Titanic tourist sub goes missing sparking search

[Dan]

That is the curve and numbers for steel. Other materials are different, perhaps quite different.

Of course. It’s just an illustration. Notice that there’s no numbers and units given in the axis.

 

[tursiops]

Of course. It’s just an illustration. Notice that there’s no numbers and units given in the axis.

The numbers are in your text.

 

[Dan]

The numbers are in your text.

What numbers in my text?

I mentioned if you want to have MAWP of 4000 m depth, you need to test it at 6000 m depth.

Here is for different material. The modulus of resilience is there, but at lower range than that of steel. The point that I try to make is if you want to operate the submersible using such material, you need to test it within the modulus of resilience of the material.

Courtesy of https://www.researchgate.net/figure...lone-dotted-line-and-reinforced_fig2_41014868

 

[Gone for diving]

If you think of it 2 dimensionally,
As a I beam or tubing, as long as it stays apart it can span along way,
The way it looks wrapped, it strong in a cylinder way, but not the long way.

A bulk head is a way to fix the existing design,
Not really what you want to do...

Not sure if all carbon fiber tanks have a thin a steel liner inside, but then the fiber gets wound around it, it becomes strong,

My thought is to build that in reverse,,,
Seems like a technical challenge, that might not work well,

 

[Blasto]

Great tragedy.
Not like anyone needed more reason to stay away from CFRP underwater. Excellent material, just not for that load profile.

I used to work at a company that built deep submersibles. Steel, titanium and aluminum, with titanium performing the best. The reason is, the least hidden problems - bad welds are detectable, everything else lasts once it's done.(Made some minor dive gear out of the scraps as well).

Composites and mixed materials are unpredictable due to differing rates of compression and expansion, including inside the material, possible galvanic corrosion (CFRP participates in it) if some barrier coatings are broken, and the ability of seawater to seep into any crack. Hull penetrations are where long-term leaks tend to arise, even if it's just slightly different grades of alloy steel. Collapse-level problems are probably due to internal delamination, though.

Another promising underwater material is reactive powder concrete, but it will need lots of testing and experience in unmanned applications first, before going to manned use at really high load factors.

 

[Gone for diving]

Another promising underwater material is reactive powder concrete, but it will need lots of testing and experience in unmanned applications first, before going to manned use at really high load factors.

Had to look that up.

Would it be light enough to float a sphere or something similar?

Seems like they should make boats with it first,

 

[Akimbo]

Another promising underwater material is reactive powder concrete, ...

The Naval Civil Engineering Laboratory in Port Hueneme, California did a lot of work on concrete spheres for external pressure vessels in the late 1960s. I visited there just before joining the Navy. They had a bunch of imploded hemispheres in the yard outside the pressure testing building.

Like glass, concrete has high compressive strength but like carbon fiber is not a homogenous material. Glass hemispheres have been used for deep ocean scientific instruments since the early 1960s.

It was never clear to me why a Civil Engineering Lab associated with the CBs (Construction Battalion) was doing this work but it was pretty interesting. My impression was that they wanted to use them more for long-term unmanned deep sea buoys and instrument housings.

I used to work at a company that built deep submersibles.

Which company (ignore if you prefer not to say)? There aren't that many.

 

[Blasto]

Had to look that up.
Would it be light enough to float a sphere or something similar?
Seems like they should make boats with it first,

About as dense as aluminum, but can get to steel-like compressive strength if cured under heat and pressure. Not as great in tension, so it can't compete with carbon for surface boats. But they're starting to use it for offshore structures and have designed underwater housings for 3,000-6,000m depths.

The big deal is how it's much easier to cast a thick hull out of a concrete-like material, even with extra-special handling and curing, than to bend and weld one out of metal plates, especially avoiding any weld defects. So one can use spherical curves, complex shapes, extreme thickness, and still keep the cost low.

The Naval Civil Engineering Laboratory in Port Hueneme, California did a lot of work on concrete spheres for external pressure vessels in the late 1960s. visited there just before joining the Navy. They had a bunch of imploded hemispheres in the yard outside the pressure testing building.

A lot has changed since then. In the 1960s, state of the art concrete was 6-10 ksi, and still included coarse aggregate and steel rebars. Now it's dust-sized aggregate, <10% water (not workable by hand at all), reinforced by thin glass or carbon fibers, and gets to 30-45 ksi in the field and 50-100 in the labs.

It's not going to beat titanium, but has already passed high-yield steel and aluminum. CFRP is an even stronger option, but it's even more expensive and doesn't do as well in seawater.

 

[Wibble]

Had to look up KSI:

ksi (unit), kilopound per square inch, a non-SI unit of stress or pressure

Pound per square inch - Wikipedia

en.wikipedia.org

 

[Gone for diving]

About as dense as aluminum, but can get to steel-like compressive strength if cured under heat and pressure. Not as great in tension, so it can't compete with carbon for surface boats. But they're starting to use it for offshore structures and have designed underwater housings for 3,000-6,000m depths.

The big deal is how it's much easier to cast a thick hull out of a concrete-like material, even with extra-special handling and curing, than to bend and weld one out of metal plates, especially avoiding any weld defects. So one can use spherical curves, complex shapes, extreme thickness, and still keep the cost low.


A lot has changed since then. In the 1960s, state of the art concrete was 6-10 ksi, and still included coarse aggregate and steel rebars. Now it's dust-sized aggregate, <10% water (not workable by hand at all), reinforced by thin glass or carbon fibers, and gets to 30-45 ksi in the field and 50-100 in the labs.

It's not going to beat titanium, but has already passed high-yield steel and aluminum. CFRP is an even stronger option, but it's even more expensive and doesn't do as well in seawater.

Very Cool.

Yeah concrete in tension....

Any floors we pour I use fiber in the concrete. Its amazing how much stronger it is.