基于膨胀系数修正的腐蚀管道失效压力预测

腐蚀管道的失效压力预测主要分为两部分:完好管道的失效压力和折减系数,其中折减系数受膨胀系数的影响。论文运用有限元方法计算不同腐蚀长度、不同腐蚀深度的腐蚀管道失效压力,拟合得到不同腐蚀尺度的管道膨胀系数计算公式。结合完好管道失效压力和膨胀系数计算方法,得到一种更为准确的腐蚀管道失效压力计算方法。与现有失效压力预测方法相比,该方法预测的破坏压力与实际管道爆破试验结果吻合较好,验证了该方法的实用性。     

腐蚀海底管道剩余强度的可靠性评估方法研究

针对常用腐蚀海底管道剩余强度评估方法的局限性,提出一套联合载荷作用下腐蚀海底管道剩余强度评估的方法,通过有限元分析联合载荷作用下腐蚀海底管道的剩余强度,考虑到腐蚀缺陷有关参数的不确定性,以腐蚀管道失效压力和腐蚀速率分析为基础,建立腐蚀管道可靠性极限状态方程,采用蒙特卡罗法计算腐蚀海底管道的失效概率.通过模型计算验证方法的可行性.     

轴向长腐蚀管道极限承载力研究

腐蚀是引起海底管道破坏的重要原因之一,其中轴向长腐蚀是海底管道常见的腐蚀形式.文中采用非线性有限元方法,对轴向长腐蚀海底管道进行了内压荷载作用下的破坏机理的研究.并分析了腐蚀长度,腐蚀深度和腐蚀位置对海底管道失效压力的影响.根据有限元分析结果,回归得到适用于轴向腐蚀海底管道极限失效压力的计算公式,并与试验结果吻合较好,为长腐蚀海底管道的评估提供依据.     

基于爆裂失效的腐蚀压力管道剩余强度研究

为真实反应海洋结构物腐蚀压力管道的结构完整性及其剩余强度,文章以爆裂失效作为腐蚀压力管道的失效准则,基于扩展有限元法,提出了腐蚀压力管道爆裂失效数值分析模型,用以评估压力管道在外表面腐蚀工况下的爆裂压力。以矩形缺陷形状表征管道的腐蚀程度,对不同的腐蚀工况进行非线性数值分析,根据分析结果可知:腐蚀区域最大等效应力随内压变化的曲线可分为线弹性阶段和塑性屈服阶段,在塑性屈服阶段的终点,当腐蚀区域中心处单元达到材料失效准则时,开始起裂并沿轴向扩展,其所对应的内部压力即为爆裂压力;腐蚀管道的爆裂压力均随缺陷区域深度、轴向长度、环向长度的增长而呈指数形式下降,将爆裂压力有限元值与ASME B31G、RSTRENG 0.85标准预测值对比可知现有标准的保守性及局限性;轴向双缺陷压力管道的爆裂压力随着轴向间距的增大而呈指数形式上升,而后爆裂压力趋近于单缺陷管道的爆裂压力值;环向间距对环向双缺陷压力管道爆裂压力在60°～90°、90°～140°、140°～180°三个阶段呈现出不同的影响程度。     

含有腐蚀缺陷海底管线失效压力研究

腐蚀是引起海底管线破坏的一种重要原因.采用非线性有限元方法,对含有腐蚀缺陷的海底管线进行了内压作用下的极限承载力分析.研究了腐蚀长度、深度、宽度、径厚比对海底管线的破坏机理和对失效压力的影响,提出了含有腐蚀缺陷的受内压作用的海底管线失效压力计算公式.与试验结果及各种规范和方法进行了对比,证明该方法是有效的,为腐蚀海底管线的评估提供了依据.     

