The bonded piezoelectric materials act as actuators in this case (converse piezoelectric effect) to help dissipate the vibrational energy. In both these methods, mechanical/structural vibrational vibrations can be attenuated by damping of energy in constrained viscoelastic layers. They can also be bonded to stiff constraining layers that are adhered to host structures by means of thin viscoelastic layers. Instead of bonding the piezoelectric materials directly to the host structures, they can be bonded via thin viscoelastic layers. However, complications may arise in manufacturing and electrical insulation. Besides, the adhesives necessary for surface bonding/gluing are not needed. On the other hand, the embedding leads to a strong mechanical and electrical coupling between the piezoelectric material and the host structure. The advantage in surface bonding is that it is easy to access and maintain, but it brings the disadvantage of being susceptible to damage during service. Piezoelectric materials can be bonded/glued to surfaces of host structures or embedded within them. In the converse action, when a tensile force is applied along the axis normal to the poling one, a voltage of the same polarity of poling is generated in the direction of poling. When the polarity is changed, the effect is opposite, i.e., the ceramic contracts in the poling direction and expands in the perpendicular one. After the poling is complete, the ceramic expands in the poling direction and contracts in the perpendicular direction when a voltage less than the poling voltage is applied.
This process is called poling, causing the ceramic to have a permanent net polarization, which leads to both direct and converse piezoelectric effects in the material. The application of a strong DC electric field has the effect of aligning most unit cells parallel to the applied field. As a result, the unit cells are elongated in one direction and an electric dipole moment is generated within the unit cell. The material is then cooled down, during which the ceramic becomes ferroelectric and its unit cells change from cubic to tetragonal structure. At this high temperature, the resulting PZT powder is mixed with a binder and is sintered into desired shapes, some of which are: plate, thin disk, ring, and tube. They are manufactured by mixing lead, zirconium and titanium oxide powders in certain proportions and heating the mixture to about 1000 oC. These ceramics are chemically inert, immune to moisture and can be manufactured in different sizes and shapes. Piezoelectric ceramic materials like PZT are made from poly-crystalline ceramics, which are versatile and can easily fit into specific applications. Mehmet Sunar, in Comprehensive Energy Systems, 2018 2.22.5.1 Design and Manufacture
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