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Artificial neural networks and their application to assessment of ultimate strength of plates with pitting corrosion 总被引：1，自引：0，他引：1
The potential for the structural capability degrading effects of both corrosion and fatigue induced cracks are of profound importance and must be both fully understood and reflected in vessel's inspection and maintenance programme. Corrosion has been studied and quantified by many researchers, however its effect on structural integrity is still subject to uncertainty, particularly with regards to localized corrosion. The present study is focused on assessing the effects of localized pitting corrosion on the ultimate strength of unstiffened plates. Over 265 non-linear finite-element analyses of panels with various locations and sizes of pitting corrosion have been carried out. The results indicate that the length, breadth and depth of pit corrosion have weakening effects on the ultimate strength of the plates while plate slenderness has only marginal effect on strength reduction. Transverse location of pit corrosion is also an important factor determining the amount of strength reduction. When corrosion spreads transversely on both edges, it has the most deteriorating effect on strength. In addition, artificial neural network (ANN) method is applied to derive a formula to predict ultimate strength reduction of locally corroded plates. It is found out that the proposed formulae can accurately predict the ultimate strength of locally corroded plates under uniaxial in-plane compression. 相似文献
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It is well known that pitting corrosion occurring on surface of hull structural plate will surely result in a significant degradation of the ultimate strength of the hull structural plate. This report aims at development of an assessing formula for ultimate strength of hull plate with pitting corrosion damage under the biaxial in-plane compression loading. The ultimate strength assessment model that is in terms of the corroded volume loss was deduced in theory, and which was then completed through numerical experiment by employing nonlinear finite element analyses for series of corroded plate models. Meanwhile, pitting corrosion in actual ship hull was analyzed and simulated, which ensured that all the assumptions for the finite element model parameters were in accord with the actual hull plate with pitting corrosion damage. Furthermore, the effects of plate slenderness, the linear factors at the plate edges and the ratio between the transverse and the longitudinal in-plane stresses on the ultimate strength reduction related to the corroded volume loss were discussed. The ultimate strength assessment formula being in terms of corroded volume loss developed in this research is expected to be applicable to assess the ultimate strength of the hull structural plate with pitting corrosion damage. 相似文献
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With the support of big data and GPU acceleration training, the artificial intelligence technology with deep learning as its core is developing rapidly and has been widely used in many fields. At the same time, feature extraction operations are required by the current image-based corrosion damage detection method in the field of ships, with little effect but consuming the large amount of manpower and financial resources. Therefore, a new method for hull structural plate corrosion damage detection and recognition based on artificial intelligence using convolutional neural network is proposed. The convolutional neural network (CNN) model is trained through a large number of classified corrosion damage images to obtain a classifier model. Then the classifier model is used with overlap-scanning sliding window algorithm to recognize and position the location of corrosion damage. Finally, the damage detection pattern for hull structural plate corrosion damage as well as other types of superficial structural damage using convolutional neural network is proposed, which can accelerate the application of artificial intelligence technology into the field of naval architecture & ocean engineering. 相似文献
5.
《Marine Policy》2013
