THE DEPENDENCE OF INTERNAL MECHANICAL LOSSES ON STRESS AMPLITUDE IN COMMON PIEZOCERAMICS.
PENNSYLVANIA STATE UNIV UNIVERSITY PARK ORDNANCE RESEARCH LAB
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The internal mechanical losses at high dynamic stress levels were investigated for low loss Barium Titanate and high and low loss Lead Zirconate Titanate. The mechanical losses were described by the mechanical quality factor, Q sub M, which was measured by the conventional resonance method. High dynamic stress amplitudes were achieved through unloaded operation at resonance. Several geometries and coupling modes were employed to determine the effect of these parameters. Over a stress range of 20,000,000 Nsq M, 1Q sub M of high and low loss Lead Zirconate Titanate increased nonlinearly by factors of four and five, respectively. 1Q sub M for low loss Barium Titanate exhibited little dependence on stress amplitude over this same range. For all materials, the stress--1Q sub M relationship was independent of geometry and coupling mode. The empirically determined relationship between stress and 1Q sub M was used to predict the efficiency and internal power dissipation resulting from a resonant sound projector operated at high drive levels. The decrease in mechanical to acoustical conversion efficiency was insignificant, while the increase in internal heating may be considerably more significant. In addition, the 1Q sub M--stress relation was shown to be closely related to the relationship between electrical loss tangent and electric field. Author
- Electrical and Electronic Equipment