【作者】 刘志伟；

【导师】 王国珍；

【作者基本信息】 华东理工大学 ， 化工过程机械， 2011， 硕士

【摘要】 本文建立了AP1000核电压力容器安全端结构的三维有限元分析模型,通过对假想存在于焊缝中不同尺寸的内表面周向裂纹进行有限元断裂力学分析,对安全端异种金属焊接接头区的缺陷评定方法进行了研究。初步构建了与安全端复杂结构几何、异种金属接头区复杂材料及裂纹尺寸相关的专用缺陷简化评定方法、失效评定图(FAD)高级评定方法和破前泄漏(LBB)分析评定方法。三种方法的评定精度和复杂程度依次提高。简化评定方法按塑性失效的极限载荷准则建立,根据安全端载荷计算的应力比及检测或计算的寿期末裂纹长度,用构建的表格插值确定出允许的裂纹深度,用寿期末裂纹深度与允许的裂纹深度相比较评价缺陷的安全性。在高级失效评定图(FAD)方法中,构建了与安全端结构、材料和裂纹尺寸相关的失效评定曲线族、极限载荷和应力强度因子；依据被评定缺陷的尺寸选择合适的失效评定曲线进行准确的计算评定。在LBB分析评定方法中,初步构建了与安全端几何、外加主载荷和材料J-R裂纹扩展阻力曲线(材料韧性)相关的LBB曲线和LBB评定图；依据被评定缺陷的尺寸和载荷,可评判安全端异种金属接头区的缺陷是否以LBB的方式失效。更多还原

【Abstract】 In this paper, three-dimensional finite element analysis models are built for the welded safe end of AP1000 nuclear pressure vessels. Through finite element analysis (FEA) of fracture mechanics for the circumferential surface cracks with different sizes in the weld metal, the defect assessment methods for the dissimilar weld joint in the safe end are studied. The simplified defect assessment method, advanced failure assessment diagram (FAD) method and leak-before-break (LBB) assessment method are constructed elementarily. And these methods are related to the complex structure of the safe end, the geometry of welding groove, the complex materials at weld joint region of the dissimilar metal and the crack sizes. The accuracy and complexity of the above-mentioned three methods are raised gradually.The simplified defect assessment method is constructed according to fully-plastic limit load criteria. The stress ratios are calculated from the loading condition; the flaw lengths are inspected or calculated at the end of service period. Allowable flaw depths for a given final flaw length are obtained by interpolation in the table which we constructed. By comparing the flaw depth at end of service period with the maximum allowable flaw depth, the safety of the defect could be assessed. In the advanced FAD assessment method, we constructed FACs, limit loads and stress intensity factors which are related to the complex structure of the safe end, the complex materials at weld joint region of the dissimilar metal and the crack sizes. The accurate FAC related to crack sizes should be selected for defect assessment. In the LBB assessment method, the LBB curves and the LBB assessment figures are constructed, and they both are related to the complex structure of the safe end, the principal load and the J-resistance curves (material toughness) of the materials at weld joint region. Based on the defect sizes and loading condition, we can assess whether the defects in the dissimilar metal weld joint in the safe end will fail in LBB mode.更多还原