  In this paper an experimental validation of numerical approaches aimed to
predict the coupled behaviour of microbeams for out-of-plane bending tests is
performed. This work completes a previous investigation concerning in plane
microbeams bending. Often out-of-plane microcantilevers and clamped-clamped
microbeams suffer the presence of residual strain and stress, which affect the
value of pull-in voltage. In case of microcantilever an accurate modelling
includes the effect of the initial curvature due to microfabrication. In double
clamped microbeams a preloading applied by tensile stress is considered.
Geometrical onlinearity caused by mechanical coupling between axial and
flexural behaviour is detected and modelled. Experimental results demonstrate a
good agreement between FEM approaches proposed and tests. A fairly fast and
accurate prediction of pull-in condition is performed, thus numerical models
can be used to identify residual stress in microbridges by reverse analysis
from the measured value of pull-in voltage.
