City
Tech Professor
Sheds New Light on Titanic
Like most of us, Dr. Richard Woytowich,
associate professor of computer engineering technology at New
York City Technical College, learned as a child of the tragic
events of April 15, 1912, when the "unsinkable"RMS
Titanic did just that on its maiden voyage, after striking
an iceberg in the North Atlantic.
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| Professor
Richard Woytowich with one example of robotic engineering,
a field in which City Tech is extensively involved. |
As a youngster, Woytowich had no reason
to question the then commonly held—but now confirmed to
be erroneous—notion that ice had sliced a long underwater
gash, or series of gashes, in the Titanic's starboard
hull, allowing the forward flooding that sealed the ship's fate.
Over the last three years, however, Woytowich has had a rare
opportunity to become closely involved with the ongoing research
into history's most famous maritime disaster. As a member of
the Marine Forensics Panel sponsored by the Society of Naval
Architects and Marine Engineers (SNAME) in co-operation with
a number of other professional societies, his role in this research
has been to investigate the design of the ship's riveted joints.
The panel had already determined, through metallurgical tests
performed on samples recovered from the wreck in 1996 and 1998,
that some of the ship's wrought-iron rivets were flawed. They
contained an unusually high concentration of slag, a product
of the smelting process, which made them brittle and prone to
fracture. Woytowich, however, suspected that high slag content
alone was not enough to explain what happened. He believed that
the design of Titanic's joints might also have played
a role in making the ship susceptible to collision damage.
His examination of late 19th- and early 20th-century technical
literature indicated that ship designers of that era took a
different approach to joint design. The practice today is to
make the joints, insofar as possible, as strong as the plates
they connect. Of course, riveted joints can never quite achieve
this ideal, because the rivet holes themselves reduce plate
strength.
In the first decade of the 20th century, designers used elaborate
tables relating the number and spacing of rivets to the jointôs
function and location within a ship. These tables appear to
have been intended to match the strength of each joint to the
forces it was expected to withstand in everyday service. Unfortunately
for most of the 2,200 passengers and crew aboard the Titanic,
the part of the hull which came into contact with the iceberg
included some of the weakest joints to be found anywhere in
the ship. In these areas, evidence indicates that the rivets
failed from the force exerted by the iceberg.
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| A
computer-generated image of the riveted plates compromised
by the iceberg. |
To better understand the behavior of these
joints, Woytowich constructed a computer model, using a "finite
element" program. (Such computer programs allow investigation
of complex shapes by breaking them down into simple ones that
can be solved mathematically.) He was able to reconstruct the
joint failure, step by step. The final stage of the failure,
in which enough rivets were overloaded to allow the hull plates
to separate, is shown in the accompanying illustration.
Woytowichôs crucial finding was that plate separations occurred
where only two rows of rivets, rather than three or more, were
specified to join the plates. These separations created a breach
in the ship's hull totaling approximately 12 square feet—about
the surface area of a human being of average size and enough
to allow more than 25,000 tons of water to flood the bow of
the 46,000-ton ship. The added weight was more than the Titanic
could withstand and stay afloat. Where three or more rows of
rivets were used, and where the rivets were made of steel rather
than wrought iron, the plates remained joined.
Woytowich completed his research too late for it to be included
in a paper presented by the Marine Forensics Panel at SNAME's
Annual Meeting in October of this year. However, with the cooperation
of the panel's chairman, William Garzke of the naval architecture
firm of Gibbs and Cox in Virginia, he was able to present his
findings as a discussion. Consequently, his results will be
published along with the rest of the Panel's findings in the
Society's Transactions for 2001.
When asked what lesson today's ship designers could learn from
these investigations, Woytowich responds that they need to think
very carefully when deciding what conditions to design for.
He noted that the sea is still a challenging environment, in
spite of all our technological sophistication, and has a way
of revealing, sometimes at terrible cost, the weaknesses in
any vessel's design and construction.
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