A Comparison of the Deformations of Various Piezoceramic Actuators

Abstract

Presented are the predicted manufactured shapes and actuated shape changes of metal-based THUNDER TM -like actuators and fiber-reinforced-polymer-based LIPCA-C1and LIPCA-C2-like actuators. As these actuators, which are laminated in nature, are manufactured flat at an elevated temperature and then cooled for use, they deform out of plane as they cool, resulting in residual curvatures. The development of the residual curvatures are predicted with a 23-term Rayleigh-Ritz model based on energy principles. Because of the large out-of-plane deformations due to cooling, geometrically nonlinear effects, in the sense of von Ka´rma´n, are included. Actuated curvatures due to activation of the piezoceramic material are also predicted. The behaviors of plate-and beam-like actuator geometries over a range of sidelength-to-thickness ratios are investigated. Finite element results for selected geometries are presented for comparison with the 23-term model. The results show that geometrically nonlinear effects are quite strong for THUNDER and LIPCA-C2 plate-like actuators, resulting in the potential for more than one cooled shape for THUNDER actuators and of a sudden change in the actuated shape, referred to here as snap-through, for LIPCA-C2 actuators. For the LIPCA-C1 actuators, and the beam-like geometries of the other two actuators, geometrically nonlinear effects are not as strong. Residual stress predictions within the cooled and activated actuators are also presented. Though the actuators considered are specific in design, the results can be interpreted more generally and point to the fact that a wide range of behaviors can be expected from geometrically nonlinear effects interacting with variations in materials (i.e., metals vs. fiber-reinforced materials) and geometry (i.e., platelike vs. beam-like and sidelength-to-thickness ratio).

Understanding piezoelectric composite–based actuators with nonlinear and 90° domain walls effects

“…The 2D model was enough to describe the actuation behavior because the width of these actuators is narrow so that the width will not influence to the actuation response. If the actuators are a beam-like type actuator, that is, aspect ratio is less than 0.33; the actuator will not exhibit a snap-through effect during actuation (Aimmanee and Hyer, 2006). Note that all the actuators used in this study possessed an aspect ratio of 0.32.…”

“…The actuation displacement of the LIPCA is very large, that is, larger than its thickness; therefore, geometric nonlinearity was taken into account in these analysis. The geometrically linear theory has been shown to be incapable to predict the actuation displacement of such actuators when actuated at large input electric potential (Aimmanee and Hyer, 2006). This is because the geometrically linear theory does not take into account the out-of-plane displacement, along the out-of-plane direction such as a z-direction, with respect to the in-plane direction such as x and y directions, that is, all the underlined terms in equation (1).…”

“…This is because the geometrically linear theory does not take into account the out-of-plane displacement, along the out-of-plane direction such as a z-direction, with respect to the in-plane direction such as x and y directions, that is, all the underlined terms in equation (1). To take into account the out-of-plane displacement, w 0 , with respect to the in-plane direction, the two sub-models must take geometric nonlinearity into account (Aimmanee and Hyer, 2006). The reference surface strains, ε x 0 , ε y 0 , and γ xy 0 , taking into account the geometric nonlinearity are shown in equation (1) (Aimmanee and Hyer, 2006).…”

Design to improve the capacitive contact quality in piezoelectric actuation

“…From the formula of the deflection of piezoelectric actuators (2) [1,3,4] and the bending of a beam (3), we can superpose the deflections and get out the equation governing the behaviour. The expression of tip deflection due to piezoelectric actuation is given by: (2) with E e the Young modulus of the elastic layer, E p the Young modulus of the PZT layer, t e the elastic layer thickness, t p the piezoelectric layer thickness, d 31 the electromechanical coefficient, V the actuation voltage.…”

“…Since the air gap has a negative influence on the capacitance; we are interested in a design that compensates the deformation coming from the technological process (initial stress …) and from the bending applied to the plate [2]. The best solution would be a pressure applied on the surface of the plate that flattens it on the electrode as in electrostatic actuation.…”