Titanic article 1

[prost]

I apologize if this is posted in the wrong forum. I considered the ocean engineering one, but this one has more readers I think and this is a materials issue too.

http://www.usnews.com/articles/news/national/2008/09/25/the-secret-of-how-the-titanic-sunk.html

I wonder if they have considered how the salt water itself has affected the microstructure of the rivets and the steel plates. Perhaps, though, at that depth, there is so little oxygen and it's so cold that metal is extraordinarily well preserved so that this isn't an issue?

 

[metengr]

I wonder if they have considered how the salt water itself has affected the microstructure of the rivets and the steel plates.

The salt water itself will have no affect on the metallurgical properties of the steel hull or rivets. This happens during heat treatment and/or forming operations during fabrication of the ship.

Perhaps, though, at that depth, there is so little oxygen and it's so cold that metal is extraordinarily well preserved so that this isn't an issue?

Marine organisms in this part of the Atlantic ocean are slowly consuming the steel ship structure. There is concern that over the next 25-50 years there will be no steel structure left to view.

 

[IRstuff]

When the steel was placed in ice water and hit with a hammer, it shattered. For much of the 1990s, scientists thought this "brittle" steel was responsible for the massive flooding. Only recently has testing on other, bigger pieces of the ship disproved this theory. The original piece, scientists discovered, had been unusually weak, while the rest of Titanic's steel passed the tests.

TTFN

FAQ731-376

 

[unclesyd]

Iron and sulphate reducing bacteria are slowly consuming the ship. I heard that it could collapse on itself in twenty years while other are saying 150 years. It goes to say it's not a matter of if, it's just a matter of time.

There have been several white papers on TV about the two theories concerning the manner of its sinking.

There was program just on TV about Ballard finding the Titanic. He was in the Navy at the time and was on a secret mission to find the sunken nuclear submarines Thresher and Scorpion. He locaed both subs and while investigating the wrecks he discovered that both wrecks left a long debris field that would lead him to the vessel itself. He used this knowledge to locate the Titanic. Instead of looking for the vessel itself he found the debris field and followed it to the vessel itself.

 

[prost]

I should have been less specific in my question, so here it is restated--presumably they did mechanical testing on the chunks of metal they brought up from the ocean floor. Can you expect a degradation in mechanical properties (yield, ultimate, etc.) caused by lying on the ocean floor for 80 years? They have presented their results as 'proof' that something is wrong with the rivets; is it possible that the rivet material was degraded by sitting in the ocean so long? If so, then it is not necessarily true that there was a problem with the rivet manufacture.

 

[metengr]

Can you expect a degradation in mechanical properties (yield, ultimate, etc.) caused by lying on the ocean floor for 80 years? They have presented their results as 'proof' that something is wrong with the rivets; is it possible that the rivet material was degraded by sitting in the ocean so long?

I understood your question the first time, and the answer is still NO.

 

[swall]

The only degradation in the steel that would occur would be loss of material do to corrosion. The remaining material would still possess the same mechanical properties as when manufactured. Now having said that, it is significant to note that the rivets, if I recall, were wrought iron rather than steel. One could hypothesize about rivet degradation due to corrosion along the iron/slag interface of the wrought iron microstructure. In that case,if a complete rivet were mechanically tested, reduction in properties due to the corrosion might be a possibility.

 

[unclesyd]

One mechanism, hydrogen embrittlement, was mentioned early on. Later testing ruled this out and essentially laid the blame on the rivet failure to the steel used in production. There was plenty of material to test due to the relative size of the rivets used in the Titanic construction.

There are several developing theories about the sinking. The main one is that the stern never rose more than 10-15 degrees before the ship broke in half.

Even though the boards of inquiry found nothing wrong with the design it is interesting that both of Titanic's sister ships were modified after the Titanic sunk.

RMS Olympic

http://philadelphia.about.com/gi/dy...637_1020_584&f=10&tt=14&bt=1&bts=1&zu=http://

http://www.ocean-liners.com/ships/olympic.asp

RMS Britannic

http://philadelphia.about.com/gi/dy...zu=http://titanic-titanic.com/britannic.shtml

 

[drawoh]

unclesyd,

I followed your link on the Olympic. I am impressed at the number of things Olympic managed to collide with. In spite of all this, Olympic does not seem to have had any structural problems during its career. I am aware of few structural problems with ships built circa[ ]1912. The marine architects back then understood their materials, and the loads they were subjected to. If you inflect enough damage on any structure, it will fail.

