Good catch - I accidentally had a permanently fixed stand on the lower-left corner that was causing these errors in the free version. Oops! It didn't affect anything in SSSS or CCCC, obviously, but did shift the low-frequency modes around for FFFF. I must've been experimenting with that at some point and forgot to set it back.
I'll upload a new version soon that gets rid of the stand and also includes the coupling resonance.
In the meantime, here are some updated results:
Happy those test cases helped in debugging. The fix should solve the frequency shift, the asymmetry in the velocity map and the unexpected peak in the FR.
We have now 3 test cases: PS CCCC, EPS FFFF, PMMA FFFF. I have prepared 2 others but I have to learn more from Eric's tap test method to get the materials parameters.
I don't know what is the features road map for PETTaLS but I have 2 have in mind :
- better plots : my preferred option would be a text export compatible with REW (csv format). In a previous version the plots were opened and enlarged in a floating window which I prefer to the current small plots.
- All the test cases confirm the LF roll of due to the open back and its effect in the 200...400Hz range. Not an easy topic but needed in my opinion for such application.
Christian
Eucy,
Here is a first version of a paper about damping.
Don't be afraid by the mathematical aspect of the document. It is a way for me to keep notes of what is in the python code. It is also an opportunity to think differently trying to explain what is implemented.
Thanks to that, I found a bug which i think fixed now in some sign mismatch. The damping parameters are now positive as expected!
In the second part of the document are plots that show the effect of each type of damping.
The parameters are not well adjusted. It is the result of few tests.
The main point is probably how the model acts in the frequency range.
The SPL level of the frequency simulation is not aligned on the SPL level of the modal decomposition; A fix to come.
Christian
@homeswinghome
@EarthTonesElectronics
In trying to provide Christian with the best possible characterization of the elastic constants for various panels, I did a series of FEA trials to show how each of the six elastic constants for orthotropic plates influences the natural frequencies. The main purpose for me was to help make my crude trial and error method for evaluation of the elastic constants just a little more rigorous/reliable. Take a look here (or at least pretend to!).
Effect of Elastic Constants on Natural Frequencies
Christian,
I realize this isn't the answer you are looking for regarding the real meaning of the additional shear moduli, but at least it gives you an idea of their impact.
Eric
@EarthTonesElectronics
Dave,
Christian's posts reminded me of something I've been meaning to ask for some time but keep forgetting. I'd be very interested to know a bit more about how you estimate (a) the elastic properties of plates and (b) their Q value. Not necessarily every detail, but at least the basic gist.
Thanks,
Eric
Dave,
Christian's posts reminded me of something I've been meaning to ask for some time but keep forgetting. I'd be very interested to know a bit more about how you estimate (a) the elastic properties of plates and (b) their Q value. Not necessarily every detail, but at least the basic gist.
Thanks,
Eric