基于非线性有限元法的海底管道剩余强度研究

考虑腐蚀海底管道材料非线性及几何非线性特点,基于塑性失效准则,采用非线性有限元法建立腐蚀海底管道剩余强度模型,以此预测腐蚀海底管道失效压力。基于非线性有限元法的计算结果,与失效压力准则法进行对比,分析腐蚀缺陷长度、深度、角度及腐蚀位置对失效压力的影响规律。     

组合应力作用下含腐蚀缺陷海管安全工作压力评价方法

在较高温度和压力作用下,由于土壤的摩擦阻力,海管会产生很大的轴向压力,以及由侧向屈曲引发的弯矩。因此对含腐蚀缺陷管道安全工作压力的评价,须考虑轴向压应力的影响。对目前工程界的评价方法进行对比分析,在内压和轴向压应力组合作用下,含腐蚀缺陷海管的安全压力评价方法还很不完善,尤其是复杂缺陷,目前的规范还不完全适用。通过对许用应力法安全系数的讨论和分析,基于Von Mises准则和有限元分析,提出了组合应力作用下含腐蚀缺陷海管的安全工作压力评价方法。通过该方法对某运行了近三十年的管道进行了安全工作压力的评估,同时考察了轴向压应力对安全工作压力的影响。此方法对应的轴向压应力限值和安全等级以及安全系数相关,当安全等级低时,其值和DNV-RP-F101规范值基本一致,当安全等级高时,其值比DNV-RP-F101规范值大。     

海底管道腐蚀后的剩余强度评价

海底管道通常会因腐蚀而形成各种不同类型的缺陷,影响管道的承载能力和使用寿命。本研究在准确掌握管道缺陷发展情况的基础上,分别根据行业规范和采用有限元方法对海上油田含有腐蚀缺陷的原油管线进行剩余强度评价,判定海底管道修复的必要性和修复的紧迫程度,以确定最终的管线修复方案,可供类似海底管道修复工程参考。     

含内腐蚀的船舶海水管道换管周期预测

文章针对船舶冷却系统的海水管道的主要失效原因——电化学腐蚀,以冷却系统中海水管道为研究对象,利用ANSYS软件分析了流速、腐蚀区域尺寸对含有电化学腐蚀的海水管道的剩余强度的影响,利用Origin得到各影响因素与最大等效应力的关系曲线图,计算了管道在各腐蚀深度下的失效压力,并选取经验公式对管道的剩余寿命进行预测,为管道的换管周期的确定提供一定的依据。结果表明,腐蚀深度和轴向长度对管道剩余强度的影响效果较为明显,在腐蚀深度达到管壁壁厚的40%时以及腐蚀轴向长度达到3.5 cm时,管道的等效应力变化速率非常快,因此,在对管道的日常检测维护中,应着重注意腐蚀的深度和轴向发展,以确保管道的正常运行,使船舶冷却水系统正常换热,从而保障船舶动力系统的正常运行。     

大型邮轮冷却水系统管道焊缝腐蚀行为研究

大型邮轮冷却水系统管道在输送介质方面扮演着极其重要的角色，而腐蚀失效是管道难以避免的问题，且管道腐蚀易发生在焊缝周围，一旦失效便会威胁系统的安全运行。针对管道的常用材料碳钢Q355，采用手工电弧焊制备无缺陷焊缝、含夹渣焊缝和含气孔焊缝3类焊缝试样，在淡水和3.5%Na Cl溶液（模拟海水环境）中分别浸泡24 h和360 h，通过电化学工作站和超景深三维显微镜等对试样浸泡腐蚀后的各项参数及形貌进行分析。结果表明：试样在3.5%Na Cl溶液中的腐蚀程度相比淡水溶液中更严重，且浸泡时间越长，腐蚀越严重；在浸泡时间和介质一致的情况下，焊缝试样的腐蚀程度由大到小依次为含气孔焊缝试样、含夹渣焊缝试样、无缺陷焊缝试样。研究成果可为大型邮轮冷却水系统管道焊缝的性能分析提供数据支撑。     

