scholarly journals Estimation of Squeeze-Film Damping and Inertial Coefficients from Experimental Free-Decay Data

1986 ◽  
Vol 200 (2) ◽  
pp. 123-133 ◽  
Author(s):  
J B Roberts ◽  
R Holmes ◽  
P J Mason
Keyword(s):  
Linear Model ◽  
Transient Response ◽  
Parametric Identification ◽  
Squeeze Film ◽  
Decay Data ◽  
Operating Range ◽  
Response Data ◽  
Squeeze Film Damping ◽  
Free Decay ◽  
Theoretical Predictions

This paper describes the results obtained from an experimental programme concerned with a parametric identification of the damping and inertial coefficients of a cylindrical squeeze-film bearing, through an analysis of transient response data. The results enable the operating range for which a linear model of the squeeze-film is appropriate to be determined. Comparisons are made between the estimated coefficients and theoretical predictions.

Determination of Squeeze-Film Dynamic Coefficients From Experimental Transient Data

1987 ◽  
Vol 109 (1) ◽  
pp. 155-163 ◽  
Author(s):  
M. D. Ramli ◽  
J. B. Roberts ◽  
J. Ellis
Keyword(s):  
Parametric Identification ◽  
Optimization Techniques ◽  
Squeeze Film ◽  
Dynamic Coefficients ◽  
Free Decay ◽  
Transient Data

A technique for obtaining estimates of the direct damping and inertial coefficients of a squeeze-film bearing is described. This involves applying parametric identification and optimization techniques to digitized, free-decay experimental displacement records. The experimentally obtained coefficients, derived by this technique, were found to be significantly higher in magnitude (in some cases by a factor of about 10) than the corresponding values derived from conventional short-bearing theory, and to be virtually independent of the frequency of vibration.

Estimation of Nonlinear Ship Roll Damping from Free-Decay Data

1985 ◽  
Vol 29 (02) ◽  
pp. 127-138 ◽  
Author(s):  
J. B. Roberts
Keyword(s):  
Initial Conditions ◽  
Spline Interpolation ◽  
Parametric Identification ◽  
Nonlinear Damping ◽  
Scale Model ◽  
Identification Procedure ◽  
Simulation Data ◽  
Decay Data ◽  
Free Decay ◽  
Ship Roll

A common method of assessing the damping present in ship rolling motion is to perform a free-decay experiment, in which, in the absence of waves, the ship is given an initial roll amplitude and then released. By processing the resulting decaying, oscillatory trace it is possible to estimate quantitatively the degree of damping, even when this is nonlinear. In this paper an approach to the estimation of nonlinear damping is proposed which involves the use of a cubic spline interpolation of the peak amplitudes, followed by a parametric identification procedure. This method is first applied to some simulation data and then to some real free-decay data, obtained from a scale model of a ship, with various initial conditions. The experimental data are analyzed using two alternative parametric forms, that is, linear-plus-quadratic and linear-plus-cubic damping. A principal advantage of the proposed technique is that, because nonlinearities in the restoring moment are properly accounted for, it is not limited to small angles of roll. Thus it can be applied to free-decay data relating to very large initial roll amplitudes.

Coupled effects of surface interaction and damping on electromechanical stability of functionally graded nanotubes reinforced torsional micromirror actuator

2021 ◽  
pp. 030932472110368
Author(s):  
Weidong Yang ◽  
Menglong Liu ◽  
Linwei Ying ◽  
Xi Wang
Keyword(s):  
Casimir Force ◽  
Volume Fraction ◽  
Nonlocal Parameter ◽  
Saddle Points ◽  
Functionally Graded ◽  
Heteroclinic Orbits ◽  
Phase Portraits ◽  
Squeeze Film ◽  
Squeeze Film Damping ◽  
Tilting Angle

