Formulation and implementation of stress-driven and/or strain-driven computational homogenization for finite strain

In this paper, we present a homogenization approach that can be used in the geometrically nonlinear regime for stress-driven and strain-driven homogenization and even a combination of both. Special attention is paid to the straightforward implementation in combination with the finite-element method. The formulation follows directly from the principle of virtual work, the periodic boundary conditions, and the Hill-Mandel principle of macro-homogeneity. The periodic boundary conditions are implemented using the Lagrange multiplier method to link macroscopic strain to the boundary displacements of the computational model of a representative volume element. We include the macroscopic strain as a set of additional degrees of freedom in the formulation. Via the Lagrange multipliers, the macroscopic stress naturally arises as the associated forces' that are conjugate to the macroscopic strain displacements'. In contrast to most homogenization schemes, the second Piola-Kirchhoff stress and Green-Lagrange strain have been chosen for the macroscopic stress and strain measures in this formulation. The usage of other stress and strain measures such as the first Piola-Kirchhoff stress and the deformation gradient is discussed in the Appendix. Copyright (c) 2015 John Wiley & Sons, Ltd.