Mistuning and Damping Analysis of a Radial Turbine Blisk in Varying Ambient Conditions

2014 ◽  
Author(s):  
Bernd Beirow ◽  
Thomas Maywald ◽  
Arnold Kühhorn
Keyword(s):  
Frequency Response ◽  
Ambient Pressure ◽  
Forced Response ◽  
Response Functions ◽  
Frequency Response Functions ◽  
Radial Turbine ◽  
Modal Damping ◽  
Resonance Frequencies ◽  
Technical Vacuum ◽  
The Impact

A mistuned radial turbine impeller is analyzed with respect to the impact of varying ambient pressures and temperatures as well on frequency response functions and modal damping ratios. Beginning at room conditions, a finite element model of an impeller wheel at rest is updated based on experimentally determined mistuning in terms of blade dominated frequencies. The following numerical forced response analyses yield a maximum blade displacement amplification of 67% compared to the tuned reference. In addition, modal damping ratios are determined in dependence on the ambient pressure ranging from technical vacuum at 1 mbar up to 6000 mbar in a pressure chamber. Shaker excitation and laser Doppler vibrometry response measurement is employed in this context. A linear dependence of modal damping ratios on ambient pressure and a dominating damping contribution of the surrounding air even for higher modes could be proved. Moreover, the experimental determination of frequency response functions (FRF) at technical vacuum yields a better separation of resonance peaks compared to room conditions at 1013 mbar and hence, this data allows for more accurate model-updates in principle. It is proved that numerical models updated regarding mistuning at room conditions are well suited to predict the forced response at arbitrary pressures if measured modal damping ratios at these pressures are considered. Finally, within analyzing the effect of increasing structural temperatures with the surrounding air at 1013 mbar included slightly decreasing resonance frequencies but strongly increasing FRF-amplitudes are determined.

Updating of Finite Element Models Based on a Double Condensation Procedure Using Frequency Response Functions Data

1995 ◽  
Author(s):  
Rémi Berriet ◽  
René Fillod ◽  
Noureddine Bouhaddi
Keyword(s):  
Frequency Response ◽  
Degrees Of Freedom ◽  
Noise Pollution ◽  
Test Case ◽  
Response Functions ◽  
Frequency Response Functions ◽  
Measured Frequency ◽  
Modal Damping ◽  
Applied Forces ◽  
Definition Of

Abstract In order to take into account information from test data, not only at the resonances, but also in the other parts of the measured frequency spectrum, it is of interest to use directly measured Frequency Response Functions (FRF) instead of modal data. We also avoid by this way an experimental modal analysis. In return we have to introduce damping terms into the analytical model, we have to weight the FRF data in a systematic manner and to compute simultaneously a large amount of data. The presented procedure analyses overall these three aspects: definition of modal damping parameters, definition of weighted FRF data and condensation of the problem. This last notion is particularly pointed out. The condensation is performed in two steps : a static condensation of the model on the degrees of freedom corresponding to the location of the sensors, and a simultaneous condensation of experimental and analytical FRF data by a common transformation matrix. The first applications are performed on a simulated test case with large stiffness, mass and modal damping perturbations introduced in the initial model as well as strong noise pollution of measured responses and applied forces.

Non-Linear Characteristics in the Dynamic Responses of Seated Subjects Exposed to Vertical Whole-Body Vibration

2002 ◽  
Vol 124 (5) ◽  
pp. 527-532 ◽  
Author(s):  
Yasunao Matsumoto ◽  
Michael J. Griffin
Keyword(s):  
Frequency Response ◽  
The Body ◽  
Dynamic Responses ◽  
Whole Body ◽  
Apparent Mass ◽  
Response Functions ◽  
Frequency Response Functions ◽  
Resonance Frequencies ◽  
Non Linear ◽  
Vibration Magnitude

The effect of the magnitude of vertical vibration on the dynamic response of the seated human body has been investigated. Eight male subjects were exposed to random vibration in the 0.5 to 20 Hz frequency range at five magnitudes: 0.125, 0.25, 0.5, 1.0 and 2.0 ms−2 r.m.s. The dynamic responses of the body were measured at eight locations: at the first, fifth, and tenth thoracic vertebrae (T1, T5, T10), at the first, third, and fifth lumbar vertebrae (L1, L3, L5) and at the pelvis (the posterior-superior iliac spine). At each location, the motions on the body surface were measured in the three orthogonal axes within the sagittal plane (i.e., the vertical, fore-and-aft, and pitch axes). The force at the seat surface was also measured. Frequency response functions (i.e., transmissibilities and apparent mass) were used to represent the responses of the body. Non-linear characteristics were observed in the apparent mass and in the transmissibilities to most measurement locations. Resonance frequencies in the frequency response functions decreased with increases in the vibration magnitude (e.g. for the vertical transmissibility to L3, a reduction from 6.25 to 4.75 Hz when the vibration magnitude increased from 0.125 to 2.0 ms−2 r.m.s.). The transmission of vibration within the spine also showed some evidence of a non-linear characteristic. It can be concluded from this study that the dynamic responses of seated subjects are clearly non-linear with respect to vibration magnitude, whereas previous studies have reported inconsistent conclusions. More understanding of the dependence on vibration magnitude of both the dynamic responses of the soft tissues of the body and the muscle activity (voluntary and involuntary) is required to identify the causes of the non-linear characteristics observed in this study.

