An Approach on Tuning the Frequency of a Rotating Blade

2008 ◽  
Author(s):  
L. Duong ◽  
K. Kazerounian ◽  
K. D. Murphy
Keyword(s):  
Structural Integrity ◽  
Natural Frequencies ◽  
Vibration Mode ◽  
The Finite Element Method ◽  
Turbine Engine ◽  
Rotating Blade ◽  
Alternative Approach ◽  
Excited Vibration ◽  
Speed Range ◽  
Analytical Expressions

In a gas turbine engine, the forced vibration of a turbine blade under resonant conditions is undesirable and may lead to premature high cycle fatigue failure. From the aspect of structural integrity, this demonstrates that it is extremely important to tune the excited vibration mode out of the operating speed range. This leads to the question: Is it possible to perform structural perturbations, namely to the mass and stiffness, in such a way that only the eigenvalue of choice significantly changes — while causing little or no change in the other natural frequencies? This is focus of the present paper. Due to the complexity of the blade structure, it is difficult to obtain an analytical solution from the eigenvalue perturbation theory. Nevertheless, the derived analytical expressions provide guidance from which the finite element method may successfully be applied as an alternative approach. This tuning approach is validated experimentally.

An Approach on Bladed-Disc Tuning

2009 ◽  
Author(s):  
Loc Duong ◽  
Kazem Kazerounian ◽  
Kevin D. Murphy
Keyword(s):  
High Cycle Fatigue ◽  
Natural Frequencies ◽  
Vibration Mode ◽  
Operating Speed ◽  
Cycle Fatigue ◽  
Finite Element Analyses ◽  
Excited Vibration ◽  
Structural Perturbations ◽  
Speed Range ◽  
Large Amplitude Vibrations

High cycle fatigue of rotating components, produced as the system is driven near to resonant conditions, is undesirable and is one of the major design concerns in engineering today. Structurally, it is imperative to tune the excited vibration mode out of the operating speed range to avoid large amplitude vibrations. It has been demonstrated that for a single blade with distinct eigenvalues, it is possible to tune the eigenvalue of choice out of the operating speed range while maintaining little change to other natural frequencies through structural perturbations. These perturbations usually come in the form of a redistribution of the stiffness and/or mass [1]. The focus of this paper is to extend this approach to the tuning of two adjacent excited frequencies of a bladed-disc by first reducing the inter-blade coupling through stiffening the disc structure followed by “individual” blade tuning. Due to the complexity of the bladed disc structure, results from direct finite element analyses are used based upon analytical eigen-perturbed expressions to investigate the dynamic inter-blade behavior of an impeller. A good correlation between analysis and laser vibrometry test measurements is obtained.

Analysis of the Leakage-Flow-Induced Vibration of a Slip Joint in a Jet Pump of a Boiling Water Reactor

2019 ◽  
Vol 390 ◽  
pp. 23-31 ◽  
Author(s):  
J. Cruz Castro ◽  
E. Hernández Palafox ◽  
I.A. Alarcón Sánchez ◽  
Luis H. Hernández-Gómez ◽  
Pablo Ruiz-López ◽  
...  
Keyword(s):  
Structural Integrity ◽  
Natural Frequencies ◽  
Excitation Frequency ◽  
Vibration Modes ◽  
The Finite Element Method ◽  
Jet Pump ◽  
Flow Induced Vibration ◽  
Ansys Fluent ◽  
Pump Assembly ◽  
Fourth Mode

The purpose of this analysis is to evaluate the structural integrity of the jet pump assembly of a BWR during the performance of its operational and safety functions. The natural frequencies and vibration modes of the jet pump assembly immersed in water were determined. It was observed that the fourth mode shape was torsional, and its associated resonance frequency was 41.82 Hz. Also, the vibration induced by the flow in the leakage of the slip joint was analyzed with an axisymmetric model. The gap of the slip joint was varied from 0.2 mm until 0.65bmm. A gap between 0.6 and 0.64, would cause flow-induced vibration because this excitation frequency matches with the fourth natural frequency of the jet pump assembly. The above was carried out using computational fluid dynamics, as well as the finite element method, with ANSYS Structural and ANSYS Fluent codes.

