Investigations of the polarization versus electric field (P-E) and strain versus electric field (ε-E) responses for “hard” Pb(Zr1−xTix)O3 piezoelectric ceramics have been performed under various uniaxial stresses (σ) and ac electrical drive fields. Investigations revealed a significant decrease in the remanent polarization of specimens with increasing σ. Subsequent calculations of the longitudinal electromechanical coupling coefficient (k33) and acoustic power density revealed significant enhancements with increasing σ.

The electromechanical performance characteristics of electrostrictive 0.9 Pb(Mg1/3Nb2/3)O3–0.1 PbTiO3 and piezoelectric 0.7 Pb(Mg1/3Nb2/3)O3–0.3 PbTiO3 ceramics have been investigated under uniaxial stress (σ). The results demonstrate that the large-signal electromechanical properties of electrostrictive ceramics are decreased with increasing σ, whereas those of the piezoelectric are increased but accompanied by significantly increased hysteretic losses.

Abstract-NUWC

There is increasing interest in relaxor ferroelectrics such as PMN-PT-La,Ba (lead magnesium niobate-lead titanate doped with lanthanum or barium) for use as high-power transducer driver materials in lightweight projector arrays. These electrostrictive materials have been shown to have induced strains an order of magnitude greater than PZT at modest electric fields. The drawback, however, is that the response of the material is dependent on frequency, prestress, temperature, and ac drive and dc bias fields. To date no measurements have been made of all these relationships for 33-mode vibration applications. In this study, using various mechanical prestresses, quasistatic room temperature measurements were made of the piezoelectric constant, d33, of the relative permittivity, ε33T/ε0, and of the short-circuit Young’s modulus, Y33E for PMN-PT-La (TRS Ceramics, Inc., 0.90 / 0.10 /1%, 31 March 1995). Electric fields of up to 2 MV/m were applied to samples (2×2×10 mm that were prestressed from 0 to 12 ksi (83 MPa). The material was found to have energy density values comparable to Terfenol-D, but its lower electromechanical coupling may compromise the useful bandwidth. [Work sponsored by the Office of Naval Research.]

Two-dimensional radiation and scattering from fluid-loaded circular elastic cylinders are addressed using two different time domain techniques. In the first method, the normal velocity of the shell is expanded as a Fourier series of angle with time-dependent coefficients whereas, in the second method, the velocity field of the shell is expressed as an in vacuo modal vector expansion with time-dependent coefficients. In both methods, the velocity coefficients are expressed as the solution of convolution integral equations and the field pressures are then expressed as a Fourier series in angle with range- and time-dependent coefficients that are convolution integrals involving the velocity coefficients. Recursive and iterative methods of solving the convolution integral equations are presented and discussed. Finally, numerical results are presented and discussed for the normal velocity and surface pressure resulting from a transient line force excitation and an incident transient plane-wave excitation.