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《船舶力学》2019,(12)
压溃作为海洋柔性管道的一种典型失效形式,对其进行研究具有重要的工程价值。文章考虑了内护套层的影响,建立了包含内护套层的海洋柔性管道骨架层湿式压溃有限元模型,采用弧长法,分别考虑了初始椭圆度、接触非线性和材料非线性的参数影响,进行了骨架层非线性压溃力学性能的数值模拟,并与不含内护套层的单纯骨架层压溃模型进行了对比。研究结果表明,随着初始椭圆度的增加,临界压溃载荷会降低,呈现负相关关系;考虑接触非线性和材料非线性因素会对临界压溃载荷产生较大影响,具体表现为随着摩擦系数和材料屈服应力的增加,临界压溃载荷也会增加,呈现正相关关系;考虑内护套影响后,临界压溃载荷略有增加,说明内护套层在承担外压载荷时也起到了一定作用,但对于计算骨架层临界压溃载荷值影响不大。 相似文献
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通过对不同性质的地基土对压杆的稳定性影响进行分析,确定了压杆欧拉临界力的计算公式,以压杆欧拉临界力计算公式为基础,建立起压杆新的截面设计稳定条件,并考虑残余应力对压杆的实际影响,用直接荷载法对压杆截面尺寸进行设计. 相似文献
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由于作业方式不同,用于计算FPSO与不限定航线条件下船舶设计载荷的规范计算公式不一样,如何将现有的关于普通海船的规范用于FPSO的设计评估是FPSO研究中的关键问题.基于现有常规钢质海船规范,文章采用环境烈度因子(ESF)对用于计算运营于无限航区船舶设计载荷的规范公式进行修正,将修正后的公式作为FPSO设计载荷的计算公式.利用所得FPSO载荷计算公式计算某30万吨FPSO设计载荷,并采用薄壁梁理论对船体梁强度进行校核.将校核结果与未经ESF修正的船体梁校核结果进行比较,发现未经ESF修正的船体梁校核结果明显偏大.同时,采用薄壁梁理论进行船体梁剪切强度评估,可以避免建立全船有限元模型. 相似文献
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Simplified methods to estimate mean axial crushing forces of plated structures are reviewed and applied to a series of experimental results for axial crushing of large-scale bulbous bow models. Methods based on intersection unit elements such as L-, T- and X-type elements as well as methods based on plate unit elements are employed in the analyses. The crushing forces and the total absorbed energy obtained by the simplified analyses are compared with those obtained from large-scale bulbous bow experiments. The accuracy and the applicability of these methods are discussed in detail. 相似文献
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The paper presents a simplified analytical method to examine the crushing resistance of web girders subjected to local static or dynamic in-plane loads. A new theoretical model, inspired by existing simplified approaches, is developed to describe the progressive plastic deformation behaviour of web girders. It is of considerable practical importance to estimate the extent of structural deformation within ship web girders during collision and grounding accidents. In this paper, new formulae to evaluate this crushing force are proposed on the basis of a new folding deformation mode. The folding deformation of web girders is divided into two parts, plastic deformation and elastic buckling zones, which are not taken into account for in the existing models. Thus, the proposed formulae can well express the crushing deformation behaviour of the first and subsequent folds. They are validated with experimental results of web girder found in literature and actual numerical simulations performed by the explicit LS-DYNA finite element solver. The elastic buckling zone, which absorbs almost zero energy, is captured and confirmed by the numerical results. In addition, the analytical method derives expressions to estimate the average strain rate of the web girders during the impact process and evaluates the material strain rate sensitivity with the Cowper-Symonds constitutive model. These adopted formulae, validated with an existing drop weight impact test, can well capture the dynamic effect of web girders. 相似文献
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For offshore wind farms which are planned in sub-arctic regions like the Baltic Sea and Bohai Bay, support structure design has to account for load effects from dynamic ice-structure interaction. There is relatively high uncertainty related to dynamic ice loads as little to no load- and response data of offshore wind turbines exposed to drifting ice exists. In the present study the potential for the development of ice-induced vibrations for an offshore wind turbine on monopile foundation is experimentally investigated. The experiments aimed to reproduce at scale the interaction of an idling and operational 14 MW turbine with ice representative of 50-year return period Southern Baltic Sea conditions. A real-time hybrid test setup was used to allow the incorporation of the specific modal properties of an offshore wind turbine at the ice action point, as well as virtual wind loading. The experiments showed that all known regimes of ice-induced vibrations develop depending on the magnitude of the ice drift speed. At low speed this is intermittent crushing and at intermediate speeds is ‘frequency lock-in’ in the second global bending mode of the turbine. For high ice speeds continuous brittle crushing was found. A new finding is the development of an interaction regime with a strongly amplified non-harmonic first-mode response of the structure, combined with higher modes after moments of global ice failure. The regime develops between speeds where intermittent crushing and frequency lock-in in the second global bending mode develop. The development of this regime can be related to the specific modal properties of the wind turbine, for which the second and third global bending mode can be easily excited at the ice action point. Preliminary numerical simulations with a phenomenological ice model coupled to a full wind turbine model show that intermittent crushing and the new regime result in the largest bending moments for a large part of the support structure. Frequency lock-in and continuous brittle crushing result in significantly smaller bending moments throughout the structure. 相似文献
