A viscoelastic cohesive zone model is employed within the framework of a finite element code to analyze a two-phase viscoelastic particle-reinforced composite material consisting of a relatively stiff aggregate embedded in a copolymer binder. The composite of interest, LX17, is noted to have a very large aggregate volume fraction and as such, aggregate grain boundaries were generated within finite element meshes along which viscoelastic cohesive zones have been embedded to model the binder. It has been observed experimentally that the majority of damage in LX17 occurs within the binder, and thus, a damage evolution law has been applied to the viscoelastic cohesive zones that is phenomenological in nature. The responses obtained for the composite from the FEM analysis are then compared to the experimental data compiled by Lawrence Livermore National Labs for various constant strain rate tests conducted by Groves and Cunningham [Tensile and compressive mechanical properties of billet pressed LX17-1 as a function of temperature and strain rate. UCRL-ID-137477. Internal report prepared for Lawrence Livermore National Laboratory, Livermore, CA].
A model is developed herein for predicting the mechanical response of inelastic crystalline solids.Particular emphasis is given to the development of microstructural damage along grain boundaries, and the interaction of this damage with intragranular inelasticity caused by dklocation dissipation mechanisms. The model is developed within the concepts of continuum mechanics, with special emphasis on the development of internal boundaries in the continuum by utilizing a cohesive zone model based on fracture mechanics. In addition, the crystalline grains are assumed to be characterized by nonlinear viscoplastic mechanical material behavior in order to account for dislocation generation and migation. Due to the nonlinearities introduced by the crack growth and viscoplastic constitution, a numerical algorithm is utilized to solve representative problems. Implementation of the model to a finite element computational algorithm is therefore briefly described. Finally, sample calculations are presented for a particular focus on effects of scale on the predicted response.polycrystalline titanium alloy with .
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