GAPUNI elements

Model setup
1

Hi,
I’m trying to model a pipe under movement. The pipe is modeled using isotropic hardening plasticity, considering large displacements and deformations (S3 elements are used). Displacement boundary conditions are applied to the pipe through GAPUNI elements, with the displacement applied at their control nodes. However, after running the analysis, the results show that the gap elements deform, but the pipe does not. Do you have any suggestions?

Here the link to the input file *.INP:

Thanks in advance

Jack

2

Some redundant commas here:

*STEP, NLGEOM,INC=1000,
*STATIC,
1.0000e-04,1.0000e+00,1.0000e-06,1.0000e-04

but I guess CalculiX ignores them.

To attach GAPUNI elements to the model, you may need to use *EQUATION constraints. I would try with a very simple test model first. For example:

*Node
1, 0.00000000E+000, 0.00000000E+000, 0.00000000E+000
2, 0.00000000E+000, 1.00000000E+001, 0.00000000E+000
3, 1.00000000E+001, 0.00000000E+000, 0.00000000E+000
4, 1.00000000E+001, 1.00000000E+001, 0.00000000E+000
5, 0.00000000E+000, 5.00000000E+000, 0.00000000E+000
6, 5.00000000E+000, 0.00000000E+000, 0.00000000E+000
7, 1.00000000E+001, 5.00000000E+000, 0.00000000E+000
8, 5.00000000E+000, 1.00000000E+001, 0.00000000E+000
9, 5.00000000E+000, 5.00000000E+000, 0.00000000E+000
10, 0.00000000E+000, 0.00000000E+000, 0.00000000E+000
11, 0.00000000E+000, 0.00000000E+000, 0.00000000E+000
12, 5.00000000E+000, 0.00000000E+000, 0.00000000E+000
13, 5.00000000E+000, 0.00000000E+000, 0.00000000E+000
14, 5.00000000E+000, 5.00000000E+000, 0.00000000E+000
15, 5.00000000E+000, 5.00000000E+000, 0.00000000E+000
16, 0.00000000E+000, 5.00000000E+000, 0.00000000E+000
17, 0.00000000E+000, 5.00000000E+000, 0.00000000E+000
18, 1.00000000E+001, 0.00000000E+000, 0.00000000E+000
19, 1.00000000E+001, 0.00000000E+000, 0.00000000E+000
20, 1.00000000E+001, 5.00000000E+000, 0.00000000E+000
21, 1.00000000E+001, 5.00000000E+000, 0.00000000E+000
22, 5.00000000E+000, 1.00000000E+001, 0.00000000E+000
23, 5.00000000E+000, 1.00000000E+001, 0.00000000E+000
24, 0.00000000E+000, 1.00000000E+001, 0.00000000E+000
25, 0.00000000E+000, 1.00000000E+001, 0.00000000E+000
26, 1.00000000E+001, 1.00000000E+001, 0.00000000E+000
27, 1.00000000E+001, 1.00000000E+001, 0.00000000E+000
*Element, Type=S4, Elset=Shell_part-1
1, 1, 6, 9, 5
2, 6, 3, 7, 9
3, 5, 9, 8, 2
4, 9, 7, 4, 8
*Element, Type=GAPUNI
5, 10, 11
6, 12, 13
7, 14, 15
8, 16, 17
9, 18, 19
10, 20, 21
11, 22, 23
12, 24, 25
13, 26, 27
*Nset, Nset=Internal_Selection-1_Fixed-1
1, 2, 3, 4, 6, 8
*Nset, Nset=Internal-1_Internal_Selection-1_Compression_Only-1_Master
1, 2, 3, 4, 5, 6, 7, 8, 9
*Nset, Nset=Internal_All_Compression_Only_Constraints_NodeSet
10, 12, 14, 16, 18, 20, 22, 24, 26
