Damping characteristics of flexural vibration for partially covered beams with constrained viscoelastic layers.

It has been known that the composite loss factor of a partially covered beam with the constrained viscoelastic layers becomes higher than that of a fully covered beam, depending on the beam geometry and the properties of the viscoelastic layer. Damping mechanism of this partial coverage effect, however, has not been examined in detail now. In this paper, the strain energy analyses of the three types of partially covered beams are carried out in order to investigate such damping mechanism. The results of analyses for the center covered beam and the end constrained beam indicate that the partial coverage effect is caused by the shear strain energy dissipation at the outer edges of the viscoelastic layers and also this dissipation depends on both the shear stiffness of the viscoelastic layer and the tensile stiffness of the constraining layers. The composite loss factor of the separately covered beam, which separates viscoelastic layers only at the beam center, becomes higher than that of the partially covered beam due to the energy dissipation of the inner edges of viscoelastic layers. The damping characteristics of these beams are confirmed by some experimental results.