Abstract
This paper deals with numerical finite element calculations of the crack driving force CTOD-δ₅ for strength-mismatch welded joints. The crack driving force, i.e. the parameter CTOD-δ₅, for bending specimens with shallow cracks in mismatch welded joints is determined at the point of instability when the first ductile or brittle fracture appeared using a numerical model with plane strain conditions at the crack tip. Yield strengths of different microstructures around the crack tip and its actual mechanical properties are taken into account in the finite element model of the specimen. It was shown that by calculated crack driving force, it is possible to predict brittle or ductile fracture initiation of bending specimens with shallow cracks in the weld metal of strength-mismatch welded joints.

Key words
finite element method (FEM), crack tip opening displacement (CTOD), welded joints, δ₅ approach

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