核电异种金属焊接接头应力腐蚀裂尖蠕变特性研究

发布时间：2018-02-07 10:44

本文关键词： 焊接接头力学性能不均匀性蠕变裂尖应力应变　出处：《西安科技大学》2016年硕士论文　论文类型：学位论文

【摘要】：应力腐蚀开裂(SCC)是核电一回路安全端异种金属焊接接头在服役过程中的一种重要失效形式,而SCC扩展是裂尖微观力学和电化学反应交互作用下的氧化膜破裂与再生成过程。近年来的研究显示,裂尖高应力区的蠕变对SCC裂尖氧化膜的破裂有一定的影响。为了了解焊接接头区高应力条件下裂尖蠕变特性及其对SCC扩展速率的影响,本文借助ABAQUS有限元分析软件,详细分析了焊接接头SCC裂纹高应力蠕变前后的裂尖力学场。主要完成的工作有:(1)以常用的核电焊接材料镍基182合金为研究对象,借助ABAQUS有限元软件及其重启动功能,对低温高应力条件下裂尖蠕变过程进行分析,得到了裂尖微观力学场及相关力学参量随蠕变时间推进的变化规律。(2)以镍基182合金-热影响区-316L不锈钢的异种金属焊接接头的简化模型为研究对象,考虑材料力学性能不均匀性的影响,建立了焊接接头的裂尖数值模拟分析模型,对蠕变前后裂尖力学场的分布变化规律和蠕变情况进行分析;并对裂纹分别萌生于焊材区和热影响区时的裂尖力学场进行研究,得到初始裂纹位置对裂尖应力应变等参量的影响规律。(3)基于修正的氧化膜破裂预测模型(FA模型),对低温高应力蠕变主导下的应力腐蚀裂纹尖端蠕变率及SCC裂纹扩展速率进行计算,得到了焊接接头材料力学性能不均匀性对SCC裂纹扩展速率的影响规律。
[Abstract]:Stress corrosion cracking (SCC) is an important failure form of safety end dissimilar metal welded joints in nuclear power plant. SCC expansion is a process of oxide film rupture and reformation under the interaction of micromechanics and electrochemical reaction of crack tip. In order to understand the creep characteristics of SCC crack tip under high stress condition and its influence on the SCC growth rate, this paper makes use of the ABAQUS finite element analysis software to study the creep behavior of the crack tip in the high stress zone of the crack tip and the rupture of the oxide film at the crack tip. The crack tip mechanical field before and after high stress creep of SCC crack in welded joint is analyzed in detail. The main work accomplished is: 1) taking the common nuclear power welding material nickel-based 182 alloy as the research object, with the help of ABAQUS finite element software and its restarting function, The creep process of crack tip under low temperature and high stress is analyzed. The micromechanical field of crack tip and the variation of relative mechanical parameters with creep time are obtained. The simplified model of dissimilar metal welded joints of Ni-based 182 alloy-heat affected zone stainless steel is studied. Considering the influence of non-uniformity of mechanical properties of materials, a numerical simulation analysis model of crack tip of welded joint is established, and the distribution of mechanical field and creep of crack tip before and after creep are analyzed. The mechanical field of crack tip is studied when the crack originates in the welding material area and the heat-affected zone, respectively. The influence of initial crack location on stress and strain of crack tip is obtained. (3) based on the modified oxide film fracture prediction model and FA model, the creep rate of stress corrosion crack tip and SCC crack expansion under low temperature and high stress creep are studied. The expansion rate is calculated, The effect of nonuniformity of mechanical properties of welded joints on SCC crack growth rate is obtained.
【学位授予单位】：西安科技大学
【学位级别】：硕士
【学位授予年份】：2016
【分类号】：TG407

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