Analysis of non-linear mode shapes and natural frequencies of continuous damped systems

2004 ◽  
Vol 275 (1-2) ◽  
pp. 283-298 ◽  
Author(s):  
S.N. Mahmoodi ◽  
S.E. Khadem ◽  
M. Rezaee
Keyword(s):  
Natural Frequencies ◽  
Mode Shapes ◽  
Linear Mode ◽  
Non Linear ◽  
Damped Systems

Non-linear free transverse vibration of thin rotating discs

2007 ◽  
Vol 221 (3) ◽  
pp. 467-473 ◽  
Author(s):  
H R Hamidzadeh
Keyword(s):  
Steady State ◽  
Free Vibration ◽  
Natural Frequencies ◽  
Mode Shapes ◽  
Stress Distributions ◽  
Rotating Speed ◽  
Rotating Discs ◽  
Non Linear ◽  
Modes Of Vibration ◽  
Free Transverse Vibration

An analytical method is adopted to determine modal characteristics of non-linear spinning discs. The disc is assumed to be isotropic and rotating under steady-state conditions. The effects of amplitude and rotating speed on natural frequencies are determined. The developed procedure is also capable of analysing natural frequencies of linear free vibration, which is independent of amplitude. Attention is confined to determine natural frequencies, mode shapes, stress distributions, and critical speeds for different numbers of nodal diameters. The developed procedure does not consider modes of vibration corresponding to nodal circles. Validity of this procedure is verified by comparing some of the computed results with those established for certain cases.

Methods of Preserving Symmetry in Model Updating

1995 ◽  
Vol 117 (3A) ◽  
pp. 349-354
Author(s):  
M. J. Lam ◽  
D. J. Inman
Keyword(s):  
Experimental Data ◽  
Analytical Model ◽  
Natural Frequencies ◽  
Model Updating ◽  
Mode Shapes ◽  
Modal Parameter ◽  
Modal Data ◽  
Model Correction ◽  
Damped Systems ◽  
Stiffness And Damping

This work examines the model updating technique for both conservative and nonproportionally damped systems. In model updating, also referred to as model correction, the analytical model is updated until it agrees with the experimental data available. In this paper it is assumed that the measured modal data, i.e., natural frequencies and in some instances mode shapes, disagrees in part with the modal parameter predicted by the analytical model. Many model updating schemes tend to produce nonsymmetric updated stiffness (and damping) matrices. The methods presented here focus on retaining the desired symmetry in the updated model

scholarly journals Non-Linear Forced Vibration of Fully Clamped FGM Skew Plates using Homogenization Technique

2019 ◽  
Vol 286 ◽  
pp. 03002
Author(s):  
H. Moulay Abdelali ◽  
R. Benamar
Keyword(s):  
Forced Vibration ◽  
Functionally Graded ◽  
Mode Shapes ◽  
Skew Angle ◽  
Linear Mode ◽  
Homogenization Technique ◽  
Skew Plate ◽  
Non Linear ◽  
Excitation Force ◽  
The Right

The present work concerns the geometrically non-linear forced vibration of fully clamped functionally graded skew plates (FGSP). The theoretical model based on Hamilton’s principle and spectral analysis previously applied to obtain the non-linear mode shapes of thin straight structures is used. A homogenization technique is developed to reduce the FGSP problem under consideration to that of an equivalent isotropic homogeneous skew plate. Results are given for the linear and non-linear fundamental frequency of fully clamped FGSP, considering different parameters, such as the skew angle, the excitation force level. The results show a non linearity of the hardening type with a shift to the right of the bent non linear frequency response function, in the neighbourhood of the fundamental mode.

Geometrically Non-Linear Free Vibration of Fully Clamped FGM Skew Plates Using Homogenization Technique

2015 ◽  
Vol 1105 ◽  
pp. 370-380
Author(s):  
Moulay Abdelali Hanane ◽  
Khalid El Bikri ◽  
Benamar Rhali
Keyword(s):  
Free Vibration ◽  
Functionally Graded ◽  
Mode Shapes ◽  
Power Law Distribution ◽  
Skew Angle ◽  
Linear Mode ◽  
Homogenization Technique ◽  
Skew Plate ◽  
Non Linear ◽  
Good Agreement

The present work concerns the geometrically non-linear free vibration of fully clamped functionally graded skew plates (FGSP). The theoretical model based on Hamilton’s principle and spectral analysis is used. A homogenization technique has been developed to reduce the FGSP problem under consideration to that of an isotropic homogeneous skew plate. The material properties of the skew plate examined herein are assumed to be graded in the thickness direction of the plate according to the power-law distribution in terms of volume fractions of the constituents. Results are given for the linear and non-linear fundamental frequency considering different parameters. The non-linear mode shapes exhibit a maximum value in the bending stress at the centre of the plate. It is found also that the non-linear frequencies increase with increasing the amplitude of vibration and increasing the skew angle, which corresponds to the hardening type effect. A good agreement is found with published results.

