FEM modelling and experimental characterization of microbeams in presence of residual stress

Abstract

Out-of-plane bending tests are here used to experimentally validate some numerical models of microbeams actuated by the electric field. Out-of-plane bending microcantilevers and clamped-clamped microbeams often suffer the presence of residual strain and stress, respectively, which affect their static and dynamic behaviour and pull-in voltage. In case of microcantilever an accurate modelling has to include the effect of an initial curvature due to microfabrication process, while in double clamped microbeams constraints may impose a pre-loading caused by a tensile stress. So-called geometrical nonlinearity sometimes occurs, when microcantilever exhibits large displacement, or because of the mechanical coupling between axial and flexural behaviours in double clamped microbeams. Modelling this kind of nonlinearity is an additional goal of this study. Experiments demonstrated a good agreement with results of FEM approaches proposed. In the case of microbridges numerical models are used to identify the residual stress. A reverse analysis is implemented, the axial pre-stress is calculated by means of the measured pull-in voltage.

On the parameters which govern the symmetric snap-through buckling behavior of an initially curved microbeam

“…On the other hand, the tensile axial force has the effect to stretch the beam, which hinders the pull-in, so more voltage (larger electrostatic force) is required. Similar conclusions have also been found by the theoretical and experimental studies in the literature (AbdelRahman et al, 2002;Ballestra et al, 2010;He et al, 2009;Huang et al, 2001;Jia et al, 2011).…”

Design and Performance of a J Band MEMS Switch

“…The DC voltage is ~30 V, which is less than calculated result (35 V), the reason is that the surface of switch beam is reduced and the hole on the switch is enlarged, which directly leads to the decrease of the elasticity coefficient of the switch, thus, the driving voltage of the switch being reduced. In addition, the out-of-plane deformation of a cantilever beam with residual stress gradient will also reduce the driving voltage [14,15].…”

Snap-Through Buckling of Micro/Nanobeams in Bistable Micro/Nanoelectromechanical Systems

“…The maximum force ratios are determined by the minimum stable deflection, i.e., deflection at pull-in instability, which is roughly half gap (w ¼ À0:5) (Ballestra et al 2010;Dequesnes et al 2002;Hu et al 2004 In the previous subsection, we have proved that the intermolecular forces can be neglected in the study of snap-through buckling of microbeams. So the governing equation (Eq.…”