The dynamic properties and performance of the bellows-type hydraulic inerter-based dynamic anti-resonance vibration isolator

Aiming to effectively isolate disturbance vibrations for heavy machines with low frequencies, a novel bellows-type hydraulic inerter-based dynamic anti-resonance vibration isolation (I-DAVI) isolator is proposed, which consists of a primary supporting bellows container and an additional inerter subsystem comprising horizontal bellows and inertial mass, and the incompressible oil liquid is filled in the vacuum of both bellows as the working medium. First of all, the mathematic model of the presented I-DAVI device is established, and then the vibration transmissibility for the systems under force excitation and motion excitation are derived. The relevant results indicate that the anti-resonance appears at specific frequency, creating near-zero energy transmission and significantly reducing vibration transmission to the base or machines. Through the nondimensionalization analysis, the four parameters including the inertial mass ratio, damping ratio, ratio of effective cross-section areas, and number of the inerter subsystem completely dominate the isolation characteristics of the proposed device. Subsequently, a comparison study is carried out between systems with and without inertial mass located at the end of the additional horizontal bellows, and furthermore the operating mechanism of the I-DAVI is explained clearly. It is proven that the inerter-based DAVI isolator exhibits high static and low dynamic stiffness characteristics, which cause the resonance frequency of the isolation system to shift toward lower frequency without changing the static bearing stiffness and also reduce the peak value of the transmissibility. The further numerical simulation verifies that the optimal isolation effectiveness at the anti-resonance frequency is attributed to the dynamic equilibrium between the elastic restoring force of the primary bellows and the internal hydraulic pressure. In practice, the bellows-type hydraulic inerter-based I-DAVI isolator device investigated in this study is suitable for machines with the narrowband low-frequency vibration, such as the marine turbines.