Rotordynamic Crack Diagnosis: Distinguishing Crack Depth and Location

2013 ◽  
Author(s):  
Philip Varney ◽  
Itzhak Green
Keyword(s):  
Fatigue Crack ◽  
Condition Monitoring ◽  
Crack Depth ◽  
Forced Response ◽  
System Response ◽  
Contour Plot ◽  
Crack Model ◽  
Finite Width ◽  
Angular Response ◽  
Crack Location

The goal of this work is to establish a condition monitoring regimen capable of diagnosing the depth and location of a transverse fatigue crack in a rotordynamic system. The success of an on-line crack diagnosis regimen hinges on the accuracy of the crack model used. The model should account for the depth of the crack and the localization of the crack along the shaft. Negating the influence of crack location on system response ignores a crucial component of real cracks. Two gaping crack models are presented; the first simulates a finite-width manufactured notch, while the second models an open fatigue crack. An overhung rotordynamic system is modeled, imitating an available rotordynamic test rig. Four degree-of-freedom equations of motion for both crack models are presented and discussed, along with corresponding transfer matrix techniques. Free and forced response analyses are performed, with emphasis placed on results applicable to condition monitoring. It is demonstrated that two identifiers are necessary to diagnose the crack parameters: the 2X resonance frequency and the magnitude of the 2X component of the rotor angular response at resonance. First, a contour plot of the 2X resonant shaft speed versus crack depth and location is generated. The magnitude of the 2X component of the rotor’s angular response along the desired contour is obtained, narrowing the possible pairs of crack location/depth to either one or two possibilities. Practical aspects of the diagnosis procedure are then discussed.

Rotordynamic Crack Diagnosis: Distinguishing Crack Depth and Location

2013 ◽  
Vol 135 (11) ◽  
Author(s):  
Philip Varney ◽  
Itzhak Green
Keyword(s):  
Condition Monitoring ◽  
Crack Detection ◽  
Fatigue Cracks ◽  
Equations Of Motion ◽  
Crack Depth ◽  
Forced Response ◽  
Contour Plot ◽  
Crack Model ◽  
Finite Width ◽  
Shaft Speed

The goal of this work is to establish simple condition monitoring principles for diagnosing the depth and location of transverse fatigue cracks in a rotordynamic system. The success of an on-line crack diagnosis regimen hinges on the accuracy of the crack model, which should account for the crack's depth and location. Two gaping crack models are presented; the first emulates a finite-width notch typically manufactured for experimental purposes, while the second models a gaping fatigue crack. The rotordynamic model used herein is based upon an available overhung rotordynamic test rig that was originally constructed to monitor the dynamics of a mechanical face seal. Four degree-of-freedom, linear equations of motion for both crack models are presented and discussed. Free and forced response analyses are presented, emphasizing results applicable to condition monitoring and, particularly, to diagnosing the crack parameters. The results demonstrate that two identifiers are required to diagnose the crack parameters: the 2X resonance shaft speed and the magnitude of the angular 2X subharmonic resonance. First, a contour plot of the 2X resonance shaft speed versus crack depth and location is generated. The magnitude of the 2X resonance along the desired 2X frequency contour is then obtained, narrowing the possible pairs of crack location and depth to either one or two possibilities. Practical aspects of the suggested diagnostic procedure are discussed, as well as qualitative observations concerning crack detection.

Development of a Novel Algorithm for a Crack Detection, Localization, and Sizing in a Beam Based on Forced Response Measurements

2008 ◽  
Vol 130 (2) ◽  
Author(s):  
M. Karthikeyan ◽  
R. Tiwari ◽  
S. Talukdar
Keyword(s):  
Natural Frequency ◽  
Crack Detection ◽  
Beam Theory ◽  
Crack Size ◽  
Forced Response ◽  
Crack Model ◽  
Beam Model ◽  
Crack Location ◽  
Forced Responses ◽  
Crack Element

The present work aims at the development of a method for the crack detection, localization and sizing in a beam based on the transverse force and response signals. The Timoshenko beam theory is applied for transverse vibrations of the beam model. The finite element method is used for the cracked beam forced vibration analysis. An open transverse surface crack is considered for the crack model, which contains standard five flexibility coefficients. The effect of the proportionate damping is also included. A harmonic force of known amplitude with sine-sweep frequency is used to dynamically excite the beam, up to few flexible modes, which could be provided with the help of an exciter. In practice, linear degrees of freedom (DOFs) can be measured quite accurately; however, rotational DOFs are difficult to measure accurately. All rotational DOFs, except at crack element, are eliminated by a dynamic condensation scheme; for elimination of rotational DOFs at the crack element, a new condensation scheme is implemented. The algorithm is iterative in nature and starts with a presumption that a crack is present in the beam. For an assumed crack location, flexibility coefficients are estimated with the help of forced responses. The Tikhonov regularization technique is applied in the estimation of bounded crack flexibility coefficients. These crack flexibility coefficients are used to obtain the crack size by minimizing an objective function. With the help of the estimated crack size and measured natural frequency, the crack location is updated. The procedure iterates till the crack size and location get stabilized up to the desired level of accuracy. The algorithm has a potential to detect no crack condition also. The crack flexibility and damping coefficients are estimated as a by-product. Numerical examples, with the simply supported and cantilevered beams, are given to justify the applicability and versatility of the algorithm in practice. With the numerically simulated forced responses, which have the noise contamination and the error in the natural frequency measurements, the estimated crack parameters (i.e., the crack location and size) are in good agreement.

