Lagrangian effective material constants for the modellng of thermal behavior of acoustic waves in piezoelectric crystals I. Theory
Résumé
After some necessary recalls on the non linear theory of thermoelectroelasticity in piezoelectric crystals, asserting the need of constitutive equations which derive from a rotationally invariant energy function, this papers presents the governing equations for a small vibration superimposed on a bias originated by a slow and homogeneous temperature variation from a well defined reference state. Thereafter, the authors define the effective coefficients appearing in the linearized incremental dynamic balance equations for linear momentum and electrical charge in Lagrange configuration, not omitting associated bondary conditions. The main features of those coefficients are discussed and explicit relations with more conventionally defined coefficients are given. Determination of numerical values of the proposed effective coefficients and examples of their use in the higher order modeling of static frequency -- temperature characteristics of either bulk acoustic waves or surface acoustic waves devices are given in a companion paper.
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