Characterization of the piezoelectric ceramic mechanical nonlinear behavior

A method to measure the mechanical nonlinear coefficients of piezoceramics with high signal excitation is presented. It consists of measuring the maximum admittance and the series resonance frequency for decreasing frequencies. At this jumping point the phase angle remains zero whatever the amplitude of the excitation is. A theoretical model previously described is used to explain the motional impedance variation due to both the nonlinear elasticity and the nonlinear mechanical losses of the piezoelectric materials. An experimental method is proposed to measure the mechanical losses tangent and the compliance variations as a function of the mean square strain in the piezoceramic. Two main coefficients characterizing the material nonlinearity are deduced. Experimental measurements have been carried out to compare the nonlinearity of different ceramic materials in longitudinal and transverse mode.