SOME STUDIES ON DYNAMIC VIBRATION ABSORBERS

Abstract

One of the main goals, of study of engineering vibrations is to suppress or eliminate unwanted vibrations Vibrations in mechanical systems can be appreciably quenched by the provision of Dynamic Vibration Absorbers (DVA). A DVA differs from a damper in that the motion from the main system is transferred to an auxiliary system, the total energy being conserved. On the other hand in the Case of a damper a part of the vibrational energy is abstracted and dissipated as heat or other forms of energy thereby lowering the total energy of the system.

DVA are necessary to limit excessive vibration of a machine element subjected to steady vibrating loads. A perfectly tuned DVA call be designed for a single degree of freedom system subjected to mono-frequency excitation of a harmonic nature But when the frequency varies the design of DVA becomes complicated owing to the introduction of damping, (introduced to extend the frequency range of of the DVA). In some cases a nonlinear spring coupling aids in extending the range of usefulness of the DVA.

When a forcing function of an impulsive type acts on a system, vibration absorbers can be designed so that if failure occurs it will be that of the absorber (because, it is made to bear the brunt of shock) and not that of the main system. (The main system is protected from the ravages of the shock). The DVA functions as a protection, against shock.

In this paper a study is undertaken on the design of DVA for various types of excitations, steady, transcient in nature, and it will be the purpose of this investigation to study how efficient these DVA are in quenching unwanted oscillations.