The US Coast Guard, who were responsible for the safety of merchant vessels, requested the setting up of a Board of Investigation into the design and construction of welded ships. The Board was set up in April 1943 and co-ordinated a major research effort into the fracture of ships.
The failure of the Schenectady initiated on the deck between two bulkheads. A defective weld was present in a region of stress concentration arising at a design detail. The nominal tensile stress in the deck was calculated to be 68N/mm2. Poor welding procedures were cited by the committee investigating the failure as contributory, however, at the time, the problems were not fully understood.
The importance of weld quality was dramatically illustrated by the experience of the T2 tankers in which 50% of fractures initiated in welds not associated with design discontinuities. The investigation into the 'Schenectady' also questioned the adequacy of steel specifications for all welded ship hulls. The steel used to build the Schenectady was of a quality which was known to be acceptable for riveted ships.
The final Report of the Board of Investigation was published in 1946. It considered 4694 welded steel merchant ships built in the emergency ship building programme, of which 970 sustained fractures. The report concluded that the fractures were due to the presence of notches in steels which were notch sensitive at the operating temperature and that the specifications current at the time were 'not sufficiently selective to exclude' such steels.
Research into ship failures continued with the Charpy V notch properties of casualty ship plates being investigated. The absorbed energy in the Charpy V notch test, one of the few standardised fracture tests then available, was found to correlate well with the observed crack initiation, propagation and arrest behaviour of the ship steels. By the early 1950s the 15ft lb or 20J Charpy transition temperature was being used as a reference as it appeared to define the highest temperature at which brittle fracture initiation would occur in ship quality steels. However research showed that the critical temperature for brittle fracture initiation corresponded to higher Charpy energy values when modifications to alloying elements, grain size, deoxidation methods and normalising heat treatments were made. Hence the approach to brittle fracture avoidance could not be based on a simple fixed reference Charpy energy level.