CRACK-STARTER TESTS OF SHIP FRACTURE AND PROJECT STEELS, PART 1

The performance of rimmed and semikilled steels involved in ship fractures is investigated by means of crack-starter tests. In these tests a sharp crack is introduced in the steel, and the relative resistance to the initiation and propagation of fracture is established over the range of service temperatures. It is demonstrated that in the presence of the sharp crack the steels have no appreciable ductility when the temperature falls below the Charpy V 10ft-lb transition; accordingly, fracture initiation is readily developed. The propagation of brittle fracutres becomes difficult at temperatures above the Charpy V 15--25 ft-lb transitions. These findings are in agreement with National Bureau of Standards data for ship fracture plates. It is demonstrated that fully killed steels do not follow these rules and that the respective initiation and propagation characteristics of fracture are related to higher Charpy V values. Wide plate, tear and Charpy V test data are discussed with reference to differences related to deoxidation practice.