Theoretical and experimental investigation of a two-stage X-structure vibration isolation system with inerter coupling for marine equipment

There is a growing concern about the use of the inerter to reduce low-frequency vibration and noise in ship and ocean engineering. The isolation performance of a traditional inerter-spring-damping vibration isolator outperforms that of a spring-damping isolator in the low-frequency range; however, it levels off at a constant value in the high-frequency range, and the resonant peak becomes large. This study proposes a novel vibration isolation system by horizontally integrating the inerter-spring-damping system into an X-structure and combining it with a two-stage vibration isolation mechanism. With the dynamic modeling, the transmissibility of the proposed vibration isolation system is derived through the frequency response function method. The acceleration, velocity inertance, and resonant frequency are theoretically analyzed by considering the influence of various structural parameters. Additionally, the effects of system parameters, including the number of layer, assembly angle, inerter ratio, and intermediate mass, on the isolation performance can improve in the low-frequency range and decline in the high-frequency range with a certain slope, and the resonant peak can be reduced, compared with the other nine types of scissor-like and vertical coupling structures. The multi-stage integrated structure can cumulatively expand the effective isolation frequency range while generating additional resonant and anti-resonance peaks. The isolation performance of the single-stage vibration system is validated using experimental prototypes and compared with the analytical method, demonstrating the correctness of the proposed theoretical model. • A two-stage X-structure vibration isolation system with inerter coupling is proposed. • The acceleration, velocity inertance, and resonant frequencies are nonlinear functions of motion and structural parameters. • The proposed system improves at low-frequencies, decreases with a slope at high-frequencies, and reduces the resonance peak. • The multi-stage structure expands isolation frequency range while generating resonant, anti-resonance peaks. • The isolation performance is validated using experimental prototypes and compared with the analytical method.