Modal Velocity Perturbation Method for Contact Fatigue at Blade Attachment Under Resonant Vibration

2020 ◽  
Author(s):  
Olivier J. Lamicq ◽  
Loc Q. Duong
Keyword(s):  
Time Domain ◽  
Contact Fatigue ◽  
Operating Conditions ◽  
Velocity Perturbation ◽  
Turbine Engine ◽  
Complex Shapes ◽  
Element Approach ◽  
The Time Domain ◽  
Oscillating Motion ◽  
Intense Vibration

Abstract In a gas turbine engine, it is often impossible to have rotating components running free of resonance at all operating conditions. As such, blades may be subject to episodes of intense vibration, resulting in fatigue damage at the connection between blade and disk. This paper presents a novel finite element approach allowing to evaluate in the time domain the behavior at the disk fir-tree or dovetail contacts caused by a high response on a resonance. The method can be applied to simple bending or torsion modes as well as to higher modes with complex shapes. The application of a one-time velocity perturbation is an efficient way to initiate an oscillating motion at the frequency of interest. The behavior of the 3D-contact is then studied in the time domain, allowing non-linear behaviors to develop. The basic principle of this approach is described in this work. In the design of turbomachinery blade attachments, this approach can be used to study in the time domain the fretting effect of load, coefficient of friction and sliding distance at different frequency regimes. In conjunction with fretting criteria such as Ruiz and Smith-Watson-Topper, fretting fatigue life can then be predicted.

A Multiple Harmonic Open-Loop Controller for Hydro/Aerodynamic Force Measurements in Rotating Machinery Using Magnetic Bearings

2002 ◽  
Vol 124 (4) ◽  
pp. 827-834 ◽  
Author(s):  
D. O. Baun ◽  
E. H. Maslen ◽  
C. R. Knospe ◽  
R. D. Flack
Keyword(s):  
Frequency Domain ◽  
Time Domain ◽  
Open Loop ◽  
Rotating Machinery ◽  
Operating Conditions ◽  
Rotor Vibration ◽  
Aerodynamic Forces ◽  
Analog Input ◽  
Input And Output ◽  
The Time Domain

Inherent in the construction of many experimental apparatus designed to measure the hydro/aerodynamic forces of rotating machinery are features that contribute undesirable parasitic forces to the measured or test forces. Typically, these parasitic forces are due to seals, drive couplings, and hydraulic and/or inertial unbalance. To obtain accurate and sensitive measurement of the hydro/aerodynamic forces in these situations, it is necessary to subtract the parasitic forces from the test forces. In general, both the test forces and the parasitic forces will be dependent on the system operating conditions including the specific motion of the rotor. Therefore, to properly remove the parasitic forces the vibration orbits and operating conditions must be the same in tests for determining the hydro/aerodynamic forces and tests for determining the parasitic forces. This, in turn, necessitates a means by which the test rotor’s motion can be accurately controlled to an arbitrarily defined trajectory. Here in, an interrupt-driven multiple harmonic open-loop controller was developed and implemented on a laboratory centrifugal pump rotor supported in magnetic bearings (active load cells) for this purpose. This allowed the simultaneous control of subharmonic, synchronous, and superharmonic rotor vibration frequencies with each frequency independently forced to some user defined orbital path. The open-loop controller was implemented on a standard PC using commercially available analog input and output cards. All analog input and output functions, transformation of the position signals from the time domain to the frequency domain, and transformation of the open-loop control signals from the frequency domain to the time domain were performed in an interrupt service routine. Rotor vibration was attenuated to the noise floor, vibration amplitude ≈0.2 μm, or forced to a user specified orbital trajectory. Between the whirl frequencies of 14 and 2 times running speed, the orbit semi-major and semi-minor axis magnitudes were controlled to within 0.5% of the requested axis magnitudes. The ellipse angles and amplitude phase angles of the imposed orbits were within 0.3 deg and 1.0 deg, respectively, of their requested counterparts.

