Record number :

1423182

Title of article :

Force and displacement transmissibility of a nonlinear isolator with high-static-low-dynamic-stiffness

Author/Authors :

Carrella، نويسنده , , A. and Brennan، نويسنده , , M.J. and Waters، نويسنده , , T.P. and Lopes Jr.، نويسنده , , V.، نويسنده ,

Issue Information :

ماهنامه با شماره پیاپی سال 2012

Pages :

8

From page :

22

To page :

29

Abstract :

Engineers often face the challenge of reducing the level of vibrations experienced by a given payload or those transmitted to the support structure to which a vibrating source is attached. In order to increase the range over which vibrations are isolated, soft mounts are often used in practice. The drawback of this approach is the static displacement may be too large for reasons of available space for example. Ideally, a vibration isolator should have a high-static stiffness, to withstand static loads without too large a displacement, and at the same time, a low dynamic stiffness so that the natural frequency of the system is as low as possible which will result in an increased isolation region. These two effects are mutually exclusive in linear isolators but can be overcome if properly configured nonlinear isolators are used. This paper is concerned with the characterisation of such a nonlinear isolator comprising three springs, two of which are configured to reduce the dynamic stiffness of the isolator. The dynamic behaviour of the isolator supporting a lumped mass is investigated using force and displacement transmissibility, which are derived by modelling the dynamic system as a single-degree-of-freedom system. This results in the system dynamics being approximately described by the Duffing equation. For a linear isolator, the dynamics of the system are the same regardless if the source of the excitation is a harmonic force acting on the payload (force transmissibility) or a harmonic motion of the base (displacement transmissibility) on which the payload is mounted. In this paper these two expressions are compared for the nonlinear isolator and it is shown that they differ. A particular feature of the displacement transmissibility is that the response is unbounded at the nonlinear resonance frequency unless the damping in the isolator is greater than some threshold value, which is not the case for force transmissibility. An explanation for this is offered in the paper.

Keywords :

vibration isolation , Duffing equation , HSDLS , Nonlinear transmissibility , Nonlinear stiffness

Journal title :

International Journal of Mechanical Sciences

Serial Year :

2012

Link To Document :