Periodic boundary conditions (PBCs)

1

Hi everybody!

I have a .inp file where I need to change the BCs to PBCs. Can you help me with this?
It should be mentioned that there are 14000 codes for nodes and Equations before the code below.

** Section: Section-EFIBER
*Solid Section, elset=EFIBER, material=GLASS
1.,
** Section: Section-EMATRIX
*Solid Section, elset=EMATRIX, material=EPOXY
1.,
**
** MATERIALS
*Material, name=EPOXY
*Elastic
** Young’s modulus, Poisson ratio
4.8e+09, 0.35
*expansion
** CTE
45.e-6
*Material, name=GLASS
*Elastic
7.0e+10, 0.2
*expansion
5.e-6
**
*INITIAL CONDITIONS,TYPE=TEMPERATURE
Nall, 273.
**
*STEP
*STATIC
1., 1.
**
*BOUNDARY,
** node, dof, value
1, 1, 0.
1, 2, 0.
1, 3, 0.
*BOUNDARY,
2001, 1, 0.
2001, 3, 0.
**
1348, 1, 0.
1348, 2, 0.
1348, 3, 0.
**
10001, 3, 0.
**
*cload
** node, dof, value
2001, 2, 1.7675E+6
**
*NODE PRINT, nset=nout
u
*NODE FILE
U
*EL FILE
s, e
*END STEP
**
** temp. load
**
*STEP
*STATIC
1., 1.
**
*BOUNDARY,
** node, dof, value
1, 1, 0.
1, 2, 0.
1, 3, 0.
*BOUNDARY,
2001, 2, 0.
2001, 3, 0.
**
1348, 3, 0.
**
**
*TEMPERATURE
** node, value
Nall, 274.
**
*NODE PRINT, nset=nout
u
*NODE FILE
U
*EL FILE
s, e
*END STEP
**

2

Hi
Dr. Martin Kraska has an script for brick-shaped RVE models on his Github. Never tested.

“This script creates equations for periodic boundary conditions of a brick-shaped RVE. We assume that it’s corners are at (0,0,0) and (lx,ly,lz).The dimensions are determined from the nodal co-ordinates.”

3

Thank you, but I just need to change the BCs code below. I know that the current BC is not Periodic.

*BOUNDARY,
** node, dof, value
1, 1, 0.
1, 2, 0.
1, 3, 0.
*BOUNDARY,
2001, 1, 0.
2001, 3, 0.
**
1348, 1, 0.
1348, 2, 0.
1348, 3, 0.
**
10001, 3, 0.

4

Regular symmetry BCs are not enough to represent periodic BCs. You should use linear equation constraint (*EQUATION). The same is done in Abaqus. This article explains it well: https://imechanica.org/files/pbc.pdf