Structurally Graded Monolithic Piezoelectric Actuators, Modeling and Optimization with FEM

In this work, novel structurally graded piezoelectric disc actuators are proposed. The monolithic gradient actuators had nonuniform thickness profiles, which caused distribution of the electric field and resulted in bending of the discs. The geometry and clamping conditions of the actuators were varied and the displacement properties were optimized using ATILA and Comsol Multiphysics finite element modeling (FEM) softwares. The material parameters of commercial PZT-5H were used in the modeling of the actuators — 25 mm in diameter with an original thickness of 0.5mm. Additional steel layers with different thicknesses were introduced under the actuators in `unimorph-fashion' in order to study their effect on the displacements and stresses of the actuators. The modeling results showed that the bending of the monolithic actuators could be realized without any additional passive layers and also that the utilization of clamping further improved the displacement capabilities. For example, ~53 μm axial displacements were enabled with a 1 V/μm electric field (corresponding to the thinnest part of the actuator) without any passive layers. The modeled displacement results were comparable to displacements obtained by pre-stressed PRESTO (~50 μm), THUNDER (~60 μm) and RAINBOW (~70 μm) actuators of 25 mm in diameter with a 1 V/μm electric field.