盐度变化对铝牺牲阳极保护效果的影响

为研究河流入海口处盐度周期变化时铝牺牲阳极对钢结构的保护效果,测试对比了盐度固定与盐度循环条件下Q235钢有无阳极保护时的腐蚀失重和电位变化、铝牺牲阳极的电流效率。结果表明盐度循环会造成Q235钢的严重腐蚀,盐度差越大腐蚀越严重,甚至可能超过天然海水的腐蚀程度;在盐度循环条件下铝牺牲阳极对Q235钢具有良好的保护效果,但与稳定的盐度相比,阳极的消耗量增加、电流效率降低;在稳定的低盐度条件（0.5%）下,虽然铝牺牲阳极的电流效率较高,被保护的Q235钢电位足够负,但是保护效果不理想。本文通过Q235钢腐蚀失重数据检验铝牺牲阳极的保护效果,得到了不同盐度循环条件下铝牺牲阳极的初步性能数据,为河流入海口处钢结构设施的阴极保护提供了依据。     

铝-镁合金的剥落腐蚀

本文介绍了铝-镁(Al-Mg)合金的快速剥落腐蚀试验方法,着重研究了6.5％Mg和9.0％Mg变形铝合金剥落腐蚀外貌特征、裂纹形态,及其与金相组织之间的关系,分析了剥落腐蚀产生的原因,提出了改善抗剥落腐蚀性的途径。     

热浸镀锌-5%铝钢材在海水中的氢脆敏感性

热浸镀锌-5％铝镀层钢材在海洋环境中使用时可能存在氢脆问题。采用慢应变速率拉伸实验法,结合扫描电镜分析,研究了锌-5％铝镀层钢材在海水中的氢脆敏感性。发现锌-5％铝镀层对钢材基体进行阴极保护引起的氢渗透,可显著降低钢材的断后延伸率和能量密度,使钢材的断裂方式由韧性向准解理转变,提高了其在海水中的氢脆敏感性。     

耐海水腐蚀10CrMoAl低合金钢的研究

由于海水对金属的腐蚀性,对海水输水管道及各种海水冷却器的使用造成严重威胁,极需研制一种成本低、生产工艺简单而又耐海水腐蚀的低合金钢。达方面研究国外已有报道。他们研制的低合金钢是以铬为主添加合金元素的铬-铝和铬-钼型钢,含铬量约在2%以上。这类钢在海水中耐蚀性一般为碳钢     

高锰铝青铜在流动海水中阴极保护参数的研究

采用稳态动电位极化法测量了螺旋桨材料ZQAl12-8-3-2高锰铝青铜在静态和流动海水中的极化曲线,分析了其在流动海水中的腐蚀电化学行为,解析了最小保护电位、最大保护电位、最小保护电流密度等阴极保护参数,其在海水中的保护电位范围为-0．45～0．72V,最大保护电位在常规阴极保护范围内没有限制,流动海水中的最小保护电流密度比静态时增加几十倍,为海水中螺旋桨阴极保护设计及应用提供参考数据。     

海洋工程用铝基牺牲阳极发展概况

阴极保护是一种重要的腐蚀防护方法,它分为外加电流保护和牺牲阳极保护。其中 ,用牺牲阳极保护金属构件是一种简单易行 ,投资较少的阴极保护方法。因此 ,在船舶、码头、海洋平台及其他海上大型钢结构的保护上 ,得到了广泛的应用［３］。阴极保护用的牺牲阳极材料有铝、镁、锌三大系列。张经磊１９８６年指出 ,与镁基、锌基牺牲阳极相比 ,铝阳极的最突出优点是单位重量的输出电量大 ,是锌阳极的３．６倍 ,镁阳极的１．３倍 ;铝资源充足 ,价格便宜 ,重量轻 ;工作电位足够负 ,发生电流量大 ,寿命长 ,在海水和含Ｃｌ-的环境中应用性能良好。而…     

平台钢在海洋环境中腐蚀因子的灰色关联分析

结合海洋平台实测的pH值、温度、溶解氧、盐度、生物附着等数据,通过灰色关联算法分析了海水腐蚀因子对平台钢腐蚀的影响,并按实际影响大小进行了排序。结果表明海水腐蚀因子对于A537-1钢和SM50B-ZC钢平均腐蚀速率的影响主次顺序不同。对平台钢的腐蚀规律研究及现场应用提供了可参考的依据。     

