On the Design of a Type of Mechanical Molecular Spring Isolator

Abstract

The mechanical molecular spring isolator (MMSI) presents the characteristics of high-static-low-dynamic-stiffness to isolate the low-frequency vibration of a heavy payload. An MMSI consists of a piston-cylinder container full of the liquid and some hydraulic spring accumulators. This paper focuses on a particular type of the MMSI that all hydraulic spring accumulators applying the conventional coil spring are identical. In the beginning, the MMSI stiffness model is modelled and the influences of critical parameters on the stiffness property are studied. The MMSI presents a piecewise linear stiffness property. The averaging method is applied to determine the primary resonance response, and the energy transmissibility is adopted to estimate the vibration isolation performance. A jump phenomenon is inevitable to be occurred around the resonance region. The jump avoidance is a critical design part of the MMSI isolation system. On the other hand, based on the stiffness model, it reveals that any stiffness of the coil spring or any size of the accumulator in the MMSI will be able to achieve the same desired stiffness property. The most significant difference between all solutions depends on the coil spring lateral stability. The coil spring lateral stability magnitude is defined as the ratio of the deflection to the buckling deflection to evaluate the quality of each solution. Then, the fundamental design criterion on the MMSI based on jump avoidance and the coil spring lateral stability is established.