There was a public outcry about Titanic's watertight bulkheads and double hull. Titanic's hull conformed to the codes of the day, and for all I know, it might conform to today's codes.

Titanic grazed the iceberg for something like 300[ ]feet along her side, ripping a hole that was estimated to have an area of 12ft². Would better quality rivets or less brittle steel have been enough to have prevented this?

The Mauretania was built from the ground up to be a Blue Riband capturing hot rod. On her maiden voyage, she failed to take it because she slowed for fog (and storms).

Moral of story: don't smash into stuff.^*

JHG

^* Except for hostile U[ ]boats!

 

[CoryPad]

It is speculated that low rivet quality and brittle steel allowed for more damage than would have occurred with higher purity metal. However, higher purity metal wasn't available at the time of Titanic's construction.

Regards,

Cory

Please see FAQ731-376 for tips on how to make the best use of Eng-Tips Fora.

 

[unclesyd]

It is my understanding that the combination mentioned in the above post above and the fact that the bulkheads were not high enough compunded the damage as the ship start to go head down. The water cascaded over the low bulkheads. The bulkheads were raised on both the sister ships at the refit after the Titanic sank.

Anecdotal:
When I was in the Army we were on a very large troop transport going to Japan by way of Okinawa, Taiwan, and Korea. The ship, MSTS General Gaffey, was a twin stacker large enough to carry 10,000 troops. One our trip we had a total 1500 dependents and military personal. When we we going to Inchon, Korea we had to wait for high tide to cross the bar due to the draft of the ship. I had a job in the galley as coffee maker for the chief of the boat, kept me out of hasty details. It was very still and with a lot of heavy fog. In the galley we had opened about 5 port holes to air the place out since we had been in bad weather for several days. At high tide we made the dash for the harbor at nearly full speed. The ship was shaking quite a bit as the propellers were close to the bottom. As we sat drinking coffee and playing cards we were rudly interrupted by the collision with an LST anchored in the channel. As the ship stated to heel to starboard water started coming in the open portholes. As we attempted to get the portholes closed the collision alarm was going off and you could hear the water tight doors closing along with the metal of the two vesels screaming, the only way to describe it. The galley was on deck five and one had to go up three decks up to have access to main deck, where the life boats were. We were essentially trapped in the galley until the water tight doodrs opened. Fortunately the ship returned to an even keel and all horns stopped. Our ship's only damage was a bent propeller blade. We had to run at half speed or less until we could get to Japan. We made it to Yokohama with only one small incident, we hit and sank a coal barge in the middle of Tokyo Bay. Needless to say Radar on this type ship wasn't very good.

The MSTS General Gaffey

http://www.msts-history.org/gaffey.html

 

[drawoh]

unclesyd,

Marine regulations of time stated that a ship should survive having any two adjacent holds opened up, and it should survive having the first four holds opened up. Titanic was built to this requirement.

Titanic's first six holds were flooded. Extending bulkheads all the way to the deck, allowed Olympic and Britannic to grossly exceed the current standards, and would would have allowed Titanic to survive its collision with the iceburg. Extending bulkheads is a technical detail. The real question is one of performance. How many holds can be flooded on a modern liner without it sinking?

JHG

 

[drawoh]

prost,

Titanic's hull was assembled with round headed rivets. In the accident, she scraped the side of the iceberg. This would have imposed a huge shear load on the heads of the rivets. The entire kinetic energy of the ship would be applied to only a few rivets at any time during contact with the iceberg. Obviously, the ice would give way too, but it appears to me that a flush riveted ship (were there any?) might have survived the accident. A ship welded to post WWII standards, might have survived too.

Is this even a design issue in the selection of rivets?

Perhaps the correct way to look at this would be to define some material, Prostium, or Drawohium, that would have remained intact during the impact with the iceberg. What would its yield stress and elastic module be? Was such a material available at the time?

JHG

 

[strider6]

this is a very good article on the metallurgy of Titanic.

Metallurgy of the RMS Titanic

http://www.metallurgy.nist.gov/webpages/TFoecke/titanic/Titanic.pdf

S


Corrosion Prevention & Corrosion Control