A Deep Neural Network Model for Learning Runtime Frequency Response Function Using Sensor Measurements

2021 ◽  
Author(s):  
Yongzhi Qu ◽  
Gregory W. Vogl ◽  
Zechao Wang
Keyword(s):  
Neural Network ◽  
Neural Networks ◽  
Fourier Transform ◽  
Time Domain ◽  
Frequency Response Function ◽  
Frequency Component ◽  
Operating Conditions ◽  
Input Output ◽  
The Fourier Transform ◽  
The Time Domain

Abstract The frequency response function (FRF), defined as the ratio between the Fourier transform of the time-domain output and the Fourier transform of the time-domain input, is a common tool to analyze the relationships between inputs and outputs of a mechanical system. Learning the FRF for mechanical systems can facilitate system identification, condition-based health monitoring, and improve performance metrics, by providing an input-output model that describes the system dynamics. Existing FRF identification assumes there is a one-to-one mapping between each input frequency component and output frequency component. However, during dynamic operations, the FRF can present complex dependencies with frequency cross-correlations due to modulation effects, nonlinearities, and mechanical noise. Furthermore, existing FRFs assume linearity between input-output spectrums with varying mechanical loads, while in practice FRFs can depend on the operating conditions and show high nonlinearities. Outputs of existing neural networks are typically low-dimensional labels rather than real-time high-dimensional measurements. This paper proposes a vector regression method based on deep neural networks for the learning of runtime FRFs from measurement data under different operating conditions. More specifically, a neural network based on an encoder-decoder with a symmetric compression structure is proposed. The deep encoder-decoder network features simultaneous learning of the regression relationship between input and output embeddings, as well as a discriminative model for output spectrum classification under different operating conditions. The learning model is validated using experimental data from a high-pressure hydraulic test rig. The results show that the proposed model can learn the FRF between sensor measurements under different operating conditions with high accuracy and denoising capability. The learned FRF model provides an estimation for sensor measurements when a physical sensor is not feasible and can be used for operating condition recognition.

scholarly journals Application of the Acoustic Emission Method for Diagnosis of On-Load Tap Changer

2017 ◽  
Vol 42 (1) ◽  
pp. 29-35 ◽  
Author(s):  
Henryk Majchrzak ◽  
Andrzej Cichoń ◽  
Sebastian Borucki
Keyword(s):  
Acoustic Emission ◽  
Frequency Domain ◽  
Time Domain ◽  
Operating Conditions ◽  
Time Frequency ◽  
Measurement Results ◽  
Tap Changer ◽  
The Time Domain ◽  
Load Tap Changer ◽  
Short Time

Abstract This paper provides an example of the application of the acoustic emission (AE) method for the diagnosis of technical conditions of a three-phase on-load tap-changer (OLTC) GIII type. The measurements were performed for an amount of 10 items of OLTCs, installed in power transformers with a capacity of 250 MVA. The study was conducted in two different OLTC operating conditions during the tapping process: under load and free running conditions. The analysis of the measurement results was made in both time domain and time-frequency domain. The description of the AE signals generated by the OLTC in the time domain was performed using the analysis of waveforms and determined characteristic times. Within the time-frequency domain the measured signals were described by short-time Fourier transform spectrograms.

Finite Element Velocity Perturbation Application in Investigating Compressor Dovetail Fretting in Time Domain

2020 ◽  
Author(s):  
Loc Q. Duong ◽  
Olivier J. Lamicq
Keyword(s):  
Finite Element ◽  
Time Domain ◽  
Fatigue Properties ◽  
Perturbation Approach ◽  
Velocity Perturbation ◽  
Element Analysis ◽  
Factors Affecting ◽  
The Difference ◽  
The Time Domain ◽  
Contact Response

Abstract In the design of a gas turbine airfoil, avoiding resonance at all conditions is impossible. The airfoil may vibrate fiercely during resonant passages, which then may induce small oscillation motion at the disk attachment. Due to microslip at the contact regions, fretting would occur in conjunction with the reduction of material fatigue properties. This paper presents a finite element analysis using the Velocity Perturbation Method (VPM) in predicting airfoil attachment nonlinear fretting-behavior in the time domain at a resonant frequency of interest. Numerical simulation, showing design fretting fatigue characteristics based on fundamental Ruiz and Smith-Watson-Topper (SWT) criteria, is demonstrated on two models, simplified and representative. The simplified model was used for detail analysis set-up and basic post-processing while the representative model illustrated the difference in nonlinear contact response of an industrial compressor under bending and torsional modes in the time domain. This Finite Element velocity perturbation approach can be used to study the main factors affecting fretting of any two bodies in contact: load, coefficient of friction, contact geometry and impact of different frequencies or modal shapes in the time domain.

