A semi-analytical method for the free vibration analysis of thick double-shell systems

A semi-analytical method is extended to analyze the natural frequencies and mode shapes of thick double-shell systems. On the basis of the semi-analytical method for the state-vector equation of circular cylindrical shells, the mathematical model for thick double-shell systems is established. The main advantage of such model is that the finite element mesh is only used in the curved surface of shells and the number of variables is independence of the wall thickness of cylindrical shells. Moreover, the presented method is also suitable for the cases of various complex support conditions and the arbitrary distributed interconnecting springs. To validate the present method, several examples are calculated numerically. Some special phenomena on the mode shapes of thick double-shell systems are found.