U.S. researchers have discovered that the builder of the Titanic struggled for years to obtain enough good rivets and riveters and ultimately settled on faulty materials that doomed the ship, which sank 96 years ago Tuesday.

The authors of a book, What Really Sank the Titanic, claim the shipyard over-reached in attempting to build three new liners at once for the White Star Line: the famously opulent Titanic, which sank with the loss of 1,500 lives, the Olympic and the Britannic. Unable to find all the good quality iron rivets it needed, it eventually resorted to buying batches of lower-quality iron.

Theories about shoddy rivets popping prematurely after the ship struck an iceberg have been around for years; officials at Harland & Wolff have consistently dismissed them.

But this time the authors, both metallurgists, say they have found fresh evidence from archives in London and from the shipyard as well as from analyzing rivets from the wreck.

By the first part of the last century, other shipyards had mostly already switched to all-steel rivets. Although steel was used for the central sections of hull of the Titanic, the design called for iron rivets for bow and aft sections. Most of the cracks that opened after its collision with the iceberg were in the iron-riveted forward part of the hull.

It appears that the yard, unable to find all the best-quality rivets needed, made of so-called No. 4 bar, eventually settled on some rivets of No. 3 bar, which is considered inferior because of greater levels of impurities, notably of slag.

In their book, Timothy Foecke and co-author Jennifer Hooper McCarty say many of 48 rivets taken from the seabed show they contained slag. They commissioned a blacksmith to make rivets according to the 1912 specifications, of 4- and 3-bar quality. The former withstood 9,000 kg of pressure under laboratory conditions, but the rivets with slag popped at 4,000 kg.

The book is likely to disturb both the shipyard and bereaved relatives because of the implication that without the alleged construction short-cuts the ship might at least have sunk more slowly, allowing for a much-diminished death toll.

A spokesman for Harland & Wolff declined to comment.

a naval historian praised the book as solving a mystery that has baffled investigators for nearly a century.

"It's fascinating," said Tim Trower, who reviews books for the Titanic Historical Society, a private group in Indian Orchard, Massachusetts. "This puts in the final nail in the arguments and explains why the incident was so dramatically bad."

(SD-Agencies)