The phenomenon of crack initiation due to dynamic contact loading is referred to as fretting fatigue. This situation is commonly encountered in mechanical couplings subjected to vibration. Whenever a material has good mechanical properties but poor fretting resistance it is advantageous to provide a layer of material having good fretting resistance instead of changing the entire material. This extra layer of material can be provided by coating or by any other surface treatment methods. Wave propagation in coated poroelastic cylinders of infinite extent is investigated employing Biot's theory. The coated poroelastic cylinder consists of two poroelastic cylinders of different poroelastic materials bonded at the curved surface such that the liquids in the poroelastic materials are immiscible. Frequency equations of coated poroelastic cylinders are derived both for pervious and impervious surfaces. Let the infinite coated poroelastic cylinder be homogeneous and isotropic and the outer boundary is free from stress. At the interface of the core and coating, the stresses and displacements are continuous. For motions having infinite wavelength or when the wavenumber is zero, the axial shear and radial modes of the coated poroelastic cylinder are uncoupled each for a pervious and an impervious surface. The frequency equation of axial shear vibrations is same for pervious and impervious surfaces. Non-dimensional phase velocity for propagating modes is computed as a function of propagation constant in the absence of dissipation. The results are presented graphically for two types of coated poroelastic cylinders and then discussed.
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Axially symmetric vibrations of a finite composite poroelastic circular cylinder are investigated employing Biot's theory of wave propagation in poroelastic media. The composite poroelastic cylinder consists of two poroelastic cylinders of different materials bonded at the plane ends. Frequency equations for such vibrations are derived both for pervious and impervious surfaces. Let the finite composite poroelastic cylinder be homogeneous and isotropic and the boundaries free from stress. Non-dimensional phase velocity for propagating modes is computed as a function of ratio of length of cylinders in the absence of dissipation. The results are presented graphically for two types of composite poroelastic cylinders and then discussed. In general, the phase velocity of composite cylinder-I is higher than that of composite cylinder-II both for a pervious and an impervious surface.
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