A consistent kinetics porosity (CKP) model

Brannon, R. M.
April 2000
AIP Conference Proceedings;2000, Vol. 505 Issue 1, p301
Academic Journal
A theory is presented for the mechanical response of porous media to high-strain-rate deformations. The model is "consistent" because each feature is incorporated in a manner that is mathematically compatible with all the other features. Unlike simple p-α models, the onset of pore collapse depends (via a user-adjustable yield function) on the amount of shear present. The elastic part of the strain rate is linearly related to the stress rate, except for nonlinear contributions due to the change in the elastic moduli upon pore collapse. The inelastic part of the strain rate includes parts from plastic deformation of the matrix material, pore nucleation, and phase transformations in the matrix material. The plastic strain rate is taken normal to the yield surface. Consequently, if phase transformation and/or nucleation are simultaneously occurring, the inelastic strain rate will be non-normal to the yield surface. The matrix yield stress is permitted to harden linearly. Plastic volume changes of the matrix material are assumed negligible in comparison to macroscopic volume changes associated with pore collapse. Rate dependence is allowed via an overstress model. The theory has been exercised under a rigorous array of canonical loading paths with special care to ensure sensible response upon unloading and reloading. Results show good progress toward modeling a particular 10% porous ferroelectric ceramic.


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