Stabilizing Effects of Speed Fluctuations on the Dynamic Response of Rolling Element Bearings With Radial Clearances

2005 ◽  
Author(s):  
A. N. Lioulios ◽  
I. A. Antoniadis
Keyword(s):  
Theory Of Elasticity ◽  
Contact Forces ◽  
Radial Clearance ◽  
Rolling Element Bearings ◽  
Governing Parameter ◽  
Frequency Distributions ◽  
Rolling Element ◽  
Stabilization Effect ◽  
Speed Fluctuations ◽  
Varying Compliance

A horizontal balanced rotor supported on ball bearings with radial internal clearance, subjected to rotational speed fluctuations is modeled. The dynamic model takes under consideration contact forces derived by the hertzian theory of elasticity between the balls and the races, the effect of varying compliance, the internal radial clearance and the rotor’s speed fluctuations. The effect of variation in speed fluctuations is examined for periodic, unstable periodic and chaotic responses with the use of frequency distributions, higher order Poincare maps, and Lyapunov exponents. All results presented show a dominant stabilization effect of the speed fluctuations to the system behavior. From the analysis performed, it is concluded that even a minimum fluctuation of the rotor speed may result to major changes of the system dynamics, indicating that speed fluctuations of the rotor are a governing parameter to the dynamic behavior of the system.

scholarly journals Autocorrelation Ensemble Average of Larger Amplitude Impact Transients for the Fault Diagnosis of Rolling Element Bearings

Energies ◽  
2019 ◽  
Vol 12 (24) ◽  
pp. 4740
Author(s):  
Lei Hu ◽  
Yuandong Xu ◽  
Fengshou Gu ◽  
Jing He ◽  
Niaoqing Hu ◽  
...  
Keyword(s):  
Signal To Noise Ratio ◽  
Vibration Signal ◽  
Ensemble Average ◽  
Rolling Element Bearings ◽  
Ensemble Averaging ◽  
Critical Elements ◽  
Phase Errors ◽  
Rolling Element ◽  
Zone Centre ◽  
Speed Fluctuations

Rolling element bearings are one of the critical elements in rotating machinery of energy engineering systems. A defective roller of bearing moves in and out of the load zone during each revolution of the cage. Larger amplitude impact transients (LAITs) are produced when the defective roller passes the load zone centre and the defective area strikes the inner or outer races. A series of LAIT segments with higher signal to noise ratio are separated from a continuous vibration signal according to the bearing geometry and kinematics. In order to eliminate the phase errors between different LAIT segments that can arise from rotational speed fluctuations and roller slippages, unbiased autocorrelation is introduced to align the phases of LAIT segments. The unbiased autocorrelation signals make the ensemble averaging more accurate, and hence, archive enhanced diagnostic signatures, which are denoted as LAIT-AEAs for brevity. The diagnostic method based on LAIT separation and autocorrelation ensemble average (AEA) is evaluated with the datasets captured from real bearings of two different experiment benches. The validation results of the LAIT-AEAs are compared with the squared envelope spectrums (SESs) yielded based on two state-of-the-art techniques of Fast Kurtogram and Autogram.

Dynamics of an Improved Inter Shaft Squeeze Film Damper: Theory and Experiment

2007 ◽  
Author(s):  
K. Gupta ◽  
S. Chatterjee
Keyword(s):  
Gas Flow ◽  
Damping Ratio ◽  
Squeeze Film ◽  
Design Parameters ◽  
Radial Clearance ◽  
Rolling Element Bearings ◽  
Squeeze Film Damper ◽  
Wide Range ◽  
Rolling Element ◽  
Theoretical Simulations

Intershaft rolling element bearings are commonly used in aero gas turbine rotors primarily to reduce the length of the engine as well as to avoid obstruction to gas flow path at the turbine end. In order to reduce cross-excitation between the LP and HP shafts of two spool rotor, researchers have proposed introduction of squeeze film in the inter shaft bearing. However, Inter Shaft Squeeze Film Damper (ISSFD) becomes unstable above a threshold operating speeds. In the present work, an improved ISSFD which is inherently stable, is analyzed and tested. It has two rolling element bearings, one each mounted on LP and HP rotor shafts. The two bearings are configured such that the squeeze film is formed between the two non rotating races/surfaces. A centralizing spring between the two races, and a supporting spring between the ground/frame and one of the non rotating races are provided. Two design modifications of this system are analyzed and tested experimentally. Experiments on an improvised two spool rotor setup under unbalance excitation are conducted for all the three designs of ISSFD. In theoretical simulations, various design parameters are varied over a wide range. Theoretical analysis as well as the experiments show that an optimum value of radial clearance exists for a given design to have maximum damping, and a damping ratio of the order of 10% and more is achievable in an ISSFD.

