Abstract
This study aimed to develop a three-dimensional constitutive model of skeletal muscle that describes anisotropy of deformation, viscoelasticity, and damage evolution. Muscle tissue has a transverse isotropic structure. We describe anisotropy of the mechanical properties of muscle using a structural tensor. Free energy function of muscle is defined and decoupled into the volumetric, isochoric elastic and isochoric viscoelastic contribution. The viscoelastic part is modeled as a three-dimensional viscoelastic model that is constructed by extending one-dimensional rheological model. Based on the framework of continuum damage mechanics, the anisotropic damage of muscle tissue is described by a damage tensor of second rank. To represent the effects on muscle activity, we incorporate a contractile element into the model. The active stress is defined as a first Piola-Kirchhoff stress tensor considering the mechanism of muscle force generation.
