Brittle Crack Arrest Toughness for Extremely Thick Steel Plates:Required Kca Value of Steel Plates with Thickness of 100 mm Used in Ultra-Large Container Ships

摘要

On the background of increasing demand in ship transportation,capacity of container ship has been growing to achieve low costshipping and ultra-large container ships of 20,000 TEU class haveappeared in the recent decade. With the enlargement of the containerships, it was expected that the extremely thick steel plates withthickness exceeding 80mm are applied to the longitudinal strengthmembers in the strength deck structures of container ship, such as hatchside coaming and upper deck, etc.International Association of Classification Societies (IACS) released itsUnified Requirements (UR) on brittle crack arrest design for the use ofextremely thick steel plates in January 2013. This UR requires theapplication of brittle crack arrest steel plates with a brittle crack arresttoughness value (Kca value; material performance required to arrest abrittle crack) of 6,000 N/mm~(3/2) or more at -10 °C in case of the use ofextremely thick steel plates. However, there are no specific rules forcases where the thickness of brittle crack arrest steel plates exceeds80mm. Therefore, there is an urgent need to clarify required Kca valuefor extremely thick brittle crack arrest steel plates with thickness ofmore than 80 mm.Against background above, Nippon Kaiji Kyokai (ClassNK) carried outthe joint research project with in collaboration with Japan WeldingEngineering Society (JWES). In this project, the verification tests werecarried out by large/ultra-large scale structural model arrest testspecimens simulating the actual construction of the hatch side coamingand upper deck with thickness of 100 mm for ultra-large containerships. Based on these verification test results, the required Kca valuefor brittle crack arrest steel plates with thickness of more than 80 mmand 100 mm or less was discussed.