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I-DEAS True Stress-Strain Data

I-DEAS True Stress-Strain Data

I-DEAS True Stress-Strain Data

(OP)
Hello -

Way back on 7Jan04 in (thread727-83231: stress is greater than yield but plastic strain is zero?), feadude wrote,

"IDEAS uses engineering stress/strain data for material nonlinear and true stress/strain data for geometric nonlinear."


Could feadude or someone please point me to where I can find that information?  I haven't seen it in the I-DEA Help files.

Also, assuming the statement is correct, does it mean that for material nonlinear analyses I-DEAS wants data of engineering stress vs. engineering strain?  And for geometric nonlinear analysis, I-DEAS wants data of true stress vs. true strain?  I ask this because sometimes "true" curves are actually true stress vs. engineering strain.

Finally, what stress-strain data does I-DEAS want when an analysis is both geometric nonlinear and material nonlinear?

Thank you in advance for your replies!

RE: I-DEAS True Stress-Strain Data

I think the fact that I-DEAS is mentioned is preventing people from responding. Is this an IDEAS question (i.e. which button to press), or a true stress-strain/FE question?

 

RE: I-DEAS True Stress-Strain Data

For infinitely small strains is there any difference between the two?A linear analysis assumes infinitely small strains.

 

Cheers

Greg Locock

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RE: I-DEAS True Stress-Strain Data

(OP)
Thanks, I agree with both questions, and yes, this is an I-DEAS question.  I'm confused as to why, per feadude's statement, I-DEAS would use engineering stress/strain data for material nonlinear and true stress/strain data for geometric nonlinear.  Not sure how you could run a combined (geometric and material) nonlinear analysis--what data should be input?  I realize that whichever data (true or engineering) is to be input, the software can convert it to the other form as needed.  The question with I-DEAS is, which is to be input for each type of analysis.  The software has been sold from company to company so many times that I'm not confident that their technical support team knows what's under the covers.  It looks like feadude hasn't posted since Sep 2006, so I'm probably out of luck.

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