Vibrations of Twisted Cantilevered Plates—Experimental Investigation

1985 ◽  
Vol 107 (1) ◽  
pp. 187-196 ◽  
Author(s):  
J. C. MacBain ◽  
R. E. Kielb ◽  
A. W. Leissa
Keyword(s):  
Research Study ◽  
Natural Frequencies ◽  
Vibration Mode ◽  
Mode Shapes ◽  
Turbine Engine ◽  
Aspect Ratios ◽  
Engine Blade ◽  
Vibrational Characteristics ◽  
Cantilevered Plates ◽  
Effect Of Support

The experimental portion of a joint government/industry/university research study on the vibrational characteristics of twisted cantilevered plates is presented. The overall purpose of the research study was to assess the capabilities and limitations of existing analytical methods in predicting the vibratory characteristics of twisted plates. Thirty cantilevered plates were precision machined at the Air Force’s Aero Propulsion Laboratory. These plates, having five different degrees of twist, two thicknesses, and three aspect ratios representative of turbine engine blade geometries, were tested for their vibration mode shapes and frequencies. The resulting nondimensional frequencies and selected mode shapes are presented as a function of plate tip twist. The trends of the plate natural frequencies as a function of the governing geometric parameters are discussed. The effect of support compliance on the plate natural frequency and its impact on numerically modeling twisted plates is also presented.

Response Prediction of Static Modal Testing on Milling Machine Tool

2014 ◽  
Vol 606 ◽  
pp. 131-135 ◽  
Author(s):  
Norlida Jamil ◽  
Ahmad Razlan Yusoff ◽  
Muhammad Hatifi Mansor
Keyword(s):  
Machine Tool ◽  
3D Model ◽  
Natural Frequencies ◽  
Mechanical Test ◽  
Response Prediction ◽  
Modal Testing ◽  
The Finite Element Method ◽  
Excited Vibration ◽  
Good Consistency ◽  
Design Software

Milling is one of the most common manufacturing processes for automotive component, but its productivity is limited by chatter. This form of chatter is undesirable because it results in premature tool wear, poor surface finish on the machined component and the possibility of serious damage to the machine itself. Modal testing is a form of vibration testing which is able to determine the Frequency Response Function (FRF) of the mechanical test structures. In this paper, the main focus is to obtain natural frequency values for machine tool components in order to establish better conditions in the cutting process on the machine tool. For this purpose, a 3D model of the machine tool’s part is made using design software and exported to analysis software. Later on, the Finite Element Method (FEM) modal analysis was used to obtain the natural frequencies. The model is evaluated and corrected through an experimental modal test. In the experiment, the machine tool vibration is excited by impact hammer and the response of excited vibration is recorded. In the end, the result of both FEM and experimental shows a good consistency in comparison.

Transient Response of Beams, Plates, and Shells to Impulsive Loads

2007 ◽  
Author(s):  
Serge Abrate
Keyword(s):  
Natural Frequencies ◽  
Vibration Mode ◽  
Analysis Method ◽  
The Finite Element Method ◽  
Fundamental Vibration ◽  
Short Pulses ◽  
Modal Expansion ◽  
Expansion Technique ◽  
Impulsive Loads ◽  
Plates And Shells

Beams, plates and shells are used in many applications where there can be subjected to short duration loads due to impacts or pressure blasts. Here the response of such distributed systems is examined using the modal expansion technique for pulse shapes typically observed during impacts and explosions. The objective is to gain an understanding of the behavior of these structures. For beams and plates the natural frequencies are generally well separated and, typically, a small number of modes participate in the response. Pulses can be classified as being either short, long, or intermediate in comparison with the period of the fundamental vibration mode. Very different behaviors are observed for the three types of pulses. For short pulses, the response depends on impulse applied not on the shape of the pulse and it can be accurately predicted by the response to an equivalent impulse. For long pulses, the maximum response depends on the magnitude of the load applied. For shells, the effect of curvature can be significant and result in several modes with close frequencies. In that case the response is more complicated since many modes participate in the response. In this work, the criteria are developed for predicting the response of each mode to a various pulses and determine how many modes participate in the response. The results obtained are applicable with any other analysis method including the finite element method.

scholarly journals Impact of Geometrical Imperfections on Estimation of Buckling and Limit Loads in a Silo Segment Using the Vibration Correlation Technique

Materials ◽  
2021 ◽  
Vol 14 (3) ◽  
pp. 567
Author(s):  
Łukasz Żmuda-Trzebiatowski ◽  
Piotr Iwicki
Keyword(s):  
Natural Frequencies ◽  
Vibration Mode ◽  
Mode Shapes ◽  
Correlation Technique ◽  
Limit Loads ◽  
Linear Buckling ◽  
Geometrical Imperfections ◽  
Linear Problems ◽  
Formed Channel ◽  
Corrugated Wall

