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1.
《Marine Structures》2003,16(7):489-515
Various design loads used in the strength evaluation of ship structures have been introduced currently by classification societies. As most of these design loads have been determined as standard loads for the sake of convenience, the relationships between the design loads and the sea states actually encountered by ships seem to be weak. Accordingly, it may be difficult to refer and utilize them as fundamental design concepts for ship designers or as operational guidelines for ship operators. In view of this background, various efforts (Trans. West-Jpn. Soc. Nav. Archi. 89 (1995) 191; 93 (1997) 121; Jap Shipbuild. Mar. Eng. 2 (1967) 13; Proceedings of the 18th International Conference on Offshore Mechanics and Arctic Engineering 1999; Mar. Struct. 13 (2000) 495; J. Ship. Res. 45 (2001) 228; J. Mar. Sci. Technol. 6 (2002) 122; J. Soc. Nav. Archi. Jpn. 186 (1999) 319; Technical guide regarding the strength evaluation of hull structures, 1999; Proceedings of the 14th International Conference on Offshore Mechanics and Arctic Engineering, 1995; Mar. Struct. 10 (1997) 611; Proceedings of the Eighth International Symposium on Practical Design of Ships and Other Floating Structures, Shanghai, Vol. 2, China, 2001, p. 1089; Mar. Struct. 12 (1999) 171; Mar. Struct. 4 (1991) 295) have been made in recent years for developing estimation methods of the design sea states in a rational manner. Furthermore, for more practical purposes, the authors have developed practical estimation methods of the design sea states, the design regular waves and the design loads having transparent and consistent backgrounds to the actual loads acting on primary structural members of tankers (Mar. Struct. 16 (2003) 275).In this paper, it is firstly confirmed that the proposed methods for tanker structures can also be applied to the primary structural members of bulk carriers. Furthermore, the necessary modifications are carried out considering the specific structural types and loading conditions of bulk carriers in order to improve the estimating accuracy of the proposed design loads. Finally, comparisons between the results obtained by the structural analysis of a hold model applying the proposed design loads and long-term values of stresses by the most advanced direct structural analyses for different loading conditions are introduced and discussed in detail. 相似文献
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《Marine Structures》2003,16(2):135-148
The Technical Committee I.2 of the 14th International Ship and Offshore Structures Congress 2000 identified the occurrence of highly peaked loads in the mooring hawser of single-point moored (SPM) ships as an important issue. Industry, research laboratories and universities were requested to contribute to a systematic study investigating the mooring load of two single-point moored tankers subject to a steady current. Contributions were received from three industrial participants, one research laboratory, and three universities. Comparative simulated time histories of the mooring load as well as the corresponding horizontal motion response of the SPM tankers were analyzed. A relatively large spread characterized the predicted results. 相似文献
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船舶舷侧细节结构的热点应力计算中的不确定性因素研究 总被引:1,自引:1,他引:0
疲劳是船舶结构一种重要的失效模式。在过去的十多年间,涌现出了一些不同的疲劳强度的评估方法,其中S-N曲线法在船级社中得到了广泛的应用。但是,仅就S-N曲线法中的热点应力法而言,不同的组织和个人所预报的疲劳寿命通常也存在很大差异,而计算所得的热点应力集中系数的不同是产生这些差异的一个重要影响因素。本文运用有限元比较研究的方法,对某船舶舷侧细节结构的热点应力计算中可能存在的不确定因素进行了综合分析。通过采用不同的单元类型,不同的建模方法以及不同的有限元软件ABAQUS和ANSYS,得出了相关结论,为正确计算此类船舶结构细节的热点应力提供了指导。 相似文献
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根据IACS共同规范(CSR),针对散货船结构,采用逐步递增破坏分析法计算船体结构的极限承载能力,同时编制了计算程序。对典型箱型梁模型和一艘散货船极限强度的计算结果表明,我们所开发的计算程序是正确可靠的。此外,对影响散货船极限强度的参数进行了敏感度探讨,计算结果表明屈服应力和板厚对船体极限强度的影响很大,应着重考虑。 相似文献
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当前,船舶经营者正不断寻求提高船舶安全性、可靠性和寿命周期成本效益,以应对全球航运业日益激烈的竞争。实施以可靠性为中心的维修计划,在消耗更少资源的基础上维持和提高船舶的可靠性,是全球船舶经营人的目标。在此介绍一个目前在美国实施的船舶作业合作计划(SOCP:Ship Operations Cooperative Program),该计划以提高船舶寿命周期成本效益和安全性为目的。主要介绍了SOCP的RAM数据库中所包含的信息、RAM数据的收集和共享方式以及RAM数据库/SHIPNET的功能结构,并给出一个该系统的应用实例,最后简述了美国海岸警备队的海上安全评估计划(MSTEP:Marine Safety Evaluation Program)及其与SOCP的RAM数据库/SHIPNET的联系。 相似文献
