A picture of Titanic in the ways in Belfast shortly before her launching.

The nearly completed Olympic alongside the frame of Titanic in the ways in Belfast.

A scanning electron microscope image of a broken wrought iron sample, this time broken at right angles to the other pictures. Note that the slag pieces are intact, because they were not bonded to the iron when it broke. Note how even a slightly larger-than-normal slag piece makes a large “hole” in the iron.

One of the vaunted safety features of the ship were the watertight doors. They could be dropped by electrical signal from the bridge (the wire above) or tripped automatically if water filled from below (the float in the lower left corner).

Wherever possible, hydraulic riveters (like here on the keel plate) were used to drive steel rivets for better consistency and extra strength. However, in the bow and stern, they used hand-driven wrought iron rivets instead.

Harland and Wolff shipyard workers on Titanic’s propeller shaft. – Note how large everything was on Titanic. This makes it easier to understand why she was slow to stop and slow to turn.

A scanning electron microscope image of a broken wrought iron sample, pulled along the direction of the slag fibers. Note the very large piece of slag, and how much bigger is the hole it formed than those around the small pieces. The big pieces are the ones causing the loss in strength.

A scanning electron…

Harland and Wolff shipyard workers

Hydraulic Riveting

A picture of Titanic…

The nearly completed Olympic…

SEM Brittle Slag

Broken wrought iron sample

Watertight Door

PORTLAND More than 1,500 people died when the Titanic sank in 1912, two hours and 40 minutes after it collided with an iceberg. Why the luxurious ocean liner sank so fast has been the subject of speculation ever since.

But a Portland scientist has done some old-fashioned detective work and laboratory tests to figure out the reason.

One prominent theory blamed the hull’s steel plates for being so brittle that they shattered during the collision. But once the sunken ship was found and examined revealing not a single, massive gash in its side but six slits, spread across a wide area some theorists focused on the wrought-iron rivets that held the steel plates together.

Jennifer Hooper McCarty, a licensing associate in the Office of Technology & Research Collaborations at Oregon Health & Science University, was a graduate student at Johns Hopkins University seven years ago. She was looking for a dissertation topic when her thesis supervisor, Tim Foecke, suggested she put the rivet theory to the test. Foecke, of the National Institute of Standards & Technology, was an early theorist about the rivets’ role.

She first confirmed earlier tests by Foecke that showed the rivets were made weak by too much slag, a byproduct of the process of making wrought iron. Rivets of purer iron would have remained strong under stress.

She examined every one of the 48 rivets recovered from the 3 million used to build the ship. What she discovered in the lab confirmed speculation. Some rivets she examined showed slag levels as high as 40 percent.

A 2 or 3 percent presence of slag is known to reinforce iron, but even slightly higher concentrations start to turn the metal brittle.

McCarty performed mechanical tests on small pieces that correlated with what she saw under the microscope: The samples broke. In computer simulations, failure followed again.

She pored over historical records, and witness accounts led her to reimagine the collision.

“A lot of survivors didn’t even feel it, and some talk about it as a glancing-blow-type thing,” she said. “The flooding and the timeline it’s not consistent with something that opened a gaping hole. Yes, it sank quickly, but the initial flooding happened with water coming through a seam.”

McCarty and Foecke compiled their findings for a National Geographic TV program that aired recently. A blacksmith in England was hired to re-create hull plates and rivets to specifications of the day for testing under strain. When the test was performed, the rivets started popping sooner than they should have. The theory that the Titanic’s hull plates opened like a zipper found its strongest evidence yet.
Copyright © 2006 The Seattle Times Company