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为了快速评估含船冰碰撞凹陷损伤下加筋板在轴向压缩载荷作用下的极限强度,本文采用非线性有限元法对低温凹陷损伤加筋板的极限强度进行研究。根据EH36钢在低温下的材料力学性能试验,通过折减因子评估法,基于完整加筋板在轴向压缩下极限强度的经验公式,提出以加筋板柔度和加筋板壳板柔度为变化参数,采用最小二乘法拟合折减系数,得到低温含凹陷损伤加筋板剩余极限强度的经验公式。结果表明,相比于凹陷长度和凹陷深度,凹陷宽度对加筋板极限强度的影响较大;对比分析凹陷损伤加筋板极限强度的经验公式和有限元法的计算结果,误差较小,验证了船冰碰撞凹陷损伤下加筋板的极限强度快速评估方法的准确性。 相似文献
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为研究基于船冰碰撞的含凹陷损伤加筋板的极限强度,结合Derradji-Aouat各向同性三维失效准则和弹脆性破坏模式,提出基于线弹性的多表面失效海冰本构模型。利用Ls-dyna二次开发技术,编译生成相应的求解器。通过与球形冰撞击刚性板和柱形冰撞击船体舷侧板架仿真对比分析,验证了基于线弹性多表面失效海冰动力本构模型更加适用于船冰碰撞问题的研究。利用Ls-dyna模拟海冰与船体加筋板碰撞,并将含凹陷损伤加筋板模型导入Ansys中进行加筋板剩余极限强度的计算,得到考虑凹陷影响的加筋板极限强度。结果表明,凹陷对加筋板极限强度的衰减主要体现在凹陷面积,并且凹陷面积和深度对加筋板极限强度的衰减作用随着面积和深度的增加而逐步减弱。 相似文献
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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。 相似文献
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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。 相似文献
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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。 相似文献
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研究铝合金加筋板结构的极限强度,有利于充分发挥铝合金材料的强度潜力和结构的后屈曲承载能力。本文将广义切线模量理论应用于铝合金加筋板结构的轴压极限强度计算,并推导了适用于加筋板的协调参数、极限弯矩系数及结构系数等相关参数的解析算式,建立了铝合金加筋板结构的强度利用率函数,从而得到结构的极限强度,进一步完善了广义切线模量理论在加筋板结构极限强度研究领域的应用。通过将广义切线模量法计算结果与经验公式、有限元计算结果进行比较,验证了其适用性与可靠性,可用于工程分析计算。 相似文献
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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 总被引:3,自引:0,他引:3
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。 相似文献
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《中国舰船研究》2017,(1)
船体板和加筋板的屈曲及极限强度是船舶结构强度设计的重要内容,近年来研究成果颇丰,为了能够更方便地对其展开学习和研究,对近十几年来国内外钢质船体板和加筋板的屈曲及极限强度研究进展进行综述。主要叙述了静态加载范畴下的研究现状,分别按照试验法、数值计算法、解析法和综合性方法 4种不同研究方法,对完整结构和含有开口、裂纹、腐蚀、凹痕几种不同损伤的非完整结构,在承受单一载荷或联合载荷作用下的极限强度研究成果进行系统的概述,并介绍加筋板低周疲劳和动力屈曲的研究必要性和部分研究成果,讨论各研究方法的优劣性,对一些重要的定性研究结论进行汇总,指出6个需要进一步展开研究的问题。 相似文献
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船体梁的总纵强度是反映船舶结构安全可靠的最基本的强度指标。船体结构极限强度评估对于船舶结构初步设计、使用、维护和维修都非常重要,因此船体梁极限强度研究成为近几十年来船舶工程界的热点研究课题之一。到目前为止有两种典型的加筋板和船体梁的极限强度分析方法,它们是直接计算法和逐步破坏分析法。本文基于加筋板单元的平均应力应变曲线和逐步破坏分拆方法,提出了加筋板和船体梁极限强度的简化分析方法,考虑了初始挠度和残余应力对加筋板单元极限强度的影响。数值结果表明,采用本文简化方法得到的结果与有限元计算结果或其它逐步破坏分析结果比较符合。 相似文献
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This paper is the second of two companion papers concerning the ultimate hull girder strength of container ships subjected to combined hogging moment and bottom local loads. The nonlinear finite element analysis in Part 1 has shown that local bending deformation of a double bottom due to bottom lateral loads significantly decreases the ultimate hogging strength of container ships. In this Part 2, extending Smith's method for pure bending collapse analysis of a ship's hull girder, a simplified method of progressive collapse analysis of ultimate hogging strength of container ships considering bottom local loads is developed. The double bottom is idealized as a plane grillage and the rest part of the cross section as a prismatic beam. An average stress-average strain relationship of plate/stiffened plate elements employed in Smith's method is transformed into an average stress-average plastic strain relationship, and implemented in the conventional beam finite element as a pseudo strain hardening/softening behaviors. The extended Smith's method is validated through a comparison with nonlinear finite element analysis. 相似文献
