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The Modeling of Viscoelastic Circular Plates for Use as Waveguide Absorbers

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Master's thesis

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The need exists to reduce structural vibrations in plates, such as ships hulls. It was proposed to use waveguide absorbers as a means to reduce structural vibrations. A waveguide absorber is a device which is made from damping material but mounted to the structure at a point rather than the full surface. A waveguide absorber removes and then dissipates vibrational energy from the structure through traveling waves. The performance of a waveguide absorber is determined from the driving point impedance, the ratio of force to velocity a the attachment point. This study has determined the theoretical driving point impedance for viscoelastic circular plates. The constitutive relations for viscoelastic material were evaluated and it was proven that a complex Youngs modulus and shear modulus can be used to represent the viscoelastic material. Mindlins theory for elastic isotropic plates, with complex moduli, was used to solve for the driving point impedance. The solutions are in terms Bessel functions. Poissons boundary conditions were used at the free edge of the circular plate, and clamped boundary conditions were used at the attachment point, solve for the driving point impedance given the appropriate equations of motion and boundary conditions. The complex Bessel functions, needed for the results of the REDUCE program, were generated by a FORTRAN program. The results were tested to determine their driving point impedance. A comparison of the theoretical results and the experimental results shows that there is agreement for all cases studied. Theses.

Subject Categories:

  • Marine Engineering
  • Mechanics

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