A new type of piezoelectric plate actuator for ultrasonic linear motors has been developed. These new piezoelectric actuators use the principle of asymmetric resonant excitation of the piezoceramic plate in a special resonant mode consisting of a standing two-dimensional extensional wave in a piezoceramic plate. The behavior of the actuator has been simulated with finite-element method (FEM) software and the simulation results checked with single-point contact measurements on the surface of the actuator. This paper describes this work and closes by describing the new ultrasonic translation stages based on this design.
The anisotropy of fracture toughness of PZT‐ and barium titanate‐based piezoelectric ceramics was studied using doubletorsion and indentation methods. The influence of elastic anisotropy and the piezoelectric effect in calculating the Kc value are discussed. The fracture toughness in the polarization plane is greater than that in the perpendicular plane. A model is suggested to explain the observed anisotropy; it is based on assumption of a stress‐induced domain reorientation zone near the crack tip.
Fracture testing of ceramics by using controlled crack growth is proposed to allow study of crack‐kinetics behavior under a given loading history. A computer‐aided, real‐time data acquisition system improves the quality of crack‐growth parameters obtained in a simple, single‐specimen bend test. Several ceramic materials were tested in the present study: aluminum nitride as a linear‐elastic material; and alumina and yttria‐stabilized zirconia, both representative of ceramics with microstructure‐dependent nonlinear fracture properties. Ambiguities in the crack‐growth diagrams are discussed to show the importance of accounting for crack‐growth history in correctly describing nonequilibrium fracture behavior.
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