Use the Cell Periodicity node to model a unit cell representing a large repetitive structure. Periodic boundary conditions will be used on the outer boundaries of this unit cell.

Select a Periodicity type — Free expansion, Average strain, Average stress, or Mixed.

With the Free expansion periodicity type, the unit cell is allowed to expand freely in a periodic manner. This option is useful to determine the thermal expansion or hygroscopic swelling coefficients of a heterogeneous unit cell. Select Calculate average properties — None, Coefficient of thermal expansion, or Coefficient of hygroscopic swelling.

The Average strain periodicity type allows to derive homogenized elastic properties of media with a periodic structure, such as a perforated plates, porous media or composites structures. In this case, you have to examine six load cases in 3D. Enter values or expressions for the components of the Average strain tensor εavg. In a geometrically nonlinear analysis, the average strains are interpreted as Green-Lagrange strains.

Select Calculate average properties — None, Elasticity matrix, Standard, or Elasticity matrix, Voigt.

The Average stress periodicity type allows to derive the homogenized compliance matrix of media with a periodic structure. Enter values or expressions for the components of the Average stress tensor σavg. In a geometrically nonlinear analysis, the stresses are interpreted as Second Piola-Kirchhoff stresses.

Select Calculate average properties — None, Compliance matrix, Standard, or Compliance matrix, Voigt.

With the Mixed periodicity type, enter either the average strain or average stress tensor components.

For all the options of Periodicity type enter the Cell volume — Solid, Void volume fraction, or User defined. The Solid option computes the volume of the RVE from the domains selected by the Cell Periodicity feature. The Void volume fraction option, which default is set to 0, scales the RVE volume when there are voids not selected as domains. The User defined option, which default is 1 m3, allows to enter the volume of the RVE directly.

The variable item.vol consider the whole volume of the domains selected under Cell Periodicity feature when computing average strains and stresses, adjust for porosity or scale the volume if needed.

This section is available when Periodicity Type is Average Strain or Average Stress.

Click the Create button to add the features needed to perform a complete evaluation of the average material stiffness for a homogenized material. The following changes will be done to the model:

To display this section, click the Show button () and select Advanced Physics Options.

Physics tab with Solid Mechanics selected:
Domains>Cell Periodicity