Some features of geometric nonlinear damping on isolation performance

The addition of nonlinear characteristics to improve the dynamic performance of isolation systems and vibration absorbers has been extensively investigated in the past decades. Both nonlinear stiffness and nonlinear damping have been largely analysed. A common way in which this can be achieved in practice, is by arranging linear elements (springs and viscous dampers) in a specific geometrical configuration. This paper focuses on the fundamental effect of geometrical nonlinear damping in a vibration isolation system, and briefly revises two of the classical implementation mechanisms. They can achieve a better performance than linear systems, by assuring lower damping force at lower displacements, and higher damping force at higher displacements. However, strong nonlinear effects can manifest around resonances, causing non-negligible higher-order harmonics to appear, and making the approximate frequency response obtained by the harmonic balance, unuseful. This paper proposes a new strategy to limit such undesired dynamic effects. For this aim, a coupling is introduced on purpose in the damping mechanism, which allows tailoring the damping force for the specific need.