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Tourist submersible visiting the Titanic is missing Part 2 68

SWC - A great article - thanks for posting it. The skull and cross bones on the graph sent by the boeing engineer was an incredible find.



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An eerie detail - when Rush was operating a steel hulled sub and got lost, how did he expect an iPhone compass application to help? Steel won't completely screen out the Earth's magnetic field, but it is so easy to magnetize regions in the steel that careful calibration to compensate is required. How did he know so little about materials?
 
Rush was an arrogant fool with just a bit too much money, and just a tiny bit of knowledge, all of which made him very dangerous. I'm just happy that he was onboard the Titan sub when it imploded, because otherwise he would have blamed (and probably sued) everyone but himself for the catastrophe.
 
Whatever the analysis states, the only part of the sub we have seen are the titanium domes. There was ZERO adhesive attached to the domes which means the failure occurred between the adhesive and the titanium. We all saw the video of the gluing process, the surface was not grit blasted immediately before assembly and it was not primed. They were also touching the surface with their bare hands.

I have not seen any of these observations made anywhere.
 
TugboatEng said:
We all saw the video of the gluing process, the surface was not grit blasted immediately before assembly and it was not primed.
Click to expand...

The Wired article contained another revelation about this, that the titanium domes and interface rings were not new to the second (disaster) hull, they were the same ones used with the first hull (the one from the gluing video?) How were they removed and how were the surfaces prepped?

The article also notes that lifting points were added to titanium segments, and that such loading was not a consideration in the original design.
 
I don't see those things as issues. The dome didn't fail so the lifting points didn't contribute and the face of the dome can be shaved to remove a few thousandth of an inch without compromising strength.
 
The dome didn't fail so the lifting points didn't contribute and the face of the dome can be shaved to remove a few thousandth of an inch without compromising strength.
Click to expand...

One cannot tell from long-distance photos whether the flanges/domes were, or were not, compromised by asymmetric lifting forces.

TTFN (ta ta for now)
I can do absolutely anything. I'm an expert! faq731-376 forum1529 Entire Forum list
 
The load at the lifting point will have pulled the dome into an egg shape in axial view which might compromise the bond between the dome and the tube. I doubt we'll ever know. Metal to composite bonds is one of the few areas I know enough to be dangerous in. Basically it is an impedance mismatch problem. If you imagine a metal plug in a tube, in side view you must taper the metal so that the stresses can gently build up in the tube.

From a very high level the 'system' worked. That is, he was told not to do things he proposed, he did them, and killed 4 other people. The rest of the industry has hence been reassured that the usual standards are useful, if not optimal.


Cheers

Greg Locock


New here? Try reading these, they might help FAQ731-376
 
Oh dear:

Tugboat says: Whatever the analysis states, the only part of the sub we have seen are the titanium domes. There was ZERO adhesive attached to the domes which means the failure occurred between the adhesive and the titanium. We all saw the video of the gluing process, the surface was not grit blasted immediately before assembly and it was not primed. They were also touching the surface with their bare hands.

I implore people to understand that adhesive bonding is a chemical process. Bond strength AND longevity depends totally on the chemical bonds (mainly covalent) that are formed that the interface at the time the bond is formed. THERE IS NO MAGIC PRIMER OR ADHESIVE. Every part of the process requires that the process addresses three things:
1. The surface must be clean and free of contaminants that will inhibit the formation of chemical bonds. Please do not use detergents because surfactants wet the surface well enough to displace the contaminants but they leave a leyer of well attached detergent that prevents adequate reaction.
2. The surface must be chemically active. It is no use applying a primer to a fully oxidised surface. You must remove the exisiting oxide layer.
3. you must IMMEDIATELY apply a primer to stabilise the surface. Of fundamental importance that the primer develops a chemical structure that is resistant to hydration. The most common form of bond failure is because the surface of the metal hydrates, for example titanium oxides hydrate to form hydrated oxides and in the process the chemical bonds between the oxides formed during original bonding processes dissociate leading to interfacial failure. The resulting separation at the surface will exhibit a total absence of adhesive, as described above by Tugboat.

The process described by Tugboat clearly does not sound like a process that would meet any of the basic essentials to produce an adhesive bond that would provide bond durability under severe exposure to a marine environment under pressure.

So sad.

Blakmax
 
The OSHA whistleblower got sued and had to sign an NDA?? Either there's more to that angle, or whistleblower protections don't seem to be worth much . . .
 
Blakmax, I am aware of the electron sharing that occurs as materials are bonded. My emphasis is that titanium readily oxidizes in air. That is what gives it it's corrosion resistance. Tbe trouble is that the electrons in titanium oxide would prefer to exchange with water instead of the amides in your typical epoxy. Hydration, the formation of titanium hydrate from exposing titanium oxide to water robs the electrons from the epoxy bond weakening it. I believe this is what has happened in this case from the evidence that I have seen.

Siloxanes are a recent development that are being used to prime surfaces and prevent hydration. I am not an expert on this subject but am very curious about it.
 
Tugboat

You are exactly like you say. The same oxidisation occurs with aluminium, where this is the exact mechanism that causes interfacial (adhesion) failure in aviation structures. We have experience with epoxy silanes to prevent hydration on aluminium surfaces with very significant results. We have treated titanium alloys with a significant improvement in results, but not to the same extent as for aluminium. The product we use is Dow Corning Z6040, but I would also try a product marketed as Boejel also sold as A C130 in kits. The best test is ASTM D3762 wedge te4st, but due to a stuff up, the upgraded version of the standard did not make it before the cut-off date so ASTM deleted the standard. If you contact me I may put you in the right direction.

Max

Adhesion Associates
 
Wonder what the substance of the whistleblower complaint was? I believe if NDAs can be enforced to leverage coverups of (engineering) safety problems by suppressing whistleblower reports that is a high priority problem needing a solution. But maybe it's just vague reporting of that detail and the complaint and law suit were coincidental rather than related.
 
I think the problem was that there was no AHJ in international waters and hence no body to blow the whistle to. If it was to OSHA, did they in fact have jurisdiction?

The information I think was being made available to the deep submersible "community" in the hope that peer pressure would bring Rush to his senses.

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Also: If you get a response it's polite to respond to it.
 
LittleInch said:
I think the problem was that there was no AHJ in international waters and hence no body to blow the whistle to.
Click to expand...

Design/build/testing were all within the US or within territorial waters, i.e. OSHA regs apply
 
Fair enough - then it doesn't look like OSHAs policy was strong enough?

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Also: If you get a response it's polite to respond to it.
 
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