CTOD設計曲線の衝撃問題への拡張

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Japan Welding Engineering Society (JWES) standard WES2805 has been widely used to evaluate unstable fracture of welded build-up steel structures. It is based on elastic-plastic fracture mechanics (CTOD criterion), because most brittle fracture may occur from the defect at structural stress concentration field. As this standard gives CTOD design curve to simply estimate CTOD, we can easily evaluate unstable fracture of welded structures. But this design curve can be applied only static loading condition. Brittle fracture initiates not only on static loading but also on intermediate or high loading rate. CTOD design curve in WES2805 can not be applied at these loading rates. Authors proposed the estimation method of fracture toughness at arbitrary loading rate taking the effect of strain rate on fracture toughness into consideration. Strain rate-temperature parameter (R) suggested by Bennet et. al. is used as a parameter of this estimation method. Besides yield stress at arbitrary loading condition can be represented as a function of R parameter. On basis of these results, it is assumed that yield stress dominates the fracture mechanics parameter such as CTOD, this is to say, it can be given CTOD at nominal strain rate by substituting the yield strain at nominal strain rate for CTOD design curve. Failure analyses of lower flange with beam scallop of box column-to-H beam connection at Hanshin earthquake (Jan. 17th 1995) were carried out by the above mentioned extended CTOD design curve. As a result of these analyses, it is clear that CTOD design curve can be applied at arbitrary loading rate by substituting the yield strain at nominal strain rate for this design curve.
社団法人日本船舶海洋工学会の論文

CTOD設計曲線の衝撃問題への拡張

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