Effect of thermal depolarization and thermomechanical coupling on harmonic oscillations and dissipative warming of conical piezoceramic shells

Abstract

The thermoelectromechanical behavior of thick-wall elements in the form of plates and cylindrical shells formed from piezoactive viscoelastic materials subjected to harmonic deformation, including depolarization of the material due to a warming temperature close to critical T c (Curie point) has been examined in [2, 3, 4, 51. Experimental data [1, 6] indicate that for piezoceramic temperatures close to T c, the piezomoduli decrease precipitously. The values of the mechanical flexibilities and dielectric constants beyond the Curie point are not, as a rule, known. The phenomenon of depolarization in the region of a body where the warming temperature attains or exceeds Tc, is therefore modeled by zeroing the piezomoduli. The flexibilities and dielectric constants are set equal to their value when T=Tc. This paper examines the problem of the axisymmetric electromechanical oscillations and the dissipative wanning of a conical shell with a half-span angle or, which is fabricated from a piezoceramic polarized throughout its thickness h in two opposing directions relative to the median surface. Convective heat exchange with the surrounding medium takes place on the contour and conical surfaces. Oscillations are excited by the harmonic difference in the electric potential V o cos cot applied to the electrified conical surfaces. The dissipative properties of the piezoceramic are described by the concept of complex electromechanical characteristics, the read and imaginary components of which are functions of temperature. Electrical-load and heat-exchange conditions are considered such that the temperature of dissipative wanning in certain regions of the shell may reach the critical value T c, for which depolarization of the piezoceramic is initiated. The solution of the stated problem involving the oscillations and wanning of a conical piezoshell is described by a system of coupled equations of shells of revolution [3], which include equations of axisymmetric harmonic oscillations