腐蚀裂纹损伤下船舶管路抗冲击时变剩余强度研究

舰艇管路系统对冲击载荷作用非常敏感,遭受冲击载荷后通常会引起管路系统应力或变形过大而破坏,而裂纹和腐蚀作为常见的一种损伤缺陷导致结构承载力下降,降低管路系统的使用寿命.因此针对典型管路系统管路段,建立仿真精度较高的典型管路有限元模型,对典型管路系统管抗冲击性能进行分析;根据仿真分析结果,确定管路结构强度的薄弱节点或分段(称之为关键节点或关键结构)作为裂纹扩展的初始点.基于管路系统腐蚀和裂纹的发展规律和有限元计算方法,建立管路系统时变剩余强度预报模型,发展一种分别计及腐蚀、裂纹2种因素作用下,舰艇管路系统在三向冲击载荷作用下剩余强度的计算方法和实现流程.在此基础上,分别研究裂纹损伤、腐蚀损伤在不同服役年限下冲击载荷对舰艇管路时变剩余强度的影响规律.     

Degradation of bond strength and deformation between TRC-confined seawater sand concrete and BFRP bars under chloride corrosion environment

The interfacial bonding performance between seawater sand concrete and basalt fiber reinforced polymer (BFRP) bars were tested under different textile reinforced concrete (TRC) confinement layers, confinement sequences and chloride salt dry-wet cycles. The results show that TRC confinement can change the failure mode of the specimen and improve the ductility of specimens. With the increase of corrosion age, compared with the specimens with the same restrained layers in the conventional environment, the ultimate bond strength of restrained specimens before corrosion gradually decreases, and the slip value when reaching the ultimate bond strength also slightly decreases. The bond strength of the pre-restrained corroded specimens has the same development trend. Based on the bond-slip model of deformed steel bars and concrete proposed by Eligehansen for the first time in 1983—BPE model, under the control of TRC confinement and corrosion age, the relationship between the TRC confinement layer and the ultimate bond strength and slip of seawater sand concrete and BFRP steel bar is established. By fitting and predicting the ultimate bond strength, corresponding slip value, and corrosion age control of different TRC confinement layers, it is found that the confinement effect will not be significantly improved when the confinement layers exceed 4 layers. Under long-term chloride corrosion, the failure mode of the specimen may still change into splitting failure when the number of restrained layers is small.     

含裂纹及腐蚀损伤FPSO结构剩余极限强度评估方法研究

裂纹及腐蚀损伤对于浮式生产储油卸油装置（FPSO）结构来说难以避免，这将削弱结构的极限强度，所以研究含裂纹及腐蚀损伤FPSO结构的剩余极限强度意义重大。目前针对裂纹及腐蚀损伤联合作用下FPSO结构剩余极限强度的研究相对欠缺，本文采用非线性有限元分析方法，研究了不同腐蚀及裂纹损伤组合形式下FPSO结构剩余极限强度的衰减规律。结果表明，腐蚀与裂纹损伤均导致极限强度线性衰减，并且腐蚀损伤对极限强度的影响远大于裂纹损伤。研究结果对FPSO结构的设计、维护与延寿具有一定的参考价值。     

海洋工程钢结构腐蚀防护的研究进展

钢结构在海水中腐蚀损伤具有复杂性和多样性的特点,对其进行研究存在一定的挑战性。针对海洋工程装备的腐蚀问题,对钢结构在海水中的腐蚀机理、防腐寿命预测和评估进行概述。对比涂料防腐技术、金属涂层防腐技术、电化学防腐技术发现:国外有严格的国家环保法规,国内环保立法滞后,尤其涉及到高压低温环境中应用困难。     

Effect of corrosion models on the time-dependent reliability of steel plated elements

Time-dependent reliability considering corrosion and fatigue has received increasing attention recently. Many corrosion models have been proposed. In this paper, a new corrosion model which could better describe the corrosion process of actual steel structures under corrosive environment is proposed. This model is also compared with other existing corrosion models. The effect of corrosion models on the time-dependent reliability is studied using a steel plated element which has found wide applications in engineering structures. The advantages and the flexibility of the present corrosion model are demonstrated.     

