Brittle crack arrest behavior and its interpretation in an isothermal crack arrest test

Abstract

Brittle crack arrest behavior in steel plates and its evaluation test technique were investigated exhaustively from the1950s to the 1980s. Nevertheless, similar discussions have been revived recently by issues related to brittle crack arrest design applicable to mega-container ships. For example, the issue of whether the brittle crack arrest properties of steel plates evaluated under isothermal conditions and gradient temperature conditions are equivalent or not, which was also an issue in earlier studies, has been discussed again since 2010. This discussion is the results of ongoing debate in the International Association of Classification Societies (IACS) concerning provisions for heavy-gauge brittle crack arrest (BCA) steel plates for mega-container ships.In the present work, the crack arrest temperature, abbreviated as CAT, was evaluated by an isothermal crack arrest test in a specimen with a crack runway embrittled by electron beam weld (EBW) re-melting. The dependence of CAT and the arrested crack length on the crack runway length were discussed. Crack arrest toughness Kca was also evaluated based on test that resulted in crack arrest in the isothermal condition, and the results were compared with those of the gradient temperature crack arrest test. An unexpected variation was observed in the Kca values in the isothermal test, but it was suggested that this represents the R-curve behavior of a running brittle crack. The R-curve concept can qualitatively explain the crack arrest behaviors with different crack runway lengths. The analogical difference in crack arrest behaviors between the isothermal condition and gradient temperature condition were also discussed.