AN EXPERIMENTAL INVESTIGATION OF VIBRATION LOCALIZATION IN DISORDEREDMULTISPAN BEAMS

The results of an experimental investigation of the effects of span le ngth disorder on the dynamics of mono-coupled, multi span beam are rep orted. Two experimental specimen are considered: a nominally periodic 12-span beam with equal spacing between simple supports, and the corre sponding disordered beam which features randomly spaced supports. Expe rimental results demonstrate that the transmission of vibration which takes place within the frequency passbands of the periodic beam is gre atly hindered when span length randomness is introduced. The spatial l ocalization of both the mode shapes and the steady state harmonic resp onse to an end excitation is observed in the disordered 12-span beam, especially for frequencies which lie within the second passband. Very goad quantitative agreement is obtained between experimental results a nd theoretical findings for both ordered and disordered configurations . Futhermore, an experimental estimation of the localization factor yi elds satisfactory agreement with the theoretical result for an infinit e multi-span beam. This work reports one of the first systematic exper iments carried out to demonstrate the occurrence of vibration localiza tion in nearly periodic structures. (C) 1995 Academic Press Limited.