ANSYS modal analysis and normalization methods
ANSYS modal analysis and normalization methods
(OP)
Hello,
As we know, ansys when post-processing results, depending on analysis options, can show either "to mass matrix" or "to unity" normalized displacements.
One thing I don't understand then is why in the results of my analysis of simply supported cylindrical structure, the location of max displacement in "mass marix" normalized analysis is different than in the other one (please see the attachement)? I thought normalization is only about setting a relative value for modal shape display purposes, therefore the distribution of displacements shouldn't be affected. Or is it just an negligible numerical calculation error?
Other question: when I went through first few modes of this analysis with "to unity" normalization, I found that in most of the cases maximum value of X, Y or Z displacement is equal to 1. However in few cases neither of those displacements are equal to 1 .. Why is that?
Thank you,
Julian
As we know, ansys when post-processing results, depending on analysis options, can show either "to mass matrix" or "to unity" normalized displacements.
One thing I don't understand then is why in the results of my analysis of simply supported cylindrical structure, the location of max displacement in "mass marix" normalized analysis is different than in the other one (please see the attachement)? I thought normalization is only about setting a relative value for modal shape display purposes, therefore the distribution of displacements shouldn't be affected. Or is it just an negligible numerical calculation error?
Other question: when I went through first few modes of this analysis with "to unity" normalization, I found that in most of the cases maximum value of X, Y or Z displacement is equal to 1. However in few cases neither of those displacements are equal to 1 .. Why is that?
Thank you,
Julian





RE: ANSYS modal analysis and normalization methods
You should ask ANSYS why some of the "to unity" normalizations are not to unity. This is very strange, since the normalisation routine is a trivial task and one wonders how this has gone astray.
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RE: ANSYS modal analysis and normalization methods
If joint A and B have the same displacement, but with different signs then which one is the "max". If normalizing to the mass matrix give A as positive and B as negative, then joint A may be said to control. If normalizing to unity gives A as negative and B as positive, then B may be said to control.
Regarding the reason why those are normalized "to unity". My guess is that they may be using a generalized algorithm for plotting contours geared more towards plotting internal stresses than joint deflections. If you look at the numerical (not plotted) results, they may be more exact.
RE: ANSYS modal analysis and normalization methods
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RE: ANSYS modal analysis and normalization methods
From "element nodal results" you can get stresses and perform averaging on the stresses of course, but not with displacements.
It would be nice to get an "official" explanation from ANSYS !
Can't the OP tackle them directly and post the explanation here?
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