This paper demonstrated the coupled surface effects of thermal Casimir force and squeeze film damping (SFD) on size-dependent electromechanical stability and bifurcation of torsion micromirror actuator. The governing equations of micromirror system are derived, and the pull-in voltage and critical tilting angle are obtained. Also, the twisting deformation of torsion nanobeam can be tuned by functionally graded carbon nanotubes reinforced composites (FG-CNTRC). A finite element analysis (FEA) model is established on the COMSOL Multiphysics platform, and the simulation of the effect of thermal Casimir force on pull-in instability is utilized to verify the present analytical model. The results indicate that the numerical results well agree with the theoretical results in this work and experimental data in the literature. Further, the influences of volume fraction and geometrical distribution of CNTs, thermal Casimir force, nonlocal parameter, and squeeze film damping on electrically actuated instability and free-standing behavior are detailedly discussed. Besides, the evolution of equilibrium states of micromirror system is investigated, and bifurcation diagrams and phase portraits including the periodic, homoclinic, and heteroclinic orbits are described as well. The results demonstrated that the amplitude of the tilting angle for FGX-CNTRC type micromirror attenuates slower than for FGO-CNTRC type, and the increment of CNTs volume ratio slows down the attenuation due to the stiffening effect. When considering squeeze film damping, the stable center point evolves into one focus point with homoclinic orbits, and the dynamic system maintains two unstable saddle points with the heteroclinic orbits due to the effect of thermal Casimir force.

Efficient dynamic analysis of a whole aeroengine using identified nonlinear bearing models

2011 ◽  
Vol 226 (1) ◽  
pp. 66-81 ◽  
Author(s):  
K H Groves ◽  
P Bonello ◽  
P M Hai
Keyword(s):  
Dynamic Performance ◽  
Computational Cost ◽  
Parametric Identification ◽  
Frequency Domain Analysis ◽  
Reduced Form ◽  
Squeeze Film ◽  
Computational Time ◽  
Parameter Study ◽  
Accurate Identification ◽  
Non Linear

Essential to effective aeroengine design is the rapid simulation of the dynamic performance of a variety of engine and non-linear squeeze-film damper (SFD) bearing configurations. Using recently introduced non-linear solvers combined with non-parametric identification of high-accuracy bearing models it is possible to run full-engine rotordynamic simulations, in both the time and frequency domains, at a fraction of the previous computational cost. Using a novel reduced form of Chebyshev polynomial fits, efficient and accurate identification of the numerical solution to the two-dimensional Reynolds equation (RE) is achieved. The engine analysed is a twin-spool five-SFD engine model provided by a leading manufacturer. Whole-engine simulations obtained using Chebyshev-identified bearing models of the finite difference (FD) solution to the RE are compared with those obtained from the original FD bearing models. For both time and frequency domain analysis, the Chebyshev-identified bearing models are shown to mimic accurately and consistently the simulations obtained from the FD models in under 10 per cent of the computational time. An illustrative parameter study is performed to demonstrate the unparalleled capabilities of the combination of recently developed and novel techniques utilised in this paper.

Deep Hole Honing Based on Squeeze Film Damping Technology

2009 ◽  
Vol 76-78 ◽  
pp. 252-257
Author(s):  
Tian Biao Yu ◽  
Ya Dong Gong ◽  
Wan Shan Wang
Keyword(s):  
Differential Equation ◽  
Experimental Result ◽  
Squeeze Film ◽  
Design Parameters ◽  
Improve Quality ◽  
Deep Hole ◽  
Squeeze Film Damper ◽  
Squeeze Film Damping ◽  
Hole Machining

In order to improve quality of deep hole machining, a new method of deep hole honing based on squeeze film damping technology is put forward. For analysis effect on damper parameters on honing quality, motion differential equation of honing spindle with a squeeze film damper (SFD) is established according to D' Alembert principle and according simulations are studied. Spindle of deep hole honing with a SFD is designed based on the result of simulations and experiments are carried on. Experimental result shows that SFD with reasonable design parameters has excellent damping function to honing spindle, and it can make the vibration of honing spindle reduced 20%～30% and the quality of deep hole machining improved 10%～20%.

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