环境介质和力学因素对高强度钢腐蚀疲劳裂纹扩展速率的影响——高强度钢腐蚀疲劳裂纹扩展速率的定量研究

本文对4330M钢在蒸馏水中的腐蚀疲劳裂纹扩展速率进行了定量研究。测出4330M钢在蒸馏水中的(da/dt)-K曲线,并在R=0.2,0.6,0.7,0.8四种情况下测出4330M钢在氩气中和在蒸馏水中的(da/dN)-△K曲线。研究了应力比R对腐蚀疲劳的影响。在上述实验基础上,拟制了一个BASIC计算程序,根据应力腐蚀和氩气气氛下疲劳的实验数据,用电子计算机对叠加模型和竞争模型分别算出以每周表示的应力腐蚀裂纹扩展速率(da/dN)_(SCC)。比较了两种模型的相互关系。计算结果表明4330M钢在蒸馏水中的腐蚀疲劳实验数据和Austen提出的竞争模型相符合。本文对竞争模型进行修正,提出要加上考虑交互作用的修正项。使用经修正后的竞争模型,就能解释腐蚀疲劳裂纹扩展速率定量研究方面存在的一些问题。试验结果表明,4330M钢适用于研究腐蚀疲劳裂纹扩展的机制问题。     

THE EFFECTS OF ENVIRONMENTAL AND MECHANICAL VARIABLES ON CORROSION FATIGUE CRACK PROPAGATION RATE IN A HIGH STRENGTH STEEL——Quantitative Understanding of the Corrosion Fatigue Crack Growth Rate in a High Strength Steel

本文对4330M钢在蒸馏水中的腐蚀疲劳裂纹扩展速率进行了定量研究。测出4330M钢在蒸馏水中的(da/dt)-K曲线,并在R=0.2,0.6,0.7,0.8四种情况下测出4330M钢在氩气中和在蒸馏水中的(da/dN)-△K曲线。研究了应力比R对腐蚀疲劳的影响。 在上述实验基础上,拟制了一个BASIC计算程序,根据应力腐蚀和氩气气氛下疲劳的实验数据,用电子计算机对叠加模型和竞争模型分别算出以每周表示的应力腐蚀裂纹扩展速率(da/dN)_(SCC)。比较了两种模型的相互关系。计算结果表明4330M钢在蒸馏水中的腐蚀疲劳实验数据和Austen提出的竞争模型相符合。本文对竞争模型进行修正,提出要加上考虑交互作用的修正项。使用经修正后的竞争模型,就能解释腐蚀疲劳裂纹扩展速率定量研究方面存在的一些问题。 试验结果表明,4330M钢适用于研究腐蚀疲劳裂纹扩展的机制问题。     

304L不锈钢在高温高压水中的腐蚀疲劳裂纹扩展行为

基于直流电压降方法(direct current potential drop,DCPD)测量得到了304L不锈钢在325℃空气和含氧超纯水中的疲劳裂纹扩展速率;采用FORD-ANDRESEN模型、Bechtel Bettis模型和PSI模型进行结果分析比较;用扫描电镜观察了断口形貌。结果表明:低频低载荷下,腐蚀对疲劳的加速作用高达1 000倍,高频高载荷下则只有1.5倍;FORD-ANDRESEN模型对于解释腐蚀疲劳机理和预测腐蚀疲劳裂纹扩展速率更加合理与准确,Bechtel Bettis模型和PSI模型可以对试验结果进行比较,但无法给出各种因素对裂纹扩展的影响;疲劳断口形貌观察到明显的疲劳辉纹,疲劳破坏形式为穿晶断裂。     

腐蚀疲劳裂纹的虚拟扩展方法研究

    以紧固孔结构件腐蚀疲劳试验为基础,研究了腐蚀疲劳裂纹虚拟扩展方法即随机过程和AFGROW模拟方法.以试验数据拟合得到的Paris公式为基础,在随机过程方法中考虑了正态随机过程和对数正态随机过程,得到裂纹长度和循环数之间的模拟曲线,给出指定循环数下裂纹长度的概率模型并和实验结果进行了比较.利用AFGROW对腐蚀疲劳裂纹扩展进行了模拟,裂纹扩展模拟曲线与实验值符合较好.     

