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Bad fasteners can sink ships

Bad fasteners can sink ships

Bad acting and sappy dialogue didn't stop Titanic from winning the best picture Oscar. But bad rivets might have stopped the actual ship from surviving its brush with an iceberg.

According to Timothy Foecke, a metallurgist with the National Institute of Standards and Technology, substandard fasteners may have been what really sank the Titanic. He examined two rivets recovered from the ship's hull and found them to contain high concentrations of slag--a residue left by the smelting process which made the fasteners dangerously brittle.

Millions of rivets held together the steel beams and plates of the 46,000-ton ship. Forensic specialists studying the disaster say the brittle rivets may have popped, causing the plates to separate and let in the icy water.

This conclusion squares with the findings of shipwreck investigators who used underwater sonar to study the Titanic about a year ago. Dispelling the theory that an iceberg slashed a 300-ft gash in the ship's hull, they say it was the force of the impact that caused the riveted seams of the hull to pop open.

No one's saying that stronger rivets would have definitely prevented Titanic from sinking, but they very well may have bought the hundreds of passengers who didn't fit in the lifeboats another hour or two. Perhaps enough time for a nearby ship to rescue them.

Fasteners aren't glamorous, but they're absolutely necessary for good product design. A digital cellular phone with so many features you can't possibly learn them all isn't terribly useful if it comes apart under heavy use. A $5,000 laptop computer doesn't seem like such a marvel anymore if the latches for opening it don't work perfectly. And when I'm driving a car, the thing that annoys me most is hearing a rattle that just won't go away.

At Design News, each editor specializes in one or more areas of technology--their beats. I handle semiconductors and CAD--pretty sexy stuff. Associate Editor Deana Colucci covers fasteners and adhesives--the screw-it-or-glue-it beat. Not usually the stuff of cover stories.

But fasteners hold their own. For example, each December we ask readers to pick the best product of the year, and the fastening product is always among the top finishers. This year, the PEM(reg) R'ANGLE self-clinching fastener from Penn Engineering and Mfg. Corp. was a strong contender. Last year, Southco's Sentinel(TM) ratchet-action captive screw drew lots of votes.

And in 1996, the Ultra-Lok bolt from Ultra-Lok Fasteners took the top prize as Design News product of the year. The self-tapping Ultra-Lok repairs stripped or damaged threads by cutting new threads as you install it. The metal shavings created pack into a reservoir, locking the bolt in place and forming a vibration damper.

These companies sweat the details. Their livelihoods depend on getting the little things right.

So, pay attention when you spec a fastener. You decision can make or break anything from a $5 calculator to a multimillion-dollar TransAtlantic ship.

Please comment on this or any other topic by sending e-mail to [email protected]

Head Work

Air at 70F is compressed during a polyropic process (n=1.2) from a pressure of 14.7 to 100 psia. If the process is adiabatic, the resulting temperature will be most nearly

A. 70F

B. 170F

C. 270F

D. 370F

E. 457

F--Answer below

Selected from Fundamentals of Engineering Examination, copyright 1986, Eugene L. Boronow, N.E.E., P.E., Simon & Schuster, Inc., NY. Reprinted with permission of the publisher. Answer 3

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