Application of Weibull Stress Criterion to Brittle Fracture Assessment of Heat Affected Zone Notched Welds With Residual Stress

Abstract

A constraint loss correction procedure using the Weibull stress criterion is specified in ISO 27306. However, this standard is applicable only to structural steel components with defects, not to welded joints. Therefore, we propose a method for estimating the brittle fracture limit of a weld with a notch in the heataffected zone (HAZ) and residual stress based on the Weibull stress criterion. Threepoint bending (3PB) tests and wideplate (WP) tension tests of HAZnotched welds made of 780MPa class highstrength steel were conducted at −40 آ°C. The minimum critical crack tip opening displacement (CTOD) of the WP specimen fracturing at the coarsegrained region of the HAZ (CGHAZ) was approximately four times that of the 3PB specimen. Then, the effects of specimen geometry, residual stress, crackfront shape, and HAZ microstructure classification on the Weibull stress were investigated by using a finite element analysis (FEA). The results of these analyses showed that the specimen geometry, the welding residual stress, and HAZ microstructure affect the Weibull stress of HAZnotched welds as crack driving force. Based on above results, the CTOD–Weibull stress curves for 3PB and WP specimens fracturing at CGHAZ were calculated by using an FEA. It was confirmed that the brittle fracture limit of an HAZnotched weld with residual stress could be predicted from the Weibull stress criterion because predicted critical CTOD of WP specimens obtained by Weibull stress included experimental critical CTOD of WP specimens.