Investigation of Fractured Steel Plates Removed from Welding Ships

摘要

Samples of fractured plates from 72 ships were examined, and various laboratory examinations and tests were made on 113 plates selected from these samples. Information regarding the structural failures involved was obtained from the cooperating agencies, and the failures were analyzed on the basis of this information combined with the results of the laboratory investigations. The failures usually occurred at low temperatures, and the origin of the fractures could be traced, invariably, to a point of stress concentration at a geometrical or metallurgical notch resulting from design details or welding defects. The fractures in the ships generally were of a brittle or cleavage type, showing little evidence of ductility, although the steels showed normal ductility in the usual type of tensile test. The chemical compositions and ordinary mechanical properties of the fractured plates indicated that the steels met the specification requirements under which they were purchased. However, Charpy V-notch bar tests showed that plates in which fractures originated were more notch sensitive than plates which did not contain a fracture source. Thus, both service experience and the results of the laboratory investigation indicate that the fractures resulted from stress concentration in steels which were notch sensitive at the operating temperature. (Author)