Download an Excel spreadsheet (http://home.earthlink.net/~jimlux/download/vactank.xls (23K)) that calculates collapse pressures for long tubes (L>20R), spheres (or hemispheres), and flat plates (clamped or unclamped). You'll need to enter material properties (Young's modulus, Poisson's ratio, yield stress) and dimensions. Equations taken from: Strong, J. , Procedures in Experimental Physics. Handy for designing vacuum chambers and underwater enclosures.
Don't forget that this application is typically cyclically loaded, so you should allow for fatigue factors. If you keep the stress for steel below around 20 kpsi, fatigue isn't an issue. It's always an issue for aluminum: remember the DeHavilland Comet. There appears to be a problem with the equation for tubes with non-zero eccentricities, which I haven't yet worked out; It seems to make eccentric tubes stronger than circular ones, which just isn't so. An example of a clamped flat plate is one that is welded, an example of an unclamped plate is one bolted to a flange.
Useful round numbers: modulus of steel is 30E6, Al is 20E6, Poisson's ratio is .3 for most metals, yield stress is 20kpsi for soft Al, 40K for 6061-T6, 30-40K for ordinary steel, 80K for the hard stuff.
An Excel spreadsheet (http://home.earthlink.net/~jimlux/download/flash.xls - 22K) to calculate circuit parameters for Xenon flash tube circuits. Based entirely on the EG&G (http://www.egginc.com) Linear Flashlamps brochure, implementing the equations contained therein.
Those 4 colored diamond shaped things on buildings. From the Uniform Documents Project: http://www.unidocs.org/un-nfpa.html
What I carry in my daypack...
Copyright 1998, Jim Lux / revised 5 Feb 2003 / Back to home page / Mail to Jim