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Tourist submersible visting the Titanic is missing 101
- Thread starter JohnRBaker
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From James Cameron:
"“This OceanGate sub had sensors on the inside of a hull to give them a warning when it was starting to crack,” he told ABC News. “And I think if that’s your idea of safety, then you’re doing it wrong. They probably had warning that their hull was starting to delaminate, starting to crack. ... [W]e understand from inside the community that they had dropped their ascent weights and they were coming up, trying to manage an emergency.”"
It sounds like they had SOME kind of monitoring system for the hull. Maybe too little, too late.
Did they mention seeing the carbon cylinder? I thought it was just a debris field with the fairing, the two end pieces (end bells), and various debris.
I wonder what the design process really looked like for this vehicle. Did these younger engineers just bust open Roark's and call it a day? (I say this as a younger engineer![[upsidedown]](/data/assets/smilies/upsidedown.gif "[upsidedown] [upsidedown]")
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"“This OceanGate sub had sensors on the inside of a hull to give them a warning when it was starting to crack,” he told ABC News. “And I think if that’s your idea of safety, then you’re doing it wrong. They probably had warning that their hull was starting to delaminate, starting to crack. ... [W]e understand from inside the community that they had dropped their ascent weights and they were coming up, trying to manage an emergency.”"
It sounds like they had SOME kind of monitoring system for the hull. Maybe too little, too late.
TugboatEng said:
Did they mention seeing the carbon cylinder? I thought it was just a debris field with the fairing, the two end pieces (end bells), and various debris.
FacEngrPE said:
I wonder what the design process really looked like for this vehicle. Did these younger engineers just bust open Roark's and call it a day? (I say this as a younger engineer
)I saw a remark that the viewport would fail optically long before it failed structurally.
There was also a comment that the viewport was laminated.
Is it reasonable that the laminations could deflect quite a bit before structural failure, but even a small deflection may affect the optics of the inter-lamination adhesive?
--------------------
Ohm's law
Not just a good idea;
It's the LAW!
There was also a comment that the viewport was laminated.
Is it reasonable that the laminations could deflect quite a bit before structural failure, but even a small deflection may affect the optics of the inter-lamination adhesive?
--------------------
Ohm's law
Not just a good idea;
It's the LAW!
GregLocock
Automotive
I think direct crush of the composite cylinder is the most likely failure to result in the spontaneous ejection of the two ends. Viewport failure would just fill the thing very rapidly.
Cheers
Greg Locock
New here? Try reading these, they might help FAQ731-376
Cheers
Greg Locock
New here? Try reading these, they might help FAQ731-376
davidbeach
Electrical
Wasn't there a time in the late '80s when NASA thought that all the 50 year old white guys were being too stodgy as well? Nah, those O-rings are fine...
I’ll see your silver lining and raise you two black clouds. - Protection Operations
I’ll see your silver lining and raise you two black clouds. - Protection Operations
Roarks formulas for stress and strain. It's actually a really popular reference for all kinds of stress calculations. You'll see it referenced all the time in engineering calc packages. I was being a bit tongue in cheek, it's a legitimate source of information. An excellent reference but not a full substitute for sound engineering judgement; e.g. not using a material that could have issues in compression, bonded with questionable methods to a titanium end cap.
That reminds me, does anybody know what kind of adhesive they used to bond the carbon fiber to the titanium? Was the titanium also heat shrunk onto the hull?
That reminds me, does anybody know what kind of adhesive they used to bond the carbon fiber to the titanium? Was the titanium also heat shrunk onto the hull?
enginesrus
Mechanical
Why haven't any pictures of said parts been released?
I posted a video above and it shows the titanium ring being glued to the main body, above poster asked how it was attached.
Around the 4 minute area.
I posted a video above and it shows the titanium ring being glued to the main body, above poster asked how it was attached.
Around the 4 minute area.
SWComposites
Aerospace
Some kind of paste adhesive. The process in the video looked sketchy. Rings were not shrunk on.
SWComposites
Aerospace
Well, it should have been a controlled facility. But apparently they knew better.
This whole thing reeks of hubris and start-up mentality and having/wanting to do things on the cheap.
This whole thing reeks of hubris and start-up mentality and having/wanting to do things on the cheap.
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SWComposites
Aerospace
Anyone interested in the art and science of shell buckling should check out the wealth of info here:
Buckling of unstiffened cylinders are particularly sensitive to imperfections.
Buckling of unstiffened cylinders are particularly sensitive to imperfections.
TugboatEng
Marine/Ocean
I was curious about the acrylic window so I googled some things about acrylic and fatigue. My experience with acrylic is that it is sensitive to damage from creep. As a result I will not use interference fit screws in the material.
I did find this interesting document that explains the failures of Plexiglass 55 (cast acrylic).
It is a long ways beyond my own understanding.
