Distortion of the sinusoidalness of the forms of vibrations of systems with a disturbed rotary symmetry and the mode localization phenomenon. Report 1

1992 ◽  
Vol 24 (10) ◽  
pp. 613-620 ◽  
Author(s):  
A. P. Zin'kovskii
Keyword(s):  
Mode Localization ◽  
Localization Phenomenon ◽  
Rotary Symmetry

Effect of a local crack on the dynamic characteristics of a rotating grouped blade disc

2001 ◽  
Vol 216 (4) ◽  
pp. 447-457 ◽  
Author(s):  
B W Huang ◽  
J H Kuang
Keyword(s):  
Dynamic Characteristics ◽  
Rotational Speed ◽  
Crack Depth ◽  
Numerical Results ◽  
Galerkin’S Method ◽  
Mode Localization ◽  
Torsion Spring ◽  
Crack Distribution ◽  
Localization Phenomenon ◽  
Blade Crack

The effects of a local blade crack and the group arrangement on the mode localization in a rotating turbodisc are studied in this paper. Periodically coupled Euler—Bernoulli beams are used to approximate the grouped and shrouded turboblades. A two-span beam with a torsion spring is used to model the cracked blade. The crack depth characterizes the stiffness of the assumed torsion spring. Galerkin's method is applied to formulate the localization equations of the grouped turbodisc system. Numerical results indicate that the crack depth, crack distribution and rotational speed in a rotating grouped blade disc may significantly affect the localization phenomenon.

Dynamic Characteristics of a Mistuned Heat Exchanger in Cross-Flow

2007 ◽  
Author(s):  
Bo-Wun Huang ◽  
Huang-Kuang Kung ◽  
Jao-Hwa Kuang
Keyword(s):  
Heat Exchanger ◽  
Shock Waves ◽  
Dynamic Characteristics ◽  
Tube Bundle ◽  
Cooling Water ◽  
Cross Flow ◽  
Water Film ◽  
Local Defect ◽  
Mode Localization ◽  
Localization Phenomenon

The dynamic behaviors of tubes of a heat exchanger are frequently affected by the existence of local flaw. These tubes are worn from the hot-cold fluid shock waves. This local defect may alter the tube dynamics and introduce mode localization in the periodically arranged tube array. The variation of the dynamic characteristics of a component cooling water heat exchanger with wear tubes in cross-flow is investigated in this study. Periodically coupled cooling tubes are used to approximate a heat exchanger. Each tube is considered to be coupled to adjacent tubes through the squeezed water film in the gaps. This work addresses the probability of mode localization is occurring in a heat exchanger in cross-flow. A dynamic model of the coupled tube bundle is proposed. The numerical results reveal that the local defect in a tube array may introduce the so-called mode localization phenomenon in a periodically coupled tube bundle.

Theoretical Study of Mode Localization Phenomenon in Bottom-Hole Assemblies in Oil-Well Drilling

1999 ◽  
Vol 121 (3) ◽  
pp. 183-188
Author(s):  
A. S. Yigit ◽  
M. D. Al-Ansary ◽  
M. Khalid
Keyword(s):  
Theoretical Study ◽  
Oil Well ◽  
Well Drilling ◽  
Mode Localization ◽  
Localization Phenomenon ◽  
Bottom Hole ◽  
Weakly Coupled ◽  
Bending Stresses ◽  
First Time ◽  
Strong Mode

The mode localization phenomena in bottom-hole assemblies (BHA) used in oil-well drilling is investigated. A fully gaged stabilizer model is shown to produce weak coupling between segments of drillcollars separated by stabilizers. It is observed that in a weakly coupled BHA, small disorder in span length can cause strong mode localization. For the first time, it is demonstrated that gravity induces a stiffness disorder, which in turn causes strong mode localization in an inclined wellbore, even though no other disorder is present. The effect of localized modes for failure is presented by examining the maximum bending stresses with and without mode localization. The results show that design and operation of drillstrings should consider the possibility of mode localization for an accurate prediction of dynamic behavior.

Localization of Natural Modes of Vibration in Bladed Disks

1987 ◽  
Author(s):  
O. O. Bendiksen ◽  
N. A. Valero
Keyword(s):  
State Physics ◽  
Periodic Structures ◽  
Solid State Physics ◽  
Mode Localization ◽  
Natural Modes ◽  
Localization Phenomenon ◽  
Modes Of Vibration ◽  
Manufacturing Tolerances ◽  
Trigger Mode ◽  
Disk Mode

A study is presented of the mode localization phenomenon in imperfect blade-disk and blade-shroud-disk assemblies. This surprising phenomenon, first discovered in solid state physics, occurs in a number of periodic structures when the periodicity is broken by disorder or imperfections. Localization is signalled by the amplitude of a global blade-disk mode becoming confined to one or more local regions consisting of just a few blades, and could have serious implications for blade fatigue life. The results of this investigation indicate that unshrouded blades mounted on stiff disks are especially susceptible, and even small blade imperfections within manufacturing tolerances are likely to trigger mode localization. Increasing the interblade coupling by adding shrouds or reducing the disk stiffness greatly reduces the localization susceptibility, although certain modes may still become localized if the shrouds are free to slip.