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采用简化方法的船体结构疲劳强度校核 总被引:2,自引:0,他引:2
本文介绍用简化方法进行船体结构疲劳强度校核的基本原理。这一方法已为中国船级社近期编制的《船体结构疲劳强度指南》所采纳。文中介绍了疲劳载荷的计算,疲劳应力的计算及疲劳累积损伤的计算,并给出例题说明这一方法的具体应用。 相似文献
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江海直达船属于浅吃水大型宽船,往复航经江段和海段,其疲劳问题不容忽视。将江段和海段载荷简化为小和大2级交变载荷,选取较为典型的船底纵骨贯穿横舱壁节点,通过对比试验探讨2级交变载荷对该船疲劳寿命的影响。试验结果表明,在试验工况下,变幅载荷中的大载荷是导致裂纹扩展的主要因素,小载荷的参与会降低大载荷作用下裂纹扩展的速率。采用等效应力法对变幅载荷下节点的疲劳寿命进行评估,发现采用Miner准则所得结果偏保守,采用均方根法所得结果偏危险,采用修正的Miner准则所得结果精度较高,推荐采用该方法评估2级交变载荷下船体结构典型节点的疲劳寿命。 相似文献
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Keith R. McAllister 《Journal of Marine Science and Technology》1997,2(3):173-181
The Mobile Offshore Base (MOB) is a multipurpose, floating logistics base which can be stationed in coastal or international
waters. The offshore base is comprised of self-propelled modules that are connected together at sea to form a runway and support
base for fixed-wing aircraft and helicopters. The MOB is used as a prepositioned cargo stowage and transshipment point, enabling
the movement of cargo to and from ships in an open seaway. Described here is an approach to developing a mobile, offshore
basing capability. The work is discussed in context of two significant MOB projects including a discussion of criteria and
major technical issues.
Presented at the International Workshop on Very Large Floating Structures (VLFS'96), 25–28 November 1996, Hayama, Japan 相似文献
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The authors have developed a simulation program, CP-System, for multiple cracks propagating in a three-dimensional stiffened
panel structure, where through-the-thickness crack propagation is formulated as a two-dimensional in-plane problem, and the
crack propagation behavior is simulated by step-by-step finite element analyses. In order to evaluate the fatigue lives of
marine structures accurately, it is necessary to take into account the load histories induced by sea waves, which may be composed
of a random sequence of certain clustered loads with variable stress range. In the proposed crack growth model, the crack
opening and closure behavior is simulated by using the modified strip yielding model, and the effective tensile plastic stress
intensity range, ΔK
RP, is calculated by considering the contact of plastic wake along the crack surfaces. The adequacy of the proposed crack growth
model is examined by comparison with fatigue tests under non-constant-amplitude loading. The usefulness of the developed method
is demonstrated for a ship structural detail under certain simulated load sequences. It is shown that the fatigue crack growth
of a ship structure is significantly retarded due to the load interaction effects, so that the conventional method for fatigue
life assessment may predict a relatively conservative fatigue life of a structure. 相似文献
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由于高强度钢的使用,船舶结构许用应力水平的提高,船舶结构的疲劳强度越来越受到关注。船舶结构的疲劳寿命取决于其焊接结构的疲劳寿命。因此,了解焊缝几何参数对焊件疲劳强度的影响以及采用经济实用的方法改善船舶结构的疲劳性能是十分重要的。本文首先对焊缝几何参数对焊件疲劳寿命的影响进行了分析,在此基础上用ABS钢和945钢两种钢板做试件,分别进行了简单拉伸实验及打磨和未打磨条件下对接接头的疲劳试验。试验结果表明焊件的疲劳寿命可以通过打磨焊缝得到改善;尤其对于高强度钢焊件。试验还说明手工打磨焊缝和机械磨削焊缝对焊件疲劳强度的改善效果差别很大,疲劳寿命的分散性也很大。因此,应当对改善焊件疲劳寿命的工艺进行更详细的研究。 相似文献
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船舶航行于江河湖海且装载各种货物,这决定了其构件常常承受交变载荷和腐蚀环境的共同作用,进行疲劳强度评估时必须对腐蚀介质的影响加以考虑。依据中国船级社2013年版《船体结构强度指南》,对某LNG船底边舱折角的节点疲劳强度进行了计算,分别采用腐蚀修正系数,腐蚀条件下S-N曲线和扣除腐蚀余量等三种修正方式来考虑腐蚀对疲劳强度评估的影响。研究表明,采用腐蚀条件下S-N曲线方法校核最为苛刻,扣除腐蚀余量1.5mm的结果和腐蚀修正系数1.08的结果接近。 相似文献
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基于雨流计数法及Corten-Dolan准则的轴承疲劳寿命预测 总被引:1,自引:0,他引:1
船舶轴承是船舶推进系统中的重要支撑部件,其稳定可靠的工作状态是推进轴系健康服役的重要保障。由于轴承的破坏形式主要为材料疲劳磨损引发的故障失效,故开展船舶轴承的疲劳磨损状态研究就显得尤为重要。本文针对轴承结构疲劳损伤问题,通过MATLAB软件实现雨流计数法原理的计算机语言编写,研究了四点雨流计数法对船舶轴承危险节点的动态应力分析应用,并提取出对应的循环应力载荷谱。考虑平均应力的影响,运用Gerber曲线对统计得到的循环载荷进行等寿命转化。最终利用轴承材料S-N曲线,结合Corten Dolan准则进行疲劳寿命预测计算,得出船舶轴承在相应外部循环载荷作用下的最终寿命。为轴承的设计和优化提供了理论参考依据,对船舶轴系运行管理具有重要的现实意义。 相似文献
