工业纯铁在3.5%NaCl水溶液中裂尖材料溶解速率与裂纹扩展速率的关系

利用形变金属的溶解模拟裂纹尖端的溶解行为,研究工业纯铁在3.5%NaCl水溶液中溶解速率与裂纹扩展速串的关系.研究表明由于腐蚀因素引起的裂纹扩展速率远大于裂纹尖端材料的溶解速率.在阳极溶解机制下,腐蚀疲劳裂纹扩展速率不能用纯机械因素引起的裂纹扩展速率和裂尖材料溶解速率的叠加来表示.     

工业纯铁在3．5％NaCl水溶液中裂尖材料溶解速率与裂纹扩展速率的关系

利用形变金属的溶解模拟裂纹尖端的溶解行为，研究工业纯铁在３．５％ＮａＣｌ水溶液中溶解速率与裂纹扩展速串的关系．研究表明由于腐蚀因素引起的裂纹扩展速率远大于裂纹尖端材料的溶解速率．在阳极溶解机制下，腐蚀疲劳裂纹扩展速率不能用纯机械因素引起的裂纹扩展速率和裂尖材料溶解速率的叠加来表示．     

应力比和频率对低合金钢腐蚀疲劳裂纹扩展机理的影响

在理论分析裂尖局部应变、应变速率及溶解速度的基础上、实验测定了低合金钢ZG20SiMn,SM50B—Zc的腐蚀疲劳裂纹扩展速率,并随着裂纹的扩展测定了裂纹内和裂纹尖端的pH值和金属电极电位、指出降低频率和增加应力比所导致的腐蚀疲劳裂纹扩展速率的增加部分主要来自于氢脆的加速作用     

散斑干涉微区应变测量术在腐蚀疲劳裂尖形变研究中的应用

建立了计算机控制自动化散斑干涉微区应变测量系统,介绍了工作原理及其在腐蚀疲劳裂尖形变行为研究中的应用,该方法可测定材料裂尖局部应变场。通过比较A537钢充氢前后裂尖应变场的变化与阳极溶解对纯Cu裂尖应变分布的改变、研究了腐蚀疲劳过程中裂尖材料的化学-力学效应,结果表明:充氢使裂尖应变减小、阳极溶解促进变形     

带镀层GC-4超高强度钢的腐蚀断裂

应用慢拉伸及断裂力学方法研齐了带镀层的GC-4钢(40CrMnSiMoVA)在3.5％NaCl中的应力腐蚀特性,并与裸钢作了对比。结合扫描电镜及宏观断口分析,探讨了失效机理。研究表明,阴、阳极镀层均使钢的KIscc降低,da/dt(Ⅱ)显著增加,其影响依无氰Cd、Cd-Ti、Cr的次序增加。慢拉伸试验结果说明,阴、阳极极化均使GC-4裸钢延性降低。根据BL-WOL试样裂纹扩展在表面处较内部为快以及阴、阳极镀层、平面应变状态对断口形貌的影响,可以认为带镀层与不带镀层GC-4钢的腐蚀断裂机理为裂尖阳极溶解与氢脆共同作用,并且裂尖溶解将直接参与导致裂纹扩展.从而对高强度钢腐蚀断裂的纯氢脆机理作出修正。     

极化和频率对A537钢在3.5%NaCl溶液中的腐蚀疲劳裂纹扩展行为的影响

利用三电极技术研究了极化和频率对A537低合金钢在3.5%NaCl活化体系的腐蚀疲劳的裂纹扩展行为,包括对裂纹扩展速率和断口形貌的影响.结果表明,在活化体系中,强极化条件,频率越小,裂纹扩展速率越大;在阴极保护条件下,频率对裂纹扩展速率的影响很小.阳极溶解和阴极析氢可以增加裂纹扩展速率.裂尖析氢量的大小决定了断口解理面大小.在裂尖塑性区内的位错结构为胞结构,而在塑性区外为长位错线     

