MATERIAL CONSTANTS OF TRIGONAL SYNGONY PYROPIEZOELECTRICS UNDER THE INFLUENCE OF PHYSICAL FIELDS OF DIFFERENT NATURE

Abstract

The article studies the previously proposed model of a prestressed thermoelectroelastic medium of class 3m trigonal syngony under the action of initial mechanical stresses, an electrostatic field at a given temperature. The model is based on linearized constitutive relations constructed within the framework of sequential linearization of nonlinear equations of continuous medium electrodynamics. Linearization is carried out within the framework of superimposing small deformations on final ones with preservation of high-order terms in the equation of state. When constructing a model based on the use of linearized constitutive relations, it is taken into account that it is impossible to use the Voigt notation, which is usual for the natural state, in this case. Within the framework of this model, the behavior of the material constants of a thermoelectroelastic medium of class 3m trigonal syngony is studied. It is shown that, unlike electrical and mechanical effects, the thermal factor linearly affects the constants: preheating leads to an increase in the elastic constants, cooling – to their decrease. The effect on the piezoelectric constants is also linear, but more complex: some constants increase, others decrease. In this case, the possibility of using the Voigt notation, which is usual for the natural state, is preserved. Mechanical and electrical effects lead to the separation of constants coinciding in the natural state; in this case, the use of the Voigt notation, which is usual for the natural state, is impossible. The decomposed constants depend nonlinearly on mechanical stresses, but linearly on the electrostatic field. The nature and magnitude of the change in the constants depend both on the type of mechanical action and on the polarity of the electrostatic field. It should be noted that in this work, the effect of minor thermal effects was investigated. The effect of high initial temperatures significantly changes the properties of the material, but goes beyond the linearized theory and requires the use of nonlinear relationships.