Bulk carriers have been linked with high risks of structural failure and foundering, and with heavy loss of human life. This study used Lloyd's casualty records to investigate the extent to which dry bulk shipping has become safer over the last 30 years, and to identify shipping factors associated with the risks of bulk carriers' foundering and crew fatalities in recent years. Although there have been reductions over time in bulk carrier casualties and crew fatalities since the early 1980s, with an interim peak during the early and mid 1990s, there have been increases since 2005, linked partly to several bulk carriers that foundered when carrying nickel ore. Of 11 shipping factors considered, the strongest independent predictors of foundering and crew fatalities in recent years were the flag state, the cargo, the location of the casualty, weather conditions and the gross tonnage. Over the study period, elevated casualty and crew fatality rates were linked strongly with newly emerging or expanding flags. 相似文献
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玻纤增强柔性管作为一种新型海底油气输送管道,具有比强度高、柔度大和抗腐蚀性强等特点,因此在深海油气开发中具有非常广阔的应用前景。玻纤增强柔性管主要由内衬层、增强层和外保护层组成,其中增强层的等效模拟是玻纤增强柔性管设计成功与否的关键。根据玻纤增强柔性管的结构特征和材料特性,选取了四种不同的等效简化模型,对比研究了玻纤增强柔性管在轴向拉压荷载、弯曲荷载以及内压荷载作用下的力学性能。将不同简化模型的计算结果与相应的试验数据进行对比,进行等效模型的优选。研究结果表明,在内压载荷和弯曲载荷作用下,基于Halpin-Tsai模型数值结果与试验结果最为接近。在轴向载荷作用下,采用分离式模型或回形模型计算精度更高,若材料达到屈服状态时,则建议采用分离式模型进行模拟。 相似文献
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In jacket-type offshore structures, corrosion damage affects the structural performance under compressive loading, which is created by the working and design loads of the main system. In this study, the effects of corrosion damage on the compressive structural behavior and strength of steel tubular members were investigated. Artificial corrosion damage was applied to the tubular specimens via mechanical processing and hand drilling to replicate the inclined nature of jacket-type offshore structures. The damage was applied to either half or all of the circumference of the specimens. The compressive failure modes of the artificially corroded tubular members were affected by the corrosion conditions. The compressive strengths were also affected by the level of corrosion. From the results of this study, the residual compressive strengths of corroded tubular steel members can be estimated based on the condition of the damaged sectional areas. 相似文献
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针对构件外表面局部区域遭受随机点蚀损伤的圆管截面,考虑点蚀随机特性的影响,建立包含点蚀坑细节的精细有限元模型;在多种腐蚀强度下,研究局部腐蚀的点蚀区分布位置(沿轴向和周向分布位置变化)及其形状(点蚀区长度和宽度独立或联合变化)影响轴压极限强度退化的规律;并比较局部随机点蚀与局部均匀腐蚀引起构件极限强度退化的差异。研究结果表明,尽管局部随机点蚀与最大初始几何缺陷的耦合作用会使极限强度的退化趋于严重,但是总体而言点蚀区分布位置变化对圆管极限强度的退化没有显著的影响。此外,同等腐蚀体积和腐蚀面积下,相比于长窄式局部腐蚀,短宽式局部腐蚀会引起更严重的极限强度退化,在严重腐蚀情形下后者导致的强度退化会高出25.5%;相比于局部均匀腐蚀,局部随机点蚀会导致更剧烈的极限强度退化,其不利影响可高出20.7%。 相似文献
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In recent years many fuller ship hull forms have been designed and constructed in various shipbuilding countries, but the data available for the development of the fuller forms are inadequate from the point of view of preliminary ship design. In this paper the authors describe how they have systematically tested vessel forms of block coefficients ranging from 0.80 to 0.90. The analysis and presentation of the test results have been made in such a manner that designers can produce hull forms like those of tankers and other bulk carriers quickly and reliably. 相似文献
10.
Jeom Kee Paik Anil K. Thayamballi P. Terndrup Pedersen Young Il Park 《Ocean Engineering》2001,28(8):51
For a ship hull with large deck openings such as container vessels and some large bulk carriers, the analysis of warping stresses and hatch opening deformations is an essential part of ship structural analyses. It is thus of importance to better understand the ultimate torsional strength characteristics of ships with large hatch openings. The primary aim of the present study is to investigate the ultimate strength characteristics of ship hulls with large hatch openings under torsion. Axial (warping) as well as shear stresses are normally developed for thin-walled beams with open cross sections subjected to torsion. A procedure for calculating these stresses is briefly described. As an illustrative example, the distribution and magnitude of warping and shear stresses for a typical container vessel hull cross section under unit torsion is calculated by the procedure. By theoretical and numerical analyses, it is shown that the influence of torsion induced warping stresses on the ultimate hull girder bending strength is small for ductile hull materials while torsion induced shear stresses will of course reduce the ship hull ultimate bending moment. 相似文献
11.
