Modeling and Stiffness Properties for the Hydro-pneumatic Near-Zero Frequency Vibration Isolator with Piecewise Smooth Stiffness

Aims Low-frequency vibrations exist commonly in practical engineering, which are difficult to be isolated effectively via a linear vibration isolator due to the inherent contradiction between large loading capacity and low-frequency isolation. The nonlinear vibration isolation technologies including high- and low-dynamic (HSLD) stiffness isolators are able to overcome the deficiency of linear device, but there are several shortcomings on aspects of insufficient loading bearing, complicated working mechanism, and weak structural reliability. Methods Therefore, to enhance the performance of HSLD stiffness vibration isolator, one novel hydro-pneumatic near-zero frequency (NZF) vibration isolator is proposed in this paper, which contains the bellows structure as a container, in which the solid and liquid mixture (SALiM) working media are filled. Based on geometry features of bellows, the plate and shell theories are used to establish the mechanics model of bellows-type container and solid elements. Then the isolation performance of vibration isolator is elevated by comparing with a linear isolation device. Conclusion The result shows that the proposed vibration isolator exhibits the piecewise linear stiffness characteristics. To verify the validity of the theoretical model, finite element method (FEM) is carried out and results show that theoretical and numerical results are consistent. And further parameter study presents that the gas pressure can significantly dominate the loading capacity of isolation device. Besides, it is also proved that the NZF vibration isolation device can effectively isolate low-frequency vibration at a relatively small static deformation, and thus, it is particularly suitable for the low-frequency vibration isolation of heavy machines on marine ship or other practical engineering.