Finite Element Modelling of Rotating Tires in the Time Domain

2002 ◽  
Vol 30 (1) ◽  
pp. 19-33 ◽  
Author(s):  
O. A. Olatunbosun ◽  
A. M. Burke
Keyword(s):  
Finite Element ◽  
Dynamic Behavior ◽  
Time Domain ◽  
Equations Of Motion ◽  
Operating Conditions ◽  
Element Analysis ◽  
Successful Model ◽  
Linear Effects ◽  
Tire Rotation ◽  
The Time Domain

Abstract Finite element analysis presents an opportunity for a detailed study of the dynamic behavior of a rotating tire under real operating conditions providing a better understanding of the influence of tire construction and material detail on tire dynamic behavior in such areas as ride, handling and noise and vibration transmission. Modelling issues that need to be considered include non-linear effects due to tire inflation and hub loading, tire/road contact and time domain solution of the equations of motion. In this paper techniques and strategies for tire rotation modelling are presented and discussed as a guide to the creation of a successful model.

A Multiple Harmonic Open Loop Controller for Hydro/Aerodynamic Force Measurements in Rotating Machinery Using Magnetic Bearings

2001 ◽  
Author(s):  
Daniel O. Baun ◽  
Eric H. Maslen ◽  
Carl R. Knospe ◽  
Ronald D. Flack
Keyword(s):  
Frequency Domain ◽  
Time Domain ◽  
Open Loop ◽  
Rotating Machinery ◽  
Operating Conditions ◽  
Rotor Vibration ◽  
Aerodynamic Forces ◽  
Analog Input ◽  
Input And Output ◽  
The Time Domain

Inherent in the construction of many experimental apparatus designed to measure the hydro/aerodynamic forces of rotating machinery are features that contribute undesirable parasitic forces to the measured or test forces. Typically, these parasitic forces are due to seals, drive couplings, and hydraulic and/or inertial unbalance. To obtain accurate and sensitive measurement of the hydro/aerodynamic forces in these situations, it is necessary to subtract the parasitic forces from the test forces. In general, both the test forces and the parasitic forces will be dependent on the system operating conditions including the specific motion of the rotor. Therefore, to properly remove the parasitic forces the vibration orbits and operating conditions must be the same in tests for determining the hydro/aerodynamic forces and tests for determining the parasitic forces. This, in turn, necessitates a means by which the test rotor’s motion can be accurately controlled to an arbitrarily defined trajectory. Here in, an interrupt driven multiple harmonic open loop controller was developed and implemented on a laboratory centrifugal pump rotor supported in magnetic bearings (active load cells) for this purpose. This allowed the simultaneous control of sub-harmonic, synchronous and super-harmonic rotor vibration frequencies with each frequency independently forced to some user defined orbital path. The open loop controller was implemented on a standard PC using commercially available analog input and output cards. All analog input and output functions, transformation of the position signals from the time domain to the frequency domain, and transformation of the open loop control signals from the frequency domain to the time domain were performed in an interrupt service routine. Rotor vibration was attenuated to the noise floor, vibration amplitude ≈ 0.2 μm, or forced to a user specified orbital trajectory. Between the whirl frequencies of ¼ and 2 times running speed, the orbit semi-major and semi-minor axis magnitudes were controlled to within 0.5% of the requested axis magnitudes. The ellipse angles and amplitude phase angles of the imposed orbits were within 0.3° and 1.0°, respectively, of their requested counter parts.

A New Boundary Element Method for Three-Dimensional Coupled Problems of Consolidation and Thermoelasticity

1991 ◽  
Vol 58 (1) ◽  
pp. 28-36 ◽  
Author(s):  
G. F. Dargush ◽  
P. K. Banerjee
Keyword(s):  
Boundary Element Method ◽  
Boundary Element ◽  
Time Domain ◽  
Three Dimensional ◽  
General Boundary ◽  
Coupled Problems ◽  
Infinite Domains ◽  
Element Approach ◽  
The Time Domain ◽  
Element Method

A general boundary element method (BEM) for the complete three-dimensional Biot consolidation theory is developed which operates directly in the time domain and requires only boundary discretization. Consequently, the dimensionality of the problem is reduced by one and the method becomes quite attractive for geotechnical analyses, particularly those that involve extensive or infinite domains. Furthermore, as a result of a well-known analogy fully elaborated here, the new BEM formulation is equally applicable for quasi-static thermoelasticity. Several detailed examples are presented to illustrate the accuracy and suitability of this boundary element approach for both consolidation and thermomechanical analyses.

Apodisation in the time domain

1992 ◽  
Vol 2 (4) ◽  
pp. 615-620
Author(s):  
G. W. Series
Keyword(s):  
Time Domain ◽  
The Time Domain
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