In recent years, bulk carriers have been identified with high risks of catastrophic structural failure and foundering, and with heavy loss of human life. This study, based upon Lloyd's of London casualty records, identified four risk factors that had significant, independent effect upon the likelihood of a bulk carrier foundering. The risk of foundering increased with the age of the ship, and was related to the ship's flag of registration. Most importantly, however, increased risks were found for heavy cargoes of iron ore and scrap steel or iron, and for trading routes to the Far East and from Europe to North America. Additional safety measures, in particular regarding ship design and high-risk trades, may well be necessary to reduce the high casualty rates. 相似文献
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Corrosion of offshore platforms is inevitable. In an ocean corrosion environment, the strength of a platform is weakened greatly. When simultaneously subjected to earthquakes or other extreme loads, the ultimate bearing capacity of the corroded platform is dramatically reduced, resulting in compounded damage from both corrosion and earthquake. Thus, the influence of corrosion cannot be neglected in the seismic performance investigation of platforms. The commonly used corrosion model in platform design is uniform corrosion, and the corrosion rate rule for any parts or zones in a platform is the same. In real cases, however, there are significant differences between the corrosion characteristics in different parts of a platform. Based on theoretical aspects and measured data, a zonal time-variant corrosion model of a platform is developed for a seismic collapse performance investigation. The pushover and incremental dynamic analysis (IDA) methods are adopted here to calculate the collapse margin ratio (CMR), there serve strength ratio (RSR) and ductility coefficient (μ) that are frequently used for the safety reserve evaluation of a platform. The failure reason and collapse probability of platforms considering different service periods are compared. The most prominent feature of the proposed time-variant zonal corrosion model is to capture potential switch of weak location and resulting failure path of corroded jacket offshore platforms although the proposed model needs further calibration by more reliable in-field measured data. As expected, corrosion can definitely cause a reduction in earthquake resistance of a jacket offshore platform, as well as ultimate deformability. The coupled effect between the time-variant vibration properties of the platform and the spectral characteristics of selected motions, the collapse-level spectral acceleration (SA) does not always decrease with increasing corrosion degree. The curves corresponding to normalized CMR and RSR agree very well with each other in the early corrosion development stage and service period beyond 30 years. Some distinct differences can be found during the two stages, with the greatest difference up to 10% for the example platform. 相似文献
13.
提出一种随机分布点蚀损伤的模拟方法,模拟点蚀在构件表面的随机生长过程,并建立了随机态点蚀损伤圆管截面的有限元分析模型;设计了三个受不同腐蚀深度点蚀损伤的圆管构件,并开展轴压试验,利用试验结果校验有限元模型的计算精度;在多种腐蚀情形下(点蚀强度和腐蚀深度变化),研究点蚀分布模式变化引起的极限强度退化及其变异性;比较随机分布点蚀模型与传统腐蚀模型(规则分布点蚀和均匀腐蚀)在计算强度和结构失效行为方面的差异。研究结果表明,点蚀的随机分布模式会引起显著的极限强度变异,且蚀坑深度越大,强度变异越大,蚀坑分布造成的强度极差与强度均值相比达到5%;随机分布点蚀相比于传统腐蚀模型,除了引起更为严重的强度削减,还会改变结构的破坏模式。提出的随机点蚀损伤的模拟方法,可替代昂贵的构件试验,应用于评估点蚀损伤圆管截面的极限强度,增强评估结果的可靠性。 相似文献
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Study on Interaction Relationship for Submarine Pipeline with Axial Corrosion Defects 总被引：2，自引：0，他引：2
Corrosion is one of the main reasons to cause the operation accident of submarine oil and gas transmission pipelines. As the major corrosion pattern in submarine pipelines, the effects of corrosion clusters consisting of the adjacent corrosion defects on failure pressure are investigated through non-linear large-deformation finite element method. Typically, the failure behavior and limit strength of submarine pipeline with axial groove-groove corrosion defect pair exposed to internal pressure are analyzed. The effects of corrosion depth and axial spacing between a pair of corrosion defects on failure pressure are concluded. An interaction relationship for corrosion defects in pipelines, as well as prediction formulations for assessing the remaining strength of corroded pipelines are proposed. The expressions based on the proposed interaction relationship give more accurate results than the methods used in the existing design guidelines. 相似文献
15.
Based on the elastic-plastic, large-deformation finite element method, burst capacity of steel pipeline with longitudinal corrosion defect subjected to internal pressure is studied. The appropriate stress-based criterion is used to predict the failure pressure of finite element model of corroded pipeline under internal pressure. By considering the pipe steel grades and geometries of corrosion defects, a series of finite element analyses is conducted. The effects of corrosion depth, length and width on burst capacity are also discussed. A specific failure pressure solution for the assessment of corrosion defects in moderate-to-high strength pipeline is proposed on the base of numerical results. The failure pressures predicted by the proposed method are in better agreement with the experimental results than the results by the other methods. 相似文献
16.
