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CTE Errors in CW?

CTE Errors in CW?

CTE Errors in CW?

(OP)
Because I don't trust myself using FEA entirley yet, I try to do a few simple examples that I can hand calculate to compare results.  I'm getting a problem with thermal expansion of a part.

I'm a newbie to CW and having trouble with a few things.  If I go into the material properties of 6061, SW/CW lists a CTE of 2.4x10^-5/deg C.  

Using that CTE (the same one that SW/CW uses) to do a hand calc for a 2" long piece and a 40 deg. C detla, I get an expansion of .00192 inches.  The FEA model shows an expansion of .00215 inches.  

Now ~.0002 doesn't seem like much, but its a 10% error.  And I'm working with optics.  I checked and the SW CTE value is constant over temperature.  

Does anyone have any insight on this?  Thanks in advance.

RE: CTE Errors in CW?

(OP)
I now have insight!  (Answering my own post).  I was viewing the resultant displacement instead of the z-axis displacement!  I changed to view the z-axis and the results agree perfectly with my hand-calculations.  I knew there had to be something to it!

RE: CTE Errors in CW?

The fact that you first analyse some benchmark problems and also do some hand calcs by far compensate for the little oversight!  

Regards!

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