Characterization of the mechanical nonlinear behavior ofpiezoelectric ceramics

摘要

A characterization of the nonlinear behavior with high signalnexcitation in piezoceramic resonators was carried out. The behavior ofnpower devices working at resonance, in which high strains are involved,nis explained. A theoretical model previously described is used tonexplain the motional impedance variation proportional to the square ofnthe motional current. This impedance increase ΔZ is independent ofnthe frequency and explains: the nonlinear elasticity that produces thenA-F effect, the nonlinear mechanical losses that increase greatly closento the resonance, and the hysteresis phenomenon produced with frequencynsweeps. Different methods for measuring the mechanical nonlinearncoefficients of piezoceramics with high signal excitation are presented.nAn experimental method is proposed to measure the mechanical lossntangent and the compliance variations as a function of the mean squarenstrain in the piezoceramic. This consists in measuring the maximumnadmittance and the series resonance frequency for downward frequencies.nAt this jumping point, the phase angle remains zero whatever thenamplitude of the excitation. Two main coefficients characterizing thenmaterial mechanical nonlinearity are deduced. Experimental measurementsnwere carried out to compare the nonlinearity of different ceramicnmaterials in longitudinal and transverse mode