Modelling Hyper-Elastic with Fluid interaction

JMB365

Hello,

I am trying to model a vertical hollow metal tube closed on both ends by caps made of a hyper-elastic material. The entire hollow space inside this tube is filled with an incompressible fluid. The model is in 3D using tetrahedral elements. A downward force is applied to the upper hyper-elastic cap. While the lower hyper-elastic cap is free to bulge outward and down. Is there an example comm file showing how a non-linear static problem can be solved using Code-Aster?

Of course, one might suggest modeling this as an axi-symmetric 2D model, but my actual problem is more complex than my simplified model's description. The attached image file with half the tube cut away, shows what I described in the paragraph above. Any suggestions or hints will be very appreciated.

Regards,

JMB

Attached file:
Tube1.png, 48603kb

JMB365

Hello!

Any comments from anybody? Users, developers...?

JMB

ThomasDESOZA

Hi,

I do not see any problems regarding the modelling of such a system except maybe for the fluid part : how do you plan to model it ?

Also the system as you describe it seems to have a rigid body motion (translation of the caps along the axis of the tube), how do you plan to treat this point ?

Otherwise everything should be OK with Aster : hyper-elastic material is described with ELAS_HYPER constitutive law in Code_Aster (coefficients for the material are C10,C01 and C20. C10 is mandatory and if alone yields a Neo-Hookean material).

Contact should be taken into account.

Good luck,

TdS

JMB365

Thomas DE SOZA wrote:
Hi,

I do not see any problems regarding the modelling of such a system except maybe for the fluid part : how do you plan to model it ?

Also the system as you describe it seems to have a rigid body motion (translation of the caps along the axis of the tube), how do you plan to treat this point ?

Otherwise everything should be OK with Aster : hyper-elastic material is described with ELAS_HYPER constitutive law in Code_Aster (coefficients for the material are C10,C01 and C20. C10 is mandatory and if alone yields a Neo-Hookean material).

Contact should be taken into account.

Good luck,

TdS

Thanks for the feedback. The outer surface of the tube will be fixed in DX,DY,DZ, which I have not show in the picture. The ELAS_HYPER is not a problem. I am familiar with it and have run it before. I was not sure if such a fluid mechanics problem combined with ELAS-HYPER elements was even possible in CodeAster. Now that you tell me it is possible, I will embark on that journey.

The part I am not sure about is the fluid in between. I have meshed it with solid (tetrahedral) elements for now, but do not know what behavior to give it... I was hoping you (or somebody) could make suggestions or give hints! ;)

Regards,

JMB

Ect

JMB365 wrote:
The part I am not sure about is the fluid in between. I have meshed it with solid (tetrahedral) elements for now, but do not know what behavior to give it... I was hoping you (or somebody) could make suggestions or give hints! ;)

My 2 cents:

- an ultra soft elastic material with NU=0.499 and 3D_INCO should make it if the foreseen displacements will not lead to extreme mesh distortion,

- hydrostatic pressure (no fluid mesh ala Abaqus) driven by the cavity volume change, would require extensive python programming and small load increments

JMB365

Ect wrote:
My 2 cents:

- an ultra soft elastic material with NU=0.499 and 3D_INCO should make it if the foreseen displacements will not lead to extreme mesh distortion,

- hydrostatic pressure (no fluid mesh ala Abaqus) driven by the cavity volume change, would require extensive python programming and small load increments

Thank you for the hints! The first suggestion is quite straightforward. I will try that. I will read and try to understand (limited though I am by language) CodeAster's 3D_INCO command. I will have extreme mesh distortion, an unfortunate outcome of many analyses with hyper-elastic problems.

I was hoping that CodeAster would have a fluid element (like as you mentioned Abaqus does). I am reading about 3D_FLUIDE. Does anybody have any caveats or advice to offer regarding the use of these combined with ELAS-HYPER. Anybody have other ideas?

Regards,

JMB

JMB365

Hello,

How can I get access to the document:

[V8.03.100] FDNV100 - Ballottement dun réservoir deau avec paroi déformable élastique (accès restreint)

Regards,

JMB

JMB365

Hello,

Any answer please? Thanks

JMB

rthhert

http://www.code-aster.org/V2/doc/v9/man_v/v8/v8.21.101.pdf

may be of some help to you

also translation here

http://translate.google.com/translate?hl=en&sl=fr&tl=en&u=http%3A%2F%2Fwww.code-aster.org%2FV2%2Fdoc%2Fv9%2Fman_v%2Fv8%2Fv8.21.101.pdf

I have never used code aster but after reading some of the documentation I think that 3d_FLUIDE is similar to FLUID80 Fluid30 in ansys and there are plenty of examples with those ansys elements similar to what you propose

please do let us know how you get on, but not till the end of the year.

good luck

Tom

JMB365

rthhert wrote:
http://www.code-aster.org/V2/doc/v9/man_v/v8/v8.21.101.pdf

may be of some help to you, also translation here

http://translate.google.com/translate?hl=en&sl=fr&tl=en&u=http%3A%2F%2Fwww.code-aster.org%2FV2%2Fdoc%2Fv9%2Fman_v%2Fv8%2Fv8.21.101.pdf

I have never used code aster but after reading some of the documentation I think that 3d_FLUIDE is similar to FLUID80 Fluid30 in ansys and there are plenty of examples with those ansys elements similar to what you propose

please do let us know how you get on, but not till the end of the year.

good luck

Tom

Hello Tom,

Thanks for the tips. I will read those docs. But I am a little puzzled by the "not till the end of the year" statement. Would you kindly explain...

Regards,

JMB

rthhert

oops, typo...,

I meant to say, "I will be doing similar problems but not till the end of the year"

Tom

ArchibaldArchambaud

Dear JMB365,

Here is the test case you asked for. Sorry for the delay....

Attached file:
FDNV100.tgz, 1125904kb