Vibration Suppression of Helicopter Blades by Pendulum Absorbers (Analytical and Experimental Investigation in Case of Rigid-Body Mode)

In tilting pad bearing design process, the selection of the proper configuration type of either a Load-Between-Pad (LBP) or Load-On-Pad (LOP) as well as preload and pivot offset conditions is to be carefully considered. Also the bearing needs to be designed in order to be suited for the rotor-bearing system and operating condition. In this paper, it is observed that the static and dynamic characteristics of a five pad tilting pad bearing for the LBP and LOP configurations are influenced by the variation of preload and pivot offset. In this context, rotor dynamic analysis of the 5 MW industrial gas turbine supported by the tilting pad bearing at the front and roller bearing at the rear is carried out based on the dynamic coefficients of the tilting pad bearing investigated. The result shows that two rigid body critical modes experience various changes according to the influence of the tilting pad bearing uniquely applied to one side of this machine. Mainly, the second critical speed, the rigid body mode of conical shape with high whirling in the tilting pad bearing, is significantly changed by preload and pivot offset regardless of the LBP and LOP configurations. And the first critical mode, the rigid body mode of conical shape with high whirling in the roller bearing, is sensitively affected by preload applied to the LOP configuration and by its asymmetric dynamic properties.

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Motions of an Unstable Retainer in an Instrument Ball Bearing

Journal of Tribology ◽

10.1115/1.2927197 ◽

1994 ◽

Vol 116 (2) ◽

pp. 202-208 ◽

Cited By ~ 25

Author(s):

E. Kingsbury ◽

R. Walker

Keyword(s):

Experimental Investigation ◽

Rigid Body ◽

Rotation Rate ◽

High Frequency ◽

Ball Bearing ◽

Stable Operation ◽

Frequency Content ◽

Outer Race ◽

Group Rotation ◽

Inner Race

We made an experimental investigation of the motions of the retainer in an instrument ball bearing during stable operation and during squeal. Radial motions of the retainer were measured with two fiber-light probes mounted 90 physical degrees apart. A signal analyzer was used to determine the phasing and frequency content of the probe signals. During squeal, a high-frequency retainer motion was found to be superimposed on the normal retainer ball group rotation rate. This high-frequency motion, which we call whirl, is a rigid-body translation in a circle. Whirl direction is opposite to the race for outer-race rotation, but in the same direction for inner-race rotation. Whirl frequency is approximately proportional to ball spin rate. The observations agree with predictions made from a squeal model based on retainer-to-ball frictional coupling that was originally presented in 1965.

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Particle damping for passive vibration suppression: numerical modelling and experimental investigation

Journal of Sound and Vibration ◽

10.1016/j.jsv.2003.11.023 ◽

2005 ◽

Vol 279 (3-5) ◽

pp. 1097-1120 ◽

Cited By ~ 75

Author(s):

Zhiwei Xu ◽

Michael Yu Wang ◽

Tianning Chen

Keyword(s):

Experimental Investigation ◽

Numerical Modelling ◽

Vibration Suppression ◽

Particle Damping

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Calculation of Rigid-Body Motion of Integrated Raft Isolation System

Applied Mechanics and Materials ◽

10.4028/www.scientific.net/amm.184-185.80 ◽

2012 ◽

Vol 184-185 ◽

pp. 80-85

Author(s):

Zhi Qiang Lv ◽

Wei Xu ◽

Chang Geng Shuai

Keyword(s):

Rigid Body ◽

Rigid Body Motion ◽

Body Motion ◽

Design Stage ◽

Motion Model ◽

Isolation System ◽

Rigid Body Mode ◽

Mode Behavior ◽

Elastic Couplings ◽

Six Degree Of Freedom

Integrated raft isolation system (IRIS) has some advantages over raft system of much smaller scale, such as higher isolation efficiency, less use of elastic couplings, etc. But the calculation of IRIS’s dynamic characteristics is complex. Finite element method usually adopted by raft designers is inefficient due to the iterative nature of design process. In this paper a six-degree-of-freedom rigid-body motion model is presented to calculate the static，quasi-static and rigid-body mode behavior of IRIS. The model is especially suitable to compare different design schemes and select out feasible ones efficiently at the initial design stage of IRIS.

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