16MnR钢应变疲劳裂纹扩展速率

本文研究了16MnR钢的应变疲劳裂纹扩展特性,用逐级递增位移双引伸计法测定了16MnR钢的应变疲劳裂纹扩展速率,给出了裂纹扩展速率与循环J积分范围△J,循环裂尖张开位移范围△δt的关系。结果表明,存应变循环条件下,循环J积分与COD这两个相互独立的断裂参量存在着内在的关系:△J=kσ_(?)△δ_t。     

腐蚀疲劳裂纹扩展的断裂模型

将修正的疲劳裂纹扩展静态断裂模型和裂尖腐蚀溶解相结合,提出了腐蚀疲劳裂纹扩展(CFCP)的腐蚀-钝化-断裂模型.根据该模型和断裂力学原理,导出了CFCP速率的定量表达式,它揭示了CFCP速率与力学条件,裂尖表面腐蚀率、加载频率、假设的裂尖材料元临界断裂应力之间的定量关系,并能说明氢脆对CFCP率的影响规律。实验结果表明,应用所提出的模型可很好地描述铝合金在35％NaCI中CFCP的一般规律。     

腐蚀疲劳裂尖形变与载荷间交互作用

腐蚀疲劳裂尖形变与载荷间交互作用魏学军(中国科学院金属腐蚀与防护研究所九七届博士研究生,沈阳110015)腐蚀疲劳过程由材料局部腐蚀行为、形变方式及它们之间的交互作用控制.本文原位测量了常幅疲劳裂纹扩展过程中一个循环周期内裂尖形变的规律;研究了氢脆和阳极溶解对金属材料裂尖形变的影响,并比较了这两种腐蚀因素对裂尖内部形变与表面形变影响的差别.结果表明:由于裂纹闭合和残余压应力的存在,疲劳裂尖塑性区尺寸与外加载....     

NaNO2对A537钢在盐水中腐蚀疲劳的缓蚀作用

利用平板及单边裂纹试样研究了１％ＮａＮＯ２对Ａ５３７钢在３．５％ＮａＣｌ水溶液中腐蚀疲劳寿命与裂纹扩展的缓蚀作用，并在不同应变速率与外加电位下研究了相应体系圆柱形应变电极的电化学响应规律．结果表明，ＮａＮＯ２对裂纹萌生过程具有抑制作用，从而提高腐蚀疲劳寿命．即使在阴极极化条件下，动态应变的一定阶段仍可有较大的阳极溶解电流密度，这显示了ＮａＮＯ２对裂纹扩展过程作用的复杂性．分析表明，ＮａＮＯ２存在的情况下，形变引起的附加阳极电流密度除受到形变速率与新表面再钝化速率控制外，还强烈地受到表面滑移状态的影响．     

A537钢在3.5%NaCl溶液中低周腐蚀疲劳的裂纹萌生

利用三电极技术研究了Ａ５３７低合金钢在３．５％ＮａＣｌ活化体系中的低周腐蚀疲劳的裂纹萌生行为．结果表明，应变速率越小，或者应变幅越大，裂纹萌生寿命越短；阳极极化和强阴极极化可以大大缩短裂纹萌生寿命，阴极保护条件下的裂纹萌生寿命与空气中的相似．裂纹主要在软的铁素体内萌生，然后穿过珠光体连接．剧烈的阳极溶解破坏了表面形变形貌，阴极析氢导致表面产生许多小裂纹．     

CORROSION FATIGUE CRACK GROWTH OF MEDIUM STRENGTH STEEL HT60 IN SYNTHETIC SEA WATER

The corrosion fatigue crack growth and near-threshold characteristics of a medium strengthsteel HT60 were investigated using compact tension specimens exposed to synthetic sea water.The da/dN-△AK_(eff) relation in air can give a conservative estimation of da/dN-△K relationsin sea water. In the case of high R, however, crack growth acceleration at high △K regionsappears to be cantrolled by the stress-assisted dissolution. The crack opening stressinlensity factor K_(op) detected by the back-face-strain method is the result of crack surface incontact with the corrosion products and therefore an overestimated value of K_(op) at the cracktip is given.     

