This should have been the headlines at the conclusion of the Official
Inquiry, except that the technical expertise and technology for molecular
analysis necessary to exonerate the Iceberg from direct
responsibility for the TITANIC sinking did not exist until decades
after the fatal maritime disaster. Cold water temperatures, about 35
degrees Fahrenheit, caused the steel to crack in a brittle manner,
like glass, when it hit the Iceberg, instead of the ductile, twisting,
tearing manner, we are all accustomed. During the first half 20th
century, the temperature above which typical high grade ship steel
changed to ductile, tearing failure mode from the brittle mode was 50
degrees Fahrenheit. Not until 1963, over 50 years after the TITANIC
sank in cold arctic water, was the first authoritative documentation
published by two researchers from the U. S. Naval Research
Laboratory providing a comprehensive, quantitative analysis
describing the phenomenon of ductile to brittle crack propagation in
steel.
How widespread and pervasive was this lack of knowledge, that
fingers should be pointed at the engineers that designed and built
the TITANIC and should be held responsible for the disaster? In all
probability, cracks in steel hull plates of ships was common place.
Except that due to the riveted construction techniques of the era, a
crack in a single plate was not catastrophic and would be attributed
to an occasional single bad steel plate from the steel mill or faulty
fit-up in manufacture. A brittle fracture, would only run to the next
riveted joint, typically not more than 20 feet in length, with
noticeable
but not catastrophic leakage which could be contained until the next
reasonable scheduled repair.
Symptoms of the low temperature brittle fracture of steel were
showing, but the engineering community, like engineers (and doctors)
even today are prone to treat the symptoms and not look into the
true cause of the failure(disease) and find a true and final
solution(cure).
The engineering community was so clueless as to the low
temperature brittle fracture of steel problem that over 5000 Liberty
ships were mass produced during World War II without accounting
for this phenomenon. Thirty years after the TITANIC sank only
because the water was about 15 degrees too cold, the US
Government built over 5000 Warships with the same fundamental
flaw. Of these 5000 Warships, 1000 suffered significant failures
between 1942-1946 because of low temperatures, while 200 suffered
serious fractures between 1942-1952. No one may ever know exactly
how many ships "just disappeared" in the North Atlantic and were
falsely chalked up as lost to German U-Boat torpedo attacks due to
low temperature brittle fractures. Some torpedoed ships may have
even survived an attack, albeit damaged, without the hull shattering
due to the low temperature brittle crack phenomenon. The
Government knew something was wrong, because the failure rate of
the welded Liberty ships was statistically astronomical in the North
Atlantic, while literally NON-EXISTENT in the warm waters of the
South Pacific.
Not until 1947, that a ship literally broke into two pieces while tied
to
a dock in the cold water of Boston Harbor, that there was enough
evidence, left accessible and dramatic enough, that the problem was
taken seriously. This parallels uncannily with the Aloha Flight 243
aircraft accident, which landed at the Maui Airport after an 18 ft.
section of the upper fuselage disintegrated inflight at an altitude of
24,000 feet above the Hawaiian skies. The Aloha Flight 243 accident
initiated the "aging aircraft program" that changed the course of
aviation engineering history with the same magnitude as the
breaking into two pieces of the USS Ponaganset changed naval
engineering history.
The USS Ponaganset (AO-86) was a T-2 tanker, a Escambia class Fleet Oiler, built at Marinship in Sausalito, California and commissioned on May 15, 1944. Only 3 years old, on a cold day at dockside in Boston, Mass., at a temperature of 35 degrees Fahrenheit, the stresses at a stray welding arc strike on the deck of the ship exceeded the yield strength of the steel. Yield strength of steel is the stress level when the steel starts to permanently deform. Typically, the yield strength is only about one-half of the ultimate tensile strength, the stress where steel actually breaks into separate pieces. Much deformation occurs in a piece of steel between when the steel starts to yield and finally fails at ultimate tensile, usually the steel will stretch between 20% to 40% of its original length before it breaks, if it acts in a "ductile" manner.
The "BIG OOPS" in the TITANIC and Liberty shipbuilding disasters is what was defined by two researchers at the U. S. Naval Research Laboratory, W. S. Pellini and P. P. Puzak, the "Nil Ductility Transition" temperature phenomenon. On March 15, 1963, Pellini and Puzak published their findings after a 15 year study, defining and also devising a method of quantifying the temperature at which steel changes from DUCTILE to BRITTLE fracture modes. Above the Nil Ductility Transition temperature, a certain piece of steel can be loaded to its ultimate tensile strength, stretching 20% to 40% before it breaks. Below the Nil Ductility Transition temperature, when a piece of steel is loaded to only the yield strength (approximately 1/2 of the ultimate strength) the piece of steel will crack in a brittle manner, like glass. Once the crack starts to run (at the speed of sound), it will only stop when it runs out of steel, the load is released or the crack is arrested by running into a piece of ductile acting steel.
In the case of the USS PONAGANSET, the stresses reached the yield strength at a location where a tiny crack existed on the deck of the ship in 35 degree Fahrenheit weather. The NDT of the steel used to build the Ponaganset was determined after the failure to be 50 degrees Fahrenheit. Consequently, the crack propagated in a brittle manner and literally ran around the ship, near instantaneously, and the ship broke in two.
The US War Machine, and not unjustifiably, was priding itself that it could build a shipyard that could deliver mammoth ships at a rate of one every 13 days. Marinship set a record of building one ship, the S.S. HUNTINGTON HILLS, from empty dock to complete ship in just 33 days.
Who would have thought that a 15 degree temperature drop and a stray welder's arc strike could destroy a ship as effectively as a German torpedo? Could a 29,000 ton ship be that fragile? How could the US Government build 5000 ships with such a flaw?
When an average person is subjected to a "Disaster", the memory of
the emotion is long, but the memory of details is short. Mention
TITANIC and the immediate response is "Sank by Iceberg". This is a
normal defense reaction. It is perfectly acceptable to even the
simplest mind that a mammoth iceberg could sink an "unsinkable"
gigantic steel ship or an errant missile could bring down a 747. But if the answer is as simple as the water was
too cold but nobody knew or frayed insulation caused an arc and explosion, how can we trust that all the other
engineering masterpieces our lives depend on, everyday, are not as
fragile? The planes we fly in, the miles long bridges we drive
across, are they also susceptible to catastrophic failure by a simple
quirk of Nature the greatest minds of our civilization are not aware?
Stay tuned to......