T3D Re: underwater housings

[john bercovitz <bercov@xxxxxxxxxxx>]

> I'm a bit surprised at this since generally materials have higher 
> compressibility ratings than expandability (I forget the technical 
> terms - it's been too long since I took strength of materials!).

You're right - some materials, cast iron is a perfect example, have
higher compressive strength than tensile strength.  However, the case 
here is not purely a compression problem.  Even a hollow sphere will 
collapse under enough pressure so what we really have is a stability 
problem.  Some little area starts to let go and then the whole thing 
collapses.  A ggod analogy might be a column.  Just because some piece 
of steel is good for 200,000 psi doesn't mean 1 square inch of it 
three feet long will support 200,000 pounds in compression.

And now I notice Greg W has already answered the question.  Oh well, 
sometimes two sources add up to more than 1 and 1.  8-)

John B


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End of TECH-3D Digest 355
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