Fabrication and characterization of THUNDER actuators—pre-stress-induced nonlinearityin the actuation response

Abstract

This paper documents an experimental and theoretical investigation into characterizing themechanical configurations and performances of THUNDER actuators, a type ofpiezoelectric actuator known for their large actuation displacements, throughfabrication, measurements and finite element analysis. Five groups of such actuatorswith different dimensions were fabricated using identical fabrication parameters.The as-fabricated arched configurations, resulting from the thermo-mechanicalmismatch among the constituent layers, and their actuation performances werecharacterized using an experimental set-up based on a laser displacement sensor andthrough numerical simulations with ANSYS, a widely used commercial softwareprogram for finite element analysis. This investigation shows that the presenceof large residual stresses within the piezoelectric ceramic layer, built up duringthe fabrication process, leads to significant nonlinear electromechanical couplingin the actuator response to the driving electric voltage, and it is this nonlinearcoupling that is responsible for the large actuation displacements. Furthermore, theseverity of the residual stresses, and thus the nonlinearity, increases with increasingsubstrate/piezoelectric thickness ratio and, to a lesser extent, with decreasing in-plane dimensions of thepiezoelectric layer.