ABSTRACT
In the fast developing world, the use of smart materials becomes more and more important to implement sophisticated functions of the designed device starting from the materials level. In a common defi nition [1], the smart materials diff er from the ordinary materials in that they can perform two or several functions sometimes with a useful correlation or feedback mechanism between them. In the case of piezoelectric or electrostrictive materials, it means that the same material can be used for both sensor and actuator functions. A piezoelectric or an electrostrictive sensor converts mechanical variable (displacement or force) into a measurable electrical quantity by means of a direct piezoelectric or electrostrictive eff ect. Alternatively, the actuator converts the electrical signal into useful displacement or force. Typically, the term transducer is used to describe actuator (transmitting ) and sensor (receiving) functions. Since piezoelectrics
and electrostrictors inherently possess both direct (sensor) and converse (actuator) eff ects, they can be considered as smart materials in the sense indicated above. Th e degree of smartness can vary in piezoelectric and electrostrictive materials: it is very oft en that the merely smart material (only sensor and actuator functions) can be engineered into a “very smart” (i.e., tunable) device or even into an “intelligent structure” where the sensor and actuator functions are mutually connected via integrated processing electronics, sometimes with learning function.
