fluid cavity in a cell

[BUBAMARA]

Dear All,

After looking up for references in meat muscle cell and good ans useful suggestions from IceBreakSours, I can manage to run a 3D model for a cell wall with fluid inside using Abaqus 6.12.

I created a 3d shell deformed cylinder geometry, then in the Properties module I defined a 2 sections (one for the wall and another for the fluid) with separate element set.
I guess I use properly the mesh module: shell elements (S4R) for the wall and surface elements (SFM3D4R) for fluid section with shared nodes.
After that, I made 2 interactions: a- fluid cavity between cavity point (a reference point) and the a prestress fluid (0.05 MPa) which is the inner surface of the wall and b- contact surface between inner and outer surface wall.
Moreover, an external high pressure load of 100 MPa was applied.I would like to make mechanichal stress in the wall an then analyses the fluid. But step by step...

I expected that the cylinder geometry was reduced its radius while the pressure is applying, but I think I did not work as I expected. I would like to receive advice so I attached my inp. to explain properly what I did.

Thanks in advanced

Bubamara

 

[IceBreakerSours]

I am not sure what you are trying to do but the attached file (flat input deck) converges; whether it converges to the correct solution or not is a whole different question.

By the way, there were a few major and some minor issues with your input deck:

a) Your original boundary conditions prevented the nodes to translate in the X-Y plane, so what did you expect the applied pressure load to do?
b) "Contact pp" interaction property is not assigned between two separate surfaces but the same surface itself.
c) In general, avoid spaces in any names (node set, element set, reference points, ..)
d) Fluid behavior seems to have only density assigned to it. Usually, there is more to the behavior.

Note: I always have a hard time making regular input files work when fluid behavior is assigned but the attached is working. A flat input deck is one in which there are no parts/instances; search the documentation for more on flat input decks.

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[BUBAMARA]

Dear IceBreakerSours,

Thank for your promt answer! I´ve never heard about "flat input deck", good to know it!
I will try to answer and maybe I can fix this...

a) I load high pressure around the cylinder so as to see if it is reduced in an concentric way or deformed. I forgot to write that i am using a static general step. Maybe if I want to see the movement of my cylinder I have to change the BC, but I thought Displacement/ rotation would be the correct way to see then strain, stress and displacement as a results.
I didnt try using Static Risk or linear perturbation- buckle...

b) so I must change surface to surface by contact itself, ok
c) yes, i agree with you, I always write everything so as no to forget
d) Yes, I think maybe define material with density, eos and viscosity, right?

Finally thank you for all

Regards,
buba

 

[IceBreakerSours]

a) If you apply a symmetric pressure load to an axisymmetric geometry and BCs, what makes you think there will be any shape change (or, deviatoric deformation)? I do not see any logic here.

I am not sure what the ultimate application (i.e., the physical phenomenon) really is so I can not say why you'd need other procedures.

b) I think you misunderstood what I was saying and I am reminded of a very similar conversation we have had previously. For contact or interaction to work you need to have, at least, two surfaces that are supposed to push or slide past each other. Contact or interaction formulation may either be node-to-surface or surface-to-surface. Each formulation has its advantages and disadvantages.

c) That's a good practice but leaving spaces causes issues. I tend to use underscores and abbreviation.

d) Correct. Bulk modulus is another example. However, the hard part is deciding which behavior to choose AND how to go about choosing one, what parameters to use, etc.

I must say I am having a hard time following the logic of what you are trying to do (or have tried to do in the past). You may need supervision. Just because you can converge a model does not mean the model is correct. Results of a model can look fantastic and be total garbage at the same time.

Are you new to this forum? If so, please read these FAQ:

http://www.eng-tips.com/faqs.cfm?fid=376

http://www.eng-tips.com/faqs.cfm?fid=1083

 

[BUBAMARA]

thank you again, I am just simulating what happend in experiment the cell break and starting to flow the citoplasm....
In the literature the cell is usually simulated as a cylindrical with high pressure load
Sorry again!

Regards,

buba