Effects of Size, Surface Energy and Casimir Force on the Superharmonic Resonance Characteristics of a Double-Layered Viscoelastic NEMS Device Under Piezoelectric Actuations

摘要

This paper investigates the nonlinear characteristics of a double-layered viscoelastic nanoelectromechanical system (NEMS) in the vicinity of superharmonic resonance. Two nanobeams are made of piezoelectric material and coupled through a visco-Pasternak medium in between. Modified couple-stress theory together with Gurtin-Murdoch surface elasticity theory is utilized to take into account the effects of size-dependency and surface energy for the nanosized structure. Kelvin-Voigt model is also implemented to consider the impact of viscoelasticity. The differential equations of motion are established based on Hamilton's principle and decomposed to a set of nonlinear ordinary differential equations via Galerkin discretization method. Arclength continuation technique is schemed to capture the frequency-response curves near superharmonic resonance of the system. The influence of the couple-stress parameter, surface strain energy and dispersion force on the nonlinear behavior of the system near superharmonic resonance has been studied. It is observed, that the hardening and softening behaviors of the system are remarkably affected by the size and surface parameters, and interatomic Casimir force. Finally, considering all the mentioned effects, the influence of the DC and AC voltage loads on the dynamic pull-in behavior of the NEMS device is investigated. For these cases, some frequency ranges are addressed as the pull-in band in which the lower nanobeam collapses.