Hydraulic Modal Analysis in Theory and Practice

2019 ◽  
Vol 141 (5) ◽  
Author(s):  
Gudrun Mikota ◽  
Bernhard Manhartsgruber ◽  
Franz Hammerle ◽  
Andreas Brandl
Keyword(s):  
Frequency Response ◽  
Theory And Practice ◽  
Mode Shapes ◽  
Pipeline System ◽  
Response Functions ◽  
Hydraulic Systems ◽  
Modal Assurance Criterion ◽  
Frequency Response Functions ◽  
Practical Applications ◽  
The Impact

Theoretical and experimental modal analyses are treated for hydraulic systems modeled by discrete capacities, inductances, resistances, and fluid lines with dynamic laminar flow. Based on an approximate multi-degrees-of-freedom description, it is shown how hydraulic natural frequencies, damping ratios, and mode shapes can be identified from measured frequency response functions between flow rate excitation and pressure response. Experiments are presented for a pipeline system that includes three side branches and an accumulator. In view of practical applications, two different types of servovalve excitation as well as impact hammer excitation are considered. Pressure is measured by 19 sensors throughout the system. Results are compared in terms of frequency response functions between 50 and 850 Hz, the first five hydraulic modes, and weighted auto modal assurance criteria of experimental mode shapes. Out of the tested excitation devices, the servovalve is clearly preferred; if valves cannot be used, the impact hammer offers a reasonable workaround. For a reduced number of five sensors, different sensor arrangements are assessed by the respective weighted auto modal assurance criteria of experimental mode shapes. A theoretical hydraulic modal model provides a similar assessment. The quality of the theoretical model is confirmed by the weighted modal assurance criterion of theoretical and experimental mode shapes from servovalve excitation.

The Effect of Stringer Width and Damping on the Response of Skin—Stringer Structures

1972 ◽  
Vol 94 (1) ◽  
pp. 159-166 ◽  
Author(s):  
J. P. Henderson ◽  
A. D. Nashif
Keyword(s):  
Frequency Response ◽  
Transfer Matrix ◽  
Forced Response ◽  
Experimental Results ◽  
Mode Shapes ◽  
Response Functions ◽  
Resonant Frequencies ◽  
Frequency Response Functions

Analytical and experimental results for a five-span skin-stringer structure are presented. The analysis uses a transfer matrix technique which considers the effects of stringer dimensions including finite stringer width and damping on the computed forced response. Resonant frequencies, frequency response functions, damping and mode shapes for the first group of modes are compared for theoretical and experimental results. This agreement is found to be good.

scholarly journals Vertical Interaction Between a Driving Wheelset and Track in the Presence of the Rolling Surfaces Harmonic Irregularities

2020 ◽  
Vol 9 (2) ◽  
pp. 38-52
Author(s):  
Traian Mazilu ◽  
Ionuţ Radu Răcănel ◽  
Marius Alin Gheți
Keyword(s):  
Frequency Response ◽  
Rigid Bodies ◽  
Response Functions ◽  
Frequency Response Functions ◽  
Rolling Surface ◽  
Track System ◽  
Resonance Frequencies ◽  
Railway Traction ◽  
Surface Irregularities ◽  
Basic Features

Abstract The driving wheelset is used in railway traction (locomotives, electric trains, trams, etc.) to support part of the weight of the suspended mass and to drive and brake the vehicle. The dynamics of the driving wheelset/track system is a very important issue in the railway engineering, and this paper is focused on basic features of the frequency response functions which describe the dynamic behavior in the presence of the rolling surfaces harmonic irregularities. To this end, a simple model of the driving wheelset/track system with the range of application limited up to 6-700 Hz is adopted. The driving wheelset model consists of a free-free uniform Euler-Bernoulli beam with three attached rigid bodies, representing the axle, the two wheels and the gear; the distinct feature of this model is the inertial asymmetry. Two independent infinite uniform Euler-Bernoulli beams, each on its foundation including two elastic layers for rail pad and ballast and an intermediate inertial layer for sleepers represent the track model. For simplicity, the moving irregularity model is applied to simulate the interaction between wheels and rails. Numerical simulations show that the driving wheelset/track system has three resonance frequencies, all situated in the frequency range of the evanescent waves in rails. FRF of the driving wheelset/track system have been calculated for left and right wheel/rail pair. The influence of the asymmetric inertia of the driving wheelset and the out of phase between the rolling surface irregularities are evaluated in terms of frequency response functions of the wheel/rail contact force.

