集装箱船舱口角隅应力集中系数的有限元分析的精度

集装箱船舱口角隅的应力集中是船舶结构强度的一个重要问题。随着有限元技术的发展，目前舱口角隅的应力集中系数大都可以通过有限元计算直接获得。由于有限元分析过程中存在着大量不确定性，通过控制其有限元分析各个步骤的质量来保证有限元分析的精度，已经成为一个重要的研究方向。本文利用现有有限元分析软件（ABAQUS），通过对不同模型简化方法的讨论，给出了正确计算舱口角隅结构应力集中系数的模型简化方法，并在此基础上讨论了网格尺度对应力集中系数的影响。     

外压圆锥壳开孔应力集中系数分析

采用有限元方法,对不同锥角开孔的应力集中系数的大小及分布规律进行分析,认为开孔倾斜角对应力集中系数影响较大,在实际应用中应严格控制。     

海洋平台T型管节点应力集中系数研究

以具有代表性的海洋平台形管接头为例,采用有限元方法,研究接头处的应力集中系数分布.分析支管6个自由度的约束条件和受载方式,基于ABAQUS计算管节点在各种载荷下的应力分布,尤其关注几何学上的最危险地带——管筒十字交叉点处的应力集中系数,并根据6种基本情况下T形管节点的有限元计算结果,得到管节点所受到的应力最大、结构强度...     

圆柱壳大开孔补强的应力集中分析

针对潜艇耐压壳体上大开孔补强处的应力集中现象,结合工程实际问题,采用规范和有限元法对潜艇耐压壳体上大开孔不同补强形式进行了研究,建立了相应的模型,并求出了应力集中系数。通过对两种方法的计算结果进行分析比较,发现当围壁加强时,最大周向应力处的弯曲应力不容忽视。结果说明,用有限单元法进行大开孔补强结构设计是合理、有效的,是对规范计算的完善和补充。     

弯曲载荷下骨材贯穿孔孔边应力分布模型试验

考虑到疲劳裂纹主要发生在船舶结构高应力区域,骨材开孔会造成孔边应力集中从而造成疲劳破坏,影响船体结构的安全性,以船舶双层底结构为研究对象,开展模型试验对船舶双层底结构在典型弯曲载荷情况下的骨材开孔孔边应力分布情况进行研究,分析弯曲载荷下不同开孔形状以及不同补强结构对孔边应力分布的影响。试验结果与有限元仿真结果对比表明,二者具有相同的规律和趋势,证明用数值仿真的方法分析骨材开槽孔孔边应力集中问题是可行的。     

有限元分析在船舶轴系设计中的应用

使用Abaqus软件建立船舶轴系中间轴的模型，通过有限元方法计算轴法兰过渡处的应力集中系数，分析应力集中系数与轴系扭振计算结果之间的关系。相比于单圆弧过渡，三段式圆弧过渡将应力集中系数减小了20%，持续运转扭振许用应力提高了38%，瞬时运转扭振许用应力提高了17%。运用有限元分析方法检验校核了船舶轴系设计的合理性。     

自升式平台的局部结构应力分析

利用有限元法对自升式海洋平台纵舱壁和横舱壁上开孔前后的应力进行计算,分析开孔形状及开孔处采用不同的加强方式对局部结构应力的影响,计算得到开孔不同形状及不同加强方式时结构的应力。在平台主体舱壁上开圆角矩形时应力较小,在开孔上增加面板可以显著降低孔边缘的应力。平台桩腿开孔时应力集中系数急剧增加,桩腿载荷不同对桩腿受力有很大影响。     

双层底肋板贯穿孔孔边应力数值仿真分析

船舶航行过程中,船体结构会受到总纵弯曲与舱外水压、货物载荷等组合载荷的交变作用,骨材开孔处会出现孔边应力集中,进而造成结构疲劳破坏的问题。针对船体骨材开孔结构开展典型载荷作用下的孔边应力分析。以船舶双层底结构为研究对象,开展典型弯曲、压缩载荷作用下的船舶双层底结构骨材开孔孔边应力分布有限元仿真研究,分析弯曲、压缩载荷作用下不同补强结构对孔边应力分布的影响,为船体骨材贯穿孔结构的优化设计提供参考。     

轴向载荷下多平面DT型管节点 应力集中系数研究

应力集中系数对于海洋平台结构中管节点的疲劳寿命评估至关重要。文章以多平面DT型管节点为研究对象,采用有限元方法分析了轴向载荷作用下沿其弦管—撑管相贯线焊缝的应力集中系数分布。在保证计算精度的前提下尽量减少网格数量,采用分区网格划分方法进行管节点建模。基于有限元分析结果,研究了不同几何形状参数对应力集中系数分布变化规律的影响,拟合得到一组应力集中系数参数公式,并通过两种相对误差验证了该参数公式的有效性。     

