extraction of negative eigenvalues
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Re: extraction of negative eigenvalues
Check if you see the results in the file produced by CalculiX. If it's there then the reader is broken, but I doubt it - it worked since it was added to the FreeCAD code. Another option is change of formatting by CalculiX, but that's unlikely. Post the model, so someone can check it.
P.S. I never dreamt that the reader code might survive that long without modifications
Re: extraction of negative eigenvalues
I can confirm the problem for 0.19 Just open FEM 3D example change from static to frequancy analysis.
Ahh it works in 0.18.2 ... which means I may am the culprit in one of the lots of code refactoring commits ... I will have a look ...
Ahh it works in 0.18.2 ... which means I may am the culprit in one of the lots of code refactoring commits ... I will have a look ...
Re: extraction of negative eigenvalues
my vault ...
I deleted this line https://github.com/FreeCAD/FreeCAD/blob ... em.py#L284 I will have a look how to fix this.
I deleted this line https://github.com/FreeCAD/FreeCAD/blob ... em.py#L284 I will have a look how to fix this.
Re: extraction of negative eigenvalues
git commit 20b78fc fixes the eigenmode reading. Back to the origin question ...
Is the eigenmode we gone read from dat file the right one ??? https://github.com/FreeCAD/FreeCAD/blob ... py#L94-L95
Is the eigenmode we gone read from dat file the right one ??? https://github.com/FreeCAD/FreeCAD/blob ... py#L94-L95
Re: extraction of negative eigenvalues
Judging from the table in the first post the entries in the frequency line are as follows:
EDIT: this is not correct. see: https://forum.freecadweb.org/viewtopic. ... 30#p319635
Code: Select all
<mode number> <real part of frequency in rad/s> <real part of frequency in Hz> <imaginary part of frequency in rad/s> <imaginary part of frequency in Hz>
Last edited by HarryvL on Tue Jul 09, 2019 12:10 am, edited 1 time in total.
Re: extraction of negative eigenvalues
A practical example of a natural frequency analysis where the imaginary part of the response needs to be considered:
https://forum.freecadweb.org/viewtopic. ... 50#p232717
EDIT: this relates to imaginary response modes and not to imaginary frequencies
https://forum.freecadweb.org/viewtopic. ... 50#p232717
EDIT: this relates to imaginary response modes and not to imaginary frequencies
Last edited by HarryvL on Tue Jul 09, 2019 12:23 am, edited 1 time in total.
Re: extraction of negative eigenvalues
- start FreeCAD
- load FEM 3D example
- change to analysis type frequency
- change from first 15 to first 8 frequencies
- delete constraint fixed and constraint force
- run analyisis
- the imaginary part in Hz is missing
- screen and file attached
- load FEM 3D example
- change to analysis type frequency
- change from first 15 to first 8 frequencies
- delete constraint fixed and constraint force
- run analyisis
- the imaginary part in Hz is missing
- screen and file attached
Re: extraction of negative eigenvalues
but I can the rad/Time use as well ... https://en.wikipedia.org/wiki/Radian_per_second just use /2pi ...