Experiments on the Pfluger column: flutter from friction

Flutter and divergence instabilities are theoretically and experimentally analysed in elastic structures with internal and external damping. Despite of the fact that only the former (and not the latter) was believed to be a destabilizing effect, it is theoretically demonstrated that the external damping plays a role similar to internal damping, so that both yield a pronounced destabilization paradox (in the Ziegler sense). This finding and other features of the Beck and Pfluger columns are substantiated by an experimental campaign in which the follower forces are obtained via dry friction with a newly designed experimental apparatus.