【作者】 薛晓峰；

【导师】 薛河；

【作者基本信息】 西安科技大学 ， 机械设计及理论， 2011， 硕士

【摘要】 应力腐蚀破裂(SCC)问题是影响核电设备长期安全运行的关键问题之一,也是核电安全研究领域的热点问题之一。由于应力腐蚀破裂是发生在裂纹尖端(断裂过程区)力学作用下的一种电化学行为,受到裂尖区域腐蚀环境、材料和力学的共同影响和作用,是多学科多尺度相交叉的复杂问题,单从某一尺度或单个学科进行研究是无法完全展示出其破坏过程的。针对目前相关研究多是直接基于宏观尺度或纳观尺度,而对微观尺度上的应力腐蚀开裂研究不足。为此,本论文将重点放在微观尺度上应力腐蚀开裂裂尖的力学特性分析上。本论文通过将数值模拟与理论计算结果对比,验证了利用ABAQUS计算紧凑拉伸试样(1T-CT试样)相关断裂参量的有效性,建立了宏观尺度下裂纹扩展的全局模型和裂尖区域的子模型。全局模型的计算结果为子模型提供边界条件,而子模型的计算为详细了解应力腐蚀破裂裂尖微观力学场提供了保证。本论文在基于应力腐蚀破裂裂尖存在沟形裂纹这一基本观点的基础上,建立了微观尺度下沟形裂纹模型和裂尖分叉裂纹模型,并利用子模型技术建立了微观尺度下沟形裂纹有限元模型和裂尖分叉裂纹有限元模型,分析了微观尺度下应力腐蚀破裂裂尖沟形裂纹长度和分叉裂纹对裂尖氧化膜和基体金属应力应变场的影响。论文研究结果表明,SCC裂尖氧化膜前端沟形裂纹和裂尖分叉裂纹的存在,会造成氧化膜和基体金属中应力应变的变化,且随着沟形裂纹的长度增加,这种变化越发明显。另一方面,与应力相比,等效塑性应变对裂尖长度变化更加敏感,从一个侧面说明,裂尖等效塑性应变是研究SCC裂尖氧化膜和基体金属比较理想的力学参量。更多还原

【Abstract】 Stress Corrosion Cracking (SCC) is one of the key factors affecting the long-term safety operation ofnuclear power equipments, which is a hot field in the nuclear safety operation research field. SCC is anelectrochemical behavior which occurred in fracture process zone at the crack tip. Which is interactivelyaffected and acted by the corrosion environment, materials and mechanics at the crack tip and is involvedmultidisciplinary and multi-scale researches. It is almost impossible to reveal the SCC process by usingsingle subject or single scale. Current researches in SCC are based on the macro-scale or directly on thenano-scale, which is skipped micro-scale. Because it is important to understand SCC process in the grainscale, the tasks will focus on the mechanical properties at the SCC tip in micro-scale in this dissertation.By comparing numerical simulation calculation with theoretical analysis of compact tension specimen(1T-CT specimen) the effectiveness of calculating fracture parameters by using ABAQUS software isverified in the dissertation. A global model involved 1T-CT specimen and a sub-model involved SCC tipregion are constructed, and the calculation of the global model provide the boundary condition forsub-model and the calculation of sub-model provide a detailed investigation on the micro-mechanical fieldat the SCC tip. Based on a basic consideration of a narrow grove-type crack existing at the SCC tip, FEmodels with a grove-type crack and FE model with branch cracks in micro scale are constructed by usingthe sub-model technology in ABAQUS. The effects of the grove-type crack length and branch crack on thestress and strain at the SCC tips are analyzed this dissertation.The results of investigation indicate that the grove-type crack and branch crack ahead of SCC tip willinduce a great change on the stress and strain in the oxidation film and base metal at the SCC tips, and thechange is more obvious as the grove-type crack length increase. Comparing with the stress, the plasticstrain is more sensitive to the length at the SCC tip. Therefore, the equivalent plastic strain should be anappropriate mechanical parameter to understand the mechanical properties in the oxide film and base metalat the SCC tip.更多还原