本文選題：應(yīng)力腐蝕開(kāi)裂　切入點(diǎn)：異種金屬焊接接頭　出處：《西安科技大學(xué)》2015年博士論文

【摘要】：核電壓力容器安全端異種金屬焊接接頭應(yīng)力腐蝕開(kāi)裂(SCC)裂尖力學(xué)狀態(tài)是分析SCC機(jī)理及定量預(yù)測(cè)裂紋擴(kuò)展速率的關(guān)鍵因素之一。本文采用理論研究和彈塑性有限元分析相結(jié)合的方法,通過(guò)建立焊接接頭三點(diǎn)彎曲試樣模型,研究了界面裂紋與亞界面裂紋裂尖局部力學(xué)特征的影響因素,并對(duì)核反應(yīng)堆壓力容器安全端異種金屬焊接接頭不同位置處界面裂紋及亞界面SCC裂紋擴(kuò)展驅(qū)動(dòng)力進(jìn)行了分析。完成的主要工作如下:(1)對(duì)高溫高壓水環(huán)境中核電結(jié)構(gòu)材料SCC機(jī)理進(jìn)行了研究,闡明了核電結(jié)構(gòu)材料裂尖局部微區(qū)域的應(yīng)力應(yīng)變是促使SCC裂尖氧化膜破裂的主要驅(qū)動(dòng)力,并在很大程度上決定了SCC裂紋擴(kuò)展速率,提出了斷裂力學(xué)和彈塑性有限元相結(jié)合的SCC裂紋擴(kuò)展驅(qū)動(dòng)力研究方法。(2)通過(guò)建立安全端焊接接頭材料的勻質(zhì)試樣模型,分析了不同材料SCC裂尖局部微區(qū)域力學(xué)特征,得到了勻質(zhì)材料裂紋擴(kuò)展對(duì)裂尖微區(qū)域局部力學(xué)場(chǎng)的影響,為研究異種金屬焊接接頭中的SCC裂紋擴(kuò)展驅(qū)動(dòng)力提供參照基準(zhǔn)。(3)針對(duì)安全端焊接接頭材料的力學(xué)性能不均勻性,通過(guò)建立雙金屬材料界面裂紋擴(kuò)展彈塑性有限元模型,得到了材料屈服強(qiáng)度失配、應(yīng)變硬化指數(shù)失配以及裂紋擴(kuò)展對(duì)界面裂紋裂尖微區(qū)域應(yīng)力及應(yīng)變分布的影響規(guī)律,并得到了核電安全端焊接接頭SCC界面裂紋擴(kuò)展驅(qū)動(dòng)力。(4)建立了異種金屬焊接接頭裂紋擴(kuò)展的擴(kuò)展有限元(XFEM)模型,通過(guò)采用XFEM中的粘性片段和虛擬節(jié)點(diǎn)法,分析了具有力學(xué)性能不均勻特征的界面裂紋擴(kuò)展行為,討論了焊接接頭裂紋擴(kuò)展趨勢(shì)特征。(5)通過(guò)建立雙金屬材料亞界面裂紋的計(jì)算模型,討論了裂紋處于界面兩側(cè),裂紋與界面之間距離以及屈服強(qiáng)度失配對(duì)亞界面裂紋裂尖局部力學(xué)特征的影響規(guī)律,得到了裂紋擴(kuò)展對(duì)亞界面裂紋裂尖局部微區(qū)域應(yīng)力及應(yīng)變場(chǎng)的影響規(guī)律。(6)建立了核電安全端異種金屬焊接接頭有限元模型,分析了低合金鋼、鎳基合金焊材及奧氏體不銹鋼焊接區(qū)界面及亞界面裂紋裂尖局部微區(qū)域應(yīng)力和應(yīng)變的分布規(guī)律,得到了焊接接頭力學(xué)性能不均勻場(chǎng)中SCC裂紋擴(kuò)展驅(qū)動(dòng)力的分析方法。
[Abstract]:The mechanical state of stress corrosion cracking (SCC) crack tip of safety end dissimilar metal welded joint of nuclear power pressure vessel is one of the key factors to analyze the mechanism of SCC and to predict the crack growth rate quantitatively.In this paper, by using the method of theoretical study and elastic-plastic finite element analysis, the influence factors of the local mechanical characteristics of the crack tip of the interface crack and the sub-interface crack are studied by establishing the three-point bending specimen model of the welded joint.The driving forces of interface crack and sub-interface SCC crack propagation at different positions of safety end dissimilar metal welded joint of nuclear reactor pressure vessel are analyzed.The main work of this paper is as follows: (1) the SCC mechanism of nuclear power structure materials in high temperature and high pressure water environment is studied. It is shown that the stress and strain in the local micro-region of the crack tip of nuclear power structure material is the main driving force to promote the rupture of the oxide film at the crack tip of SCC.The crack growth rate of SCC is determined to a great extent. A new method for studying the driving force of crack growth in SCC is proposed, which combines fracture mechanics with elastic-plastic finite element method. The homogeneous specimen model of welded joint material with safe end is established.The local micromechanical characteristics of SCC crack tip of different materials are analyzed, and the effect of crack propagation on the local mechanical field of crack tip is obtained.In order to study the driving force of SCC crack growth in dissimilar metal welded joints, the reference datum is provided. Aiming at the inhomogeneity of mechanical properties of welded joints at the safety end, an elastic-plastic finite element model for interfacial crack propagation of bimetallic materials is established.The effects of yield strength mismatch, strain hardening exponent mismatch and crack propagation on the stress and strain distribution in the micro-region of the interfacial crack tip are obtained.A finite element finite element model for crack growth of dissimilar metal welded joints is established by using the viscous segment in XFEM and virtual node method, and the driving force of crack growth at SCC interface of safety end welded joint of nuclear power plant is obtained.The crack propagation behavior of interface with inhomogeneous mechanical properties is analyzed. The crack propagation trend characteristics of welded joints are discussed. The calculation model of sub-interface crack in bimetallic material is established and the crack is located on both sides of the interface.The effect of the distance between crack and interface and the failure of yield strength on the local mechanical characteristics of crack tip of sub-interface crack is studied.The effect of crack growth on the stress and strain field in the local micro-region of the crack tip of sub-interface crack is obtained. The finite element model of dissimilar metal welded joints at the safety end of nuclear power plant is established, and the low alloy steel is analyzed.The distribution of stress and strain at the interface and crack tip of Ni-base alloy and austenitic stainless steel is studied. The analysis method of the driving force of SCC crack propagation in the inhomogeneous field of mechanical properties of welded joints is obtained.
【學(xué)位授予單位】：西安科技大學(xué)
【學(xué)位級(jí)別】：博士
【學(xué)位授予年份】：2015
【分類(lèi)號(hào)】：TL351.6;TG407

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