AN APPLICATION OF SPI TECHNIQUE FOR STUDING STRA DISTRIBUTION AT CRACK TIP

A computerized digital speckle-interferometry(SPI)system has been set up to determinethe in-plane distribution of displacement and strain at crack tip of CF specimens.Theprinciple and the experimental method of this technique are described in detail.Theeffect of corrosion factors on plastic deformation at crack tip in CF process has beenexamined by comparing the near-tip strain fields of steel A537 before and after hydrogencharging,and of pure copper before and after applying an anodic current in 3.5% NaCl.The results shows that the clasic finite element mathematical models are not suitable todescribe the near-tip deformation under the experimental conditions.Hydrogen chargingmade the crack tip plasticity decreased for steel A537 and the anodic dissolution enhancethe near tip deformation of pure copper specimen.     

S690高强钢腐蚀疲劳裂纹扩展行为拘束效应

S690高强钢由于其良好的综合力学性能广泛用于海洋平台中. 海洋平台结构易产生腐蚀疲劳失效,海水腐蚀、循环载荷和结构本身的拘束水平对裂纹扩展有重要的影响. 通过空气中和海水环境中的S690高强钢疲劳裂纹扩展试验,结合显微断口分析,研究了拘束水平对S690高强钢腐蚀疲劳裂纹扩展行为的影响. 结果表明,在阳极溶解和氢致开裂的共同作用下,海水环境对S690高强钢疲劳裂纹扩展具有明显的加速作用. 同时随着裂纹的不断扩展,拘束水平对S690高强钢腐蚀疲劳裂纹的影响不断增加,且裂纹扩展速率与裂纹扩展前后的拘束水平增量和结构本身的拘束水平均密切相关.     

Quantitative characterization by micro-electrochemical measurements of the synergism of hydrogen, stress and dissolution on near-neutral pH stress corrosion cracking of pipelines

Occurrence of stress corrosion cracking of pipelines under a near-neutral pH condition depends on the synergism of stress, hydrogen and anodic dissolution at the crack tip of the steel. In this work, micro-electrochemical techniques, including localized electrochemical impedance spectroscopy and scanning vibrating electrode technique, were used to characterize quantitatively the synergistic effects of hydrogen and stress on local dissolution at crack-tip of a X70 pipeline steel in a near-neutral pH solution. Results demonstrate that, upon hydrogen-charging, the anodic dissolution of the steel is enhanced. The resistance of the deposited corrosion product layer depends on the charging current density. There is a non-uniform dissolution rate on the cracked steel specimen, with a highest dissolution current density measured at crack-tip. For a smooth steel specimen, the synergistic effect factor of hydrogen and stress is equal to 5.4, and the total effect of hydrogen and stress on anodic dissolution of the steel is 7.7. In the presence of a crack, the hydrogen effect factor, stress effect factor and the synergistic effect factor are approximately 4.3, 1.3 and 4.0, respectively. The total effect factor is up to 22.4, which is very close to the 20 times of difference of crack growth rate in pipelines in the presence and absence of the hydrogen involvement recorded in the field.     

高强铝合金裂纹尖端在3.5%NaCl溶液中的微区电化学特性

采用毛细管微电极测试方法、扫描Kelvin探针技术和数值分析方法,对2024 T351高强铝合金裂纹尖端在3.5%NaCl溶液中的微区电化学特性和腐蚀行为进行了研究.结果表明,裂纹尖端的腐蚀电位较远离裂纹尖端的基体位置更负,裂纹尖端处的电化学活性明显增加.在外加应力的作用下,裂纹尖端处表面氧化膜的厚度减薄,其稳定性和保护性变弱.裂纹尖端处优先发生阳极溶解,浸泡24 h后在裂纹尖端处出现腐蚀产物的堆积.由于腐蚀电位和电化学活性的差异,在裂纹尖端(阳极)和远离裂纹尖端的基体(阴极)之间可形成电偶对,进一步促进裂纹尖端局部区域内腐蚀过程的进行.