17. Evaluation of Brittle Fracture Strength from Surface Notch at Fillet Weld Toe based on CTOD Criterion

概要

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As a model of the stress concentrators in the welded structures, wide plate tests with stiffener were carried out, and brittle fracture characteristics from a surface notch at the toe of the fillet weld were studied. The results of the investigation are summarized as follows. The CTOD values obtained from the wide plate test agree well with those from three-point bend CTOD test with a/W=0.5, even for the very shallow surface notch in the wide plate test. It is confirmed from these results that the CTOD criterion can be applied to evaluate the elastic-plastic fracture from a surface crack in the highly strain concentrated regions. The brittle fracture strength from the surface notch at the fillet weld toe was evaluated using the CTOD design curve, which was obtained by modifying WES 2805. The strain at the weld toe used in the evaluation was estimated for an "average" value in the cracked area. The strain concentration factor at the weld toe was predicted from the elastic stress concentration factor by means of the modified Neuber's relation. Based on such estimated strain and the CTOD design curve, the brittle fracture strength of the wide plate with stiffener was well evaluated.
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