Smart Materials & Structures

Biography

Biography: Jacek Przybylski

Abstract

Flextensional actuators belong to a group of piezoelectric transducers of great practical importance. A typical flextensional transducer consists of a piezoceramic connected to a flexible structure which amplifies and changes the direction of the generated piezoceramic displacement. The process of designing a flextensional actuator leads to the construction of such a flexible structure, coupled to a piezoceramic element or piezoceramic stack, which maximizes the output displacement and generative force as a result of piezoelectric actuation. Hence, two goals must be well balanced during the development of new actuators, i.e. high output displacement, which requires adequate high structure compliance, and high generative force, which is obtainable for high structure stiffness. Topology optimization is a technique used for designing flextensional actuators which ensures fulfilling those two opposing requirements. Piezoelectric actuators combined with a hinge lever mechanism and described by Uchino exemplify such structures. In this paper, the effects of hinge flexibility, material properties and dimensional changes on the output displacement and the generative axial force of the flextensional transducer have been investigated. The actuator is composed of two rectilinear or initially deflected beams placed equidistantly from a centrally located piezoceramic rod. A link with a hinge strengthened by a rotational spring placed symmetrically on both ends of the structure is adopted as a flexible joint. A simplified analytical mathematical model has been developed on the basis of the stationary value of the total potential energy principle with the application of Bernoulli-Euler theory and von Karman non-linear strain-displacement relations. The numerical calculations show that the output displacement and internal axial force generated by both the externally distributed load and the electric field application can be manipulated easily by changing the actuator material, the distance between the beams and the rod, the amplitude of beam initial displacement as well as the flexibility of the hinge. To keep the piezoelectric rod compressed during the operation, the application of structure prestressing has been considered in the model and computations. The obtained results may have applications in the design process of such actuators.