#1 2020-10-16 09:35:43

Chris60

Member

Registered: 2020-10-16

Posts: 5

[SOLVED] ressort spiral

L'objectif est de simuler l'enroulement d'un ressort spiral en 2d. Pour cela, on impose aux noeuds du centre des ddls de déplacement (circulaire), et on encastre l'autre extrémité. On se place en élasticité non linéaire + grands déplacements + déformation plane.  La solution converge mais le résultat n'est pas satisfaisant : les spires se touchent (voir pbAster.png)
Visiblement, je n'applique pas les bonnes conditions de calculs. Un conseil serait le bienvenu, merci d'avance.

Last edited by Chris60 (2020-10-21 11:55:52)

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Attachments:
spiralAster.zip, Size: 153.21 KiB, Downloads: 62

mf

Member

Registered: 2019-06-18

Posts: 176

Re: [SOLVED] ressort spiral

Bonjour,

le calcul est plus réaliste si vous introduisez un DEFI_CONTACT entre les bords.

Sorry for the bad french,

Mario.

Chris60

Member

Registered: 2020-10-16

Posts: 5

Re: [SOLVED] ressort spiral

Merci Mario pour ce conseil.
Mais normalement, les spires ne devraient pas se toucher. Le ressort devrait s'enrouler sur lui même.

mf

Member

Registered: 2019-06-18

Posts: 176

Re: [SOLVED] ressort spiral

Hi,

well, I'm not sure about that. The center of rotation is not in the center of the spring, whatever the 'center' is. If I estimate the center of mass of the spring without the holding thingy, there is for sure an offset between rotation center and center of mass. And also, the distances of the windings are different on either side,

Mario.

Last edited by mf (2020-10-16 21:59:59)

sameer21101970

Member

Registered: 2019-09-06

Posts: 299

Re: [SOLVED] ressort spiral

refer modified files upload and study further

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Attachments:
CurrentCase.unv, Size: 645.11 KiB, Downloads: 65

sameer21101970

Member

Registered: 2019-09-06

Posts: 299

Re: [SOLVED] ressort spiral

.comm

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Attachments:
CurrentCase.comm, Size: 2.6 KiB, Downloads: 66

Chris60

Member

Registered: 2020-10-16

Posts: 5

Re: [SOLVED] ressort spiral

thank you for your replies.
- the origin of the referential is corresponding to the internal circle center
- It's not necessary to define the displacement condition on the whole border of the spring, only on the internal circle (close to its center)
I think the issue is about the model definition, and/or missing key word in STAT_NON_LINE, ...

sameer21101970

Member

Registered: 2019-09-06

Posts: 299

Re: [SOLVED] ressort spiral

any other solver you hv done, share image of result.

Chris60

Member

Registered: 2020-10-16

Posts: 5

Re: [SOLVED] ressort spiral

You can see the capture.png which shows the results after a 180 ° rotation (producted by Elmer solver)

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Attachments:
capture.png, Size: 339.64 KiB, Downloads: 43

mf

Member

Registered: 2019-06-18

Posts: 176

Re: [SOLVED] ressort spiral

Hi,

ok, I see. At first, I must say there is nothing obviously wrong with your calculation. It seems that your geometry is very sensitive to the choice of parameters in STAT_NON_LINE, so we are seeing some kind of numerical effect here. Your choice of 2nd order elements is obviously correct. Here is what I changed:
1.) increased the number of timesteps to 400. Anything lower, and there are timesteps where the spiral 'blows up'. I haven't seen anything like it before. It is very sensitive.
2.) In NEWTON I changed PREDICTION to ELASTIQUE. MATRICE = ELASTIQUE didn't work--> enormous RESI_GLOB_RELA--> ERROR.
3.) Set RESI_GLOB_RELA to 1E-6, although this is probably not important.

With these settings you'll get a similar result compared to Elmer (never used it, can't say anything about it). But I can't say which one of the results is 'better' per se,

Mario.

Last edited by mf (2020-10-19 16:40:11)

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Attachments:
new_results.zip, Size: 382.98 KiB, Downloads: 59

mf

Member

Registered: 2019-06-18

Posts: 176

Re: [SOLVED] ressort spiral

I made a small mistake in my last post, A was still at 0.62. For 180° it should be equal to 1.

Then the result is similar to the result calculated by Elmer, although it needs 1000 timesteps here,

Mario.

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Attachments:
new_results_2.zip, Size: 378.57 KiB, Downloads: 65

Chris60

Member

Registered: 2020-10-16

Posts: 5

Re: [SOLVED] ressort spiral

Thank you for your advice and the sharing files.
I've reloaded my study with your Stat_non_line parameters, the results are ok.
As an attchment file, the displacement results provided by Aster and Elmer

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Attachments:
valid_depl_Elmer-Aster.png, Size: 183.55 KiB, Downloads: 43

mf

Member

Registered: 2019-06-18

Posts: 176

Re: [SOLVED] ressort spiral

Hi,

so it is solved? Could you please mark it as [SOLVED] (edit post title in first message)?

Thanks,

Mario.