Crack Identification in a Rotating Shaft via the Reverse Directional Frequency Response Functions

2009 ◽  
Vol 131 (1) ◽  
Author(s):  
Yun-Ho Seo ◽  
Chong-Won Lee ◽  
K. C. Park
Keyword(s):  
Frequency Response ◽  
Transverse Crack ◽  
Crack Identification ◽  
Response Functions ◽  
Flexible Rotor ◽  
Rotating Shaft ◽  
Frequency Response Functions ◽  
Rotor Systems ◽  
Crack Location ◽  
Reference Map

A method is proposed for identifying the location of an open transverse crack in flexible rotor systems by modeling the crack as a localized element with rotating asymmetry. It exploits the strong correlations between the modal constants of the reverse directional frequency response functions (r-dFRFs) and the degree and location of asymmetry. A map of the modal constants of the r-dFRFs for all elements is constructed to identify the location of crack by comparing the identified modal constants to those of the reference map. This paper also addresses practical issues associated with measurement noises and limited number of sensors. The proposed crack identification method is finally applied to a flexible rotor system with an open transverse crack in order to demonstrate the identification procedure for detection of the crack location.

In-Plane Vibration and Crack Detection of a Rotating Shaft-Disk Containing a Transverse Crack

1998 ◽  
Vol 120 (2) ◽  
pp. 551-556 ◽  
Author(s):  
Ming-Chuan Wu ◽  
Shyh-Chin Huang
Keyword(s):  
Crack Detection ◽  
Transverse Crack ◽  
Rotation Speed ◽  
Crack Depth ◽  
Multiple Scale ◽  
Crack Identification ◽  
Response Curves ◽  
Rotating Shaft ◽  
Crack Location ◽  
Depth Rotation

Dynamic response and stability of a rotating shaft-disk containing a transverse crack is investigated. FFT analysis of response amplitudes showed that the 2Ω component (Ω: rotation speed) was excited by crack breathing and could serve as a good index for crack identification. Intensive numerical studies of crack location, crack depth, rotation speed, and sensing position on response amplitudes displayed a feasible technique for the identification of crack depth and crack location. It is achieved by intersecting the two equi-amplitude response curves of two separated sensing probes. Finally, the instability of the system caused by a crack is examined via Floquet theory and the multiple scale method. The stability diagrams, illustrated as functions of crack depth, rotation speed, and damping, are shown and discussed.

Dynamic characterization of a mechanical coupling for a rotating shaft

2010 ◽  
Vol 225 (3) ◽  
pp. 604-616 ◽  
Author(s):  
A T Tadeo ◽  
K L Cavalca ◽  
M J Brennan
Keyword(s):  
Frequency Response ◽  
Response Functions ◽  
Dynamic Characterization ◽  
Rotating Shaft ◽  
Frequency Response Functions ◽  
Mechanical Coupling ◽  
Lumped Parameter ◽  
Parameter Coupling ◽  
Stiffness And Damping

This article concerns the dynamic characterization of a flexible coupling that connects two co-axial shafts. Four different lumped parameter coupling models from the literature are investigated to see which model could best predict the dynamic behaviour of the coupling. The finite-element method was used to model the rotor dynamic system incorporating the coupling. Frequency response functions from this model were compared with measured frequency response functions from the rotor test rig with the shaft and coupling rotating at a specific speed. Parameters from the model were adjusted to minimize an objective function involving the measured and predicted frequency response functions. It was found that the simplest model of the coupling that could reasonably represent the coupling involves rotational (bending) stiffness and damping.

Structural Change Quantification in Rotor Systems Based on Measured Resonance and Antiresonance Frequencies

2013 ◽  
Author(s):  
Adam C. Wroblewski ◽  
Alexander H. Pesch ◽  
Jerzy T. Sawicki
Keyword(s):  
Structural Change ◽  
Frequency Response ◽  
Numerical Optimization ◽  
Element Model ◽  
Sufficient Information ◽  
Response Functions ◽  
Frequency Response Functions ◽  
Magnetic Actuators ◽  
Rotor Systems ◽  
Spatial Domains

A structural change quantification methodology is proposed in which the magnitude and location of a structural alteration is identified experimentally in a rotor system. The resonance and antiresonance frequencies are captured from multiple frequency response functions and are compared with baseline data to extract frequency shifts due to these features. The resulting expression contains sufficient information to identify the dynamic characteristics of the rotor in both the frequency and spatial domains. A finite element model with carefully selected tunable parameters is iteratively adjusted using a numerical optimization algorithm to determine the source of the structural change. The methodology is experimentally demonstrated on a test rig with a laterally damaged rotor and the frequency response functions are acquired through utilization of magnetic actuators positioned near the ball bearings.