基于应力集中系数的SWATH船疲劳节点筛选方法研究

小水线面双体船的疲劳强度问题十分突出,疲劳强度校核节点众多且目前还没有一个明确的疲劳节点筛选原则。针对这些问题,研究基于典型节点的热点应力集中系数有限元计算和名义应力分析,对小水线面双体船全船结构中可能发生疲劳强度失效的节点进行疲劳寿命估算,并根据估算结果对需要进行热点应力分析的疲劳节点进行筛选。计算结果表明,该方法在处理大量结构节点的疲劳寿命估算问题中,计算效率较高,能够反映全船的节点疲劳强度特性,且估算结果较为可靠。该方法不仅适用于小水线面双体船,对于其他类型的船舶,该方法同样具有适用性。     

Fatigue analysis of ship structures with hinged deck design by finite element method. A case study: Fatigue analysis of the primary supporting members of 4900 PCTC

In the design phase of a 4900 PCTC (Pure Car/Truck Carrier) with hinged deck design, fatigue behavior and fatigue life is investigated for various structural details. The global finite element analysis shows high local stress concentrations at the connections of various details. In this article, the detailed analysis of the investigation of fatigue analysis and fatigue life of the connection between the vertical side web and the main deck (deck 5) of the entire vessel is performed according to Det Norske Veritas (DNV) Rules. In order to achieve more accurate results, three types of finite element analysis (global finite element model, fine-mesh finite element model and stress concentration models) are hierarchically used. The investigation for finite element analysis for fatigue analysis is based on the approach using hot spot stresses.     

Stress analysis of a transversely loaded aluminum weldment

The analysis of welded structural details is an important component in determining life cycle estimates. As part of a project to develop guidelines for reducing cracks in aluminum ship structures, the authors performed experiments showing that the stress levels developed strongly depend on the welded connection details. To properly quantify the effects of connection details, a stress analysis of the detail is required. This investigation summarizes the analysis of a common structural detail, one that results in a transversely loaded weldment.This paper is motivated by two sets of experimental test results. The first is the stress concentration observed at the intersection of the longitudinal and transverse members in a 1.5-m×3-m aluminum bottom panel tested under uniform pressure loading. The second is the reduction in fatigue life due to weld geometry variations between manually welded and machine-welded aluminum specimens. In order to clarify these two observations, the authors completed a detailed finite element analysis of a welded aluminum T-stiffener. The results show a significant stress concentration in the weld toe area. This stress concentration is shown to be strongly dependent on the weld toe geometry.     

Stress concentration factors in FRP-reinforced tubular DKT joints under axial loads

The stress concentration factors (SCFs) in uniplanar fibre-reinforced polymer (FRP) DKT joints are calculated under five axial loading conditions to determine the maximum SCFs. To this end, 108 finite element models of reinforced DKT joints with different FRPs and geometrical parameters are analysed. Available experimental data and formulas are used to validate the finite element models. The validated finite element models are utilized to investigate the effects of the FRP parameters along with different geometrical parameters on the stress concentration factors in uniplanar DKT joints. The simulations show a reduction of the maximum SCF by around 40% compared to unreinforced DKT joints. The reduction effect increases significantly with increasing the FRP thickness and the number of layers. Despite the notable efficacy of the FRP sheets on the drop of the SCFs in the X-connections, there is not any study or equation on the X-joints with FRP. Therefore, a precise equation is proposed for quantifying the SCFs in X-connections with FRP and is checked against the UK DoE acceptance standard.     

FPSO延寿疲劳评估和疲劳寿命改善设计

以“南海胜利”FPSO原作业区的第三次延寿项目为研究对象，对纵骨与横舱壁、横向强框的连接节点，舱内桁材大肘板趾端节点，模块支墩与主甲板连接处的肘板趾端节点，以及与内转塔装置连接处的结构节点，分别采用了简化疲劳方法、热点应力法及谱疲劳分析法，对不同部位节点进行疲劳评估，并针对疲劳高危节点，通过合理的结构形式改造，进行结构的疲劳寿命改善设计。本文旨在探索疲劳评估方法与寿命改善设计在FPSO延寿改造中的应用。     

Stress concentration factors of multi-planar tubular KT-joints subjected to in-plane bending moments

Numerical research on the stress concentration factors (SCFs) in uniplanar tubular joints is abundantly reported in literature. However, it has been shown that SCF equations for uniplanar joints can lead to both under- or overestimation of the SCFs in multi-planar joints. In this paper, a parametric finite element study of 81 different three-planar KT joints subjected to five different in-plane bending loading conditions is performed. The effects of different non-dimensional geometrical parameters on the SCF values at the crown locations of the central and outer braces are studied. Based on nonlinear regression analyses of the finite element results, a new set of SCF equations is developed and presented.     

