Accession Number : ADA201621


Title :   The Modeling of Viscoelastic Circular Plates for Use as Waveguide Absorbers


Descriptive Note : Master's thesis


Corporate Author : NAVAL POSTGRADUATE SCHOOL MONTEREY CA


Personal Author(s) : Hettema, Charles D


Full Text : https://apps.dtic.mil/dtic/tr/fulltext/u2/a201621.pdf


Report Date : Sep 1988


Pagination or Media Count : 210


Abstract : The need exists to reduce structural vibrations in plates, such as ship's 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 Young's modulus and shear modulus can be used to represent the viscoelastic material. Mindlin's theory for elastic isotropic plates, with complex moduli, was used to solve for the driving point impedance. The solutions are in terms Bessel functions. Poisson's 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.


Descriptors :   *SHIP PLATES , *SHIP HULLS , *VIBRATION ISOLATORS , *DAMPING , STRUCTURAL PROPERTIES , MATERIALS , EDGES , VISCOELASTICITY , ENERGY , ELASTIC PROPERTIES , THESES , WAVEGUIDES , SURFACES , BOUNDARIES , FORTRAN , ABSORBERS(MATERIALS) , ISOTROPISM , MOUNTS , ATTACHMENT , TRAVELING WAVES , POISSON EQUATION , CIRCULAR , BESSEL FUNCTIONS , EQUATIONS OF MOTION , VIBRATION , MECHANICAL IMPEDANCE , COMPUTER PROGRAMS , RATIOS


Subject Categories : Marine Engineering
      Mechanics


Distribution Statement : APPROVED FOR PUBLIC RELEASE