A beam with arbitrarily placed lateral dampers: Evolution of complex modes with damping

2016 ◽  
Vol 24 (2) ◽  
pp. 379-392 ◽  
Author(s):  
Y Chen ◽  
DM McFarland ◽  
BF Spencer ◽  
LA Bergman
Keyword(s):  
Free Vibration ◽  
Natural Frequencies ◽  
Numerical Study ◽  
Frequency Equation ◽  
Mode Shapes ◽  
Dynamic Features ◽  
Complex Modes ◽  
Orthogonality Conditions ◽  
Boundary Condition Method ◽  
Damped Systems

Free vibration of a beam with multiple arbitrarily placed lateral viscous dampers is investigated to gain insight into the intrinsic dynamic features of non-proportional damped systems. In terms of virtual boundary condition method, complex modes of a damper-beam system are achieved, and the solution is also suitable for the beams that have different boundary conditions. The features of the wave numbers satisfying the frequency equation were discussed in theory. The orthogonality analysis conducted in this paper provides two orthogonality conditions for complex modes. Pseudoundamped natural frequencies, damping ratios and complex modes are surveyed via numerical study. The analysis on the evolution of complex modes shows that the increasing damping would lead to over damped modes, and the mode shape that corresponds to the small one of a pair of real-valued natural frequencies is close to the static deformation shape of a beam subjected to static forces located at the positions of the dampers. For the rest modes that would never be over damped with increasing damping, the mode shapes and corresponding psuedoundamped natural frequencies will converge to that of a beam with rolling supports located at where dampers are placed. The exact solution of free vibration of a multiple-span beam is presented in addition.

Tire Vibrations

1977 ◽  
Vol 5 (4) ◽  
pp. 202-225 ◽  
Author(s):  
G. R. Potts ◽  
C. A. Bell ◽  
L. T. Charek ◽  
T. K. Roy
Keyword(s):  
Natural Frequencies ◽  
Standing Waves ◽  
Resonant Mode ◽  
Mode Shapes ◽  
Resonant Vibrations ◽  
Resonant Frequencies ◽  
Radial Tire ◽  
Analysis Techniques ◽  
Thin Ring ◽  
Good Agreement

Abstract Natural frequencies and vibrating motions are determined in terms of the material and geometric properties of a radial tire modeled as a thin ring on an elastic foundation. Experimental checks of resonant frequencies show good agreement. Forced vibration solutions obtained are shown to consist of a superposition of resonant vibrations, each rotating around the tire at a rate depending on the mode number and the tire rotational speed. Theoretical rolling speeds that are upper bounds at which standing waves occur are determined and checked experimentally. Digital Fourier transform, transfer function, and modal analysis techniques used to determine the resonant mode shapes of a radial tire reveal that antiresonances are the primary transmitters of vibration to the tire axle.

Dynamic model for high-speed rotors based on their experimental characterization

2017 ◽  
Vol 2 (4) ◽  
pp. 25
Author(s):  
L. A. Montoya ◽  
E. E. Rodríguez ◽  
H. J. Zúñiga ◽  
I. Mejía
Keyword(s):  
Dynamic Model ◽  
High Speed ◽  
Natural Frequencies ◽  
Mode Shapes ◽  
Experimental Characterization ◽  
Rotating Systems ◽  
Computing Performance ◽  
The Impact ◽  
Stiffness Distribution ◽  
Good Agreement

Rotating systems components such as rotors, have dynamic characteristics that are of great importance to understand because they may cause failure of turbomachinery. Therefore, it is required to study a dynamic model to predict some vibration characteristics, in this case, the natural frequencies and mode shapes (both of free vibration) of a centrifugal compressor shaft. The peculiarity of the dynamic model proposed is that using frequency and displacements values obtained experimentally, it is possible to calculate the mass and stiffness distribution of the shaft, and then use these values to estimate the theoretical modal parameters. The natural frequencies and mode shapes of the shaft were obtained with experimental modal analysis by using the impact test. The results predicted by the model are in good agreement with the experimental test. The model is also flexible with other geometries and has a great time and computing performance, which can be evaluated with respect to other commercial software in the future.

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