CURVILINEAR PIEZOELECTRIC ACTUATORS OF BENDING TYPE WITH CONTROLLED CROSS-SECTIONAL SHAPE

A new principle of functioning of a bending-type piezoelectric actuator using the effect of interaction of its initial curvature and controlled piezoelectric transformation of the shape of its cross-section is proposed. As a result, the bending of the longitudinal axis of the curvilinear actuator does not arise from its direct bending (as is realized according to the traditional bimorph type scheme), but indirectly from a controlled change in the shape - a bending of its cross-section in the transverse plane. Piezoelectric transformations of cross-section are carried out through a "bimorph" bend of its initial rectangular shape with transition of single-layer cross-section to convex "arched" and two-layer to biconvex tubular - "lentil" forms. Such transformations of the cross section increase the axial moment of inertia and, as a result, cause the appearance in the cross sections of the considered curvilinear rod PlatCB (Plate Curvilinear Bimorphic) or TubCB (Tubular Curvilinear Bimorphic) actuators of unbalanced bending moments, the action of which is partially straightening, i.e. reduces the value of initial curvature of the longitudinal axis of the rod actuator in the working longitudinal plane. Mathematical models of deformations of PlatCB, TubCB actuators have been developed as the interaction of two related processes: "active" is a controlled piezoelectric transformation of the cross-section shape, and "reactive" is a transition of the actuator to a new equilibrium curvilinear shape in order to increase its bending characteristics - maximum displacements and blocking forces produced by the actuators in the working longitudinal plane. Numerical results are presented and regularities of influence on the resulting bending characteristics of various structural parameters are revealed: initial curvature, width and thickness of initial rectangular sections of PlatCB, TubCB actuators. It was found that the resulting bending characteristics for the TubCB actuator are most significantly improved with the transformation of its thin two-layer rectangular section to a biconvex "lentil" - tubular shape.