An experimental study on Kca value to arrest a running brittle crack in structural model specimens with steel plate of 100 mm thickness for container ships

Abstract

With demand for ultra-large container ships, high-strength steel plates with extremely large thicknesses are applied to the structural elements around hatch side structures. The two longitudinal plates of the upper deck and hatch side coaming are the main structural elements that support bending stress during hogging of the ship structure, and brittle crack arrest toughness as well as crack initiation toughness are required in these steel plates to avoid the catastrophic ship damage. Although the International Association of Classification Societies prescribes a unified requirement for brittle crack arrest steel plates providing the value of brittle crack arrest toughness Kca at − 10 °C for plate thicknesses of 80 mm or less, ultra-large container ships using steel plates with thicknesses exceeding 80 mm are continuously required and built. In the present work, brittle crack arrest tests with large scale structural model specimens which simulate the structural element of the hatch side structure were performed to investigate the Kca value required to arrest a running brittle crack for steel plates with the thickness of 100 mm. The present investigation suggested that the test plate simulating upper deck could arrest a running brittle crack at the plate Kca of 6000 N/mm3/2, nevertheless the Kca value of 8000 N/mm3/2 was needed in the test plate simulating hatch side coaming. The different Kca values required to arrest a running crack between the test plates simulating the upper deck and the hatch side coaming are also discussed from the viewpoint of the arrested crack size and shape.