Damping of beams. Optimal distribution of cuts in the viscoelastic constrained layer

To damp the flexural vibrations of homogeneous beams or plates in a large frequency range, one of the most efficient methods is the use of constrained viscoelastic layers. Since most of the damping ability is due to shearing stresses in the viscoelastic layer, it is interesting to determine the most appropriate distribution of the shear in the layers. This paper presents the influence of a new parameter involved in this repartition, i.e. the distribution of cuts in the elastic constraining layer. It will be demonstrated that modal damping may be significantly modified in this way. The number and the locations of the cuts may vary and are determined to optimize the damping. The vibrating beam modal analysis is performed by a finite element analysis using special finite elements which have variable d.o.f. in order to take into account the lack of continuity of the viscoelastic constrained displacement field. Using a genetic algorithm, an optimal distribution of the cuts has been determined for a maximum damping of one or serval flexural modes.