Coupling of Turbomachine Blade Vibrations Through the Rotor

1967 ◽  
Vol 89 (4) ◽  
pp. 502-512 ◽  
Author(s):  
J. T. Wagner
Keyword(s):  
Forced Vibration ◽  
Natural Frequencies ◽  
Vibration Response ◽  
Analytical Models ◽  
Finite Mass ◽  
Blade Vibration ◽  
Resonant Frequencies ◽  
Vibration Tests ◽  
Flexible Disk ◽  
Turbomachine Blade

The forced vibration response of subsystems with different natural frequencies and damping, attached to a foundation with finite stiffness or mass, is calculated. Analytical models include simulations of turbomachine blading on a flexible disk or on a rotor with finite mass. Coupling through the disk or rotor explains variations in resonant frequencies and amplitudes that have been observed in blade-vibration tests. Effects on damping measurements are also determined.

Forced Vibration of Thick Viscoelastic Cylinders

1993 ◽  
Author(s):  
H. R. Hamidzadeh ◽  
G. R. Minor
Keyword(s):  
Forced Vibration ◽  
Elastic Moduli ◽  
Natural Frequencies ◽  
Three Dimensional ◽  
Dimensional Theory ◽  
Material Loss ◽  
Resonant Frequencies ◽  
Frequency Responses ◽  
Infinite Extent ◽  
Hollow Cylinders

Abstract Harmonic forced vibration of thick viscoelastic hollow cylinders of infinite extent is considered. The cylinder is excited by stresses applied at the inner and outer boundaries. The governing equation of motion is developed by utilizing three dimensional theory of elastodynamics. The material damping is allowed using complex elastic moduli for the viscoelastic medium. Modal displacements and stresses at any point in the medium are formulated in terms of boundary stresses. Frequency responses for radial, tangential and axial displacements are computed for different circumferential and axial wave numbers. The effect of different material loss factors on the frequency responses is examined for axial and nonaxisymmetric modes. The dimensionless resonant frequencies for zero loss factor are compared with dimensionless natural frequencies available for elastic material. Comparison indicates excellent agreement between the results.

Flutter and Forced Vibration Characteristics of a Turbo Fan Bladed Disk Rotor

2013 ◽  
Author(s):  
Madhavan Srinivasan ◽  
Sankarkumar Jeyaraman ◽  
Rajeev Jain ◽  
Sujatha Chandramohan ◽  
Sekhar AnandaRao Seshadri
Keyword(s):  
Forced Vibration ◽  
Natural Frequencies ◽  
Fluid Dynamic ◽  
Mode Shapes ◽  
Blade Vibration ◽  
Engine Operation ◽  
Bladed Disk ◽  
Blade Flutter ◽  
Loss Of Thrust

Aero-elastic excitation can result in excessive blade vibration, which can cause blades to fail in high cycle fatigue (HCF). A severe aero-elastic failure can result in a complete blade separation and loss of thrust and loss of a blade can mean the loss of an aircraft. The primary aeromechanical design concerns are blade flutter and forced vibration that need to be quantified at the early part of engine tests. This paper details the experimental investigation carried out on a transonic shroudless low aspect ratio fan bladed disk that experienced subsonic/transonic stall flutter and forced vibration excitation. Experiments are performed on a full scale engine using tip timing sensors flush mounted on the fan casing to characterize the vibratory responses during flutter and forced vibration conditions during engine operation. Numerical simulations are performed using computational fluid dynamic (CFD) analysis. Blade natural frequencies and mode shapes are obtained from finite element (FE) modal analysis. The experimental data captured from engine tests are used to validate the predicted results.

scholarly journals Nonlinear forced vibration response of smart two-phase nano-composite beams to external harmonic excitations

2015 ◽  
Vol 2 (1) ◽  
Author(s):  
Soraya Mareishi ◽  
Hamed Kalhori ◽  
Mohammad Rafiee ◽  
Seyedeh Marzieh Hosseini
Keyword(s):  
Carbon Nanotubes ◽  
Frequency Response ◽  
Distribution Pattern ◽  
Temperature Change ◽  
Elastic Foundation ◽  
Forced Vibration ◽  
Natural Frequencies ◽  
Composite Beams ◽  
Vibration Response ◽  
Nano Composite

AbstractThis paper presents an analytical solution for nonlinear free and forced vibration response of smart laminated nano-composite beams resting on nonlinear elastic foundation and under external harmonic excitation. The structure is under a temperature change and an electric excitation through the piezoelectric layers. Different distribution patterns of the single walled aligned and straight carbon nanotubes (SWCNTs) through the thickness of the beam are considered. The beam complies with Euler-Bernoulli beam theory and von Kármán geometric nonlinearity. The nonlinearity is due to the mid-plane stretching of the beam and the nonlinear stiffness of the elastic foundation. The Multiple Time Scales perturbation scheme is used to perform the nonlinear dynamical analysis of functionally graded carbon nanotube-reinforced beams. Analytical expressions of the nonlinear natural frequencies, nonlinear dynamic response and frequency response of the system in the case of primary resonance have been presented. The effects of different parameters including applied voltage, temperature change, beam geometry, the volume fraction and distribution pattern of the carbon nanotubes on the nonlinear natural frequencies and frequency-response curves are presented. It is found that the volume fractions of SWCNTs as well as their distribution pattern significantly change the behavior of the system.

