brittle/ductile transition and the titanic

so they tell us the titanic failed due to embrittlement in cold water (as many other ships even 40 years later). now, the hull was made out of steel plates. would the riveted joints not act as excellent crack arrestors?

also, is there any info on the type of steel used? i mean, mild steel has a no ductility temp. of around -40°c, right?

Recently an extensive survey of the entire debris field was done and every major piece of the ship examined. The researchers came to the conclusion that far from being weak the ship was quite strong and stayed afloat much longer than the builder (who was aboard) predicted after the collision with an iceberg. The cause of sinking was a massive gash that spanned more than four compartments. Apparently the ship could have remained afloat with up to three compartments flooded, but not four. Had there been more lifeboats probably most could have been saved.

Iirc there was not water tight bulkheads to the ceilings.

the water tight bulkheads did not extend all the way to the ceiling and when she row’ed deep with 4 compartments flooding it started spilling over flooding additional compartments. Just was underprepared for such a catastrophic event.

But take that with salt as every theory under the son exists.

dian said:

so they tell us the titanic failed due to embrittlement in cold water (as many other ships even 40 years later). now, the hull was made out of steel plates. would the riveted joints not act as excellent crack arrestors?

also, is there any info on the type of steel used? i mean, mild steel has a no ductility temp. of around -40°c, right?

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The second war Liberty ships had a reputation for this type of cold temperature failure.

Liberty Ship Failures | Metallurgy & Materials Engineering


Aluminum aircraft fuselages, even though the major sections are reinforced with riveted ribs and stringers, require additional reinforcement to prevent cracks from rapidly propagating.

The L1011 had a titanium sheet metal grid on 16" centers epoxied to the inside surface of the fuselage before attaching the ribs. The grid prevented a crack from propagating beyond the 16" grid cell.

The concern was that there might be a mid air collision, or a turbine disk might shatter, or a bomb might go off in the cargo hold and poke a hole in the fuselage. The grid prevented the cracks surrounding the puncture from expanding outward.

The aluminum skin, titanium rip stop grid and the stringers where glued together in a large autoclave. There were three 120 degree glued sections that were then riveted together to form the complete fuselage section.

The problem was phosphorus, it depresses the ductile brittle transition to as high (sounds backwards) 5deg C, a lot of steels then were 030 P or higher, at 025 the steel in cold water was somthing like 60/40 ductile brittle as a comparison, add in high phos rivets, stress raisers etc and bingo brittle failure, you are correct about rivet joints and in fact Liberty ships retrofitted crack arresting plates at known failure points,
I read a book once, Griphiths I think, crack dynamics or some such, griffiths crack theory predicts the tip of the crack can have sufficient strain energy for the crack to self propagate, the crack would go supersonic almost instantly.
Beside titanic which followed the polar route the infamous PQ convoys did the same, apparently ships would break in half, as everyone knows the Liberty ships were the first revolutionary monolithic hulls, welded, plus square deck hatches
(The square cornered hole came to bite the dehavalland comet too) fracture was inevitable and catastrophic
Mark

it would be interesting to know, how the "massive gash" developed. were the plates torn appart at the rivet joints (then one might suspect ultimate stress failure) or did they crack one by one upon contact with the ice? well, maybe the failure at the rivets was brittle, although the orientation of a crack propagating from the holes outwards would encounter the highest possible fracture toughness in an anisotropic material. i assume the plates were not cast, or were they? another possibility would be that the rivets failed. actually most likely on second thought, because had they yielded this would have led to some flexibility of the hull.

scot, can you point me to the survey you mention?

on a side note, apparently 3 years after titanic another cruise ship flipped over in the harbor. number of people killed supposedly higher than on titanic (hard to believe). the reason being the additional weight of a larger number of lifeboats on deck mandated by regulations after titanic sank (hard to belive also, as there seem to be 8 boats in the pictures).

It had a coal fire in one of the bunkers Started in port already
Right at the place were it collided with the iceberg
Pictures show a discoloration in port already It was testified that the hull was tarnished with oil to hide that
That I heard on discovery at least
Never been there myself

Peter

I read the bunker fire thing too, apparently the ship berthed the other way about to hide the heat affected zone, and that watertight walkways were open due to hoses running there, preventing the hatches complete closure.
I think there’s a lot of information about that particular disaster that will remain off the table, whether silly mistakes or outright neglect, binoculars, speed ( ok I know the blue ribbon was highly sought after, the course was still odd, perhaps a big bow wave was helping cool the hull?)
Bunker fires are notoriously difficult to extinguish, we had a railway embankment on fire outside Swansea for years, that town in the US, centralia or somthing is still burning, we had a mine on fire near the school I went, it had been burning since the 30s, apparently whisps of smoke still coming out the ventilation stack in the 70s
Mark

They ran at max speed because they were loading the burning coal in the boilers as quick as possible
Apperently they could not slow down anymore because that would have cost too much coal They would have ran out of that before arrival at New York

Peter

It seems so improbable that they would leave port with a fire in the coal bunkers.
Just a different era where such things were in the normal run of things- time and tide and all that..

