核压力容器异种金属焊接接头延性断裂行为数值研究

Numerical Research of Ductile Crack Growth Behavior for Dissimilar Metal Welded Joint of Nuclear Pressure Vessel

使用GTN损伤模型与有限元计算相结合的方法,对核电安全端异种金属焊接接头试样裂纹扩展路径及J-R阻力曲线进行数值研究。结果表明:异种金属接头中的堆焊层及焊缝中心裂纹扩展路径和均质材料基本相同,而界面及近界面裂纹的扩展路径显著地偏离初始裂纹位置。界面裂纹及近界面裂纹倾向于向屈服强度低的软材料一侧扩展,这是由裂尖前区域不同材料的强度失配所致。不同初始位置和不同尺寸的裂纹具有不同的材料拘束和几何拘束,其J-R裂纹扩展阻力曲线不同。宏观断裂力学无法预测这种裂纹的扩展路径和扩展阻力,基于GTN损伤模型的数值计算方法可以预测这种裂纹的扩展路径及扩展阻力,可望用于安全端焊接结构的完整性评定和破前漏分析。

Based on GTN damage model and finite element method （FEM）, numerical simulations are performed on the specimens of a nuclear power dissimilar metal welded joint （DMWJ）, and the crack growth paths and J-R resistance curves were obtained. Results show that the crack growth paths for the central cracks in the buttering and weld material are nearly the same as those of the homogenous material crack, while the growth paths for interface crack and near interface crack in the DMWJ deviate from their initial positions significantly. The initial interface crack and near interface crack tend to grow in the soft material with low yield stress, and is mainly caused by the strength mismatch of the different materials. The cracks with different initial location and depth have different strength mismatch and geometry constraint, and result in different J-R resistance curves. The growth paths and resistance curves of these cracks could not be predicted by macroscopic fracture mechanics; while the numerical simulation of f＇mite element based on GTN damage model is expected to be used in structural integrity assessment for safe-end DMWJ and leak-before-break analysis,