Fracture toughness of a high-strength low-alloy steel weldmentJelena Vojvodič-Tuma
, Nenad Gubeljak
, Borivoj Šuštaršič
, Borut Bundara
, 2006, original scientific article
Abstract: The use of high-strength low-alloy steels for high-performance structures, e.g., pressure vessels and pipelines, requires often high-strength consumables to produce an overmatched welded joint. This globally overmatched welded joint contains local mis-matched regions, which can affect the unstable fracture behaviour of the welded joint and the welded structure itself. If local mis-matched regions are present in the vicinity of a crack tip, then the fracture toughness of the weld metal can be significantly lower than that of the base metal. In this paper, the influence of the weld-metal microstructure on the fracture behaviour is estimated enabling an evaluation of the resistance to stable crack growth through different microstructures. The lower bound of the fracture toughness for different microstructures was evaluated using a modified Weibull distribution. The results, obtained using specimens with a through thickness crack front, indicated a low fracture toughness, caused by the strength mis-matching interaction along the crack front. In the case of through-the-thickness specimens, at least one local brittle zone (LBZ) or a local soft region is incorporated into the process zone in the vicinity of the crack tip. Hence, an unstable fracture occurred with small stable crack propagation, or without it. Despite the fact that the differences between the impact toughness of the weld metal and the base metal can be insignificant, the fracture toughness of a weld metal can be significantly lower.
Keywords: fracture mechanics, welded joint, crack-tip opening displacement, resistance curves
Published: 16.03.2017; Views: 742; Downloads: 65
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