“…Moreover, the presence of the companion mode in the nonlinear response of rings was shown to arise when large-amplitude oscillations are excited by large external excitations. More recently, in [15,28] a numerical method based on a finite-element procedure was adopted to study nonlinear vibrations of elastic oval rings. The numerical simulations, aimed at reproducing the backbone curves of the lowest three driven modes of both oval and circular rings, showed a very good agreement with the analytical results existing in the literature [14,33], and confirmed the softening behavior theoretically and experimentally predicted by Evensen. Nonlinear dynamics of circular cylindrical shells were also studied from different standpoints, such as equilibrium states under pressures [2,4], parametric resonances of breathing and flexural motions [5,8,16,17,21,26,30], or interactions between coupled modes in nonlinear flexural motions [19].…”