-------- 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>
To: J. Sanz <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/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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