On the analysis of a piecewise nonlinear-linear vibration isolator with high-static-low-dynamic-stiffness under base excitation

A piecewise nonlinear vibration isolator with high-static-low-dynamic-stiffness (HSLDS) is presented in this paper. This nonlinear vibration isolator is comprised of a vertical spring and two pre-compressed cam-roller-spring mechanisms used as the stiffness correctors. Firstly, the static analysis of the vibration isolator is analyzed. The primary resonance of the system under harmonic base excitation is derived by applying the averaging method and further verified by the direct numerical integration. The effect of base excitation amplitude and damping ratio on the resonance frequency is considered. The stability analysis of the primary resonance is also studied. Then, the frequency island phenomenon is found and confirmed by numerical method. The parameter analysis on the appearance of frequency island is also considered. Finally, the absolute displacement transmissibility of the vibration isolator is defined and compared with the conventional HSLDS vibration isolator and the equivalent linear one. The results show that it exhibits a wider frequency range of vibration isolation than the equivalent linear vibration isolator. When the base excitation amplitude takes a larger value, the unbounded response which occurs in the conventional HSLDS vibration isolator can also be avoided, then a better isolation performance can be achieved.