本文關鍵詞： 應力腐蝕 陽極溶解 腐蝕產(chǎn)物膜 氫 有限元模擬　出處：《北京科技大學》2015年博士論文　論文類型：學位論文

【摘要】：應力腐蝕是一種低應力、無征兆的脆斷過程,往往會導致災難性的惡性事故,造成巨大的經(jīng)濟損失和人員傷亡。據(jù)統(tǒng)計,應力腐蝕造成的安全事故在腐蝕事故中所占的比例高達35%。因此,一個多世紀以來,應力腐蝕一直是一個重要的研究領域。 對于大多數(shù)陽極溶解型應力腐蝕(SCC),應力腐蝕過程中會在金屬表面或裂紋尖端形成一層腐蝕產(chǎn)物膜,腐蝕產(chǎn)物膜在SCC中起著重要的作用。盡管人們開展了大量的研究,但是還存在爭議。本論文利用有限元模擬研究了腐蝕產(chǎn)物膜力學性質(zhì)和生長規(guī)律對陽極溶解性應力腐蝕的影響規(guī)律,重點研究了腐蝕產(chǎn)物膜應力的分布,以及對應力腐蝕裂紋尖端應力場的影響規(guī)律；同時,也建立了陽極溶解型應力腐蝕的內(nèi)聚力模型,研究了腐蝕產(chǎn)物膜破裂和應力腐蝕裂紋擴展的動態(tài)過程,以及腐蝕產(chǎn)物膜的力學性能(楊氏模量、破裂強度)和腐蝕產(chǎn)物膜導致的應力與應力腐蝕敏感性和門檻應力強度因子的關系。本論文還以310奧氏體不銹鋼在42%沸騰氯化鎂溶液中陽極溶解型應力腐蝕為例,研究了陰極過程為析氫反應的陽極溶解型應力腐蝕,氫在應力腐蝕中的作用,提出了定量鑒別氫在陽極溶解中作用的方法。獲得如下結(jié)論： 1)腐蝕產(chǎn)物膜中的殘余應力若為壓應力,根據(jù)力平衡則在金屬基體中產(chǎn)生拉應力。有限元模擬研究發(fā)現(xiàn),腐蝕產(chǎn)物膜在金屬基體中產(chǎn)生的拉應力非均勻分布,最大應力出現(xiàn)在膜與基體的界面；對于U型單邊缺口試樣中,最大拉應力出現(xiàn)在試樣表面距界面一定距離處,其大小和腐蝕產(chǎn)物膜厚度,膜楊氏模量,缺口的寬度和深度有關。存在兩種可能的膜破裂的機制：一是腐蝕產(chǎn)物膜內(nèi)的大拉應力使膜破裂。二是膜致應力疊加外加應力提高分切應力,促進裂尖前端局部塑性變形,使膜發(fā)生破裂。 2)建立了陽極溶解型應力腐蝕的內(nèi)聚力模型,通過模擬研究發(fā)現(xiàn)：對于光滑試樣,隨著腐蝕產(chǎn)物膜厚度,膜楊氏模量的增加和膜破裂強度的降低,應力腐蝕敏感性增加。膜致拉應力的存在使得試樣提前達到屈服階段,促進應力腐蝕的發(fā)生；對于U型單邊缺口試樣,歸一化門檻應力強度因子隨腐蝕產(chǎn)物膜厚度和缺口深度的增加而降低。無論是光滑試樣還是U型單邊缺口試樣,裂紋都起源于腐蝕產(chǎn)物膜內(nèi)。膜致拉應力產(chǎn)生的應力強度因子會疊加在外加應力強度因子上。因此,陽極溶解型的應力腐蝕裂紋在外加應力保持恒定的情況下也可以形核擴展。 3)運川慢應變速率拉仲、電化學以及陰陽極極化的方法研究氫在陽極溶解型應力腐蝕中的行為,獲得如下研究成果：310s奧氏體不銹鋼在濃度為42%沸騰氯化鎂溶液中的應力腐蝕,陰極極化阻礙了應力腐蝕,陽極極化促進了應力腐蝕。開路電位下Iscc(H)/IscC=0.035,應力腐蝕斷口形貌和大電流動態(tài)充氫下斷口形貌完全不同。310s奧氏體不銹鋼在濃度為42%沸騰氯化鎂溶液中開路電位下的應力腐蝕是由陽極過程控制,氫在其中所占的分量可以忽略不計。
[Abstract]:Stress corrosion is a low stress brittle fracture process, without warning, often lead to disastrous accidents, causing huge economic losses and casualties. According to statistics, accidents caused by stress corrosion should be accounted for in Corrosion Accident in the proportion as high as 35%. therefore, more than a century that stress corrosion has been an important research field.
For most of the anodic dissolution of stress corrosion, stress corrosion cracking (SCC) process will form a layer of corrosion product film on the metal surface or the crack tip, the corrosion product film plays an important role in SCC. Although people carry out a lot of research, but also controversial. Study on mechanical properties and corrosion product film the growth law of stress corrosion on the anodic dissolution of finite element simulation in this paper, the distribution of corrosion product film stress, and stress corrosion crack tip stress field; at the same time, also established the anodic dissolution should be cohesive zone model of stress corrosion, the corrosion product film the dynamic process of stress corrosion rupture and crack propagation, and the corrosion product film mechanical properties (Young's modulus and fracture strength) and corrosion product film caused by stress and stress corrosion sensitivity and threshold stress intensity The relationship between the factors. This thesis also takes 310 austenitic stainless steel in boiling 42% anodic dissolution of magnesium chloride solution stress corrosion for example, anodic dissolution of the cathode process for hydrogen evolution reaction to stress corrosion, stress corrosion of hydrogen in the role, and puts forward the method of quantitative identification of hydrogen in the anode dissolution the conclusion was as follows:
1) the residual stress in the corrosion film if the compressive stress is generated according to the force balance of tensile stress in the metal matrix. The finite element simulation results show that the corrosion product film on the metal matrix tensile stress in non uniform distribution, the maximum stress appears in the film and the substrate on the interface; U type single notched specimen, the maximum tensile stress occurs at the surface of the sample at a certain distance from the interface, the size and thickness of corrosion product film, the young's modulus, gap width and depth. There are two possible mechanisms of rupture of membranes: one is the corrosion product in the film tension stress to rupture. The two film is caused by the stress superposition stress increase the shear stress and the crack tip front, promote local plastic deformation, the membrane was broken.
2) anodic dissolution should be cohesive zone model of stress corrosion is established, the simulation results indicate that: for the smooth sample, with the thickness of corrosion product film, and increase of Young's modulus of rupture strength decrease, increase of stress corrosion sensitivity. The membrane induced by tensile stress due to the existence of the sample in advance to yield stage, promote stress corrosion; for U type of single edge notched specimen, the normalized threshold stress intensity factor increases with the thickness of corrosion product film and the notch depth decreased. Both the smooth specimen or U type single notched specimen, cracks originate in the corrosion product film. The film caused by the tensile stress produced by stress intensity factor will be superimposed on the applied stress intensity factor. Therefore, anodic dissolution of stress corrosion crack when the stress is kept constant under the condition of nucleation can be extended.
3) the slow strain rate tensile, electrochemical method and anode polarization studies of hydrogen in the anodic dissolution of stress corrosion behavior in the obtained results are as follows: 310S concentration of 42% austenitic stainless steel in boiling magnesium chloride solution stress corrosion, cathodic polarization hinder stress corrosion, anodic polarization promoted the stress corrosion. The open circuit potential Iscc (H) /IscC=0.035, stress corrosion fracture and large current dynamic hydrogen charging under completely different fracture morphologies of.310s austenitic stainless steel in a concentration of 42% boiling magnesium chloride solution under open circuit potential stress corrosion is controlled by the anodic process of hydrogen, in which the share of components negligible.

【學位授予單位】：北京科技大學
【學位級別】：博士
【學位授予年份】：2015
【分類號】：TG172.9

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