Thermal contact calinput warnings

1

Every time I use contacts in Prepomax version 1.3.1, I get these warnings about conductivity and specific heat not being assigned to the surface interaction card. In prepomax I do add the thermal properties to the surface interaction, which is basically the gap conductance. There is however, no option to add specific heat to the contact and it is illogical since its not a material, nor does it have mass to hold heat.

Anyone else noticed this?

*WARNING in calinput: no specific heat
was assigned to material SURFACE_INTERACTION-1 in a transient
heat transfer calculation

*WARNING in calinput: no specific heat
was assigned to material SURFACE_INTERACTION-2 in a transient
heat transfer calculation

*WARNING in calinput: no specific heat
was assigned to material TIED in a transient
heat transfer calculation

*WARNING in calinput: no conductivity
constants were assigned to material SURFACE_INTERACTION-1
in a thermo(mechanical) calculation

*WARNING in calinput: no conductivity
constants were assigned to material SURFACE_INTERACTION-2
in a thermo(mechanical) calculation

*WARNING in calinput: no conductivity
constants were assigned to material TIED
in a thermo(mechanical) calculation

2

Hi imgprojts ,

Those properties are assigned to the material each surface belongs to, like in the example below.

*NODE
1,0.0007,0.0005,0.007
2,0.0007,0.0005,0.0065
3,0.0007,0.001,0.007
4,0.0012,0.001,0.0065
5,0.0005,0,0.007
6,0.001,0,0.007
7,0.001,0.0005,0.0065
8,0.0005,0,0.0065
9,0.0007,0.001,0.0065
10,0.001,0,0.0065
11,0.0005,0.0005,0.0065
12,0.0012,0.001,0.007
13,0.0005,0.0005,0.007
14,0.0012,0.0005,0.0065
15,0.001,0.0005,0.007
16,0.0012,0.0005,0.007
*ELEMENT,TYPE=DC3D8
1,12,4,14,16,3,9,2,1
2,8,5,6,10,11,13,15,7
*NSET,NSET=temperature_nodes
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
*NSET,NSET=temperature_faces
5
6
8
10
*NSET,NSET=temperature_faces(2)
3
4
9
12
*ELSET,ELSET=Component1
2
*ELSET,ELSET=Component2
1
*SURFACE,NAME=Master-Material-1
2,S2
*SURFACE,NAME=Slave-Material-2
1,S5
*MATERIAL,NAME=Material1
*DENSITY
7850
*CONDUCTIVITY,TYPE=ISO
0.2,0
*SPECIFIC HEAT
200
*MATERIAL,NAME=Material2
*DENSITY
5000
*CONDUCTIVITY,TYPE=ISO
3,0
*SPECIFIC HEAT
10
*SOLID SECTION,ELSET=Component1,MATERIAL=Material1
*SOLID SECTION,ELSET=Component2,MATERIAL=Material2
*INITIAL CONDITIONS,TYPE=TEMPERATURE
temperature_nodes,273.15
*CONTACT PAIR,INTERACTION=SI_1,TYPE=SURFACE TO SURFACE
Slave-Material-2,Master-Material-1
*SURFACE INTERACTION,NAME=SI_1
*SURFACE BEHAVIOR,PRESSURE-OVERCLOSURE=TIED
1
*GAP CONDUCTANCE
100000,0,0
*STEP,INC=100,AMPLITUDE=STEP
*HEAT TRANSFER
0.1,1,0,0.1
*BOUNDARY
temperature_faces,11,273.15
temperature_faces(2),11,373.15
*NODE FILE,GLOBAL=YES
NT
*END STEP

3

Make sure that you specify thermal conductivity, density and specific heat for each material used in a transient thermal analysis.