Myung Hyun Kim Sang Min Lee Jae Myung Lee Byung Jae Noh Wha Soo Kim 《Ocean Engineering》2010,37(14-15):1243-1252
The aim of this paper is to investigate the fatigue strength of the GTT Mark-III type LNG insulation system. The LNG insulation system consists of several composite layers with various connections; plywood, triplex, reinforced polyurethane foam and mastic. Consequently, the LNG insulation system may include mechanical failures such as cracks as well as delaminations within the layers due to sloshing impact loads and fatigue loadings. In addition, these failures may cause a significant decrease of structural integrity. In this study, a series of fatigue tests have been carried out for Mark-III type LNGC insulation systems at room temperature considering the effect of sloshing impact. The load levels have been determined based on the ultimate strength of reinforced polyurethane foam. The aim of the study is to investigate the typical failure characteristics of the MARK-III LNG insulation system and to obtain the S–N data under fatigue loading. A consolidated single S–N curve is obtained based on a systematic finite element procedure. Future use of the S–N data in fatigue analysis requires that the response analysis is carried out using a finite element model with the same mesh density and material properties. This study can be used as a fundamental study for the fatigue assessment of the LNGC insulation system as well as a design guideline. 相似文献
17.
Slamming on bracings of column stabilized units shall be considered as a possible limiting criterion under transit condition based on the requirements in DNV-OS-C103. However, the wave slamming loads under survival condition were ignored for the strength analysis of the brace structures in many semi-submersible projects. In this paper, a method of strength analysis of brace structure is proposed based on the reconstruction and extrapolation of numerical model. The full-scale mooring system, the wind, wave and current loads can be considered simultaneously. Firstly, the model tests of the semi-submersible platform in wind tunnel and wave tanker have been carried out. Secondly, the numerical models of the platform are reconstructed and extrapolated based on the results of model tests. Then, a nonlinear numerical analysis has been conducted to study the wave slamming load on brace in semi-submersible platform through the reconstructed and extrapolated numerical model. For the randomness of wave load, ten subcases under each condition have been carried out. The value of the 90% Gumble distribution values of the ten subcases are used. Finally, the strength on brace structure has been analyzed considering the wave slamming. The wave slamming loads have been compared between the survival condition and transit condition with the method. The results indicate that wave slamming under survival condition is more critical than that under transit condition. Meanwhile, the wave slamming is significant to the structural strength of the brace. It should be overall considered in the strength analysis of the brace structure. 相似文献
18.
从实际问题出发,扼要阐述了平衡剖面技术的基本概念,并结合实例着重探讨了其应用研究.在介绍了与平衡剖面有关的基本概念的基础上,总结平衡剖面技术的研究流程和平衡剖面结果的评价标准,结合缅甸区块实际资料深入探讨其在断层相关褶皱构造模式建立和检验调整地震解释以及在恢复挤压构造发育史方面的应用情况,显示了其在缅甸区块叠瓦状断层转折褶皱的良好应用效果,并获得剖面的水平延展量,同时也认识到许多潜在的客观问题,有待进一步探索. 相似文献
19.
船舶与海洋结构在服役期间会遭受电化学和微生物侵蚀等多种腐蚀环境影响,加筋板作为此类结构的主要受力构件,其表面易产生不规则形态的点蚀,引起构件的强度退化。利用ANSYS有限元软件构建加筋腹板遭受随机点蚀损伤的加筋板有限元模型,研究带板长宽比、带板长细比、加筋长细比和腐蚀体积损失率对加筋板极限强度的影响。研究结果表明,加筋遭受同等腐蚀体积损失率下,带板长宽比变化对极限强度退化的影响很小,但带板长细比和加筋长细比变化产生的影响明显;带板长细比越大,极限强度退化越严重,而加筋长细比越大,极限强度退化反而越小。针对文中研究的加筋板,当加筋长细比为 0.2时,腐蚀体积率为14%的随机点蚀导致结构极限强度退化程度达到约14.0%。因此,加筋的随机点蚀损伤会显著削弱加筋板结构的极限强度,其影响不可忽略。 相似文献
20.
Resistance and propulsion characteristics of various commercial ships based on CFD results 总被引：2，自引：0，他引：2
This paper uses computational tools to examine the speed performance of various types of commercial ships including resistance and propulsion characteristics. Eight commercial ships built in the last decade were selected for the study. They include four large-sized container carriers, one bulk carrier, one VLCC, and two LNG carriers. The Reynolds averaged Navier-Stokes equation has been utilized, and the computations were executed under the same conditions of the model tests to predict the speed performance, i.e., resistance and self-propulsion. The self-propulsion point was obtained from load-varying tests. The speed performance was predicted based on the model-ship performance analysis method of the revised ITTC’78 method. The limiting streamlines on the hull, wave characteristics around the model ship, and the wake characteristics on the propeller plane were also investigated. After completing the computations, a series of model tests were conducted to evaluate the accuracy of the computational predictions. The predictions clearly reveal the differences in the resistance and propulsion characteristics regarding the various types of commercial ships, and may be applicable to hull-form design. 相似文献