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Re: MATRIX ANALYSIS

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>I'm so glad to read that someone is actually thinking of
>checking The Computer!  I was beginning to think that checking The
>Computer was regarded as heresy!!
More accurately you need to check the results the computer provides. 
Computers are exceptionally consistent. They do what they're told and 
they do it the same way every time. But it doesn't care what we mean only 
what we say. If I, as FEA boffin, tell it to run 3000 lb at the bottom 
when I meant 5000 lb at the top, I get a wrong answer. The answer will be 
just as accurate either way, but only one is right and I need to insure 
that that, like Horton, I said what I meant and I meant what I said.

>left handed architect thought that the right
>hand rule relating forces and axes was a nuisance
Such people are often confused by the term 'user-friendly' in the ads. 
Software isn't user friendly, it's user indifferent at best and it's 
never your friend. It doesn't do sanity checks, it doesn't care if you 
meant one load and input another and it won't fix a misplaced a comma or 
an inadvertently omitted boundary constraint. If you're in a hurry and 
forgot a command context or the yield strength of ASTM A-490 bolts, tough 
beans. In a similar vein, neither the programmer nor the marketeer are 
paid to make your life easy or do your engineering--they're paid to move 
software. Unlike software, they can be your friend, but they won't be 
friendly or knowledgeable enough do your job for you, no matter what the 
ads say.

> accepted first and second modes of vibration a fraction of a Hertz apart 
when, in fact,
> they had two approximations of first mode in each of X and Z directions.
A third point of confusion with a lot of FEA users--that whizzy graphics 
mean no need to remember applied mechanics. Incorrectly interpreted 
results are worse than no results at all, and 'Um...well... gee... the 
plot looked OK.' is the wrong answer to 'What in God's name could you 
possibly have been thinking?' Anyone who doesn't understand the physics, 
not only doesn't understand the problem, he's likely clueless that his 
micrometrically precise calculations answer the wrong question.

Christopher Wright P.E.    |"They couldn't hit an elephant at
chrisw(--nospam--at)skypoint.com        | this distance"   (last words of Gen.
___________________________| John Sedgwick, Spotsylvania 1864)
http://www.skypoint.com/~chrisw



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