4

Here is an example of the material definitions:

*Material, Name=Al6061-T6
*Density
2.7E-09
*Elastic
68900, 0.33
*Expansion, Zero=20
2.34E-05
*Conductivity
167
*Specific heat
900000000
*Material, Name=18CrMo4
*Density
7.8E-09
*Elastic
210000, 0.28
*Expansion, Zero=20
1.1E-05
*Conductivity
14
*Specific heat
440000000

** Surface interactions ++++++++++++++++++++++++++++++++++++
**
*Surface interaction, Name=Surface_interaction-1
*Surface behavior, Pressure-overclosure=Linear
350000000, 1
*Friction
0.3
*Gap conductance
11

5

I would post in the Prepomax forum. Maybe it’s a preprocessor error.

6

For me, it still seems to be related to CalculiX rather than PrePoMax. If the results look correct (heat us transferred through the interface) then maybe this warning can be ignored.

7

I don’t have an account there, but just requested one. I got another burning question at the moment, so maybe someone will answer.

8

I think you can dismiss these warnings. In verification example contact7.inp that you can find in CCX source files distribution you have same warnings. I think the reason is that surface interaction is stored in a material data block as said in the manual.

Captura de pantalla 2022-05-24 a las 17.48.14

contact7.inp follows:

**
**   Structure: two cubes on top of each other.
**   Test objective: gap conductance; heat transfer
**
*NODE, NSET=Nall
       1,  1.00000e+00,  1.00000e+00, -1.49012e-08 
       2,  1.00000e+00,  0.00000e+00, -1.49012e-08 
       3,  1.00000e+00,  0.00000e+00,  1.00000e+00 
       4,  1.00000e+00,  1.00000e+00,  1.00000e+00 
       5, -7.45058e-09,  1.00000e+00, -1.49012e-08 
       6, -7.45058e-09,  0.00000e+00, -1.49012e-08 
       7, -7.45058e-09,  0.00000e+00,  1.00000e+00 
       8, -7.45058e-09,  1.00000e+00,  1.00000e+00 
       9,  5.00000e-01,  6.41421e-01,  1.00000e+00 
      10,  6.41421e-01,  5.00000e-01,  1.00000e+00 
      11,  6.41421e-01,  5.00000e-01,  1.20000e+00 
      12,  5.00000e-01,  6.41421e-01,  1.20000e+00 
      13,  3.58579e-01,  5.00000e-01,  1.00000e+00 
      14,  5.00000e-01,  3.58579e-01,  1.00000e+00 
      15,  5.00000e-01,  3.58579e-01,  1.20000e+00 
      16,  3.58579e-01,  5.00000e-01,  1.20000e+00 
*ELEMENT, TYPE=C3D8I, ELSET=Eall
     1,     1,     2,     3,     4,     5,     6,     7,     8
     2,     9,    10,    11,    12,    13,    14,    15,    16
*NSET,NSET=Nfix1 
1, 
2, 
5, 
6, 
*NSET,NSET=Nfix2 
11, 
12, 
15, 
16, 
*BOUNDARY
Nfix1,1,3
Nfix2,1,3
*MATERIAL,NAME=EL
*ELASTIC
210000.,.3
*DENSITY
7.8E-9
*EXPANSION
60.E-6
*CONDUCTIVITY
1.E-2
*SPECIFIC HEAT
1.E+3
*SOLID SECTION,ELSET=Eall,MATERIAL=EL
*ELSET,ELSET=Emast
1
*NSET,NSET=Nslav
9,10,13,14
*SURFACE,NAME=Smast
Emast,S5
*SURFACE,NAME=Sslav,TYPE=NODE
Nslav
*CONTACT PAIR,INTERACTION=SI1,TYPE=NODE TO SURFACE
Sslav,Smast
*SURFACE INTERACTION,NAME=SI1
*SURFACE BEHAVIOR,PRESSURE-OVERCLOSURE=LINEAR
1.E7,3.
*GAP CONDUCTANCE
1.
*INITIAL CONDITIONS,TYPE=TEMPERATURE
Nall,0.
*STEP
*HEAT TRANSFER
.0001,.006
*CONTROLS,PARAMETERS=TIME INCREMENTATION
100,100,9,100,10,4,,5
.25,.5,.75,.85,,,1.5,,
*BOUNDARY
Nfix1,11,11,0.
Nfix2,11,11,1000.
*NODE PRINT,NSET=Nall
NT
*END STEP
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