The governing differential equations of vibrations of double-layered cylindrical shells are derived from classical thinshell theory. The outer layer of the shell is assumed to be viscoelastic, possessing high damping capacity to control vibrations (loss factor, β = 0.3). Decoupled torsional and coupled radial-longitudinal vibration modes are analysed by the method of ‘damped normal modes’. The present theory refines Kagawa and Krokstad's former analysis (1)‡. The results obtained point to a strong dependence of mechanical losses upon the thickness-to-radius ratio, h1/R, even in the case of axisymmetric modes. This phenomenon was not recognized in Kagawa-Krokstad's approach.
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