Analyses and Applications of Nonlinear Liquid Systems on Vibration Isolation

Softening nonlinear elements are usually effective for vibration reduction. However, most stress-train relations of structural systems are not exact and have limitation of materials and scale. On the other hand, one is desirable to develop nonlinear isolators to improve vibrations. Anticipating the effect of such a system is similar to a softening spring system, one can have a certain extend to design diverse kinds of softening spring terms. Especially, liquid is used to build isolation systems. In this paper, three types of nonlinear liquid systems (NLS) are introduced, which are the exchange, buoyance and loading types. In fact, they are variable mass systems. The equations of motion of these systems are also derived to verify their nonlinearities. Numerical simulations are followed for several example shapes. The analysis results show that softening spring effects. An experimental model is displayed to verify its softening spring effects in the next steps. This paper gives guidelines and suggestions for using NLS as vibration isolators.