I have an account from the accident quoting a stoker on the ship that the fire would never be controlled till NY port was reached and fire ships with their pumps could be brought to assist.

Less then ten years latter they built ocean going ships out of concrete because the war limited steel availability. Some of those hulls are still floating. Some were described as taking on ocean storm waves like a tea cup, shattering on impact.
Bill. D

This was a much bigger problem with the Liberty ships during WW2. Dozens of Liberties were lost due to embrittlement and subsequent sinking. Ships breaking in half during transit in the cold North Atlantic crossings.

I don't object to analyzing why the ship sank on the whole.....yet I can't help but detect a definite sense that at the core of all this analysis lies the idea that if we can just determine exactly why it sank, we can save her from sinking.

It's like sitting next to your Cousin Lewis at the family reunion as he rehashes every possible scenario of why his wife LaQueesha-Mirquinthria left him 7 years ago. All you know for sure is her ass is gone because you seen her driving around town in the passenger seat of Jamaar's Escalade. You feel sorry for Lewis, but after a few hours you realize the only recourse is to smash a beer bottle over his head.

LockNut said:

This was a much bigger problem with the Liberty ships during WW2. Dozens of Liberties were lost due to embrittlement and subsequent sinking. Ships breaking in half during transit in the cold North Atlantic crossings.

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That may have had "help". Apparently there were many cases of getting the production out by stuffing the weld with a piece of steel or a few welding rods, and welding over it, as opposed to taking time to do a full depth fusion weld.

I think that has been referred to here as "slugging the weld".

JST said:

That may have had "help". Apparently there were many cases of getting the production out by stuffing the weld with a piece of steel or a few welding rods, and welding over it, as opposed to taking time to do a full depth fusion weld.

I think that has been referred to here as "slugging the weld".

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There is a Navy report on the problems, and solutions.

It's become a bible of sorts, can't recall the name.

GregSY said:

It's like sitting next to your Cousin Lewis at the family reunion as he rehashes every possible scenario of why his wife LaQueesha-Mirquinthria left him 7 years ago. All you know for sure is her ass is gone because you seen her driving around town in the passenger seat of Jamaar's Escalade. You feel sorry for Lewis, but after a few hours you realize the only recourse is to smash a beer bottle over his head.

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The fuck you on about?

Packing welds was a problem, bad fit up etc, yards like kaiser were under tremendous pressures to launch ships, they got fast, like every 4 days, that is frightening, however, speed, quality price pick
Mark

RC Mech said:

The fuck you on about?

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Think he's sayin he doesn't understand the fascination with knowing the >exact< cause of death for this ship because it's been gone so long it's moot.

Sent via CNC 88HS

The issue was supposedly contamination in the rolling process.
What has been shown is that other then hitting the iceberg design flaw
Was the major cause of the sinking maybe full height water tight bulkhead
Might have saved the ship

I’d certainly be interested in the concept of contamination during rolling, the only things I’ve seen is rolled in debris and skin lamination, the RID is usually scalebraker failure and foreign object ( old nuts and bolts etc) the skin lamination is not applicable as it’s a continuous cast slab thing, mould powder aka slag gets entrained in the steel during casting then when rolled it turns into a dirty streak below the surface, sometimes hundreds of meters long, forms a kind of blister, all the ships were on about including Liberty were ingot route steel, mostly a kind of ingot called bottle top aluminium killed
With this you fill the ingot mould, throw in a couple of bags of Ali, drop a lid on shove a bar through to hold the lid down and get ou the way, the reaction brings the steel up to the lid really fast, kind of foams up almost, you had to time it with a stopwatch “ hit cap time”, too long insufficient Ali, to quick too much plus high oxygen activity, once the ingots were stripped from the mould the ends got cropped in a crop shear, crap gone
I’m sure there are ways to contaminate that I don’t know of, but I can’t think of any.
I’m going to stick with Phos myself, there is another phenomenon called lamellar tearing with plate steels, you have to control a thing called “carbon equivalent “ or C,E.V, there are formulas, carbon plus manganese plus this and that divided by 10 times blah blah, they can get really silly sometimes, in length of formula not importance, but they tend to apply to welded structures and post weld treatment, shrink and tear so Liberty ships would be affected
I think the titanic was quantity not quality myself, really rough work on the hull, the interior was par excellence at least for the first class bit,
There’s the remains of a Liberty ship you can see sticking out my local beach
It was the San Tampa, ran aground, still there, a friend of mine who I also worked with was there as a kid, he described the poor guys who drowned lined up on the beach, hard to get your head round is life
Mark