| This dissertation presents an investigation into modeling and analyzing the nonlinear structural mechanics of micro and nanoelectromechanical systems (MEMS and NEMS). The first part of this dissertation is concerned with micro systems. Instability problems of microbeams under the effect of capillary forces and mechanical shock loads are investigated. It is demonstrated that capillary forces has significant effect on the stability of microbeams. Also it is shown that by biasing stiff microbeams with electrostatic voltages, their stiffness is weakened, which enables testing them with the in-house shock testing equipments, such as drop table tests. The majority of the work of this part is focused on investigating theoretically and experimentally the dynamics of clamped-clamped micromachined arches when actuated electrically. The results show softening-type behavior for the fundamental frequency, frequency bands with dynamic snap-through for both the fundamental and the third natural frequencies, dynamic pull-in for high level of AC loads, and possibility of internal resonance among some of the modes. The second part of the dissertation is concerned with the dynamics of electrically actuated carbon nanotubes (CNTs) resonators. The behaviors of both straight and curved (slacked) CNTs are investigated. The results show complex nonlinear dynamics phenomena, such as hysteresis, dynamic pull-in, hardening and softening behaviors, and frequency bands with an inevitable escape from a potential well. Also, for slacked CNTs, various scenarios for mode crossing and mode veering (with possibility of energy exchange) are demonstrated as the levels of slack and DC load are varied. |
