Micromechanical criteria of steel weldments ductile fracture

Abstract

Welding is one of the most often applied joining procedures for different metallic structures. Due to the nature of the process, i.e. heating, additional material (for some methods), usage of protective atmosphere and cooling, it typically causes inhomogeneity in the joint zone. This inhomogeneity influences the fracture behaviour, and can significantly endanger the integrity of the welded structures. This work deals with micromechanical criteria for initiation and development of ductile fracture in welded joints. These criteria are applied within the framework of local approach to fracture, through experimental-numerical procedure. Welded joints with a single weld metal or two different weld metals are examined; the influence of constraint and heterogeneity (mismatch) is analysed. Also, the defects in the heat affected zone are considered, as well as pipeline materials with sharp and blunt initial defects. Micromechanical model CGM, complete Gurson model, is used for modelling the damage initiation and development in the material.