STABLE PHENOMENOLOGICAL DESCRIPTIONS OF ELECTROMECHANICAL CREEPING IN POLYCRYSTALLINE FERROCERAMICS

M. I. IDIART; C. J. BOTTERO

Milan

Congreso; 25th International Congress of Theoretical and Applied Mechanics; 2021

Ferroceramics display nonlinear creep effects under both electrical and mechanical loadings at room temperature. These effects have been described by certain phenomenological theories that additively decompose the strain and the dipole density into reversible parts associated with elasticity and dipole perturbations, and irreversible parts associated with dipole switching, and generate constitutive relations from suitably chosen free-energy densities and dissipation potentials. It is shown in this work that the creeping responses predicted by those theories can be unstable, and it is argued that these instabilities are unphysical artifacts of the theories arising from the use of non-convex free-energy densities. Motivated by these findings, a novel class of convex free-energy densities is proposed and employed to generate stable responses emulating the essential features of ferroelectric creeping.