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#1 2015-08-27 16:36:11

stephaneberger
Member
From: Strasbourg (France)
Registered: 2012-10-15
Posts: 70

Strain in large deformation

Hi

I'm trying to simulate a tensile test up to 20% of strain. My issue is that I cannot obtain the real strain in large deformation.
In small deformation I obtain the right one (with EPSI_NOEU), but in large deformation (with EPSG_NOEU), I'm obtaining a strain which is larger than the strain EPSI.
This results is not posssible.

For this I have made a comparison between MECA_STATIQUE and STAT_NON_LINE.
In both case, if i plot EPSI I obtain the same results. But when I plot EPSG, each time the strain is greater than EPSI

I have tried several COMPORTEMENT and several DEFORMATION. Each time the strain in large deformation is not correct.

I don't understand where is my mistake.

I attach my comm file

Here under are the results with EPSI and EPSG

EPSG - EPYY_0      EPSI - EPYY_0
0.00000E+000       0.00000E+00
1.00500E-02        1.00000E-02
2.02000E-02        2.00000E-02
3.04500E-02        3.00000E-02
4.08000E-02        4.00000E-02
5.12500E-02        5.00000E-02
6.18000E-02        6.00000E-02
7.24500E-02        7.00000E-02
8.32000E-02        8.00000E-02
9.40500E-02        9.00000E-02
1.05000E-01        1.00000E-01
1.16050E-01        1.10000E-01
1.27200E-01        1.20000E-01
1.38450E-01        1.30000E-01
1.49800E-01        1.40000E-01
1.61250E-01        1.50000E-01
1.72800E-01        1.60000E-01
1.84450E-01        1.70000E-01
1.96200E-01        1.80000E-01
2.08050E-01        1.90000E-01
2.20000E-01        2.00000E-01

Thanks for your help

Stephane

Last edited by stephaneberger (2015-08-27 16:36:51)


Attachments:
traction.comm, Size: 2.77 KiB, Downloads: 273

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#2 2015-08-28 10:36:30

stephaneberger
Member
From: Strasbourg (France)
Registered: 2012-10-15
Posts: 70

Re: Strain in large deformation

HI,

I have made some more test and I have redo the test-case SSNP159A which is a tensile test on a rod (what I want to simulate also).
Originally, the test consists in comparing the difference between deformation PETIT/GDEF_LOG/SIMO_MIEHE based on energy calculation.

I have post-processed the strain of this test and I obtain the same difference than I have observed. The strain EPSI is lower than EPSG.

INST      EPSG      EPSI
0,00E+00	0,00E+00	0,00E+00
1,00E-01	1,46E-02	1,45E-02
2,00E-01	2,94E-02	2,90E-02
3,00E-01	4,44E-02	4,35E-02
4,00E-01	5,97E-02	5,80E-02
5,00E-01	7,51E-02	7,25E-02
6,00E-01	9,08E-02	8,70E-02
7,00E-01	1,07E-01	1,02E-01
8,00E-01	1,23E-01	1,16E-01
9,00E-01	1,39E-01	1,31E-01
1,00E+00	1,56E-01	1,45E-01
1,10E+00	1,72E-01	1,60E-01
1,20E+00	1,89E-01	1,74E-01
1,30E+00	2,06E-01	1,89E-01
1,40E+00	2,24E-01	2,03E-01
1,50E+00	2,41E-01	2,18E-01
1,60E+00	2,59E-01	2,32E-01
1,70E+00	2,77E-01	2,47E-01
1,80E+00	2,95E-01	2,61E-01
1,90E+00	3,13E-01	2,76E-01
2,00E+00	3,32E-01	2,90E-01

What I would want to obtain is the strain F (in V6.03.159) approx. LN(1+EPSI).

Maybe I'm not post processing the right parameters ?

Thanks

Stephane

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#3 2015-08-28 11:29:04

stephaneberger
Member
From: Strasbourg (France)
Registered: 2012-10-15
Posts: 70

Re: Strain in large deformation

HI,

I have understood a little bit more. In fact What I want to post process is the transformation gradient F.
This was the topic of the following discussion.  [SOLVED] Computing the deformation gradient

The issue is now how to obtain F. In this old topic, the technic described to obtain the transformation gradient is not applicable anymore. (CALC_ELEM integrated in CALC_CHAMP, ...)

Does anyone knows the technic to create and obtain this transformation gradient ?

Thanks

Stephane

Last edited by stephaneberger (2015-08-28 18:26:20)

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