*Elset, Elset=Internal-1_Internal_Selection-1_Compression_Only-1_Master_S2
1, 2, 3, 4
*Elset, Elset=Internal_Selection-1_Shell_Section-1
1, 2, 3, 4
*Elset, Elset=Compression_Only-1_ElementSet-1
5
*Elset, Elset=Compression_Only-1_ElementSet-2
6
*Elset, Elset=Compression_Only-1_ElementSet-3
7
*Elset, Elset=Compression_Only-1_ElementSet-4
8
*Elset, Elset=Compression_Only-1_ElementSet-5
9
*Elset, Elset=Compression_Only-1_ElementSet-6
10
*Elset, Elset=Compression_Only-1_ElementSet-7
11
*Elset, Elset=Compression_Only-1_ElementSet-8
12
*Elset, Elset=Compression_Only-1_ElementSet-9
13
*Surface, Name=Internal_Selection-1_Compression_Only-1_Master, Type=Element
Internal-1_Internal_Selection-1_Compression_Only-1_Master_S2, S2
*Material, Name=Material-1
*Elastic
210000, 0.3
*Shell section, Elset=Internal_Selection-1_Shell_Section-1, Material=Material-1, Offset=0
1
*Gap, Elset=Compression_Only-1_ElementSet-1
0, 0, 0, -1, , 62500000000, 6.25E-05
*Gap, Elset=Compression_Only-1_ElementSet-2
0, 0, 0, -1, , 125000000000, 0.000125
*Gap, Elset=Compression_Only-1_ElementSet-3
0, 0, 0, -1, , 250000000000, 0.00025
*Gap, Elset=Compression_Only-1_ElementSet-4
0, 0, 0, -1, , 125000000000, 0.000125
*Gap, Elset=Compression_Only-1_ElementSet-5
0, 0, 0, -1, , 62500000000, 6.25E-05
*Gap, Elset=Compression_Only-1_ElementSet-6
0, 0, 0, -1, , 125000000000, 0.000125
*Gap, Elset=Compression_Only-1_ElementSet-7
0, 0, 0, -1, , 125000000000, 0.000125
*Gap, Elset=Compression_Only-1_ElementSet-8
0, 0, 0, -1, , 62500000000, 6.25E-05
*Gap, Elset=Compression_Only-1_ElementSet-9
0, 0, 0, -1, , 62500000000, 6.25E-05
*Equation
2
11, 1, 1, 1, 1, -1
*Equation
2
11, 2, 1, 1, 2, -1
*Equation
2
11, 3, 1, 1, 3, -1
*Equation
2
13, 1, 1, 6, 1, -1
*Equation
2
13, 2, 1, 6, 2, -1
*Equation
2
13, 3, 1, 6, 3, -1
*Equation
2
15, 1, 1, 9, 1, -1
*Equation
2
15, 2, 1, 9, 2, -1
*Equation
2
15, 3, 1, 9, 3, -1
*Equation
2
17, 1, 1, 5, 1, -1
*Equation
2
17, 2, 1, 5, 2, -1
*Equation
2
17, 3, 1, 5, 3, -1
*Equation
2
19, 1, 1, 3, 1, -1
*Equation
2
19, 2, 1, 3, 2, -1
*Equation
2
19, 3, 1, 3, 3, -1
*Equation
2
21, 1, 1, 7, 1, -1
*Equation
2
21, 2, 1, 7, 2, -1
*Equation
2
21, 3, 1, 7, 3, -1
*Equation
2
23, 1, 1, 8, 1, -1
*Equation
2
23, 2, 1, 8, 2, -1
*Equation
2
23, 3, 1, 8, 3, -1
*Equation
2
25, 1, 1, 2, 1, -1
*Equation
2
25, 2, 1, 2, 2, -1
*Equation
2
25, 3, 1, 2, 3, -1
*Equation
2
27, 1, 1, 4, 1, -1
*Equation
2
27, 2, 1, 4, 2, -1
*Equation
2
27, 3, 1, 4, 3, -1
*Step, Nlgeom
*Static
*Boundary
Internal_Selection-1_Fixed-1, 1, 6, 0
*Boundary
Internal_All_Compression_Only_Constraints_NodeSet, 1, 1, 0
Internal_All_Compression_Only_Constraints_NodeSet, 2, 2, 0
Internal_All_Compression_Only_Constraints_NodeSet, 3, 3, -1
*Node file
RF, U
*El file
S, E, NOE
*End step
3

Now it’s working!

Thank you so much.

Jack