Energy flow and performance of a nonlinear vibration isolator exploiting geometric nonlinearity by embedding springs in linkages

This study presents nonlinear vibration isolators with nonlinear elements created by the geometric nonlinearity of a linkage mechanism with embedded linear springs and investigates their dynamic behaviour and performance. Applications of the proposed isolator to single degree-of-freedom (DOF) systems subjected to force and base-motion excitations and to a two-DOF system with a flexible foundation are considered. The steady-state responses of systems with such isolators are obtained using the harmonic balance (HB) method and a numerical time-marching method. Force and displacement transmissibilities as well as time-averaged energy flow of the nonlinear isolator are employed as indices for performance evaluations. It is shown that the use of the proposed nonlinear element can enlarge the frequency range of effective isolation. Substantial reductions can be found in the peak values of frequency response, displacement transmissibility and kinetic energy of the SDOF nonlinear isolation systems. The peaks in the curves of energy transmission and force transmission are shifted to low frequencies with reduced peak values, beneficial to the suppression of vibration transmission to the flexible base.