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Subject: [Modal] Extracting stress results for a cyclic symmetry
Author: Dan Bohlen
Date: 2008-04-17 11:59:27
Hi All,
I've been running the subject modal analysis and have been pulling
stresses off and postprocessing the results quite easily with the
/CYCEXPAND and CYCPHASE commands. I'm scaling my results based on
engine test strain gages. What I've done so far is to pick nodes in the
region of the model where the gage is located and have done my best at
interpolating stresses at the gage location. (The modeling and
instrumentation were done independently so there are no nodes/elements
conveniently located.) The results based on this method agree with the
testing and previous results.
After a while I got the idea of having Ansys do the interpolation. I've
done the old trick of creating a node right where I want it and using
the PATH operations to map/interpolate the model stresses onto that
location. I figured out I need to do the operation once for each the
real and imaginary solutions (sine and cosine) and then add up with the
phase angle sine and cosine function outlined in the Fabulous Manual.
For instance, I'd pull Sx with the base model and then Sx off the
"duplicate" model.
The problem is these two individual results are WAY off from what I pull
from the surrounding individual nodes. I looked at it several ways of
combining the two numbers I got - including that perhaps I needed to
change the sign on one of them. There was no way to conjure up a way to
combine them to make any sense or be anywhere close to the nodal
stresses I was getting.
Just wondering if anyone had tried this with any success. Or perhaps is
if someone knows this cannot be done. It's not critical because my
manual interpolation is OK. But after spending a couple hours toying
with it I though it'd be worth a few more minutes here.
Thanks in advance,
Dan Bohlen
RPC Military Stress Analysis
Senior Engineer
GE Aircraft Engines
1 Neumann Way, Evendale, OH