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Ship structures are submitted to variable cyclic loading during navigation. The cyclic motion of waves induces variable and complex loadings in the structure, which could generate fatigue damage. Moreover, most of these metallic structures are welded assemblies. This technique generates local stress concentrations at the weld toe, which becomes a critical area regarding fatigue. In previous works, a methodology to predict fatigue life was developed and tested on butt-welded and cruciform joints. The present work focuses on other welded assemblies in order to extend fatigue crack initiation life evaluation to a wider range of ship details. The strategy could be split into two steps. First, a finite element calculation is performed under constant or variable amplitude loadings, in order to analyze the elastic shakedown of the structure. To characterize the material heterogeneity of the welded joint, experimental tests together with micro-hardness measurements, are performed on a simulated heat-affected zone. If there is a shakedown in the structure, a post-treatment is applied to predict the fatigue crack initiation. It is based on a two-scale damage model, initially developed by Lemaitre et al. and again includes the heterogeneity of fatigue properties. To validate this methodology, some experimental tests have been performed on welded assemblies which are typical of shipbuilding applications, using a fatigue machine. These comparisons between experimental and numerical fatigue lives are encouraging. 相似文献
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从船舶航速预报、耐波性能和操纵性能预报的市场需求出发,分析了国内外船舶综合性能预报的现状,详细介绍了由上海船舶运输科学研究所承担,中国船舶工业集团第708所、中国船舶重工集团第702所参加开发的船舶综合性能预报系统(SPPS1.0)。该预报系统首次将计算机网络技术、母型船航速预报技术和优良船型水动力试验动态数据库有机结合起来,并应用耐波性理论、操纵性理论,建立起依托互联网,面向船舶行业,实时远程预报船舶性能的共性技术平台;开发的系统软件有效解决了数据库中核心技术资源的保密性和全行业共享应用的矛盾,具有良好实用性和预报指标的先进性。 相似文献
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The behavior of a ship in regular waves during maneuvering was studied by using a two-time scale model. The maneuvering analysis was based on Söding’s (Schiffstechnik 1982; 29:3–29) nonlinear slender-body theory generalized to account for heel. Forces and moments due to rudder, propeller, and viscous cross-flow follow from the state-of-the-art procedures. The developed unified theory of seakeeping and maneuvering was verified and validated for calm water by comparing it with experimental and calculated zigzag and circle maneuvers. Linear wave-induced motions and loads were determined by generalizing the Salvesen-Tuck-Faltinsen (Trans SNAME 1970; 78:250–287) strip theory. The mean second-order wave loads in incident regular deep water waves in oblique sea conditions were estimated by the potential flow theories of Faltinsen et al. (Proc 13th Symp Naval Hydrody 1980), Salvesen (Proc Intl Symp Dynam Mar Vehicl Struct Wave 1974), and Loukakis and Sclavounos (J Ship Res 1978; 22:1–19). The considered theories cover the whole range of important wavelengths. Comparisons between the different mean second-order wave load theories and available experimental data were carried out for different ship hull forms when the ship was advancing forward on a straight course. The mentioned methods have been incorporated into the maneuvering model. Their applicability from the perspective of the maneuvering ability of the selected types of ships was investigated in given wave environments. The wave conditions are valid for realistic maneuvering cases in open coastal areas. It was demonstrated that the incident waves may have an important influence on the maneuvering behavior of a ship. The added resistance, mean second-order transverse force, and yaw moment also play important roles. 相似文献
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K.Vikestad文章中预报出的立管疲劳寿命特别长,经过仔细校核发现作者用于计算的弹性模量与试验值不同.是否这一错误会导致疲劳寿命的重要差别,本文对这一问题做了进一步研究.本文采用了与上述文章中类似的方法来重新计算立管的涡激振动疲劳损伤.利用作者所在课题组开发的涡激振动预报程序来确定立管动力响应,并假设涡激振动引起的长期应力范围分布是Rayleigh分布,运用Palmgren-Miner线性累积损伤准则来预报海洋立管涡激振动疲劳损伤.和依据试验测量数据计算得到的疲劳损伤以及ⅤⅣANA预报的结果比较表明,本文的预报方法是合理的.研究表明上述文章中过高的疲劳寿命是由错误的弹性模量引起的.结果显示,立管的弹性模量对于涡激振动疲劳损伤是个重要的参数.弹性模量越大,疲劳寿命越低. 相似文献