New type steel having superior brittle crack arrestibility and its application to improve structural integrity

Studies on the crack arrestability of steel have revealed that the shear lips formed at the surface of steel when brittle cracks propagate offer great resistance to the further propagation of these cracks. This knowledge led to the development of steel (SUF steel) having ultra fine grains at the surface and in the subsurface region (surface layers) that promote the formation of shear lips. Plates of SUF steel have extremely high crack arrestability and do not require any special alloy additions. It is expected that the use of such plates for ship structures will remarkably increase the structural integrity. In this paper, new type steel plate having extremely high crack arrestability is introduced. Large-scale fracture model tests were conducted to determine the effect of the use of SUF steel plates in a ship structure as a crack arrestor. Furthermore, required value of crack arrestability to prevent long brittle crack propagation is discussed.