OceanGate Expeditions Titan DSV loss

That is well worth watching, and DSV Limiting factor is another example of deep-sea vehicles done right. This one is designed for full ocean depth (Challenger Deep).
 
Arjen said:
It depends on what you're used to. I grew up with the metric system and the Celsius scale - any temperature below zero means imminent danger of iced up roads (danger! danger!) as well as a decent chance of skating (yay!). Win some, lose some. 37 degrees centigrade was hammered into my brain as normal body temperature - any weather hotter than that is, as you put it, 'stupidly hot'. 100 degrees centigrade is dead easy to remember as the boiling point of water at sea level.
The beauty of SI - (pedant warning!) which, by the way, uses the Kelvin scale - is the interconnectedness of its units, which spares any astronomer/physicist/biologist/chemist/engineer/mechanic the need to use endless arbitrary conversion constants to calculate what reality is likely to throw their way.
But, again, it's mostly whatever you're used to. Like those antique monetary units of twelve pence to the shilling, twenty shillings to the pound, guineas, crowns et cetera et cetera...

Remind me - how many Ningi go into a Triganic Pu?
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Well, its the other way round, Kelvin uses the Celsius Scala. When temperature was new defined (of course, it is no longer the boiling water), the Kelvin scala was choosen to ease calculations from Celsius to Kelvin. At the time when the Celsius scala was introduced, now none newed there was a minimal temperature of -273° C.
 
(full pedant-mode) From wiki:
Historically, the Kelvin scale was developed from the Celsius scale, such that 273.16 K was 0 °C (the approximate melting point of ice) and a change of one kelvin was exactly equal to a change of one degree Celsius.
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They are two different scales, the difference being that the Kelvin scale has its zero at absolute zero, unlike the Celsius scale's zero which is at 273.16 K - the point where water freezes at sea level. The magnitude of the one degree increment is identical in both scales.

The Kelvin scale is used in SI.
The Celsius scale isn't, although you could argue the Celsius degree increment is still in use in SI.
(/full pedant-mode)
 
What I really hate is when your physicists work exclusively in metric and your technicians work exclusively in imperial and you the engineer are stuck in the middle with a design thats in metric using imperial fasteners... And thats before getting to the absolute cluster that is working with pressure units...
 
Desertfox said:
What I really hate is when your physicists work exclusively in metric and your technicians work exclusively in imperial and you the engineer are stuck in the middle with a design thats in metric using imperial fasteners... And thats before getting to the absolute cluster that is working with pressure units...
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That's probably one of the easiest ones. Round hole size up to next drill bit size from the imperial->metric conversion.

The one I always hated was fractional versus numbered drill bits.
 
Scott Kenny said:
That's probably one of the easiest ones. Round hole size up to next drill bit size from the imperial->metric conversion.

The one I always hated was fractional versus numbered drill bits.
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Fractional, numbered, and letter drills.

And let's not get started on the different wire and sheet metal gauges. It's a rabbit hole almost as bad as turtle evolution.
 
1635yankee said:
Fractional, numbered, and letter drills.

And let's not get started on the different wire and sheet metal gauges. It's a rabbit hole almost as bad as turtle evolution.
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Lettered drills are part of the same sequence as numbers in my mind.

And gauges as a measure of diameter or thickness can go DIAF.
 
Nicknick said:
somthing intresting about carbon fibre, especially regarding compression loading:

View: https://www.youtube.com/watch?v=8b2EgTu9_GU&ab_channel=DarkAero%2CInc
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I don't think that video really covered the use of composites in externally compressed structures, though.

"Carbon Fiber fails without warning" may be a myth, but it's also a useful rule of thumb because there's no plastic deformation to warn you that you're exceeding the yield strength.

assuming a sufficiently quiet environment, you absolutely can hear the resin crackling before it fails. Wasn't there a report that Titan was on the way back up after hearing a bunch of crackling before she imploded?
 
Nicknick said:
I don't care, Cabron...
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Perhaps you can elucidate on your use of the word "cabron" please? There being more than one definition.
Scott Kenny said:
I don't think that video really covered the use of composites in externally compressed structures, though.

"Carbon Fiber fails without warning" may be a myth, but it's also a useful rule of thumb because there's no plastic deformation to warn you that you're exceeding the yield strength.

assuming a sufficiently quiet environment, you absolutely can hear the resin crackling before it fails. Wasn't there a report that Titan was on the way back up after hearing a bunch of crackling before she imploded?
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I can remember there being a suggestion noises were heard from the rear of the hull before they started their ascent but not sure if the noise was described as cracking or what.
 
Nicknick said:
Hi, don't take it too personal, in Spanish everyone can be called "cabron"....
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Not taking anything personal mate, if I do not understand I ask, simples. Have a great day mate.

If I were taking it personal like I could have reacted differently but language is a multi faceted thing after all and changes with generations.
 
So I leave it up to you :)

About the noise, yes I read the same, they heard some cracking but than it was allready too late...
 
Nicknick said:
About the noise, yes I read the same, they heard some cracking but than it was allready too late...
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Exactly.

Each crack sound is the creation of a void, a delamination. Each void is a weakness. At some point pretty quickly, the material strength will drop below the level of force being applied to it. And because each void is in an unpredictable location, the catastrophic failure point is also unpredictable.
 
Given the basic properties of materials and structures, any damage incurred under sustained load is progressive and exponential, not linear.
 
Scott Kenny said:
Exactly.

Each crack sound is the creation of a void, a delamination. Each void is a weakness. At some point pretty quickly, the material strength will drop below the level of force being applied to it. And because each void is in an unpredictable location, the catastrophic failure point is also unpredictable.
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Yes, but I was just the guy who linked that video and didnt produce it myself... Still, here ist was more related to cracking noises during inspection and less so during operation. The other aspect is the compression strength of carbon fibre, which isnt bad at all under the right circumstances.
 
Nicknick said:
Yes, but I was just the guy who linked that video and didnt produce it myself...
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While I replied to you, I'm really challenging the statements on the video.


Nicknick said:
Still, here ist was more related to cracking noises during inspection and less so during operation. The other aspect is the compression strength of carbon fibre, which isnt bad at all under the right circumstances.
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And a basic cylinder without even CF endcaps is NOT the right circumstances.
 
As said before, I believe, the tangential load on the cylinder wasnt the problem, but the connection to the endcaps. It allway depend how you apply the compression load on the carbon fibre, you should not press on the endings on the fibres directly, which makes it hard to find a proper solution for the longitudenal loads in the sub.

BTW; I dont agree to every point in the video, steel is still the best material when it comes to fatigue, it can have a virtual ivinite live when you keep the strain under a certain limit. There is hardly any other material which can do that, not even carbon fibre or titanium. Valve springs are a perfect example, they do see a very high load everytime a valve is fully open (even at idle) but they keep on working reliably for the whole engine life, sometimes a million miles...
 

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