The paper examines effectiveness of the vibration correlation technique which allows determining the buckling or limit loads by means of measured natural frequencies of structures. A steel silo segment with a corrugated wall, stiffened with cold-formed channel section columns was analysed. The investigations included numerical analyses of: linear buckling, dynamic eigenvalue and geometrically static non-linear problems. Both perfect and imperfect geometries were considered. Initial geometrical imperfections included first and second buckling and vibration mode shapes with three amplitudes. The vibration correlation technique proved to be useful in estimating limit or buckling loads. It was very efficient in the case of small and medium imperfection magnitudes. The significant deviations between the predicted and calculated buckling and limit loads occurred when large imperfections were considered.

scholarly journals Isospectrals of non-uniform Rayleigh beams with respect to their uniform counterparts

2018 ◽  
Vol 5 (2) ◽  
pp. 171717 ◽  
Author(s):  
Srivatsa Bhat K ◽  
Ranjan Ganguli
Keyword(s):  
Boundary Condition ◽  
Cross Section ◽  
Natural Frequencies ◽  
Rectangular Cross Section ◽  
Beam Equation ◽  
The Finite Element Method ◽  
Rayleigh Beam ◽  
Uniform Beam ◽  
Governing Differential Equation ◽  
The Given

In this paper, we look for non-uniform Rayleigh beams isospectral to a given uniform Rayleigh beam. Isospectral systems are those that have the same spectral properties, i.e. the same free vibration natural frequencies for a given boundary condition. A transformation is proposed that converts the fourth-order governing differential equation of non-uniform Rayleigh beam into a uniform Rayleigh beam. If the coefficients of the transformed equation match with those of the uniform beam equation, then the non-uniform beam is isospectral to the given uniform beam. The boundary-condition configuration should be preserved under this transformation. We present the constraints under which the boundary configurations will remain unchanged. Frequency equivalence of the non-uniform beams and the uniform beam is confirmed by the finite-element method. For the considered cases, examples of beams having a rectangular cross section are presented to show the application of our analysis.

scholarly journals Modal analysis of an iced offshore composite wind turbine blade

2021 ◽  
pp. 0309524X2110116
Author(s):  
Oumnia Lagdani ◽  
Mostapha Tarfaoui ◽  
Mourad Nachtane ◽  
Mourad Trihi ◽  
Houda Laaouidi
Keyword(s):  
Wind Turbine ◽  
Modal Analysis ◽  
Turbine Blade ◽  
Natural Frequencies ◽  
Wind Turbine Blade ◽  
Resonance Phenomenon ◽  
Mode Shapes ◽  
The Finite Element Method ◽  
Numerical Work ◽  
Composite Blades

In the far north, low temperatures and atmospheric icing are a major danger for the safe operation of wind turbines. It can cause several problems in fatigue loads, the balance of the rotor and aerodynamics. With the aim of improving the rigidity of the wind turbine blade, composite materials are currently being used. A numerical work aims to evaluate the effect of ice on composite blades and to determine the most adequate material under icing conditions. Different ice thicknesses are considered in the lower part of the blade. In this paper, modal analysis is performed to obtain the natural frequencies and corresponding mode shapes of the structure. This analysis is elaborated using the finite element method (FEM) computer program through ABAQUS software. The results have laid that the natural frequencies of the blade varied according to the material and thickness of ice and that there is no resonance phenomenon.

Effect of Delamination on Natural Frequencies of E-glass and S-glass Epoxy Composite Plates

2021 ◽  
Author(s):  
P. K. Karsh ◽  
Bindi Thakkar ◽  
R. R. Kumar ◽  
Abhijeet Kumar ◽  
Sudip Dey
Keyword(s):  
Natural Frequencies ◽  
Epoxy Composite ◽  
Orientation Angle ◽  
Laminated Composite ◽  
Composite Plates ◽  
Mode Shapes ◽  
Transverse Shear Deformation ◽  
The Finite Element Method ◽  
Modes Of Failure ◽  
Ply Orientation

The delamination is one of the major modes of failure occurring in the laminated composite due to insufficient bonding between the layers. In this paper, the natural frequencies of delaminated S-glass and E-glass epoxy cantilever composite plates are presented by employing the finite element method (FEM) approach. The rotary inertia and transverse shear deformation are considered in the present study. The effect of parameters such as the location of delamination along the length, across the thickness, the percentage of delamination, and ply-orientation angle on first three natural frequencies of the cantilever plates are presented for S-glass and E-glass epoxy composites. The standard eigenvalue problem is solved to obtain the natural frequencies and corresponding mode shapes. First three mode shape of S-Glass and E-Glass epoxy laminated composites are portrayed corresponding to different ply angle of lamina.

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