The Dynamic Response of Tuned Impact Absorbers for Rotating Flexible Structures

Abstract

This paper describes an analytical investigation of the dynamic response and performance of impact vibration absorbers fitted to flexible structures that are attached to a rotating hub. This work was motivated by experimental studies at NASA, which demonstrated the effectiveness of these types of absorbers for reducing resonant transverse vibrations in periodically excited rotating plates. Here we show how an idealized model can be used to describe the essential dynamics of these systems, and used to predict absorber performance. The absorbers use centrifugally induced restoring forces so that their nonimpacting dynamics are tuned to a given order of rotation, whereas their large amplitude dynamics involve impacts with the primary flexible system. The linearized, nonimpacting dynamics are first explored in detail, and it is shown that the response of the system has some rather unique features as the hub rotor speed is varied. A class of symmetric impacting motions is also analyzed and used to predict the effectiveness of the absorber when operating in its impacting mode. It is observed that two different types of grazing bifurcations take place as the rotor speed is varied through resonance, and their influence on absorber performance is described. The analytical results for the symmetric impacting motions are also used to generate curves that show how important absorber design parameters—including mass, coefficient of restitution, and tuning—affect the system response. These results provide a method for quickly evaluating and comparing proposed absorber designs.

A Review of Nonlinear Dynamics of Mechanical Systems in Year 2008

“…2, No.3, 2008 lytically investigated (130) , and experimentally studied (131) . Among the interesting features of these systems are the possibilities of instabilities that arise when multiple identical absorbers are employed (132) - (134) , impact responses (135) , and superharmonic resonances (136) . There have been very recent applications to automotive engines that employ cylinder deactivation (137) .…”

Vibration absorbers for a rotating flexible structure with cyclic symmetry: nonlinear path design

“…It is shown that the linear absorber tuning should be selected in the no-resonance zone and that, to avoid some undesirable nonlinear effects, the path should be slightly softening. Of course, the nonlinear dynamics are ultimately hardening as the absorber encounters rattle-space limits imposed by the geometry of the primary system [6,19]. The present work deals with the nonlinear behavior that occurs before such limits are reached.…”

“…These absorbers, which essentially consist of masses that move along prescribed paths relative to the structure [6], have the advantage that they remain tuned over all rotation speeds. Order-tuned absorbers have been widely studied and employed for reducing torsional vibrations in rotating systems [7][8][9][10][11][12][13][14][15][16][17], and more recently they have been proposed for reducing flexural vibrations in rotating systems [2,5,6,[18][19][20][21]. Recent studies have also included impacting dynamics of single flexible elements with absorbers, which will occur if loading becomes large [6,19].…”

“…The design of an absorber to maintain small motions requires large absorber mass since its placement is constrained by system hardware. To avoid designs with undesirably large absorber mass, it is of interest to consider large amplitude absorber responses, which necessarily leads to either impacts [6,19,32] or smooth nonlinear path effects, as considered here, or both. This work investigates whether or not the desirable response features predicted by the linear theory persist when absorber amplitudes become large.…”

Numerical modeling of the momentum and thermal characteristics of air flow in the intercooler connection hose

“…Drexel and Ginsberg [20] investigated the scenario where the system is irritated with multiple vibration sources with different frequencies; they aimed to enlighten the absorber effect of distinct damping configurations. The concept of impact absorbers was taken as well into consideration by Shaw and Pierre [21]. By foregrounding the important absorber design parameters including mass, coefficient of restitution, and tuning effect, they showed how an idealized model can be used to describe the essential dynamics and performance of absorbers.…”