Study on the Rate of Elastic-plastic Crack Propagation of Heterogeneous Metal Welded Joints in Nuclear Power

In the high-temperature water environment of nuclear power, austenitic stainless steel, nickel-based alloy materials and welded joints composed thereof are the key locations for environmental cracking (EAC) problems such as stress corrosion cracking (SCC). In order to understand the crack propagation behavior and expansion rate of welded joints under the condition of abrupt and heterogeneous material properties of welded joints, this paper uses the extended finite element technique (XFEM) in the large nonlinear finite element software ABAQUS, based on the elastoplastic material model. Under the condition of welding residual stress field, the effects of different initial crack length and strength mismatch ratio on the crack growth rate of stress corrosion crack under constant load were studied. The results show that the SCC crack growth rate increases with the increase of the initial crack length. When the crack length of the initial welded joint is constant, different mismatch ratio has a certain effect on the crack growth rate. In the low ratio range(less than 1), the crack growth rate also increase if the strength mismatch ratio increase. but the crack growth rate is gradually reduce in high ratio range(more than 1). This indicates that the mismatch ratio of 1 is favorable for crack propagation, and the larger the mismatch ratio, the crack propagation is hindered.