40CrNiMoA钢在水介质中的腐蚀疲劳行为

本文对40CrNiMoA钢在870℃淬火200℃回火和1200℃淬火200℃回火两种热处理状态下在蒸馏水中的应力腐蚀和腐蚀疲劳裂纹扩展过程进行了研究,考察了载荷波形、载荷频率、应力比、淬火温度等因素对腐蚀疲劳裂纹扩展特征和裂纹扩展速率da/dN的影响。依据本文的实验结果,对R.P.Wei和Landes提出的用来定量描述腐蚀疲劳裂纹扩展速率的叠加模型进行了计算,得出了该模型适用于40CrNiMoA钢——水介质条件的结论。并给出了可供实际使用的公式、数据和程序。     

预腐蚀铝合金贯穿疲劳裂纹扩展行为的统一表征模型

在环境腐蚀损伤以及疲劳载荷的联合作用下,铝合金结构更容易萌生裂纹,威胁结构安全。腐蚀疲劳短裂纹扩展行为与长裂纹扩展行为差别很大,而且往往短裂纹阶段占据构件疲劳寿命的90%以上。通过对线弹性裂纹扩展模型进行修正,得到了预腐蚀弹塑性裂纹扩展表征模型,并对LD2铝合金进行预腐蚀疲劳验证性试验。结果表明,改进后的模型能够统一地表征预腐蚀弹塑性短裂纹和线弹性长裂纹的扩展行为,对于铝合金构件的腐蚀疲劳寿命预测和损伤容限评估具有重要的参考价值。     

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。     

海洋工程装备材料腐蚀疲劳裂纹扩展研究综述

对海洋工程装备材料腐蚀疲劳进行综述。介绍了环境因素、力学因素以及材料自身因素对腐蚀疲劳裂纹扩展的影响。总结了描述腐蚀疲劳裂纹扩展速率的理论模型,分析了各种模型的优缺点。最后,指出了腐蚀疲劳裂纹扩展模型的研究趋势。     

E690高强钢腐蚀疲劳裂纹扩展速率曲线与S-N寿命曲线转换研究

以E690高强钢为研究对象,结合实验获得的裂纹扩展速率曲线与寿命S-N曲线,研究这两种腐蚀疲劳性能模型之间的内在联系,量化并建立两者之间转换的关系模型,实现将裂纹扩展速率曲线转换为对应的S-N曲线。结果表明,所提的方法能较好地实现材料裂纹扩展速率曲线与寿命S-N曲线之间的转换,具有很好的可行性和通用性,有助于优化E690高强钢腐蚀疲劳寿命预测与损伤定量评估体系。     

WC-Co硬质合金热机械腐蚀疲劳性能的研究

采用自行设计的实验装置对两种WC-Co硬质合金在压压循环载荷和循环加热冷却同时作用下的热机械腐蚀疲劳行为进行了研究,研究了冷却介质pH值和Co含量对硬质合金热机械腐蚀疲劳性能的影响,同时采用SEM对断口形貌进行了分析.实验结果表明:疲劳断裂的宏观形貌主要是切断型的断裂,疲劳裂纹稳定扩展区上存在很多摩擦碎屑,在稳定扩展区并没有发现疲劳条纹的存在,瞬断区的断裂形貌与静态断裂特征一致.在本文所提供的热机械腐蚀疲劳实验条件下,并未发现冷却介质pH值对两种WC-Co系列的硬质合金的热机械腐蚀疲劳性能的影响,低Co含量的硬质合金YGH30具有比高Co含量硬质合金YGH60更优异的热机械腐蚀疲劳性能.     

腐蚀疲劳裂纹内溶液的两维运动模型

以单边穿透裂纹为背景,建立了描述腐蚀疲劳裂纹内溶液的流体运动两维方程。通过解偏微分方程组,用解析法得到了腐蚀疲劳裂纹内溶液的两维运动规律。据此,以紧凑拉伸试样为例,讨论了影响速度的各参数及裂纹内的流态。     

Corrosion fatigue crack propagation behavior of A7N01P-T4 aluminum alloy welded joints from high-speed train underframe after 1.8 million km operation

Using the potentiodynamic polarization analysis, the fatigue crack propagation behavior of A7N01P-T4 aluminum alloy metal inert gas welded joints cut from a high-speed train underframe after 1.8 million km operation was studied in air and in a 3.5 wt% NaCl solution. The fracture surface and crack growth path were analyzed using optical microscopy, scanning electron microscopy, and electron backscattered diffraction. The results reveal that the corrosion fatigue crack growth rate of an A7N01P-T4 welded joint in a 3.5 wt% NaCl solution is higher than that in air. Furthermore, the corrosion fatigue crack growth rate is noted to be the fastest in the heat-affected zone, followed by the base metal, whereas it is the slowest in the weld metal, which is consistent with the corrosion resistance of the A7N01P-T4 joints. The second phase is observed to exhibit a significant influence on the corrosion fatigue crack propagation path. The cracks are noted to grow toward the soft orientation and have obvious plastic deformation during the propagation process, which indicates that the anodic dissolution is the main cause of the corrosion fatigue crack growth.     