Parametric Study of a Piezoceramic Patch Actuator for Proportional Velocity Feedback Control Loop

2010 ◽  
Vol 132 (6) ◽  
Author(s):  
Y. Aoki ◽  
P. Gardonio ◽  
M. Gavagni ◽  
C. Galassi ◽  
S. J. Elliott
Keyword(s):  
Feedback Control ◽  
Frequency Response ◽  
Parametric Study ◽  
Open Loop ◽  
Response Functions ◽  
Control Performance ◽  
Frequency Response Functions ◽  
Velocity Feedback ◽  
Sensor Actuator ◽  
Resonance Frequencies

This paper presents a parametric study on the stability and control performance of proportional velocity feedback control with square piezoceramic patch actuators of various widths and thicknesses, used to suppress the vibration of a thin rectangular plate. A simple stability-performance formula has been derived, which, using the open loop sensor-actuator frequency response function, gives the maximum control performance that can be produced by such a feedback loop at resonance frequencies of the lower order modes of the plate. The parametric study has been carried out using simulated sensor-actuator frequency response functions. The results have been validated using measured frequency response functions on sets of rectangular panels with a square piezoceramic patch of various widths and thicknesses. The parametric study has shown that the control performance is significantly improved by increasing the width and reducing the thickness of the square actuator.

Crack characterisation by detection and classification of nonlinear behaviour using the Hilbert transform

2012 ◽  
Vol 226 (11) ◽  
pp. 2610-2626
Author(s):  
Anees U Rehman ◽  
Keith Worden ◽  
Jem A Rongong
Keyword(s):  
Frequency Response ◽  
Hilbert Transform ◽  
Fatigue Cracks ◽  
Nonlinear Behaviour ◽  
Response Functions ◽  
Frequency Response Functions ◽  
Dependent Frequency ◽  
Resonance Frequencies ◽  
The Hilbert Transform

The presence of a crack in a structure causes a local variation in the stiffness that alters the dynamics of the entire system. This article introduces an approach for crack characterisation by detection and classification of the nonlinearities arising from a crack operating in flexural and torsion modes of vibration. Nonlinearity detection is accomplished by obtaining amplitude dependent frequency response functions, whereas classification is achieved by processing those frequency response functions through the Hilbert transform. For the purpose of illustrating this process, a dog-bone-type specimen is tested. Fatigue cracks of various depths are generated and propagated in the specimen by vibration at resonance. For varying crack depths, a range of excitation levels are used to obtain amplitude dependent frequency response functions from which resonance frequencies and damping levels are extracted. While utilising the Hilbert transform for nonlinearity classification, Haoui correction terms are incorporated for accommodating the issues associated with truncated data, either baseband or zoomed. Corrections terms for residual modes outside the frequency range of interest are neglected.

Viscoelastic Responses of Finite Bodies by Quadrature Form of Correspondence Principle

1981 ◽  
Vol 48 (1) ◽  
pp. 206-207
Author(s):  
G. Dasgupta
Keyword(s):  
Frequency Response ◽  
Correspondence Principle ◽  
Numerical Quadrature ◽  
Response Functions ◽  
Frequency Response Functions ◽  
Harmonic Response ◽  
Resonance Frequencies

Alternative forms of the elastic-viscoelastic analogy for numerically obtained frequency response functions have been reported for solids of similarly and dissimilarly viscoelastic in bulk and shear in [1, 2], respectively. It is herein demonstrated that the same integrals can be numerically evaluated to obtain viscoelastic responses of finite bodies even though the harmonic response functions have singularities at the resonance frequencies. Crucial aspects of the algorithm regarding the truncation of numerical quadrature in the neighborhood of the poles are addressed in this Note.

scholarly journals Identification of relevant acoustic transfer paths for WT drivetrains with an operational transfer path analysis

2021 ◽  
Author(s):  
W. Schünemann ◽  
R. Schelenz ◽  
G. Jacobs ◽  
W. Vocaet
Keyword(s):  
Path Analysis ◽  
Wind Turbine ◽  
Frequency Response ◽  
Mechanical System ◽  
Reference Point ◽  
Response Functions ◽  
Frequency Response Functions ◽  
Transfer Path ◽  
Transfer Path Analysis ◽  
Turbine Model

AbstractThe aim of a transfer path analysis (TPA) is to view the transmission of vibrations in a mechanical system from the point of excitation over interface points to a reference point. For that matter, the Frequency Response Functions (FRF) of a system or the Transmissibility Matrix is determined and examined in conjunction with the interface forces at the transfer path. This paper will cover the application of an operational TPA for a wind turbine model. In doing so the path contribution of relevant transfer paths are made visible and can be optimized individually.

Sign in / Sign up

Export Citation Format

Share Document