胶州湾中溶解态铝的初步研究

本文利用改进的铝-荧光镓(Al-LMG)荧光光度法测定了2001年夏季和秋季胶州湾水样中的痕量溶解态铝,分析了夏、秋季胶州湾内溶解态铝的分布及其影响因素,在此基础上讨论了胶州湾中悬浮颗粒物对溶解态铝的贡献,并进一步探讨了溶解态铝在研究水团运动中的作用。计算了河流输入、大气干、湿沉降向胶州湾中溶解态铝的输送,及湾内外交换对胶州湾内溶解态铝的影响和胶州湾铝的存留时间。     

DH36钢焊接件海水腐蚀行为研究

海洋环境中的钢焊接件除了易发生电化学腐蚀之外,还容易发生电偶腐蚀等局部腐蚀。本文通过失重法、开路电位、强极化曲线、金相显微观测和X射线衍射等测试方法研究了DH36海洋用钢焊接件S-189-2在海水介质中的电化学腐蚀行为、电偶腐蚀倾向及其腐蚀产物成分。结果表明,焊接件各个部位在海水中的腐蚀速率均较小,腐蚀电流密度在15～29μA.cm-2范围内,阴极反应由氧扩散过程控制。开路电位和电极电位均随时间负移,各个位置电极电位差较小且负移幅度接近,发生电偶腐蚀的倾向较小。腐蚀产物以γ-FeO(OH)为主。     

海水流动对A3钢腐蚀速度的影响

为了定量考察海水的流动对钢铁材料在海水中的腐蚀速度的影响,通过室内和实海挂片失重测试比较了A3钢在静止和流动海水中的腐蚀速度差异,并在控制流速条件下使用动电位法测试了A3钢的腐蚀速度,同时测试了不同流速海水中的环境参量。室内和实海挂片失重测试比较结果表明,海水流动能够加快A3钢在海水中的腐蚀速度,腐蚀初期尤其明显。在控制流速条件下采用动电位极化方法测试了腐蚀初期A3钢的腐蚀速度,并且通过拟合处理得到了海水流动对其腐蚀速度影响因子的表达式。     

南海A平台导管架阴极保护监测结果讨论与分析

通过对南海A平台导管架阴极保护监测结果的分析,研究了该平台下水一年后导管架的阴极保护状态。结果表明,该平台下水后,导管架各节点电位及牺牲阳极电位均达到保护,阴极保护状态良好。阴极保护监测系统运行稳定,双电极探头未发现损坏,所得监测结果翔实可靠,对该海域新建平台导管架监测系统有着重要的借鉴价值。     

Sub-seismic scale fracture pattern and in situ permeability data in the chalk atop of the Krempe salt ridge at Lägerdorf, NW Germany: Inferences on synfolding stress field evolution and its impact on fracture connectivity

Chalk is exposed in the Heidestrasse quarry at Lägerdorf, at the top of the NE-SW trending Krempe salt ridge. Structural data indicate the presence of two joint sets, striking almost parallel and perpendicular to the salt ridge, respectively, and of a set of conjugate extensional faults and fault zones striking NW-SE, i.e. almost perpendicular to the salt ridge. Within the overall NW-SE trend of joints and faults, strike variations occur from the massive chalk exposed in the lower half of the quarry, to the overlying layered chalk. A large variability characterizes the normalized spacing of both joint sets, which does not show any clear trend with layer dip. In situ measurements indicate that the cross-sectional permeability of tight joints increases 1-2 orders of magnitude with respect to the undeformed chalk. We propose that joint and fault azimuthal variability resulted from changes through time of the stress ellipsoid at the top of the salt ridge, while joint spacing variability is associated with the weak mechanical influence of bedding in chalk. Azimuthal variability improves fracture connectivity and, hence, permeability and fluid flow.     

