基于三维XFEM计算的非匹配异种接头裂纹偏转验证

Crack deflection verification of the dissimilar joint based on 3D XFEM calculation

现有完整性评定将异种接头分为母材、焊缝、母材3个部位,然而低匹配接头实际存在母材、热影响区(HAZ)、交界面、焊缝4个部位。以CF62(母材)-316L(焊材)组合的低匹配接头为例,对其进行结构细分,对该低匹配接头进行断裂韧度试验时,裂纹向软质焊缝区偏转。笔者建立了低匹配接头的异质材料(交界面和HAZ)扩展有限元(XFEM)模型,对裂纹的偏转现象进行数值模拟,通过对不同匹配比(M=0.3~1.0)热影响区进行扩展有限元模拟,研究不同匹配比下裂纹偏转过程和含异种界面的J积分值,分析匹配比和裂纹偏转对接头断裂韧度的影响。结果表明:低匹配接头形式可提升HAZ的断裂韧度,断裂韧度随着匹配比的增大而增大;裂纹偏转现象会影响裂纹长度的测量,裂纹发生偏转后接头的断裂韧度有所下降。

The dissimilar joint is divided into three parts by integrity identification:base metal,weld and base metal.In fact,the geometry of the under-matched dissimilar joint has four different parts:base metal,heat affected zone(HAZ),interface and weld.The under-matched dissimilar joint of the combination of CF62(base metal)and 316L(weld metal)was researched considering these four different parts.The crack deflection had been observed by fracture toughness experiments.The extend finite element method(XFEM)models of the heterogeneous material(interface and HAZ)of under-matched dissimiliar joint had been built to simulate and verify the crack deflection.The XFEM models of HAZ with different matching ratio from 0.3 to 1.0 had been built up as well.The crack deflection route and J-integral value had been researched under different matching ratios.The influence of the matching ratio and crack deflection on the fracture toughness had been analyzed.Results showed that the crack deflection existed in the under-matched dissimilar joint.The under-matched dissimilar joint enhanced the fracture toughness of HAZ and increased with the increasing of the matching ratio.The crack deflection affected the crack length measurement,and the fracture toughness decreased when considering the crack deflection.