At 11pm on the 16 January 1943,
a few days after completing sea trials,
the 152m long T2 tanker 'Schenectady' broke in two amidships
while lying at the outfitting dock
in the constructors yard in Portland, Oregon, USA.
The temperature of the harbour water was about 4°C
and the conditions were still.
The air temperature was approximately -3°C
and the winds were light.
The failure was sudden and
accompanied by a report that was heard a mile away.
The fracture extended through the deck, the sides
of the hull, the longitudinal bulkheads
and the bottom girders.
The vessel jack-knifed,
hinging on the bottom plate which had remained intact.
The central part of the ship rose clear of the water
so no flooding of the hull through the fracture occurred.
The Schenectady was built by the Kaiser Company
as part of the huge World War II emergency ship building programme.
This programme produced 2580 Liberty ships, 414 Victory ships
and 530 T2 tankers over the years 1941-1946.
Although fractures in the emergency programme ships had been reported,
the Schenectady was the first catastrophic failure,
made all the more impressive by the still conditions
under which it occurred.
Then, in March 1943, a sister ship to the Schenectady'
the 'Esso Manhattan', broke in two at the entrance to New York harbour
in sea conditions described as very moderate.
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.
The failure of the Schenectady and other war-time ships
gave a significant impetus to the study of brittle fracture.
These failures highlighted the influence of temperature on
material toughness and the need to specify toughness requirements for welded ships.