Effect of preloading on corrosion fatigue of 70/30 brass

The effects of a single tensile overload and precycling load in air on subsequent corrosion fatigue cracking in 70/30 brass exposed to 1 M sodium nitrite solution were studied. A single tensile overload caused a decrease in subsequent corrosion fatigue crack propagation rate. Precycling load also showed retardation effects, depending on the load conditions for precycling and corrosion fatigue. A transsition from a higher mean stress for precycling to a lower mean stress for corrosion fatigue decreased corrosion fatigue crack growth rate, while an opposite transition did not appreciably change the corrosion fatigue crack propagations. The responses of bulk mechanical properties to a presingle overload and precycling load in air were measured, showing hardening which may probably be responsible for the observed retardation.     

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.     

环境对双相钢疲劳性能的影响

本文研究了自来水和3.5％NaCl水溶液分别在全浸和干湿交替状态下对热轧双相钢疲劳性能的影响.结果表明:与空气中的疲劳寿命相比,腐蚀环境有不同程度的降低作用,并以喷雾盐水影响最大.在相同腐蚀条件下,环境的影响随应力幅的降低而增强.马氏体抗疲劳断裂的能力高于铁素体.试样表面和断口的观察结果发现,腐蚀疲劳裂纹萌生与腐蚀坑密切相关,蚀坑以阳极溶解方式形成.     

Fatigue life prediction of aviation aluminium alloy based on quantitative pre-corrosion damage analysis

A new method of quantitative pre-corrosion damage of aviation aluminium (Al–Cu–Mg) alloy was proposed, which regarded corrosion pits as equivalent semi-elliptical surface cracks. An analytical model was formulated to describe the entire region of fatigue crack propagation (FCP). The relationship between the model parameters and the fatigue testing data obtained in the pre-corroded experiments, crack propagation experiments and S–N fatigue experiments was discussed. The equivalent crack sizes and the FCP equation were used to calculate the fatigue life through numerical integration based on MATLAB/GUI. The results confirm that the sigmoidal curve fitted by the FCP model expresses the whole change from Region I to Region III. In addition, the predicted curves indicate the actual trend of fatigue life and the conservative result of fatigue limit. Thus, the new analytical method can estimate the residual life of pre-corroded Al–Cu–Mg alloy, especially smooth specimens.     

腐蚀疲劳过程中载荷间交互作用的研究

介绍了近年来进行了Ａ５３７钢在３．５％ＮａＣｌ水溶液中阴极溶解与阴极充氢条件 下腐蚀疲劳裂纺扩展中载荷交互作用方面的一些研究结果。其中包括恒△Ｋ控制下的单周超载延迟作用, 裂纹扩展率的波型响应以及小幅载荷的幅度与相对主载荷的位置对裂纹扩展的影响规律等。     

Corrosion fatigue crack initiation life of ship structural steel in dilute sulfuric acids

This paper describes corrosion fatigue for notched specimens in dilute sulfuric acids. The acids are typical corrosion environments of condensate from coal vapor in a coal cargo hold. Fatigue data were consolidated as the relationships between the equivalent stress at a notch root and a fatigue crack initiation life. Life in dilute sulfuric acids was shorter than that in seawater because of the severe dissolution of iron. Long term corrosion fatigue was also estimated from the relationship between the stress intensity factor range to the fatigue crack initiation and the life. Corrosion wastage was considered as an estimate of the fatigue crack initiation life.     

Untersuchung des SwRK-Verhaltens des hochreinen martensitaushärtenden Stahles X5CrNiCuNb 17 4 PH im Vergleich zum weichmartensitischen Stahl X4CrNiMo 16 5 1 ESU in chloridhaltigen wäßrigen Medien. Teil 2: SwRK-Untersuchungen und Rißeinleitungsmechanismen

Investigations of the corrosion fatigue behaviour at a super pure martensitic stainless steel X5CrNiCuNb 17 4 PH in comparison to the soft martensitic stainless steel X4CrNiMo 16 5 1 ESR in chloride containing aqueous media — Part 2: Corrosion fatigue tests and crack initiation mechanisms The following report concerns the study of the corrosion fatigue behaviour of the soft martensitic steel X4CrNiMo 16 5 1 ESR and the precipitation hardened X5CrNiCuNb 17 4 PH in sodium solution in the temperature range between 20° and 150 °C and the determination of their general corrosion properties and the mechanism of crack propagation. Their corrosion fatigue limits were compared with each other. A comparision was also made between an electro-slag-remelted soft martensitic steel and a charge without an ESR aftertreatment. Microfractographical fracture and crack path investigation were carried out for interpretation of the experimental results. It was observed that in both super pure steels (soft martensitic and precipitation hardened) the oxidic inclusions are not responsible for the crack intiation, as it was found in the non ESR treated steels. In the 17-4 PH steel copper containing inclusions in the crack initiation areas were observed. In concentrated sodium solution pitting corrosion was found at both steels.