A Flexible Rotor on Flexible Bearing Supports: Stability and Unbalance Response

2000 ◽  
Vol 123 (2) ◽  
pp. 137-144 ◽  
Author(s):  
Jose´ A. Va´zquez ◽  
Lloyd E. Barrett ◽  
Ronald D. Flack
Keyword(s):  
Experimental Data ◽  
Frequency Response ◽  
Transfer Functions ◽  
Structure Stability ◽  
Response Functions ◽  
Flexible Rotor ◽  
Support Structure ◽  
Frequency Response Functions ◽  
Critical Speeds ◽  
Unbalance Response

An experimental study of the effects of bearing support flexibility on rotor stability and unbalance response is presented. A flexible rotor supported by fluid film bearings on flexible supports was used with fifteen support configurations. The horizontal support stiffness was varied systematically while the vertical stiffness was kept constant. The support characteristics were determined experimentally by measuring the frequency response functions of the support structure at the bearing locations. These frequency response functions were used to calculate polynomial transfer functions that represented the support structure. Stability predictions were compared with measured stability thresholds. The predicted stability thresholds agree with the experimental data within a confidence bound for the logarithmic decrement of ±0.01. For unbalance response, the second critical speed of the rotor varied from 3690 rpm to 5200 rpm, depending on the support configuration. The predicted first critical speeds agree with the experimental data within −1.7 percent. The predicted second critical speeds agree with the experimental data within 3.4 percent. Predictions for the rotor on rigid supports are included for comparison.

Structural Change Quantification in Rotor Systems Based on Measured Resonance and Antiresonance Frequencies

2013 ◽  
Vol 136 (2) ◽  
Author(s):  
Adam C. Wroblewski ◽  
Alexander H. Pesch ◽  
Jerzy T. Sawicki
Keyword(s):  
Structural Change ◽  
Frequency Response ◽  
Numerical Optimization ◽  
Element Model ◽  
Sufficient Information ◽  
Response Functions ◽  
Frequency Response Functions ◽  
Magnetic Actuators ◽  
Rotor Systems ◽  
Spatial Domains

A structural change quantification methodology is proposed in which the magnitude and location of a structural alteration is identified experimentally in a rotor system. The resonance and antiresonance frequencies are captured from multiple frequency response functions and are compared with baseline data to extract frequency shifts due to these features. The resulting expression contains sufficient information to identify the dynamic characteristics of the rotor in both the frequency and spatial domains. A finite element model with carefully selected tunable parameters is iteratively adjusted using a numerical optimization algorithm to determine the source of the structural change. The methodology is experimentally demonstrated on a test rig with a laterally damaged rotor and the frequency response functions are acquired through utilization of magnetic actuators positioned near the ball bearings.

Model Identification of a Rotor With Magnetic Bearings

2002 ◽  
Vol 125 (1) ◽  
pp. 149-155 ◽  
Author(s):  
J. A. Va´zquez ◽  
E. H. Maslen ◽  
H.-J. Ahn ◽  
D.-C. Han
Keyword(s):  
Frequency Response ◽  
Dynamic Stiffness ◽  
Model Identification ◽  
Magnetic Bearing ◽  
Response Functions ◽  
Flexible Rotor ◽  
Frequency Response Functions ◽  
Rotor Model ◽  
Reconciliation Process ◽  
Piano Wire

The experimental identification of a long flexible rotor with three magnetic bearing journals is presented. Frequency response functions are measured between the magnetic bearing journals and the sensor locations while the rotor is suspended horizontally with piano wire. These frequency response functions are compared with the responses of a rotor model and a reconciliation process is used to reduce the discrepancies between the model and the measured data. In this identification, the wire and the fit of the magnetic bearing journals are identified as the sources of model error. As a result of the reconciliation process, equivalent dynamic stiffness are calculated for the piano wire and the fit of the magnetic bearing journals. Several significant numeral issues that were encountered during the process are discussed and solutions to some of these problems are presented.

A Flexible Rotor on Flexible Bearing Supports: Part II — Unbalance Response

1999 ◽  
Author(s):  
José A. Vázquez ◽  
Lloyd E. Barrett ◽  
Ronald D. Flack
Keyword(s):  
Experimental Data ◽  
Frequency Response ◽  
Transfer Functions ◽  
Response Functions ◽  
Flexible Rotor ◽  
Support Structure ◽  
Frequency Response Functions ◽  
Critical Speeds ◽  
Vertical Stiffness ◽  
Unbalance Response

Abstract An experimental study of the effects of bearing support flexibility on rotor unbalance response is presented. A flexible rotor supported by fluid film bearings on flexible supports was used with fifteen support configurations. The horizontal support stiffness was varied systematically while the vertical stiffness was kept constant. The support characteristics were determined experimentally by measuring the frequency response functions of the support structure at the bearing locations. These frequency response functions were used to calculate polynomial transfer functions that represented the support structure. The second critical speed of the rotor varied from 3690 rpm to 5200 rpm, depending on the support configuration. The predicted first critical speeds agree with the experimental data within −1.7%. The predicted second critical speeds agree with the experimental data within 3.4%. Predictions for the rotor on rigid supports are included for comparison.

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