Thin film self-contact causing buckling

1

Hello,

I am attempting to model a thin film wrapping around a wire. I have put self-contact on the film. By this, I mean I have taken the top and bottom surfaces and used them for the contact input. However, when I enable the contact, the film buckles but if I disable the film-to-film contact, the film stays flat. Why is the film-to-film self-contact causing the buckling?

The film is ~30 microns thick, and I have 3 elements through the thickness.

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If more information is needed, please let me know!

Thanks,
Frank

2

Hi Frank,
could you share your .inp file?

4

Here ya go…let me know if you have troubles with the link

Here’s the liml file also:

5

Hi all,

I believe the problem is the contact surfaces are “seeing” each other through the thin film. Is there a way to set the contact search distance?

Thanks,
Frank

6

Here’s a much simpler file showing the problem. It’s a block with no loads but it spontaneously rolls itself up.

Is there some way to restrict the contact search as @mdsimulationgroup suggested?

selfcontact

*NODE
1,0.4,0,0
2,0.2,0,0.4
3,0.2,0,0.2
4,0.2,0.1,0.4
5,0,0,0
6,0.4,0,0.2
7,0,0.1,0
8,0,0,0.2
9,0.2,0.1,0.2
10,0,0.1,0.4
11,0.2,0.1,0
12,0.4,0.1,0
13,0.4,0.1,0.2
14,0.4,0.1,0.4
15,0.2,0,0
16,0,0,0.4
17,0,0.1,0.2
18,0.4,0,0.4
*ELEMENT,TYPE=C3D8,ELSET=FILM
1,3,6,13,9,2,18,14,4
2,5,15,11,7,8,3,9,17
3,15,1,12,11,3,6,13,9
4,8,3,9,17,16,2,4,10
*SURFACE,NAME=CONTACT_FACES(6)
1,S3
3,S3
2,S3
4,S3
*SURFACE,NAME=CONTACT_FACES
1,S5
3,S5
2,S5
4,S5
*MATERIAL,NAME=FILM
*ELASTIC,TYPE=ISOTROPIC
2500000000,0.333
*DENSITY
1300
*SOLID SECTION,ELSET=FILM,MATERIAL=FILM
*BOUNDARY
5,1,3,0
7,1,3,0
8,1,3,0
10,1,3,0
16,1,3,0
17,1,3,0
*CONTACT PAIR,INTERACTION=SI_1,TYPE=SURFACE TO SURFACE
CONTACT_FACES(6),CONTACT_FACES
*SURFACE INTERACTION,NAME=SI_1
*SURFACE BEHAVIOR,PRESSURE-OVERCLOSURE=LINEAR
1000000000000,1
*STEP,NLGEOM=YES
*STATIC
0.01,1,0,0
*NODE FILE,GLOBAL=YES
U
*END STEP
7

When I said self-contact worked fine for me in this problem, I wasn’t referring to what you or mdsimulationgroup have set up.

It’s convenient to distinguish Contact between surfaces in the same body but located in different areas and Self-contact (Contact of a surface with itself). That’s useful when you can’t predict where the contact will take place or like in this problem, very close or initially opposite.

8

Oh yes, inconsistent wording, sorry.

But that gave me an idea to define both sides as both master and slave, which solves the problem in my simplified model and sort of might help in the bigger one but the sheet is still bending strangely so I don’t trust it.