考虑点腐蚀影响的海洋钢结构剩余极限强度研究进展

为得到考虑点腐蚀影响的海洋钢结构剩余强度研究领域的发展趋势,本文对国内外该领域公开发表的文章进行综述,根据本文的研究可以发现:由于海洋钢结构的大尺度和复杂性,数值模拟已成为受蚀船体结构剩余强度的主要研究方法,但模拟结构的有效性仍需进一步检验;对于点腐蚀,就研究参数而言,长细比、DOP、体积损失是学者们最为关注的指标,但对点蚀板强度缺少时变可靠性研究;计算模型中都缺乏对焊接残余应力的考虑.本文所做的研究可为该领域下一步研究方向提供参考.     

Experimental and numerical study of localized pitting effect on compressive behavior of tubular members

Locally pitted tubular members are usually considered as stub columns to assess the ultimate strength. However, it is not suitable for those with relatively larger slenderness ratios as their failure behavior is more complex and closely related to corrosion features of localized pitting. This paper presents compressive column tests on locally pitted tubular members of a moderate slenderness ratio. Corrosion pits were artificially introduced on local surface of the members, forming corrosion patches with various corrosion features. A numerical modelling method was proposed to reproduce the test specimens. Localized pitting damage was proven to cause substantial declines in the load deformation capacity and ultimate strength, and have a significant effect on the failure mode. The failure of a pitted member is mostly initiated by local buckling after yielding occurs in the corrosion patch, concurrent with pitting closure, and even shear cracking of member wall due to the perforated pits. Moreover, shape change of the corrosion patch most likely results in the failure mode to alter from column buckling to local buckling or interactive buckling. The shape ratio of the corrosion patch is one of the critical factor to influence the ultimate strength of locally pitted members. The proposed modelling method is applicable for extensive stochastic simulations so as to develop an empirical formula and to clarify the probabilistic characteristics of ultimate strength.     

柴油机耐压排气管段材料优选及结构优化设计分析

考虑到在保证耐压排气管段的承压能力和耐腐蚀性能的前提下尽可能降低管段的重量是潜艇柴油机排气系统耐压管段材料优选及结构优化设计的主要目标,针对多种材料配套体系和多结构设计方案,用有限元计算方法对耐压排气管段的强度分布及稳定性进行计算分析,提出材料优选和结构优化设计方案,形成柴油机排气系统耐压管段材料优选和结构优化设计准则。     

不锈钢焊接接头晶间腐蚀性能的控制

文章介绍不锈钢焊接件焊接接头抗晶间腐蚀能力的检验方法,并对焊接接头晶间腐蚀的原因进行分析并就提高不锈钢焊件抗晶间腐蚀的能力进行探讨。     

A computational investigation of the effects of both-sides general corrosion on the buckling/plastic collapse behaviour and strength of stiffened plates

This paper presents the results of an investigation into the post-buckling behaviour and ultimate strength of imperfect corroded stiffened steel plates used in ships and other marine-related structures. A series of elastic–plastic large deflection finite element analyses is performed on stiffened steel plates suffering general corrosion wastage with random distribution. General corrosion is introduced into the finite element models using a random thickness surface model. The effects of corroded stiffened plate parameters on the post-buckling and ultimate strengths are evaluated in detail. The stiffeners of different symmetrical or unsymmetrical cross-sections are introduced into the models for analysis. Some distinctions are explored and highlighted between the behaviours of steel plates suffering general corrosion in unstiffened and stiffened cases. Finally, a proposal is given in order to simulate the average stress–average strain relationship of stiffened steel plates having both-surface general corrosion wastage.