Elastic guided waves in a coated spherical shell

Elastic-guided wave inspection technique is important in non-destructive detection of coated shell structures. It is based on the wave propagation characteristics and various factors which influences it. In this paper, the dispersion equations of the spherical shell are derived by the decomposition approach in order to investigate the influences of the coating thickness and viscoelastic damping on the dispersion characteristics. The viscoelastic properties of the coating layer are modelled by the standard linear solid with two damping factors in the Lame constants. The dispersion equation of the coated shell is deduced by the transfer matrix method, and the dispersion and attenuation curves for different thicknesses and damping factors are calculated. The frequency range which is less affected by coating is identified by comparing the dispersion curves of the bare shell to those of the coated shell with different coating thicknesses. The effect of damping factors on the mode shapes is also examined. The present numerical results on the elastic guided wave in coated spherical shell would provide a theoretical basis for non-destructive inspections in layered spherical shell structures.