Compliant curved beam support with flexible stiffness modulation for near-zero frequency vibration isolation

Passive isolation of low-frequency vibrations poses a significant challenge due to the requirement of possessing a low stiffness. Herein, a compliant curved beam support (CCBS) for near-zero frequency vibration isolation is proposed and systematically investigated. The CCBS exploits nonlinear negative stiffness provided by an arc-shaped beam support to modulate nonlinear positive stiffness of a spiral-shaped beam support. This nonlinear configuration gives rise to an interesting phenomenon, that is, the stiffness modulation of the CCBS for quasi-zero stiffness (QZS) can be flexibly fulfilled by performing a translation transformation on negative stiffness instead of reshaping it. A thorough static analysis is implemented to reveal this stiffness modulation mechanism. The dynamic governing equation is derived and solved analytically and numerically to calculate the displacement transmissibility, and the effects of excitation amplitude, damping, and applied load are dissected. Finally, various excitation tests are conducted to experimentally evaluate vibration isolation performance. The results demonstrate that the CCBS exhibits a remarkably low resonance frequency of 0.5 Hz and achieves near-zero isolation starting at 0.8 Hz, showcasing excellent performance in isolating low-frequency vibrations. The proposed CCBS provides a novel paradigm for achieving flexible low stiffness modulation in compact QZS isolators, making it highly deserving of promotion.