The application of the variation method for the estimation of the viscosity of solid

During long time for the analysis of the mechanical oscillations of the solid samples with finite sizes and for determination of their material constants the variational method was widely used. However the calculations have been performed without considering the loss of the energy of the mechanical oscillations. In this paper the experimental study of the frequency dependence of the real and imaginary parts of the electrical admittance of the piezoelectric samples having the cube form was carried out in order to determine the resonant frequencies of the mechanical oscillations and estimate their Q-factors. Then we performed the theoretical analysis of these oscillations by the variation method and made the comparison of the theoretical data with experimental one. This allowed us to find the coefficients of viscosity, which was considered as only source of the mechanical loss for the samples of piezoceramics of PZ27, PMN34.5%PT, and PZ26.