engleski

Effects of materials heterogeneity on the stress and strain distribution in the vicinity of the crack front

In this investigation a high strength low allowed steel (HSLA) with 700 MPa strength class was used as a base material. A butt welded joint with X grooves was produced with an overmatched metal with yield strength value greater for 22% than base material. Three-point bending Bx2B test specimens (thickness B=36 mm) were extracted from the welded joints. The straight crack front (a0=35, 571 mm) crosses over different materials through the thickness of the specimen. Both, fracture tests and 3-D finite element modelling are performed. Regarding the symmetry of the specimen, only one half is modelled. The CTOD parameter of fracture toughness was calculated for each load up to the load at which stable crack growth occurs. The comparison between experimental and numerical values of CTOD (d5) displacements is in good accordance. Principal stress Sy and Mises equivalent stress Seq as well as plastic equivalent strain Epl, eq in the moment of crack initiation have been presented for 10 layers through the thickness. Crack opening stress (Sx in this case) over the local fracture toughness value could be considered as the parameter which determinates the direction of crack front propagation. The results show that the presence of a low strength base metal contributes to the crack path deviation in the mid-thickness of the specimen. Both the crack path deviation and a higher toughness of base metal increase the critical fracture toughness value of the welded joint.

overmatch welded joint; crack; stress and strain distribution; finite element analysis

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