Micromechanical assessment of mismatch effects on fracture of high-strength low alloyed steel welded joints

• CGM micromechanical model is used to study the fracture of HSLA steel welded joints.
• Constraint effects are analysed on over- and undermatched joints.
• Parameters are then transferred to joints with two weld metals.
• The effect of FE size/formulation on prediction of fracture initiation is determined.

Fracture of steel welded joints produced with one or two weld metals is analysed; the latter (double mismatched) consist of overmatched and undermatched portion. Specimens with a pre-crack in the symmetry plane of each joint are examined. In double mismatched joints, the pre-crack front passes through both weld metals. Micromechanical approach (complete Gurson model) is used for ductile damage development modelling. Influence of joint width, crack length, as well as size and formulation of finite elements, is examined. The constraint effect caused by the different joint geometry is predicted and the effect of material inhomogeneity along the crack front of the double mismatched joint is assessed by transferring the parameters from the joints with one weld metal.