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

Abstract

Brittle crack arrestability is extremely important in welded joints of heavy gauge steel plates used in large container ships. Recently, much attention has been focused on potential crack propagation along welds fabricated by large heat input welding. This paper examines the application of a T-joint to the strength deck structure of container ships to enhance crack arrestability. The unwelded face and the crack arrest toughness, K ca, for crack arrest were varied. In the case of a T-joint with an unwelded face, the ESSO test of the T-joint components showed that a brittle crack arrested at the T-joint embedding the unwelded face. In the case of a full penetration T-joint, the brittle crack was arrested if the steel plate used for the flange had a high K ca value in the range from 4900 to 7300 N/mm3/2. FEM analysis of the stress intensity factor K indicated that brittle crack propagation was arrested under the condition that the K value at the running crack tip was less than the K ca of the material. In the T-joint, it was noted that the K value around the deepest point of the crack decreased and was finally less than the K ca of the flange plate when the brittle crack penetrated into the flange plate. This phenomenon shows the advantage of using a T-joint for brittle crack arrest in the flange plates of strength deck structures. In order to verify the long brittle crack arrestability of the T-joint structure, ultra-large-scale tests were carried out under the recommended conditions obtained from a dynamic FEM analysis. The test results showed that long brittle cracks could arrest at the aforementioned T-joint structures.