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This paper is the first of two companion papers concerning the ultimate hull girder strength of container ships subjected to combined hogging moment and bottom local loads. In the midship part of container ships, upward bottom local loads are usually larger than the downward ones. This leads to the increase of biaxial compression in the outer bottom plating and the reduction of the ultimate hull girder strength in the hogging condition. In this Part 1, the collapse behavior and ultimate strength of container ships under combined hogging moment and bottom local loads are analyzed using nonlinear finite element method. Buckling collapse behavior of bottom stiffened panels during the progressive collapse of a hull girder is closely investigated. It has been found that major factors of the reduction of ultimate hogging strength due to bottom local loads are (1) the increase of the longitudinal compression in the outer bottom and (2) the reduction of the effectiveness of the inner bottom, which is on the tension side of local bending of the double bottom. The obtained results will be utilized in the Part 2 paper to develop a simplified method of progressive collapse analysis of container ships under combined hogging moment and bottom local loads. 相似文献
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The hull girder moment capacity of a very large crude oil carrier (VLCC) called Energy Concentration (EC), for which many benchmark studies have been carried out using the simple progressive collapse method (SPCM), is predicted. In this study, three approaches are used to represent the load-shortening behavior, so-called average compressive strength, of a stiffened panel, comprising the hull section: 1) kinematic displacement theory (KDT); 2) nonlinear finite element analysis (FEA); and 3) simple formulas in the common structural rule (CSR) for tankers. Load-shortening curves for various kinds of stiffened panels in EC are compared for five different scenarios with variations of load-shortening approaches and initial imperfections. In order to verify the effect of load-shortening on the prediction accuracy of the hull girder moment-carrying capacity, load-shortening curves are imported into an SPCM-based in-house program called Ultimate Moment Analysis of Damaged Ships (UMADS). Comparison of the hull girder ultimate strength for general heeling conditions, including hogging and sagging conditions, reveals that the load-shortening curves significantly affect the hull girder moment-carrying capacities. Based on our comparison of these capacities with other benchmark results, it is concluded that nonlinear FEA provided the most conservative results, KDT provided the second most conservative results, and the CSR formulas predicted the upper bound. 相似文献
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Ultimate collapse tests of stiffened-plate ship structural units 总被引:2,自引:0,他引:2
An increasingly popular approximate method for assessing ship hull girder ultimate strength is to combine the individual elasto-plastic load-carrying characteristics of each single stiffened-plate unit comprising the ship hull cross section. In order to evaluate methods (numerical and experimental) for developing the load-carrying characteristics (load–shortening curves), a full-scale testing system was designed and constructed to provide data for stiffened steel plate units under combined axial and lateral loads. The system included an assembly of discrete plate edge restraints that were developed to represent symmetric boundary conditions within a grillage system. Twelve full-scale panels including ‘as-built’, ‘deformed’ and ‘damaged’ specimens were tested in this set-up.
The specimens failed by combined plate and flexural buckling, stiffener tripping or local collapse, depending on the magnitude of lateral loads and local damage. Load-shortening curves associated with different failure modes were found to be distinctly different and it was found that a small lateral load could change the failure mode from flexural buckling to tripping. Current design criteria should directly consider effects of the lateral loads on the failure modes and the collapse loads of stiffened plates. 相似文献