Brittle fracture assessment of embedded flaw in heat-affected zone based on Weibull stress criterion

Abstract

This paper presents a method for estimating the condition for the brittle fracture limit of a welded joint with an embedded flaw in the heat-affected zone (HAZ) based on the Weibull stress criterion. A welded joint with an embedded flaw generated by cold cracking was subjected to a wide plate (WP) tension test, and a welded joint with a fatigue crack was subjected to three-point bending (3PB) tests; both tests were conducted at −30 °C. Brittle fractures occurred in all specimens, and the microstructure of the fracture initiation point for the WP specimen in the coarse-grained HAZ (CGHAZ) was upper bainite with M-A constituents. The critical Weibull stress distribution of the CGHAZ was calculated by finite element analyses for the 3PB specimens. The predicted fracture load and global displacement of the WP specimen at the brittle fracture obtained by the critical Weibull stress distribution were in agreement with experimental results from the WP tensile test. This confirmed that the brittle fracture limit of a welded joint with an embedded flaw could be predicted from the Weibull stress criterion.