双壳型船体结构稳态温度场和温度应力

用简化解析方法和有限元数值方法,分析了双壳型船体货舱区域在运载高温液货时的稳态温度场;根据船体结构的温度分布,用有限元法计算了其温度应力,同时与货物压力、海水静动压力、总纵弯矩等载荷作用下的结构应力做了比较。研究结果表明：在货舱结构温度场分析中用简化分析方法和有限元数值方法所得的计算结果相当一致;高温液货大幅度增加船体结构的纵向应力和横向应力,同时加剧结构不连续处的应力集中;槽型舱壁可以有效地释放     

基于LR规范的豪华邮轮全船有限元分析流程及应用

对豪华邮轮进行全船结构强度分析是其结构设计的必要条件。文章基于LR规范,介绍豪华邮轮有限元分析流程,包括边界条件、设计载荷、计算工况和强度准则等,以某艘14万总吨级的豪华邮轮为实例,采用有限元手段对其全船结构强度进行计算,并分析应力分布特点和主要纵向连续结构的有效度,结果表明:该邮轮结构的总纵正应力和剪应力主要分别由甲板结构及连续纵舱壁结构参与传递。该结论可为豪华邮轮结构设计提供一些参考。     

FPSO节点焊趾处的裂纹修理形状研究

对焊缝处出现的裂纹进行修理以阻止其进一步扩展,能够有效地延长FPSO焊接结构的疲劳寿命.考虑到应力集中而造成的疲劳寿命的降低,要谨慎选取修理时所采用的形状和尺寸,避免在修理后产生的表面缺陷处出现过高的应力集中.文中旨在进行三维T型焊接节点焊趾处的裂纹修理分析,为了选取合理的修理切口,首先对不同几何形状和尺寸的二维焊接修理切口,如抛物线型和椭圆型等,进行了应力集中系数的计算,并与相类似尺寸的U型切口的计算结果进行了比较.结果表明,当切口的表面半宽长于其深度时,椭圆型的裂纹修理切口具有更低的应力集中系数.随后,选择应力集中较小的椭圆型和U型切口焊接修理形状,并采用更加精确的三维有限元分析方法进行分析,给出了通过打磨等修理方式消除裂纹后得到的三维表面缺陷的应力集中系数,为工程上焊趾处裂纹的修理提供决策依据.     

冰区加强LNG船舷侧抗撞性能仿真研究

航行于北冰洋海域的LNG船必须具备抵抗冰山撞击的能力。针对LNG船纵骨架式和横骨架式冰区结构加强方案,开展比较分析,评价LNG船舷侧抵抗冰山撞击的能力。根据CCS规范对LNG船舷侧分别进行纵骨架式与横骨架式冰区加强设计。利用有限元数值仿真技术和LS_DYNA软件,模拟冰山撞击LNG船舷侧场景,得到船体结构变形、碰撞力和能量吸收等结果。研究发现：横骨架式在相邻强横肋位之间结构较弱,纵骨架式表现出更好的抗冰撞击性能;冰带加强骨材在抵抗冰载荷过程中发挥重要作用;在提高抗冰撞击性能的前提下,纵骨架式加强方案拥有更佳的经济效益。     

双平面焊接圆管截面DKT节点的中心撑杆鞍点及冠点位置的应力集中系数(英文)

A set of parametric stress analyses was carried out for two-planar tubular DKT-joints under different axial loading conditions.The analysis results were used to present general remarks on the effects of the geometrical parameters on stress concentration factors(SCFs) at the inner saddle,outer saddle,and crown positions on the central brace.Based on results of finite element(FE) analysis and through nonlinear regression analysis,a new set of SCF parametric equations was established for fatigue design purposes.An assessment study of equations was conducted against the experimental data and original SCF database.The satisfaction of acceptance criteria proposed by the UK Department of Energy(UK DoE) was also checked.Results of parametric study showed that highly remarkable differences exist between the SCF values in a multi-planar DKT-joint and the corresponding SCFs in an equivalent uni-planar KT-joint having the same geometrical properties.It can be clearly concluded from this observation that using the equations proposed for uni-planar KT-connections to compute the SCFs in multi-planar DKT-joints will lead to either considerably under-predicting or over-predicting results.Hence,it is necessary to develop SCF formulae specially designed for multi-planar DKT-joints.Good results of equation assessment according to UK DoE acceptance criteria,high values of correlation coefficients,and the satisfactory agreement between the predictions of the proposed equations and the experimental data guarantee the accuracy of the equations.Therefore,the developed equations can be reliably used for fatigue design of offshore structures.