Localization investigation of stationary random wave transmission along damped ordered substructural chains

1997 ◽  
Vol 211 (3) ◽  
pp. 217-228 ◽  
Author(s):  
F W Williams ◽  
P N Bennett ◽  
J Lin
Keyword(s):  
Internal Force ◽  
Wave Transmission ◽  
Random Point ◽  
Random Wave ◽  
Eigenvalues And Eigenvectors ◽  
Mode Localization ◽  
Localization Phenomenon ◽  
Hysteretic Damping ◽  
Pseudo Excitation ◽  
Excitation Method

Based on the symplectic eigensolution and the pseudo-excitation method, the localization of structural chains subjected to stationary random point excitation is investigated. The stiffness, mass and the hysteretic damping distributions are all continuously variable. The cause of the displacement and internal force localization is explained in terms of the symplectic eigenvalues and eigenvectors of a typical substructure of the structural chain. When duplicate symplectic eigenvalues occur, the degeneration of the stopband as well as the corresponding degeneration of the mode localization phenomenon are discussed.

Mistuning parameter identification and vibration localization analysis of the integration rotor

2021 ◽  
pp. 095441002098146
Author(s):  
Hongyun Sun ◽  
Huiqun Yuan
Keyword(s):  
Synthesis Method ◽  
Coupling Factor ◽  
Coupling Vibration ◽  
Mode Localization ◽  
Reduced Order ◽  
Vibration Localization ◽  
Localization Phenomenon ◽  
Localization Analysis ◽  
Mode Truncation ◽  
Hybrid Interface

This paper deals with the coupling vibration characteristic of the disk-blade-shaft integration rotor. First, a reduced-order model (ROM) based on an improved hybrid interface component mode synthesis method (IHISCMSM) is carried out, which takes the prestress effect into account. The frequency of the disk-blade-shaft integration rotor at different rotating speeds are calculated and the influence of selecting different mode truncation numbers is investigated. In order to quantitatively evaluate the coupling degree of blade and disk, the coupling factor is defined from the perspective of strain energy, and the influence of prestress on system’s dynamic is discussed. Then, an experimental modal analysis is performed on blades to identify the mistuning parameters, and the mode localization of the disk-blade-shaft integration rotor is analyzed with and without blade mistuning. The results indicate that there are several types of coupling modes among blade, disk and shaft of the integration rotor. After considering the prestress, the frequency increases, and the axial coupling vibration degree and radial coupling vibration degree of the integration rotor change. The mode localization of mistuned rotor is more likely to occur in the modes dominated by mistuning stage blades. There also exists a subtle mode localization phenomenon for tuned integration rotor.

Anderson Localization Phenomenon in Periodic Structures

2013 ◽  
Author(s):  
Reyolando M. Brasil
Keyword(s):  
Anderson Localization ◽  
Periodic Structures ◽  
Small Variation ◽  
Slight Variation ◽  
Vibration Modes ◽  
Axial Loads ◽  
Mode Localization ◽  
Localization Phenomenon ◽  
Stiffness Matrices ◽  
Light Coupling

We study the occurrence in structures of a phenomenon similar to Anderson localization. This the vibration modes localization in structures composed of several nominally identical lightly coupled modular substructures. In an ideal perfect model, the vibration modes are global in nature, spreading to the whole structure. In real structures there are no two completely identical segments. Constructive or loading imperfections generate slight variation of the dynamic characteristics of each module. As the level of disorder grows and coupling between modules becomes lighter, the resulting vibration modes change considerably. Vibration energy may become confined to a few segments. This is the Mode Localization Phenomenon. We present models of long modular planar trussed structures. Light coupling is considered between the initially identical modules. A certain degree of imperfection is introduced by adopting a slight variation in the loading of the modules. This will generate a small variation in the global stiffness of the system as the axial loads in the bars affect their Geometric Stiffness Matrices.

Mode Localization of a Cracked Blade Disk

1999 ◽  
Vol 121 (2) ◽  
pp. 335-341 ◽  
Author(s):  
J. H. Kuang ◽  
B. W. Huang
Keyword(s):  
Equations Of Motion ◽  
Crack Depth ◽  
Numerical Results ◽  
Rotating System ◽  
Mode Localization ◽  
Rotating Speed ◽  
Rotating Blade ◽  
Localization Phenomenon ◽  
Blade Crack ◽  
Plane Mode

In this paper, the effect of blade crack on the mode localization of a rotating blade disk is studied. Pretwisted taper beams are used to simulate blades of a blade disk. The crack on the blade can be regarded as a local disorder of this periodically coupled blades system. An application of Hamilton’s principle and Galerkin’s method is used to formulate the equations of motion of the mistuned system. Effects of pretwisted angle, rotating speed, and crack depth of the blade on the in-plane and off-plane mode localizations of a rotating system are investigated. Numerical results indicate that the increase of rotating speed, pretwisted angle, and crack depth could enhance the localization phenomenon significantly.

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