# 2. Representative Volume Elements

This chapter describes the Representative Volume Element (RVE) capability, which is a multi-scale technique that uses a separate finite element model to represent the material response at a point.

The use of representative volume elements (RVEs) is a multi-scale technique in which the material response at element integration points in a reference mesh is computed using an RVE that is itself discretized with finite elements. RVEs are typically used to represent local, periodic material inhomogeneities such as fibers or random microstructures to avoid the requirement of a global mesh with elements small enough to capture local material phenomena.

In the current implementation of RVEs, periodic boundary conditions are applied to each RVE representing the deformation of a parent element and the stresses are computed in the elements of the RVE. These stresses are then volume-averaged over the RVE and the resulting homogenized stresses are passed back to the parent element.

This chapter explains how to use the RVE capability. Section 2.1 gives a detailed description of how RVEs are incorporated into an analysis. Details of the mesh requirements are delineated in Section 2.2 and the commands needed in an input file are described in Section 2.3.

Known Issue

The capability to use RVEs with reference mesh multi integration point elements is still under development and should be used with caution.