Effect of Strength Matching of Welded Joint on Stress Corrosion Cracking in Nuclear Power Structures

Abstract

Stress corrosion cracking (SCC) is one of the key issues of welded structure failure in nuclear power plants. To understand the effect of strength matching on SCC growth rate in welded joint of primary coolant circuit safe end in pressured water reactor, a model of the safe end welded joint with mismatched strength was established by using elastic-plastic finite element method (EPFEM).The effect of weld strength matching on SCC growth rate was analyzed in this paper, by adopting crack tip strain rate as SCC mechanical driving force. The investigated results indicate that the distribution of plastic strain and plastic strain rate nearby the crack front is similar when the crack located at welded metal, and the driving force of SCC along the crack front in the over-match, even-match and under-match welded joint are from small to large, respectively, which implicit SCC growth rate along the crack front in the over-match, even-match and under-match welded joint also are from slow to fast, respectively. The investigating establishes a foundation for improving the predicting capability of SCC growth rate in nuclear power structures.

Numerical Investigation of the Influence of Ultimate-Strength Heterogeneity on Crack Propagation and Fracture Toughness in Welded Joints

“…For example, Fan et al [ 19 , 20 , 21 ] established the sandwich structure finite element model and studied the local fracture resistance, and analyzed that the local material constraint effect and crack path deviation are strongly affected by the “local strength mismatch” in the bi-material interface area of dissimilar metal-welded joints, as well as constraint of the work hardening mismatch effect on the crack tip, the near-tip stress field, and the J-integral of the bi-material interface crack. Xue et al [ 22 , 23 ] used the sandwich structure finite element model to analyze the effect of material yield strength mismatch on the stress field at the crack tip, and the effect of work hardening mismatch on the fracture toughness. Zhao et al [ 24 , 25 ] used the finite element model of the sandwich structure to analyze the difference in the crack tip field caused by the heterogeneity of yield strength in the heat-affected zone of the welded joint, and they discussed its influence on the driving force of yield strength mismatch crack propagation.…”

Effect of Yield Strength Distribution Welded Joint on Crack Propagation Path and Crack Mechanical Tip Field

“…Fan et al [ 10 , 11 , 12 ] used this method to evaluate the safety of welded joints, established a finite element model of welded joints with dual material sandwich structure, and analyzed the effects of work hardening, initial crack location, and yield strength mismatch on fracture toughness and the crack propagation path. Xue et al [ 13 , 14 ] ignored the heat affected zone and fusion zone of welded joints, simplified them into sandwich structure, and gave different homogeneous material properties in different regions. The influence of yield strength mismatch on the stress–strain field at the crack tip and the driving force of crack growth were analyzed to predict the crack growth rate.…”