Fracture Mechanics of Ship Structures

Abstract

Using international cooperative exchange programs, the Department of Defense is currently working with U.S. steel makers to improve the technology base so that they can produce new highly weldable, low alloy, high strength alloys. The development program for these alloys should insure adequate strength and toughness, but not impose excessive requirements. That program justifies the need for a greater understanding of the use of fracture mechanics for the selection of structural materials. There have been several recent independent extensive studies of the application of fracture mechanics to ship structures sponsored by the Ship Structure Committee, the Naval Research Laboratory, David Taylor Research Center, and the Admiralty Research Establishment. The recommendations of these experts range from continued use of existing material parameters, use of linear elastic fracture mechanics, and the use of ductile fracture mechanics for determining the requirements for hull material. This paper reviews the results of these studies and recommends an approach to the development of rational criteria. The Navy is starting an extensive research and development program to verify the chosen methodology, including the testing of large scale sections that will replicate ship hulls. The result of this application of theory and verification through testing will be a new basis for the determination of the toughness requirements for ship structures, avoiding excessive requirements as we seek to use the latest materials that will be available during this decade and in the twenty-first century.