Safety of Mega Container Ship Focusing on Brittle Crack Initiation and Arrest Behavior of Heavy Thickness Plate

Abstract

The enlargement of containership requires the higher tensile strength steel and thicker plate around the hatch coaming more than the prescribed classification rules. These call the concerns about the safety of brittle crack initiation and arrestability of hull structure. It is known that increasing of stress and thickness of plates will reduce the toughness of base metal and welding joints. Therefore, the authors conducted to assure the toughness of base metal and welding joint for new higher tensile strength steel of 460MPa yield strength (YP460) and 60mm thickness. It has been considered that weld assembled steel plate structure has some arrestability at intersections of plates, though there are no prescription on the rules. And it was reported that very thicker mother plate has not enough toughness to arrest brittle crack recently. The authors investigated the structural arrestability by model testing and FE analysis and established it. Furthermore, structural details for intersections were also established. Both preventing the brittle crack initiation and arresting the brittle crack of weld structure were described, focusing on developing higher yield strength and heavier thickness of YP460 for containership in this paper.

Brittle crack propagation/arrest behavior in T-joint structure of heavy gauge steel plate

“…[18,20] The fact that brittle cracks in heavy-thickness steel plates can be arrested by fabricating a T-joint structure having an unwelded face in the part where a brittle crack extends into the joint was demonstrated by model experiments, as described in Chapter 2, and the appropriateness of the results was shown by FEM analysis. However, it is also necessary to confirm that a similar crack arrest effect can be obtained with actual long brittle cracks.…”

“…This paper presents a comprehensive summary of the results of the experimental research and analyses [18][19][20][21][22][23] by the authors to date.…”

“…In our previous research [18][19][20], we conducted model experiments supposing that a brittle crack that has undergone linear propagation in a weld in the hatch coaming extends into a T-joint of the hatch coaming and strength deck, and investigated and analyzed the effect of the unwelded face on brittle crack propagation/arrest behavior in the T-joint with the aim of arresting brittle cracks in Tjoints.…”

“…2 Brittle crack propagation/arrest behavior in T-joint with an unwelded face [18][19][20] 2.1 Experimental method…”