Fundamental study on fracture criterion of a crack in a weld line between two different steels

The behavior of a crack in a weld line between two different steels and its fracture criterion were studied by employing the CED in an arbitrary direction that can be successfully applied to the behavior of a mixed-mode crack in a homogeneous material from elastic fracture through fracture with large scale yielding. The fracture experiments of the specimens with a crack in a weld line between high tension steel (HT 60) and mild steel (SPC) were carried out, first, under tensile type loading, and it was made clear by observing fracture surface that the mode II type fracture occurs even under tensile type loading in this material combination. Moreover, the CED in an arbitary direction was evaluated through the finite element analyses corresonding to the experiments. It was confirmed through the analyses that the crack here becomes a mixed-mode one with the extension of yielding region because of the difference of yield stress and, by applying the numerical results to the experimental ones, it was shown that the observed crack behavior can be explained by the mode II fracture criterion based on the CED in an arbitrary direction.