Moonie transducer

The highly elastic material region of the displacement amplifier in Fig. 6.19a is locally concentrated, while the designs in Fig. 6.19b and c make use of the global elastic behaviour of metallic materials. The so-called moonie transducer in Fig. 6.19b consists of a piezoelectric disk sandwiched between two metal end caps. The ceramic is poled in the thickness direction and uses the dai mode. In this way the small radial displacement of the disk is transformed into a much longer axial displacement normal to the surface of the... 

Fig. 6.19. Mechanical displacement amplification, a Implementation with elastic hinges, b moonie transducer, c amplified piezo actuator, APA (derived from [5])...

Other devices, like the moonie transducer for example, have an even larger amplification factor, but the largest displacements could probably be obtained with the bimorphs (see Figure 11.44), to the detriment of the generated force (see Table 11.18) ... 

The best today s composite structure with 2-2-0 (air cavity) connectivity - Moonie - uses flextensional principle (Dogan et al. 1997 Fernandez et al. 1998 Xu et al. 1991 Zhang et al. 1999). Composite is made from the ceramic disc (PZT ceramics) and from two metallic plates (e.g. brass) with small air cavities (Fig. 7.29) glued together. By means of the metallic caps the hydrostatic pressure on major transducer surface is transferred to the longitudinal tension of the ceramic disc. This stress transfer will improve significantly the effective hydrostatic piezoelectric coefficient of the structure due to the different signs of ( 33 and d-n coefficients in PZT ceramics. The effective hydrostatic coefficient d could be further tuned in the value by the... 

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