FEA vs. Strain Gage analysis
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Posted by: larryfoley ® 02/21/2008, 23:34:51 Author Profile eMail author Edit

I am trying to reconcile stress and strain values from strain gage analysis to those determined by Cosmos DesignStar nonlinear FEA. The values differ by as much as 160%. Does anyone have any ideas where the differences may come from? The FEA values are at elements under the strain gage locations. Thanks,

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Re: FEA vs. Strain Gage analysis
Re: FEA vs. Strain Gage analysis -- larryfoley	Post Reply	Top of thread	Forum

Posted by: ME from RI ® 07/10/2008, 12:44:15 Author Profile eMail author Edit

Here are some things to think about. 1) Does the part have residual internal stress from manufacturing? If so stress relieve the part and then HT prior to test. Make sure you use the same process on a test sample and run some testing to assure proper material properties for FEA. 2) Does the nonlinear portion of the material properies reflect the true material? if not change some settings if possible. 3) If the part is loaded past the elastic limit (at any location on the part) that is it you can not take another shot at running the test. You need to start with a vergin part. What your doing is actually a hard thing to do. (non-linear) Good luck, C

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Re: FEA vs. Strain Gage analysis
Re: FEA vs. Strain Gage analysis -- larryfoley	Post Reply	Top of thread	Forum

Posted by: Kelly Bramble ® 02/22/2008, 07:16:50 Author Profile eMail author Edit

Sounds normal to me, the differences can be attributed to many variables. Material characteristics imperfect (normal), complex imperfect geometry (normal), assembly induced stresses (normal), loading not applied exact (normal), strain gages not calibrated perfect (normal), insufficient mesh density, etc. Unless you have simple, almost perfect geometry, strain gages calibrated perfect, no assembly induced stresses you will always have differences between analysis and measured. Modified by Kelly Bramble at Fri, Feb 22, 2008, 07:17:46

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