An energy-based constitutive model for elastoplastic anisotropic solids subject to damage
Description
An energy-based constitutive model for anisotropic elastoplastic materials has been developed in this dissertation. The model is restricted to small strains. It accounts for elastic degradation due to damage microcracking. Further, it treats plastic deformation utilizing strain-hardening plastic yield criteria suitable for anisotropic materials The Cauchy stress can be additively decomposed into six eigenstresses, each proportional to corresponding eigenstrains. This decomposition allows for calculation of six independent, noninteracting strain energy modes A material damage state is characterized by a symmetric, second-rank tensor. Damage is postulated to occur when any of the six energy modes reaches a threshold value. Damage growth rate is formulated in terms of the energy domains Anisotropic plasticity is modeled using the eigenstresses. The yield conditions are formulated from the second invariants of the eigenstresses. This criterion reduces to that of von Mises upon specialization to isotropic symmetry. An associated flow rule is developed for the general case The elastoplastic damage model shows good agreement when compared to uniaxial data for transversely isotropic paperboard Material failure is postulated to occur when any of the energy modes reaches a critical value. The failure model shows good agreement with unidirectional off-axis tensile rupture of Douglas Fir. Further, the criterion shows good agreement with biaxial failure data for paperboard