Fracture characteristics in Cretaceous platform and overlying ramp carbonates: An outcrop study from Maiella Mountain (central Italy)

This article focuses on field- and laboratory-based characterization of vertically persistent fractures that are part of oblique-slip normal fault zones and crosscut the Cretaceous platform and overlaying ramp carbonates outcropping at Maiella Mountain (central Italy). The achieved results show that: (i) fault damage zones are wider and more densely fractured in the platform carbonates than in the ramp ones; (ii) joints and sheared joints composing the fault damage zones are taller, better connected and less spaced within the former rocks than in the ramp carbonates. The aforementioned structural differences are interpreted to be a consequence of the different mechanical properties of the platform and ramp carbonates during failure. At Maiella Mountain, platform carbonates are, indeed, made up of overall stiffer (higher Uniaxial Compressive Strength values) and less porous rocks, due to more abundant intergranular void-filling cement and presence of matrix.In terms of hydrocarbon flow and recovery, geometric and dimensional attributes of fractures suggest that the well-connected network of closely spaced fractures cutting across the platform carbonates may form efficient pathways for both vertical and horizontal hydrocarbon flow. In contrast, the relatively poorly connected and low-density fracture network affecting the ramp carbonates is likely less efficient in providing fairways for flowing hydrocarbons.     

平台钢焊接接头在海洋中的腐蚀疲劳研究

随着近海石油开采事业的迅猛发展,我国已自行设计和建造了许多固定式导管架钢结构海上平台,它们在海洋环境中承受着波浪引起的交变载荷作用,与惰性环境中承受交变载荷条件下得到的疲劳结果相比,交变载荷与侵蚀性环境的联合作用往往导致疲劳性能显著下降。这种损伤可能是疲劳开裂和腐蚀性破坏的简单叠加,也可能是这两者之间某些更为复杂的协同交互作用的结果(贾斯克,1989)。钢结构海上平台是由钢构件(如钢管、钢板、角钢等)焊接而成,海水腐蚀疲劳裂缝大都产生于焊缝区的焊趾处,该部位存在焊接残余应力,以及焊接缺陷和儿何缺陷,形成应力集中。本文通过对海上平台用钢板在空气中、海水中和海水中有阴极保护三种条件下腐蚀疲劳性能的研究,探讨了钢材在海上平台不同部位、不同保护状况下的腐蚀疲劳寿命,为海上采油平台设计与选择提供了理论依据。     

Fatigue Behaviour of Tubular Joints Made of China-Made Platform Steel

In China, a nationwide research program on fatigue behaviour of tubular joints made of China-made platform steel was carried out from 1983 to 1990, which was set by the Tubular Joint Research Committee for Offshore Structures (TJCOS) of China. This paper gives an outline of the basic properties of the China-made platform steel and fatigue test of tubular joints, including test specimens, test particulars and test results. A p-S-N curve based on the test results was established which reveals that the fatigue strength of tubular joints is fairly good. The thickness effect and effect of corrosion on fatigue strength in sea water are briefly discussed.     

Mechanical test study on corroded marine high performance steel under cyclic loading

It is inevitable that marine structures suffer from corrosion and extreme cyclic loading. In order to study the influence of corrosion damage and cumulative fatigue damage on mechanical properties of marine steel, high performance steel NV-D36 was analyzed under electrochemical corrosion and cyclic loading. It was found that corrosion damage can reduce the elastic modulus, yield strength, ultimate stress and ultimate strain of steel NV-D36. And it was also found that cumulative fatigue damage will increase the ultimate stress of steel NV-D36 and reduce the ultimate strain of steel NV-D36. The effect of double damage on mechanical properties of steel NV-D36 was coupled with these two kinds of damage. The Chaboche model parameters calibrated under incremental cyclic loading scheme can exactly describe the stiffness and peak stress of steel NV-D36.     

Structural properties of fractured and faulted Cretaceous platform carbonates,Murge Plateau (southern Italy)

