RESUMO
A constitutive material law for linear thermo-viscoelasticity in the time domain is presented. The time-dependent relaxation formulation is given for full anisotropy, i.e., both the elastic and the viscous properties are anisotropic. Thereby, each element of the relaxation tensor is described by its own and independent Prony series expansion. Exceeding common viscoelasticity, time-dependent thermal expansion relaxation/creep is treated as inherent material behavior. The pertinent equations are derived and an incremental, implicit time integration scheme is presented. The developments are implemented into an implicit FEM software for orthotropic material symmetry under plane stress assumption. Even if this is a reduced problem, all essential features are present and allow for the entire verification and validation of the approach. Various simulations on isotropic and orthotropic problems are carried out to demonstrate the material behavior under investigation.
RESUMO
The susceptibility to deformation localization of simple cubic arrangements of struts, which are a simple approximation of the micro-architecture in cancellous bone, is analyzed. The coherence between structural disorder and the tendency towards deformation localization is investigated and its relevance from a biological point of view is discussed. A systematic study on the spatial deformation distribution of regular and disordered open cell structures is carried out. To this end, finite element models are employed which account for elastic-plastic bulk material and large strain theory, and a methodology for the estimation of the degree of deformation localization is introduced.