Experiments and Numerical Results for Varying Compliance Contact Resonance in a Rigid Rotor–Ball Bearing System

2017 ◽  
Vol 139 (4) ◽  
Author(s):  
Yulin Jin ◽  
Rui Yang ◽  
Lei Hou ◽  
Yushu Chen ◽  
Zhiyong Zhang
Keyword(s):  
Vertical Direction ◽  
Numerical Results ◽  
Hertzian Contact ◽  
Radial Clearance ◽  
Rigid Rotor ◽  
Rolling Element ◽  
Run Up ◽  
Varying Compliance ◽  
Bearing System ◽  
Contact Resonance

This paper investigates the nonlinear characteristics of varying compliance contact resonance in a rotor–bearing system and takes into consideration the Hertzian contact deformation and internal radial clearance. We created an experimental rig of a rigid rotor supported by rolling element bearings. In the course of the rotational speed run up and down, the frequency–amplitude curves of the varying compliance vibrations were observed during experiments using different radial loads and compared with the results of our numerical simulations. The experimental and numerical results indicate that the varying compliance contact resonance in the vertical direction presents the soft spring characteristic, while the soft and hard spring characteristics coexist for the horizontal resonance.

scholarly journals A Simplified Mathematical Model for the Analysis of Varying Compliance Vibrations of a Rolling Bearing

2020 ◽  
Vol 10 (2) ◽  
pp. 670 ◽  
Author(s):  
Radoslav Tomović
Keyword(s):  
Mathematical Model ◽  
Parametric Analysis ◽  
Rolling Bearing ◽  
Influential Factors ◽  
Radial Clearance ◽  
Radial Load ◽  
Simplified Approach ◽  
Rolling Element ◽  
Rolling Elements ◽  
Varying Compliance

In this paper, a simplified approach in the analysis of the varying compliance vibrations of a rolling bearing is presented. This approach analyses the generation of vibrations in relation to two boundary positions of the inner ring support on an even and an odd number of the rolling element of a bearing. In this paper, a mathematical model for the calculation of amplitude and frequency of vibrations of a rigid rotor in a rolling bearing is presented. The model is characterized by a big simplicity which makes it very convenient for a practical application. Based on the presented mathematical model a parametric analysis of the influence of the internal radial clearance, external radial load and the total number of rolling elements on the varying compliance vibrations of rolling bearing was conducted. These parameters are the most influential factors for generating varying compliance vibrations. The results of the parametric analysis demonstrate that with the proper choice of the size of the internal radial clearance and external radial load, the level of the varying compliance vibrations in a rolling bearing can be theoretically reduced to zero. This result opposes the opinion that varying compliance vibrations of rolling bearing cannot be avoided, even for geometrically ideally produced bearing.

scholarly journals Multi-Dimensional Harmonic Balance Applied to Rotor Dynamics

2007 ◽  
Author(s):  
Mikhail Guskov ◽  
Jean-Jacques Sinou ◽  
Fabrice Thouverez
Keyword(s):  
Harmonic Balance ◽  
Dynamical Behavior ◽  
Steady State Solution ◽  
Rotor Dynamics ◽  
Radial Clearance ◽  
Rolling Element Bearings ◽  
Arc Length ◽  
Test Rig ◽  
Rolling Element ◽  
Non Linear

A large number of technical systems feature multi-frequency dynamical behavior. Multiple shaft rotating machinery, subject to simultaneous unbalances spinning at different speeds is a particular case of such systems. Common methods of steady state solution are not valid when the addressed systems have non-linear properties. This study presents a generalized version of harmonic balance coupled with arc-length continuation, developed in order to treat the dynamics of a dual shaft test rig provided with an inter-shaft bearing. The non-linearities are brought about by the presence of rolling element bearings with radial clearance. Numerically, the non-linear terms are taken into account via an AFT (alternating frequency-time domain) procedure, involving multi-dimensional FFT. The numerical results show the presence of response peaks corresponding to the rig’s eigenmodes predicted by linear eigensolution and from experiments. The overall behavior is consistent with the counter-rotating character of the machine operation. Non-linear phenomena due to bearings are also observed, especially the stiffening shape of peaks and apparent pedestal anisotropy involving the presence of backward whirling components in the system’s motion.

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