FE Results Superposition

[struclearner]

Hello Respectables,

I need clarification regarding superposition of the FEA results from different load cases. When the results are added, I am wondering, the reactions loads are not added each time. When the area of the concern is close to reactions/supports/boundary conditions, the reaction load would not be added twice and the FEA stresses won't be correct, when I will add the stresses from two different load cases. I am looking for the interference stresses, I will run FEA for interference fit of two contact surfaces first, then run the analysis under the other load cases,then, when I will add the stresses from press fit to other load case, i will not be adding the reaction load twice.
Thanks for the input.

 

[rickfischer51]

The reactions will be different for the loads in each load case, so adding them is OK. Contact surfaces? Contact is nonlinear, and load case superposition is only valid for linear results.

Rick Fischer
Principal Engineer
Argonne National Laboratory

 

[ukbridge]

Yes the principle of superposition (and many other things) goes out of the window in a nonlinear analysis, whether it be a geometric/material/contact analysis.

Please don't take this the wrong way, but it is absolutely critical you understand the implications of a nonlinear analysis if you're going to use it. You shouldn't be anywhere near a nonlinear solver until you grasp fundamental things like this, always be sure to thoroughly read your product manual as they're (usually) pretty well written.