Vibration Localization in Plates With Misplaced Intermediate Supports in Two Orthogonal Directions

2003 ◽  
Author(s):  
Wei-Chau Xie ◽  
Zhihua Chen
Keyword(s):  
Forced Vibration ◽  
Natural Frequencies ◽  
Current Approach ◽  
Vibration Response ◽  
Vibration Modes ◽  
The Finite Element Method ◽  
Concentrated Load ◽  
Vibration Localization ◽  
Vibration Responses ◽  
Simple Supports

This paper investigates the effect of small misplacements on both the free vibration modes and forced vibration responses of a four-panel simply supported plate with two intermediate simple supports in two orthogonal directions. Kantorovich’s method is employed to obtain the natural frequencies and the corresponding vibration modes. Galerkin’s method is applied to determine the forced vibration response of the four-panel plate subjected to a harmonic concentrated load at the center of one of its four panels. Comparisons between numerical results obtained using the current approach and those using the exact solution and the finite element method are made to demonstrate the accuracy of the current approach. It is found that the small misplacements of the intermediate supports have dramatic effects on the vibration response of the plate. The larger the misplacement of the intermediate supports, the larger the degree of vibration localization. By judiciously introducing misplacements in the intermediate simple supports, the vibration of some of the four panels may be controlled.

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.

Measurement of Young’s Modulus and Shear Modulus of Some Structures Welded Using Flux Cored Wire by Vibration Tests

2014 ◽  
Vol 216 ◽  
pp. 151-156 ◽  
Author(s):  
Liviu Bereteu ◽  
Mircea Vodǎ ◽  
Gheorghe Drăgănescu
Keyword(s):  
Shear Modulus ◽  
Arc Welding ◽  
Natural Frequencies ◽  
Free Vibrations ◽  
Vibration Modes ◽  
Cored Wire ◽  
Flux Cored Arc Welding ◽  
Longitudinal Elastic Modulus ◽  
Vibration Tests ◽  
Non Destructive

The aim of this work was to determine by vibration tests the longitudinal elastic modulus and shear modulus of welded joints by flux cored arc welding. These two material properties are characteristic elastic constants of tensile stress respectively torsion stress and can be determined by several non-destructive methods. One of the latest non-destructive experimental techniques in this field is based on the analysis of the vibratory signal response from the welded sample. An algorithm based on Pronys series method is used for processing the acquired signal due to sample response of free vibrations. By the means of Finite Element Method (FEM), the natural frequencies and modes shapes of the same specimen of carbon steel were determined. These results help to interpret experimental measurements and the vibration modes identification, and Youngs modulus and shear modulus determination.

scholarly journals Ambient Vibration Tests of an Arch Dam with Different Reservoir Water Levels: Experimental Results and Comparison with Finite Element Modelling

2014 ◽  
Vol 2014 ◽  
pp. 1-12 ◽  
Author(s):  
Sergio Vincenzo Calcina ◽  
Laura Eltrudis ◽  
Luca Piroddi ◽  
Gaetano Ranieri
Keyword(s):  
Finite Element ◽  
Natural Frequencies ◽  
Water Levels ◽  
Arch Dam ◽  
Experimental Results ◽  
Ambient Vibration ◽  
Reservoir Water ◽  
Ambient Vibration Tests ◽  
Vibration Properties ◽  
Vibration Tests

This paper deals with the ambient vibration tests performed in an arch dam in two different working conditions in order to assess the effect produced by two different reservoir water levels on the structural vibration properties. The study consists of an experimental part and a numerical part. The experimental tests were carried out in two different periods of the year, at the beginning of autumn (October 2012) and at the end of winter (March 2013), respectively. The measurements were performed using a fast technique based on asynchronous records of microtremor time-series. In-contact single-station measurements were done by means of one single high resolution triaxial tromometer and two low-frequency seismometers, placed in different points of the structure. The Standard Spectral Ratio method has been used to evaluate the natural frequencies of vibration of the structure. A 3D finite element model of the arch dam-reservoir-foundation system has been developed to verify analytically determined vibration properties, such as natural frequencies and mode shapes, and their changes linked to water level with the experimental results.

FORCED VIBRATION TESTS AND THEORETICAL STUDIES ON DAMS.

1980 ◽  
Vol 69 (3) ◽  
pp. 605-634 ◽  
Author(s):  
RT SEVERN ◽  
AP JEARY ◽  
BR ELLIS ◽  
Keyword(s):  
Forced Vibration ◽  
Theoretical Studies ◽  
Vibration Tests
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