The Upper Cretaceous carbonates cropping out in the Murge Plateau are good analogues of the fractured and faulted carbonate oil reservoirs of southern Italy. For this reason, a detailed field analysis focused on structural architecture of fault and fracture networks has been carried out in the Murge Plateau. The well-bedded carbonates exposed there are crosscut by a set of bed-parallel stylolites and two sets of bed-perpendicular cross-orthogonal joints/veins. These structural elements were likely formed under vertical loading during burial diagenesis and flexure of the Apulian foreland of the Southern Apennines fold-and-thrust belt. Bed-parallel stylolites and bed-perpendicular cross-orthogonal joints/veins represent the background deformation that was overprinted by the fault-related localized deformation. The fault sets documented in the study area are arranged in two kinematically-compatible fault networks. The first one is made up of WNW-ESE and NNW-SSE oriented strike-slip faults, right- and left-lateral, respectively, and NW–SE oriented normal faults. The second fault network consists of WNW-ESE oriented left-lateral strike-slip faults, and NE–SW oriented normal faults.First, both architecture and dimensional parameters of the fault and fracture networks have been characterized and computed by means of statistical analysis. Then, the permeability structures associated to the aforementioned networks have been assessed in order to determine the role exerted by fault architecture and dissolution/cementation processes on the fluid storage and migration pathways within the studied platform carbonates. Network 1 faults show a quite variable fluid behavior, in which the fluid flow is strongly affected by inherited structural elements and karst dissolution, whereas network 2 faults show a more uniform, fluid conduit behavior.     

A Global Refiability Assessment Method on Aging Offshore Platforms with Corrosion and Cracks

Corrosion and fatigue cracks are major threats to the structural integrity of aging offshore platforms.For the rational estimation of the safety levels of aging platforms,a global reliability assessment approach for aging offshore platforms with corrosion and fatigue cracks is presented in this paper.The base shear capacity is taken as the global ultimate strength of the offshore plaffoms,it is modeled as a random process that decreases with time in the presence of corrosion and fatigue crack propagation.And the corrosion and fatigue crack growth rates in the main members and key joints are modeled as random variables.A simulation method of the extreme wave loads which are applied to the structures of offshore platforms is proposed too.Furthermore,the statistics of global base shear capacity and extreme wave loads are obtained by Monte Carlo simulation method.On the basis of the limit state equation of global failure mode,the instantaneous reliability and time dependent reliability assessment methods are both presented in this paper.Finally the instantaueous reliability index and time dependent failure probability of a jacket platform are estimated with different ages in the demonstration example.     

Residual compressive strength of inclined steel tubular members with local corrosion

In jacket-type offshore structures, corrosion damage affects the structural performance under compressive loading, which is created by the working and design loads of the main system. In this study, the effects of corrosion damage on the compressive structural behavior and strength of steel tubular members were investigated. Artificial corrosion damage was applied to the tubular specimens via mechanical processing and hand drilling to replicate the inclined nature of jacket-type offshore structures. The damage was applied to either half or all of the circumference of the specimens. The compressive failure modes of the artificially corroded tubular members were affected by the corrosion conditions. The compressive strengths were also affected by the level of corrosion. From the results of this study, the residual compressive strengths of corroded tubular steel members can be estimated based on the condition of the damaged sectional areas.     

Multibody dynamical modeling of the FPSO soft yoke mooring system and prototype validation

The Soft Yoke Mooring System (SYMS) is a single point mooring system for shallow water. It is composed of a mooring framework, mooring legs, yoke, and single point, and is located at the Floating Production Storage and Offloading (FPSO) through 13 hinge joints, such as universal joints and thrust bearings. Mooring restoring force, motions and postures of mooring components, and mechanical behaviors of hinge joints are major criteria for the structural design of the SYMS. Aiming at the difficulties of the multibody dynamics in traditional design of the SYMS, a multi-body dynamic mathematical modeling with seven independent degrees of freedom (DOFs) which is applicable to prototype field engineering was developed in this study. The proposed mathematical modeling of the SYMS multibody dynamic system has several advantages: 1. Internal tribological behaviors in hinge joints are considered within the presented multibody dynamics model to illustrate the good dynamic effects of the SYMS. 2. The multibody dynamic model can be applied in field service. Correctness and feasibility of the proposed multibody dynamic simulation method for describing motions and postures of hinges and single-body were validated by the prototype monitoring data. 3. The horizontal restoring force of the SYMS was calculated according to field measurement data. The motion state of each single body and internal stress distributions at each hinge joint in the SYMS are given. 4. The multibody dynamics calculation program can be directly used for the real-time monitoring of mechanical behaviors of the SYMS under the service state. The simulated results can provide real-time guarantee for safety alarming of the system. The vulnerability of the mooring system in service was evaluated based on long-term monitoring data analysis.