压水堆核电构件安全端焊接接头由于需要承载腐烛、高温、高压、中子福照、疲劳 载荷以及冲击载荷和热应力的共同作用，故其往往是发生失效的薄弱环节。应力腐蚀裂 纹、疲劳裂纹、制造缺陷等是引起异种金属焊接接头各种缺陷的常见因素。针对晶间腐 蚀裂纹，核电构件安全端焊接接头的应力腐蚀裂纹都是沿晶扩展，晶间断裂是其众多失 效形式中较为常见的一种。 本文利用有限元仿真软件 ABAQUS， 以压水堆核电构件安全 端焊接接头为研究对象，对晶间扩展裂纹尖端力学场进行数值模拟计算，旨在分析不同 参数对晶间扩展裂纹尖端力学场相关表征量的影响，研究不同因素对晶间扩展裂纹尖端 力学场的作用方式和影响规律，进一步加深对晶间扩展裂纹尖端力学场的了解和认识， 为正确的预防和处理晶间扩展裂纹提供有效的依据。本文的主要研究内容如下： (1)区分晶粒与晶界组织材料，确定用于分析计算的材料模型和几何模型，建立有限 元模型，利用剖分法思维划分晶粒和晶界的显微结构，对其分别赋予不同的材料属性， 并以此为基础建立晶间扩展裂纹的有限元计算模型； (2)宏观尺度下，利用变参量法，在建立晶间扩展裂纹全局计算模型的基础上，观察 力学和材料因素对子模型边界的作用方式和影响规律； (3)介观尺度下，通过建立不同晶粒尺寸的有限元分析模型，得到晶间扩展裂纹尖端 力学场的各个参量随晶粒尺寸的变化规律； (4)介观尺度下，通过建立不同裂纹长度的有限元计算模型，得到尖端场的各个表征 参量随裂纹长度的变化规律； (5)此外，本文还对由全局模型传递给子模型的不同边界条件(材料因素、力学因素) 对晶间扩展裂纹尖端力学场分布的影响规律作了具体的分析。

Because of the complexity of needing to carry rot candle, high temperature, high pressure, according to the neutron blessing, fatigue loads and shock loads and thermal stress joint action, welded joints of safety end of PWR nuclear components are often the key parts of the occurrence of failure. SCC, fatigue cracking, manufacturing defects are common factors that cause a variety of defects. For intergranular corrosion cracking, SCC of welded joints of safety end of PWR nuclear components are extended along the grain. Intergranular fracture is one kind of its many failure forms. Research on the intergranular fracture morphology and fracture mechanism is still deepening. In order to analysis of the influence of different parameters on characterization of the intergranular crack tip field, to research the action and effect of different factors on intergranular crack, to further deepen the knowledge and understanding of intergranular crack tip field, the crack tip field of intergranular crack was simulated and analyzed in this dissertation based on finite element software ABAQUS. The main contents are as follows: (1)Making a distinction between grain and grain boundary material, determining the material and geometry used for the analysis model, the global macro model of standard compact tension specimen and micro sub-model of grains and grain boundary microstructure were constructed by finite element software ABAQUS using triangulation method; (2)On the macroscopic scale, in order to observe the impact of mechanics and material factors on the boundary conditions of sub-model passed from global model by using variable parameter method, a global intergranular cracks computing model was established; (3)On the meso scale, in order to get the impact of geometric factors on the crack tip field, FEA model of different grain size were established； (4)On the meso scale, in order to get the impact of crack length on the crack tip field, FEA model of different crack length were established； 5.In addition, the impact with the boundary conditions（mechanical factors and material factors） of meso scopic model transformed from the global model on crack tip field was specific analysis in this paper.