Problem in nonlinear damped vibration

Numerical methods and mathematical models of Elmer
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Sayan
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Problem in nonlinear damped vibration

Post by Sayan »

Hiii Team,
Hope all of you are doing well. I am facing one problem again, which I confronted 2 3 months back and also discussed here. Though that time problem was solved after using VM as per suggestion but recently I am facing the same issues both in windows and Virtual Machine. I even used git pull option to update VM. But it's not solved.
The problem is, in case of nonlinear damped vibration effect of damping is not reflecting in the result. I have attached the result I am getting, along with .msh and .sif file for your kind look. Please help me to solve this issue. I am facing this problem frequently and getting stucked in the middle of my work.
Attachments
nonlinear.jpg
(135.6 KiB) Not downloaded yet
case.sif
(2.44 KiB) Downloaded 136 times
damageAx.msh
(45.23 KiB) Downloaded 121 times
raback
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Re: Problem in nonlinear damped vibration

Post by raback »

Hi Sayan,

Could you share your version by copy-pasting the line from the start of the output:

Code: Select all

MAIN: Version: 9.0 (Rev: fcf9f683, Compiled: 2021-07-07)
Your sif seems legit to me. Have you tried to increase the damping by a large factor (say 1e10) to verify that there is no effect of the parameter?

-Peter
Sayan
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Re: Problem in nonlinear damped vibration

Post by Sayan »

Yahh I tried with different damping. Even in this file the factor is 10 times more than what I want to use. With beta=0.001 the damping ratio will come around 1.5% as natural frequency for my case is 30.5. Even I got damping effect previously and in linear case also it's pretty prominent with same load and material property. For nonlinear case only problem is arising.
Here is some lines from output for windows system
"ELMER SOLVER (v 9.0) STARTED AT: 2021/07/07 10:06:39
MAIN:
MAIN: =============================================================
MAIN: ElmerSolver finite element software, Welcome!
MAIN: This program is free software licensed under (L)GPL
MAIN: Copyright 1st April 1995 - , CSC - IT Center for Science Ltd.
MAIN: Webpage http://www.csc.fi/elmer, Email elmeradm@csc.fi
MAIN: Version: 9.0 (Rev: Release, Compiled: 2021-06-27)
MAIN: Running one task without MPI parallelization.
MAIN: Running with just one thread per task.
MAIN: Lua interpreter linked in."

and this is copied from VM.

ELMER SOLVER (v 9.0) STARTED AT: 2021/07/06 12:54:13
ParCommInit: Initialize #PEs: 1
MAIN:
MAIN: =============================================================
MAIN: ElmerSolver finite element software, Welcome!
MAIN: This program is free software licensed under (L)GPL
MAIN: Copyright 1st April 1995 - , CSC - IT Center for Science Ltd.
MAIN: Webpage http://www.csc.fi/elmer, Email elmeradm@csc.fi
MAIN: Version: 9.0 (Rev: 5d27ebd8, Compiled: 2020-11-26)
MAIN: Running one task without MPI parallelization.
MAIN: Running with just one thread per task.
MAIN: HYPRE library linked in.
MAIN: MUMPS library linked in.
MAIN: Lua interpreted linked in.
MAIN: Zoltan library linked in.
Sayan
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Re: Problem in nonlinear damped vibration

Post by Sayan »

Hiii,
To check the disparity between damped and undamped condition, I analysed the same without damping and it's showing good result. Analysed many times today in my windows system,( even installed new updated one from github) and I found a horrific result when analysed using windows system even at reduced load. The result is very much fluctuating and not even close to the result which I got yesterday (this is when using elastic solver and damping both),but getting good response when using without damping case.
I am surprised, the same system generated good result few weeks back when I tested with 75N load using nonlinear damping condition. But when using now even with 75N load it's show fluctuating response history.
(**Using VM I am getting same result even today which I have got yesterday and posted here).
raback
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Re: Problem in nonlinear damped vibration

Post by raback »

Hi

Where from did you download your fresh Windows version?

This is where nightly builds appear:
https://www.nic.funet.fi/pub/sci/physic ... s/?C=M;O=D

-Peter
Sayan
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Re: Problem in nonlinear damped vibration

Post by Sayan »

Hii,
Yess..I always download from there only...Still it happened
Sayan
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Re: Problem in nonlinear damped vibration

Post by Sayan »

Hii,
Has anybody found any solution? The problem still persists...
raback
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Re: Problem in nonlinear damped vibration

Post by raback »

Hi

Is this the same case where the Dirichlet conditions were not active?

Generally, if a code works for some setup but after changing BCs or mesh it does not any more, it is not very likely that the error would be in the actual physical model.

-Peter
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