Pointer to some fairly standard mechanical problem?

Question

Let me preface that I'm NOT a mechanical engineer - I'm just trying to do a back-of-the-envelope design of a little gadget. The internal part is pretty straightforward, but the whole thing needs to sit in a case that can be submerged in water to a couple tens of meter.

Now I'm assuming that there's such a thing like a "collection of formulas for standard geometries" (or such) where I could look up how thick I need to make the walls of an oblong cylinder made of material X if it is supposed to survive indefinitely external overpressures of Y psi. What I don't know is where I'd start looking for this kind of thing.

So if someone could give me the name of an author I should look for in the library or the pointer to a web-page that has this kind of thing, I'd be grateful.

Thanx

Jim Y · Accepted Answer

Piping Handbook, Crocker and King, 5th ed., McGraw-Hill, Chapter 3 the first 20 pages

Look at :

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It has formulas and information that may be of some help.

Remember, when you are working with pressure, flat surfaces are NOT generally acceptable because they deflect easily. Use a cylinder or a ball shaped vessel. In general though, avoid flat surfaces. Look at a can of soda, it has a very thin wall and is cylindrical - economically feasible.

Ten meters is approximately 33 feet. Water weighs 62.428 LB per cubic feet. At that depth, the pressure on your vessel would be 2,046 LB. per sq. ft or 14 PSI.

Jim Y

DThompson · Answer

Here are a couple of websites with engineering calculators, you may need to sign on the first time:

Al Adrian · Answer

I used to use a memo from Woods Hole Institute of Oceanography when I did this...

I think this may be the one, but I'm not sure:

Woods Hole Oceanographic Institute Technical Memorandum 3-81Failure Curves of Cylindrical/Spherical Pressure Vessels and Flat End Caps.By Arnold G. Sharp, August 1981

Depending on what you are doing you may find that the pressure case is no problem, but the through-hull connectors can be. There are a lot of quite expensive connectors designed for underwater use. Faking it with a poured eurathane bulkhead could work, but if you are too deep the cable will extrude it's inners into the case over time.

Al...

Daniel Kiracofe · Answer

Roark and Young published a pretty nice handbook: "Formulas for Stress and Strain" I think. It is a general book, not specific to pressure vessels, but I do believe there is a section on them.

/* Daniel */

Narasimham G.L. · Answer

pressures, an oblong cylinder ..You have not mentioned the size of cylinder. One could choose  a steelbellows (Convolutions) cylinder to withstand 6-8  Atm ( 90- 120 psi)INTERNAL pressure that does the job of external pressure as well. ( Itis perhaps not a "standard" problem.)

Pointer to some fairly standard mechanical problem?

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