Introduction
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Here we describe the implementation of Maxwell's viscoelasticity model (keyword VISC_MAXWELL). A variant of this model has been added for poromechanics (keyword VISC_MAXWELL_MT) which predicts the evolution of parameters with porosity according to a Mori-Tanaka homogenization model. This law was first developed and used as part of G. Mélot's thesis [:ref:`1 <RefNumPara__1521_266055922>`] on bituminous materials.

For each of these models, it is assumed that the material is isotropic. They can be used in 3D, in plane deformations (D_ PLAN) and in axisymmetry (AXIS).

In this note, the equations constituting the models and their implementation are presented.