界应力和非线性断裂临界应力计算的切线模量理论;利用切线模量理论的平衡状态模型建立了强度利用率相等模型实验原理,将其应用于疲劳试验数据的处理,提出了采用切线模量理论计算疲劳强度和断裂强度的新思路;最后对基于切线模量理论的强度稳定综合理论的发展和应用进行了展望.     

Sensitivity analysis on ultimate strength of aluminium stiffened panels

This paper presents the results of an extensive sensitivity analysis carried out by the Committee III.1 “Ultimate Strength” of ISSC’2003 in the framework of a benchmark on the ultimate strength of aluminium stiffened panels.Previously, different benchmarks were presented by ISSC committees on ultimate strength. The goal has typically been to give guidance to the designer on how to predict the ultimate strength and to indicate what level of accuracy would be expected.This time, the target of this benchmark is to present reliable finite element models to study the behaviour of axially compressed stiffened aluminium panels (including extruded profiles). Main objectives are to compare codes/models and to perform quantitative sensitivity analysis of the ultimate strength of a welded aluminium panel on various parameters (typically the heat-affected zone).Two phases were planned. In Phase A, all members analysed the same structure with a defined set of parameters and using different codes. It was expected that all the codes/models predict the same results. In Phase B, to boost the scope of the analysis, the different members (using their own model) performed FE analyses for a range of variation of different parameters (sensitivity analysis).     

Influence of boundary conditions on the collapse behaviour of stiffened panels under combined loads

A series of finite element analyses are conducted to investigate the influence of boundary conditions and geometry of the model on the predicted collapse behaviour of stiffened panels. Periodic and symmetric boundary conditions in the longitudinal direction are used to calculate the ultimate strength of stiffened panels under combined biaxial thrust and lateral pressure. The calculated ultimate strength of stiffened panels are compared with those by different FEM (finite element method) code and are assessed. The periodic boundary condition in the longitudinal direction for two spans or bays model provides an appropriate modelling to a continuous stiffened panel and can consider both odd and even number of half waves and thus, is considered to introduce the smaller model uncertainty for the analysis of a continuous stiffened panel.     

复合材料船体纵向极限强度可靠性分析

把船体甲板或船底板结构视为是一系列加筋板单元的组合，然后利用复合材料梁柱理论计算船体加筋板单元构件的极限承载能力，最后用Smith法计算复合材料船体的极限承载能力。由于复合材料船体纵向极限强度的极限状态方程不能简单地用船体各参数显式表达，故将近年发展起来的响应面法与JC法相结合，对复合材料船体纵向极限强度进行了可靠性分析。并讨论了影响船体纵向极限强度可靠性各变量的敏感性。     

Buckling and ultimate capability of plates and stiffened panels in axial compression

This paper presents extensive non-linear finite element (FE) analysis and formulation development work carried out on the ultimate compressive strength of plates and stiffened panels of ship structures. A review of contemporary designs for large ships was carried out. The existing formulae for plate ultimate compressive strength were reviewed and compared with non-linear FE analysis results. A semi-analytical formula for ultimate compressive strength assessments of stiffened panels was proposed and is described. The developed formula was verified against results using ABAQUS non-linear FE software for a series of 61 stiffened panels and a good agreement between the proposed formula and FE results were achieved. The method was verified against a large number of published FE results and was also compared with 58 experimental results. The developed method was also applied to the deck and bottom structures for a range of various sizes oil tankers and bulk carriers.     

Ultimate strength assessment of a tanker hull based on experimentally developed master curves

A geometrically similar scaling was made from small-scale specimen to full-scale stiffened panels and then their collapse behaviour is investigated. It is considered that the stiffened panel compressive ultimate strength test was designed according to geometrical scaling laws so that the output of the test could be used as representative of the stiffened panels of the compressive zone of a tanker hull subjected to vertical bending moment. The ultimate strength of a tanker hull is analysed by a FE analysis using the experimentally developed master stress-strain curves which are obtained by the beam tension test and the compressive test of the stiffened panel, and are then compared with the result achieved by the progressive collapse method.     

基于试验获取主应力应变曲线的油船极限强度评估研究(英文)

A geometrically similar scaling was made from small-scale specimen to full-scale stiffened panels and then their collapse behaviour is investigated. It is considered that the stiffened panel compressive ultimate strength test was designed according to geometrical scaling laws so that the output of the test could be used as representative of the stiffened panels of the compressive zone of a tanker hull subjected to vertical bending moment. The ultimate strength of a tanker hull is analysed by a FE analysis using the experimentally developed master stress-strain curves which are obtained by the beam tension test and the compressive test of the stiffened panel, and are then compared with the result achieved by the progressive collapse method.     

基于J积分的含裂纹加筋板在单轴拉伸载荷下的极限强度计算

为研究含裂纹加筋板的极限拉伸强度,本文建立一系列不同长细比、不同裂纹长度、不同裂纹位置的含裂纹加筋板有限元模型,并基于J积分理论对其在单轴拉伸载荷下的极限强度进行了计算。结果发现含裂纹加筋板极限拉伸强度随加筋板长细比的增大略有减小,但减小的程度并不明显;含裂纹加筋板极限拉伸强度随裂纹长度的增大而减小,且减小的幅度逐渐增大;加强筋上的裂纹对含裂纹加筋板极限强度的影响小于底板上的裂纹,而裂纹同时出现在底板和加强筋上时对含裂纹加筋板极限拉伸强度的影响最大。表明含贯穿型裂纹的加筋板在单轴拉伸载荷下的剩余强度对加筋板长细比不敏感,而对裂纹长度较为敏感。     

初始缺陷对加筋板结构极限强度的影响研究

采用非线性有限元软件Ansys研究包含3种初始缺陷加筋板结构在单轴压缩载荷作用下极限强度的变化趋势,即初始变形、残余应力和凹陷.以单筋单跨加筋板模型为研究对象,考虑初始变形,不同半径及不同速度的撞击球所形成的凹陷及残余应力对加筋板极限强度的影响.结果表明,初始缺陷的存在降低了结构的极限承载力,而且缺陷的叠加作用比单独缺陷存在时对结构极限强度的影响大;加筋板的极限强度随着凹陷深度的加深而减小;3种初始缺陷中,残余应力相对于初始变形和凹陷对结构极限强度的削弱影响更大.