Tabular contact

1

I’m having trouble with tabular contact–the solver does not see the contact. So I simplified my problem–I took a simple contact example problem (cubes.inp) and changed it to tabular contact. The original surface stiffness was 1e7, I changed this to (0.,0.) and (1e7,1.), which should be the same (or perhaps this is my problem, please advise). Using the original pressure loading didn’t converge, often seen in contact problems, so I changed the loading to a small displacement. The model behaves perfectly, it just ignores the contact condition.
Input file below, I apologize if there is a way to attach a file, I didn’t see it.

*NODE, NSET=Nall
1,1.000000000000e+00,1.000000000000e+00,0.000000000000e+00
2,1.000000000000e+00,0.000000000000e+00,0.000000000000e+00
3,1.000000000000e+00,0.000000000000e+00,1.000000000000e+00
4,1.000000000000e+00,1.000000000000e+00,1.000000000000e+00
5,0.000000000000e+00,1.000000000000e+00,0.000000000000e+00
6,0.000000000000e+00,0.000000000000e+00,0.000000000000e+00
7,0.000000000000e+00,0.000000000000e+00,1.000000000000e+00
8,0.000000000000e+00,1.000000000000e+00,1.000000000000e+00
9,1.000000000000e+00,5.000000000000e-01,0.000000000000e+00
10,1.000000000000e+00,0.000000000000e+00,5.000000000000e-01
11,1.000000000000e+00,5.000000000000e-01,1.000000000000e+00
12,1.000000000000e+00,1.000000000000e+00,5.000000000000e-01
13,5.000000000000e-01,1.000000000000e+00,0.000000000000e+00
14,5.000000000000e-01,0.000000000000e+00,0.000000000000e+00
15,5.000000000000e-01,0.000000000000e+00,1.000000000000e+00
16,5.000000000000e-01,1.000000000000e+00,1.000000000000e+00
17,0.000000000000e+00,5.000000000000e-01,0.000000000000e+00
18,0.000000000000e+00,0.000000000000e+00,5.000000000000e-01
19,0.000000000000e+00,5.000000000000e-01,1.000000000000e+00
20,0.000000000000e+00,1.000000000000e+00,5.000000000000e-01
21,7.500000000000e-01,7.500000000000e-01,1.000000000000e+00
22,7.500000000000e-01,2.500000000000e-01,1.000000000000e+00
23,7.500000000000e-01,2.500000000000e-01,1.500000000000e+00
24,7.500000000000e-01,7.500000000000e-01,1.500000000000e+00
25,2.500000000000e-01,7.500000000000e-01,1.000000000000e+00
26,2.500000000000e-01,2.500000000000e-01,1.000000000000e+00
27,2.500000000000e-01,2.500000000000e-01,1.500000000000e+00
28,2.500000000000e-01,7.500000000000e-01,1.500000000000e+00
29,7.500000000000e-01,5.000000000000e-01,1.000000000000e+00
30,7.500000000000e-01,2.500000000000e-01,1.250000000000e+00
31,7.500000000000e-01,5.000000000000e-01,1.500000000000e+00
32,7.500000000000e-01,7.500000000000e-01,1.250000000000e+00
33,5.000000000000e-01,7.500000000000e-01,1.000000000000e+00
34,5.000000000000e-01,2.500000000000e-01,1.000000000000e+00
35,5.000000000000e-01,2.500000000000e-01,1.500000000000e+00
36,5.000000000000e-01,7.500000000000e-01,1.500000000000e+00
37,2.500000000000e-01,5.000000000000e-01,1.000000000000e+00
38,2.500000000000e-01,2.500000000000e-01,1.250000000000e+00
39,2.500000000000e-01,5.000000000000e-01,1.500000000000e+00
40,2.500000000000e-01,7.500000000000e-01,1.250000000000e+00
*ELEMENT, TYPE=C3D20, ELSET=Eall
1, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10,
11, 12, 17, 18, 19, 20, 13, 14, 15, 16
2, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30,
31, 32, 37, 38, 39, 40, 33, 34, 35, 36
*NSET,NSET=Nfix
1,
2,
5,
6,
9,
13,
14,
17,
*BOUNDARY
Nfix,1,3
*NSET,NSET=Nfix2
23,
24,
27,
28,
31,
35,
36,
39,
*BOUNDARY
Nfix2,1,2
*SURFACE,NAME=Sslav
2, S3
*SURFACE,NAME=Smast
1, S5
*CONTACT PAIR,INTERACTION=SI1,TYPE=SURFACE TO SURFACE
Sslav,Smast
*SURFACE INTERACTION,NAME=SI1
*SURFACE BEHAVIOR,PRESSURE-OVERCLOSURE=TABULAR
0.,0.
1e7,1.
*FRICTION
0.2,1.E5
*MATERIAL,NAME=EL
*ELASTIC
210000.,.0
*SOLID SECTION,ELSET=Eall,MATERIAL=EL
*NSET,NSET=Nload
23,
24,
27,
28,
31,
35,
36,
39,

*STEP,NLGEOM
*STATIC
***DLOAD
**2, P5, 100.000000
**2, P1, 10.000000
*BOUNDARY
NLOAD,3,3,-.1
*NODE FILE
U, S
*EL FILE
S
*CONTACT FILE
CDISP
*EL FILE
U,S
*END STEP

2

This definition means that there’s zero contact pressure for zero overclosure (perfect contact) and then the pressure jumps to 1e7 for overclosure (penetration) of 1.

3

Yes, for linear contact (cubes.inp) the slope was 1e7, and I believe linear assumes zero pressure at zero over-closure. So my idea was to mimic that with a table, since the linear model did converge and see contact.

4

That’s right:

The linear pressure-overclosure behavior (Figure 130) simulates a linear relationship between the pressure and the overclosure. At zero overclosure the pressure is zero as well.

linear
linear823×530 35.5 KB

But you have to keep in mind that for tabular pressure-overclosure you specify pressure instead of slope.

5

It works for me but just for node-to-face contact not surface-to surface.
Curiously , in the manual it is shown under the node-to-face group when talking about *GAP CONDUCTANCE. That’s what made me try it and worked.

*Surface interaction, Name=Surface_interaction-1
*Surface behavior, Pressure-overclosure=Tabular

imagen
imagen950×719 51.9 KB

*Friction
0.3, 1000000
**
** Contact pairs +++++++++++++++++++++++++++++++++++++++++++
**
*Contact pair, Interaction=Surface_interaction-1, Type=Node to surface, Small sliding
Sslav, Smast

6

Yes. For Linear you provide the slope, for tabular you provide pressure / overclosure pairs (theoretically, but I can’t make it work).

7

Ah, thank you. I thought I’d tried everything, but node-to-surface I didn’t. Thank you again.