Resonance Characteristics of Unidirectional Viscous and Coulomb-Damped Vibration Isolation Systems

Abstract

Elementary vibration theory based on transfer response analyses of single-degree-of-freedom systems indicates that an increase in isolation system damping causes a decrease in resonant transmissibility. This theory further specifies that, for viscous-damped systems, an increase in damping decreases the resonant frequency whereas, for Coulomb-damped systems, an increase in damping increases the resonant frequency. It is frequently found in practice that an increase in damping may increase the resonant transmissibility and cause a change in resonant frequency opposite to that predicted by elementary theory. This paper presents a more extensive evaluation of the resonance characteristics of unidirectional vibration isolation systems, including the effects of directly coupled and elastically coupled damping elements. Mathematical models and absolute transmissibility characteristics of viscous and Coulomb-damped vibration isolation systems are discussed and resonance characteristics are analyzed in terms of the resonant frequency ratio, the resonant transmissibility, and the rate of change of these parameters with damping. Design data are presented graphically for parametric variations of stiffness and damping which are sufficiently broad to encompass a wide range of practical engineering problems.