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- ItemSolvability of an unsaturated porous media flow problem with thermomechanical interaction(Berlin : Weierstraß-Institut für Angewandte Analysis und Stochastik, 2016) Albers, Bettina; Krejc̆í, Pavel; Rocca, ElisabettaA PDE system consisting of the momentum balance, mass balance, and energy balance equations for displacement, capillary pressure, and temperature as a model for unsaturated fluid flow in a porous viscoelastoplastic solid is shown to admit a solution under appropriate assumptions on the constitutive behavior. The problem involves two hysteresis operators accounting for plastic and capillary hysteresis.
- ItemAnalysis of an operator-differential model for magnetostrictive energy harvesting(Berlin : Weierstraß-Institut für Angewandte Analysis und Stochastik, 2016) Davino, Daniele; Krejc̆í, Pavel; Pimenov, Alexander; Rachinskii, Dmitrii; Visone, CiroWe present a model of, and analysis of an optimization problem for, a magnetostrictive harvesting device which converts mechanical energy of the repetitive process such as vibrations of the smart material to electrical energy that is then supplied to an electric load. The model combines a lumped differential equation for a simple electronic circuit with an operator model for the complex constitutive law of the magnetostrictive material. The operator based on the formalism of the phenomenological Preisach model describes nonlinear saturation effects and hysteresis losses typical of magnetostrictive materials in a thermodynamically consistent fashion. We prove well-posedness of the full operatordifferential system and establish global asymptotic stability of the periodic regime under periodic mechanical forcing that represents mechanical vibrations due to varying environmental conditions. Then we show the existence of an optimal solution for the problem of maximization of the output power with respect to a set of controllable parameters (for the periodically forced system). Analytical results are illustrated with numerical examples of an optimal solution.