Rotary-oscillatory nonlinear energy sink of robust performance

The rotary nonlinear energy sink (NES) reported in the literature is inertially coupled to an associated linear primary structure by a rigid rotating arm. In this work, the rigid coupling arm is replaced by an elastic arm, with a linear coupling radial stiffness element used to provide the rotating NES with the added capacity for radial oscillation in order to achieve robust performance concerning passive nonlinear energy transfer and dissipation. Accordingly, the NES mass in addition to rotating about a fixed vertical axis, is now capable of oscillating in the radial direction along the coupling arm as well. In accordance to this structural modification, the resulting NES is referred to as rotary-oscillatory NES (RO NES), and as such, is capable of dissipating the transferred energy from the linear primary structure through its angular and radial damping elements during its combined angular rotation and radial oscillation. Moreover, this new NES configuration enables enhanced energy absorption and dissipation over a wide range of initial input energies. The optimized RO NES is compared to the corresponding optimized rotary NES, with the numerical results showing significant improvement in NES performance. In addition, the effectiveness of the RO NES to passively ‘redistribute’ the modal energies of the primary structure by means of nonlinear energy scattering of the input energy from low to high structural modes is studied.