Modelling of ductile fracture initiation in strength mismatched welded joint

• Published in: Engineering fracture mechanics 2008-07, Vol.75 (11), p.3499-3510
• Main Authors: Rakin, M., Gubeljak, N., Dobrojević, M., Sedmak, A.
• Format: Article
• Language: English
• Subjects: Applied sciences; Constraint effect; Ductile fracture initiation; Exact sciences and technology; Fracture mechanics (crack, fatigue, damage...); Fundamental areas of phenomenology (including applications); Joining, thermal cutting: metallurgical aspects; Metals. Metallurgy; Physics; Solid mechanics; Structural and continuum mechanics; Void volume fraction; Welded joint; Welding
• ISSN: 0013-7944; 1873-7315
• DOI: 10.1016/j.engfracmech.2007.04.026

In this paper, the effect of strength mismatch and width of the welded joints on the stress–strain distribution in the crack tip region has been discussed. The single-edge notched bend (SENB) specimens (precrack length a 0/ W = 0.32) were experimentally and numerically analysed. The model of local approach to fracture, proposed by Gurson, Tvergaard and Needleman, was used. High-strength low-alloyed (HSLA) steel was used as a base metal in quenched and tempered condition. The flux-cored arc-welding process in shielding gas was used. Two different fillers were selected to make over- and undermatched weld metal. The experimental analysis of fracture behaviour of the over- and undermatched welded joints was followed by numerical computations of void volume fraction in front of the crack tip. The critical void volume fraction, f c, used in prediction of the crack growth initiation on the SENB specimen had been previously determined on a round smooth specimen. Three widths of weld metal were considered: 6, 12 and 18 mm. A comparison of the crack tip opening displacement (CTOD) values corresponding to crack initiation in the SENB specimens is given, as determined both experimentally and using the GTN model.