With the evidence available today, despite the concerns about the acrylic window, there was a hull failure.
I did find this interesting document that explains the failures of Plexiglass 55 (cast acrylic).
It is a long ways beyond my own understanding.
With the evidence available today, despite the concerns about the acrylic window, there was a hull failure.
LittleInch
Petroleum
I can't find it now but I'm sure I read from Cameron that the deep sea "community" thinks that some of the weights were dropped and the sub was trying to rise to the surface.
Probably difficult to know now and not sure how they knew but as probable as anything. Horrible to think that they knew it was failing just before it finally went. Ugh.
The forces when you think about them are just huge. About 2.5 tonnes per square inch, on every square inch and this thing wasn't small. I get about 7,500 tonnes axial compressive force from the ends alone. Have I got that right?
Remember - More details = better answers
Also: If you get a response it's polite to respond to it.
Probably difficult to know now and not sure how they knew but as probable as anything. Horrible to think that they knew it was failing just before it finally went. Ugh.
The forces when you think about them are just huge. About 2.5 tonnes per square inch, on every square inch and this thing wasn't small. I get about 7,500 tonnes axial compressive force from the ends alone. Have I got that right?
Remember - More details = better answers
Also: If you get a response it's polite to respond to it.
"[W]e understand from inside the community that they had dropped their ascent weights and they were coming up, trying to manage an emergency."
Maybe they did have time to say oh sh*t...
The problem with sloppy work is that the supply FAR EXCEEDS the demand
Maybe they did have time to say oh sh*t...
The problem with sloppy work is that the supply FAR EXCEEDS the demand
Just read this vessel carried 46 passengers in 2021 & 2022, min of 9 trips with 5 passengers, 11 trips if there were 4 passengers.
The sandbag theory could be based on the location of the bags, vs the wreckage.
The buckling link was informative for thin walled shells of revolution.
Kevin Kelleher, P.E. (retired)
Internal Mechanical Eng'g Consultant
DuPont ESD Specialists
The sandbag theory could be based on the location of the bags, vs the wreckage.
The buckling link was informative for thin walled shells of revolution.
Kevin Kelleher, P.E. (retired)
Internal Mechanical Eng'g Consultant
DuPont ESD Specialists
EdStainless
Materials
Other than the Titanic this section of the ocean floor is very flat and clean.
And this was about 1mi from the Titanic.
Yes, the US Navy hears everything. Their report was from very shortly after communications was lost on the decent.
That would be before the vessel was reported lost.
= = = = = = = = = = = = = = = = = = = =
P.E. Metallurgy, consulting work welcomed
And this was about 1mi from the Titanic.
Yes, the US Navy hears everything. Their report was from very shortly after communications was lost on the decent.
That would be before the vessel was reported lost.
= = = = = = = = = = = = = = = = = = = =
P.E. Metallurgy, consulting work welcomed
From another discussion on reddit:
Bristol Composites Institute | Realising the Potential of Carbon Fibre Composites in Compression (2017)
"It appears to be due to the stress-strain curve of carbon fiber being very different from the stress-strain curve of the matrix of epoxy that holds it together. For that reason, "yield" is misleading, because carbon fiber has a non-linear stress-strain curve. At high loads the divergence between the stress-strain curve of carbon fiber and that of epoxy is quite a lot, and this causes the two to unbond from each other, at a microscopic level, which might not even be detectable if it is all held together by other fibers around it.
When the two stress strain curves begin to diverge, it causes even more delamination and concentration of force on the remaining bonded parts, worsening the mismatch and accelerating further delamination, resulting in a feedback cycle that ends in failure.
For this reason, carbon fiber composite materials fatigue and fail with repeated cycling to extremely high loads that take it into the part of the stress-strain curve where this divergence happens, so "stressed beyond yield" should be "stressed beyond onset of microscopic delamination"."
@SWcomposites
Bristol Composites Institute | Realising the Potential of Carbon Fibre Composites in Compression (2017)
"It appears to be due to the stress-strain curve of carbon fiber being very different from the stress-strain curve of the matrix of epoxy that holds it together. For that reason, "yield" is misleading, because carbon fiber has a non-linear stress-strain curve. At high loads the divergence between the stress-strain curve of carbon fiber and that of epoxy is quite a lot, and this causes the two to unbond from each other, at a microscopic level, which might not even be detectable if it is all held together by other fibers around it.
When the two stress strain curves begin to diverge, it causes even more delamination and concentration of force on the remaining bonded parts, worsening the mismatch and accelerating further delamination, resulting in a feedback cycle that ends in failure.
For this reason, carbon fiber composite materials fatigue and fail with repeated cycling to extremely high loads that take it into the part of the stress-strain curve where this divergence happens, so "stressed beyond yield" should be "stressed beyond onset of microscopic delamination"."
@SWcomposites
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