Hello,

the modal analysis example using the PRIMME eigenvalue solvers is now merged in the main SfePy branch, so you can download the development version from git:

git clone git://github.com/sfepy/sfepy.git

and install the solver package:

pip install primme

The example is in

sfepy/examples/linear_elasticity/modal_analysis_declarative.py

Regards, Vladimir

On 26. 05. 23 20:39, J. Sanz wrote:

Hello, Thanks, It looks great!, But I am not able to test it with Sfepy. Do you have any example or steps to follow? Regards, J.Sanz

El mié, 24 may 2023 a las 16:14, Vladimir Lukes (<vlukes@kme.zcu.cz <mailto:vlukes@kme.zcu.cz>>) escribió:

-------- Forwarded Message --------
Subject: Re: [sfepy] Problem with Modal Analysis
Date: Wed, 24 May 2023 15:36:40 +0200
From: Vladimir Lukes <vlukes@kme.zcu.cz <mailto:vlukes@kme.zcu.cz>>
To: J. Sanz <jsanz451@gmail.com <mailto:jsanz451@gmail.com>>

Hi Jesus,

try the new PRIMME eigenvalue solver which is now integrated in SfePy.
Have a look at the following pull requests:

https://github.com/sfepy/sfepy/pull/995
<https://github.com/sfepy/sfepy/pull/995>
https://github.com/sfepy/sfepy/pull/982
<https://github.com/sfepy/sfepy/pull/982>


Regards
Vladimir

On 19. 05. 23 9:29, J. Sanz wrote:
 > Hello,
 > I have calculated the modal frequencies of a part with Sfepy. The
 > results have been compared to Ansys. Unfortunately, the results
 > are different.
 >
 > I have repeated the calculation by changing the next parameters
trying
 > to find stable results.
 > -Solver: eig.scipy/eigsh
 >
 > -Solver:eig.scipy_lobpcg -
 > -i_max(iterations)
 > -Mesh size. I have tested different mesh from 12k cells to 22k cells.
 > -Order
 >
 > I am not able to get results in a reasonable time by using
 > eig.scipy/eigsh . (as reference for 13k cell, time is around 10 min)
 > The calculation runs with the solver eig.scipy_lobpcg. In all the
 > tests, I am not able to reach good tolerance. So, the results are
quite
 > dependent on the number of elements, i_max parameter, and order.
On the
 > other hand, if I try to make  it more accurate, the time
processing is
 > too long.
 >
 > Could you give any hint or recommendation?
 >
 > The simulation condition is free, without boundary conditions.The
first
 > modes from Ansys are 4746 Hz, 5118 Hz, 5426 Hz, 6906 Hz. The six
first
 > modes corresponding to rigid motion have been discarded.
 > The modes with Sfepy are 8710 Hz, 12954 Hz,  13138 Hz , 15213 Hz
 > Ansys use tetrahedrons with quadratic formulation (midside nodes)
and
 > fine mesh.
 >
 > You can find attached code and commands to run it.
 > To run the model write in the terminal:
 > python modal_analysis.py Dummy_Modal_4_1.mesh
 > --solver="eig.scipy_lobpcg,i_max:1000,largest:False" --young 74854
 > --density 2.7e-9 --poisson 0.3 --order 1
 > Units: mm, N, MPa, Tn/mm3
 > Thanks,
 > Jesus S.
 >
 >
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