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海底管道在服役期间由于各种原因会在某些管段形成悬空段,悬空段的存在会影响管道的安全运行。文中以渤中海域某管道为例,基于DNV规范,对海底管道允许悬空长度和海底管道疲劳寿命的影响因素(工作内压、海流流速、沟槽深度)进行分析。 相似文献
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纤维增强热塑性复合管(FRTP)由于较小的弯曲刚度、较轻的自身质量和良好的抗腐蚀性能等优点,在海洋工程领域具有广阔的应用前景。本文以FRTP为研究对象,首先通过开展拉-拉单轴疲劳实验得到S-N曲线,并基于剩余刚度理论确定FRTP刚度衰减模型。通过Abaqus有限元软件建立FRTP三维有限元模型,利用Fortran语言编写UMAT子程序模拟其在σmax=80%σs、65%σs、55%σs、40%σs等4种应力水平疲劳荷载下的疲劳过程。从应变和变形两方面进行疲劳分析,基于刚度衰减模型对60%σs应力水平疲劳荷载下的FRTP疲劳过程进行预测。结果表明管道刚度随着荷载循环周次的增加而逐渐衰减,在疲劳寿命前期,荷载应力水平越高,刚度衰减越快。 相似文献
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E50作为表征材料变形特性的参数,在有限元计算中有着重要作用。E50由无侧限抗压强度试验得出,由于试验过程中的某些不确定性因素,E50的值一般具有较大的离散性。利用Logistic函数拟合土体的的应力应变关系曲线,推导出的曲线具有(σ1)f、(ε1)f、Rf三个独立的参数,再利用最小二乘法求解E50,对于提高有限元计算精度具有重要意义。 相似文献
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根据《散货船结构共同规范》(CSR)中疲劳强度评估的要求,使用MSC.Patran/Nastran和中国船级社开发的CSR自动加载程序,对176 000 dwt散货船货舱口角隅处进行疲劳强度分析。建立货舱口角隅处的结构有限元模型并细化网格,进行热点应力分析,根据线性疲劳累计损伤原理,进行了疲劳累计损伤计算,结果表明货舱口角隅处的疲劳强度满足规范要求。 相似文献
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基于散货船共同结构规范(CSRBC)的热点应力法,对一艘30000t级散货船内底板与底凳的斜板相交处进行了疲劳强度分析。通过对疲劳热点位置建立精细网格模型,采用中国船级社开发的软件CCS-Tools及英国劳氏船级社开发的SHIPRIGHT进行了热点应力分析及疲劳寿命计算。另外,还介绍了采用电子表格计算疲劳寿命的方法。 相似文献
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在焊接接头处,由于几何的不连续造成了局部的应力集中,对其疲劳强度评估的研究是十分必要的。文章提出采用奇异强度(as)来计算接头处的几何应力,并基于N-SIF方法分析了不同几何尺寸下十字接头的疲劳强度。结果表明该修正公式可以十分简便地评估出焊接接头处的疲劳强度。 相似文献
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Compared with thick plate welded joint, the welding joint of thin plate will produce initial deformation due to its low bending rigidity. The existence of initial deformation will cause the welded structure to produce secondary bending effect, which will produce greater stress magnification effect at the weld toe and seriously affect the fatigue strength of thin plate welded joints. Therefore, based on the correction formula of thick plate, considering the influence of initial deformation and geometric nonlinearity of thin plate, this paper deduces the stress magnification factor formula at the weld toe of T-shaped and cruciform specimens. The accuracy of the revised formula is further verified by comparing the notch stress calculated by the modified formula with the FE results. Finally, the modified formula is applied to the notch stress and fatigue evaluation of typical thin plate welded joints respectively. The results show that the proposed notch stress calculation formula can fully consider the stress amplification effect of thin plate structure, and can be used to quickly evaluate the notch stress field and fatigue strength of thin plate welded joints. 相似文献
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Yukinobu Nagata Koji Gotoh Masahiro Toyosada 《Journal of Marine Science and Technology》2009,14(1):104-114
Many accidents are caused by fatigue in welded built-up steel structures, and so it is important to estimate the fatigue lives
of such structures quantitatively for safety reasons. By assuming that fatigue cracks cannot grow without an accumulation
of alternating tensile/compressional plastic strain, one of the authors identified an improved effective stress intensity
factor range ΔK
RPG based on the re-tensile plastic zone generating (RPG) load, which represents the driving force for fatigue cracks, and suggested
that ΔK
RPG should be used as the parameter to describe fatigue crack growth behavior. The “FLARP” numerical simulation code in which
ΔK
RPG is implemented as the fatigue crack growth parameter, was developed in order to predict fatigue crack initiation and propagation
behavior. In this paper, it is demonstrated that FLARP gives accurate estimates for fatigue life by comparing the estimated
fatigue crack growth curves and S–N curves with the experimental results for in-plane gusset welded joints, which are used in many welded steel structures. Moreover,
the effect of induced bending moment due to the linear misalignment in the out of plane direction on the fatigue strength
of in-plane gusset welded joints is investigated through numerical simulations. 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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In order to simplify the assessment method of notch stress and fatigue strength for cruciform welded structures in ocean engineering, a simple stress assessment formula based on singular strength values and was presented according to linear elastic fracture mechanics and notch stress strength theory. In view of the stress singularity caused by the V-notch, the stress of the corresponding U-notch was recommended and used for fatigue evaluation. Therefore, on the basis of V-notch stress formula, a simplified U-notch stress field evaluation formula was obtained by theoretical analysis and numerical calculation. After a series of verification, it is found that the stress distribution and fatigue strength evaluation formula for cruciform welded joints based on singular strength values proposed in this paper can simply and accurately predict the notch stress at welded joints. The result of fatigue strength evaluated by the simplified formula has a smaller scatter band. 相似文献
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TIG熔修提高船体钢焊接接头腐蚀疲劳抗力的研究 总被引:1,自引:0,他引:1
对经TIG熔修和未经TIG熔修的45kg级船体钢焊接试样进行了全面模拟实船肥役条件的腐蚀疲劳实验研究。结果表明,按一定工艺规范熔修处理的焊接接头,其海水介质腐蚀疲劳抗力得到了显著的提高。 相似文献