More on Mixed Mode Cracking and Integrity Assessment of a Dissimilar Metal Weld for Ageing Nuclear Power Piping

摘要

This paper addresses a mixed mode driven cracking and relevant integrity assessment for applications in aging nuclear power facilities. Following our earlier discussion on the use of mode-I based criteria in the current practice using R6-method, linear and non-linear finite element analyses of a full-scale laboratory test, a Benchmark four-point bending test of a straight pipe with an obliquely inserted crack in a dissimilar metal weld of ferritic steel (A508), austenitic steel (316L), weld material (308L) and buttering material (309L/308L), is conducted. The behavior of the crack front at the load level, at which the crack initiation is observed in the test, are computed and examined. Computed results confirm our earlier observation: For cases when mixed mode loading conditions are significant, it is not conservative to use a purely mode-I based criterion for the fracture failure assessment, refined approaches using J-integral or others must be used in order to achieve a reliable assessment.