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Results from full scale fatigue tests of offshore mooring chains are analyzed. The data set includes new and used chains, tested at a variety of mean load levels. The used chains have been retrieved after operation offshore and include samples with varying surface conditions, ranging from as-new to heavily corroded. Based on a parameterized S–N curve intercept parameter, the effects of mean load and chain condition are estimated empirically by regression analysis. A hierarchical linear model is used, to account for and quantify correlations within subsets of the data. The choice of grouping criterion for the hierarchical model is discussed, and assessed based on the current data. Results show that the mean load and corrosion effects are both significant. Differences in the fatigue performance of new versus used chains are quantified and discussed. 相似文献
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针对豪华邮轮在每次航行中每餐都会产生大量的餐厨垃圾,设计一款餐厨垃圾处理系统。该系统研究了一种新型的斜齿圆柱齿轮磨辊粉碎方式和微波干燥脱水方式相结合而成的餐厨垃圾粉碎脱水一体机,并对脱水后的处理工艺压缩储存进行研究。应用CATIA软件对邮轮用餐厨垃圾粉碎脱水一体机和压缩装置进行三维建模并基于Workbench软件对粉碎装置的齿轮磨辊进行接触分析和自由模态分析,验证此设计的可行性。 相似文献
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Ice loads are important environmental loads that can influence the structural safety of ships during navigation in ice-covered waters. The identification of ice loads on ship hulls is the core of ice load monitoring. In this study, a new ice load identification model based on Green kernel and regularization methods is established. First, the forward model for ice load identification is developed through the discretised convolution integral of ice loads. Next, three commonly used regularization methods, including Tikhonov, truncated singular value decomposition, and least square QR-factorization (LSQR) are adopted to reduce solution errors. The LSQR method is thereafter selected as the optimal regularization operator, and its regular property is proved by numerical cases with ice-induced strains that contain noise. Finally, two load identification cases are conducted on an experimental rig to evaluate the feasibility of the model in ice load identification. The identified loads can determine the signal features of applied loads in the time domain with good accuracy. This identification model provides new insights for full-scale ice load monitoring. 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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Yasumi Toyama 《Marine Structures》2009,22(1):24-41
Impact load estimation of drift-wood hitting against the bow structure of high-speed vessels has been investigated. It may be difficult for the craft operator to detect in advance a drift-wood floating just below the ocean surface and to avoid the collision with it. It is particularly difficult for operators of the high-speed vessels in night cruising mode. The probability of the accident may be higher than that of the collision with rocks or other ships because of the difficulties of early detection of the floating object. Impact loads are estimated for drift-wood of different sizes and craft speed considering whipping motion and local crushing of the wood at the hitting region. A simplified formula for the load estimation is proposed based on the modal approach and the energy balance. Predicted impact loads can be applied to the initial design of the bow structure and collision bulkhead of the craft to secure the structural safety against a possible accident. 相似文献
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The interaction of ice with a polar ship is complex, which may involve several ice failure mechanisms such as local crushing, tensile, cracking, bending, shearing, sliding and the ship structures could attain permanent deformations. A reasonable modeling of ice behavior is, therefore, critical to the analysis of ship-ice interactions. This paper reports an experimental and numerical study on the behavior of stiffened panels subject to the impact of a wedge-shaped ice block/indenter. The tested stiffened panel was mounted to a Falling Weight Impact Tester, and measurements were taken to help understand the dynamic responses of the structure and the ice, and also the permanent deformations. Finite element analyses using ABAQUS/EXPLICIT were also performed for the lab tests. The proposed ice model features a multi-surface yield function, empirical failure criteria for a few ice failure modes, and a representation of the remaining load carrying capacity of crushed ice. This ice model is implemented in a user-defined subroutine VUMAT and uses the cohesive element in a numerical solution. The predicted and measured impact force and structural deformation compared very well with the tests, indicating that the proposed ice model coded in VUMAT is reasonable. A series of parametric studies was then carried out to identify the key parameters of this new ice model that would have major effects on the prediction of ice impacts. The paper intends to provide test data that may be useful in understanding the complex ice-ship interaction and to introduce a numerical solution with a new ice model that improves the simulation of high-energy ice-ship impacts. 相似文献