Vibration Characteristics of Fatigue Crack Damage in Simplified Beam Structure

2006 ◽  
Vol 324-325 ◽  
pp. 999-1002
Author(s):  
Pei Qiang ◽  
Gui Xuan Wang ◽  
Xun Guo
Keyword(s):  
Fatigue Crack ◽  
Free Vibration ◽  
Boundary Conditions ◽  
Fracture Mechanic ◽  
Crack Depth ◽  
Vibration Characteristics ◽  
Beam Structure ◽  
Torsion Spring ◽  
First Order ◽  
Crack Location

Free vibration characteristics of an elastic simple beam with a fatigue notch crack damage located any where of the beam is investigated. The notch crack is modeled by an elastic torsion spring whose stiffness is taken to be finite and is determined from fracture mechanic theory. On the assumption that the crack is always open when the beam vibrates transversely, the motion equation and the boundary conditions of a simple-supported beam with a crack located anywhere of the beam is deduced. The first-order to the sixth-order frequencies varying with the crack depth and the crack location are calculated.

Dynamics of Large Power Rotating Machine with Cracked Shaft

2005 ◽  
Vol 293-294 ◽  
pp. 337-346
Author(s):  
Slawomir Banaszek
Keyword(s):  
Crack Detection ◽  
Crack Depth ◽  
Computer Code ◽  
Crack Model ◽  
Simulation Research ◽  
Large Power ◽  
Crack Location ◽  
Rotating Machine ◽  
Diagnostic Indicator ◽  
Cracked Shaft

The paper presents the course and results of crack propagation simulation research. The object taken into account is a large power turbo-set rotor. The computer code system NLDW is presented. It uses a non-linear model of journal bearings, and well known crack model. Crack depth is marked by a crack coefficient. It is shown the crack generates a coupled forms of lateral, axial and torsional vibrations in multi-support rotor. Their intensity depends on the axial and circumferential crack location on the shaft. The attempt at pointing a proper diagnostic indicator for crack detection in large rotating machine is made according to obtained results.

Nonlinear Analysis of Rotor-Bearing Systems Using Component Mode Synthesis

1983 ◽  
Vol 105 (3) ◽  
pp. 606-614 ◽  
Author(s):  
H. D. Nelson ◽  
W. L. Meacham ◽  
D. P. Fleming ◽  
A. F. Kascak
Keyword(s):  
Forced Response ◽  
Component Mode Synthesis ◽  
Squeeze Film ◽  
System Response ◽  
Reduced Order ◽  
Squeeze Film Dampers ◽  
Rotor Bearing ◽  
System Equations ◽  
Transient System ◽  
Blade Loss

The method of component mode synthesis is developed to determine the forced response of nonlinear, multishaft, rotor-bearing systems. The formulation allows for simulation of system response due to blade loss, distributed unbalance, base shock, maneuver loads, and specified fixed frame forces. The motion of each rotating component of the system is described by superposing constraint modes associated with boundary coordinates and constrained precessional modes associated with internal coordinates. The precessional modes are truncated for each component and the reduced component equations are assembled with the nonlinear supports and interconnections to form a set of nonlinear system equations of reduced order. These equations are then numerically integrated to obtain the system response. A computer program, which is presently restricted to single shaft systems has been written and results are presented for transient system response associated with blade loss dynamics, with squeeze film dampers, and with interference rubs.

A Simplified Method Study of Aluminium Alloy Fatigue Crack Tip Parameters Computed by Elastic-Plastic Finite Element Model

2010 ◽  
Vol 97-101 ◽  
pp. 2748-2751
Author(s):  
Xin Song ◽  
Jing Zhong Xiang ◽  
Jia Zhen Zhang
Keyword(s):  
Finite Element ◽  
Fatigue Crack ◽  
Aluminium Alloy ◽  
Crack Tip ◽  
Element Model ◽  
Crack Model ◽  
Dynamic Crack ◽  
Elastic Plastic ◽  
Static Crack ◽  
Element Computation

Fatigue crack propagation of aluminium alloy 7049-OA has been studied by non-linear finite element business-oriented software ABAQUS, and elastic-plastic finite element models of static fatigue crack and dynamic fatigue crack of center crack panel (CCP) specimens are also built. Based on the finite element computation results, the differences of stress and crack opening displacement around crack tip of static crack model have been compared with those of dynamic crack model. The compared results showed that the finite element computation results of dynamic crack model can be replaced by the results calculated by the static crack model. Fatigue crack tip parameters of aluminium alloy CCP specimens can be calculated by elastic-plastic finite element model of static crack. This is an effective method to cut down the computation expense and promote the computational efficiency.

scholarly journals Comparison of machine learning methods for crack localization

2019 ◽  
Vol 23 (1) ◽  
pp. 125-142
Author(s):  
Helle Hein ◽  
Ljubov Jaanuska
Keyword(s):  
Machine Learning ◽  
Random Forests ◽  
Crack Depth ◽  
Haar Wavelet ◽  
Extensive Investigation ◽  
Learning Methods ◽  
Data Set ◽  
Crack Location ◽  
Machine Learning Methods ◽  
Discrete Transform

In this paper, the Haar wavelet discrete transform, the artificial neural networks (ANNs), and the random forests (RFs) are applied to predict the location and severity of a crack in an Euler–Bernoulli cantilever subjected to the transverse free vibration. An extensive investigation into two data collection sets and machine learning methods showed that the depth of a crack is more difficult to predict than its location. The data set of eight natural frequency parameters produces more accurate predictions on the crack depth; meanwhile, the data set of eight Haar wavelet coefficients produces more precise predictions on the crack location. Furthermore, the analysis of the results showed that the ensemble of 50 ANN trained by Bayesian regularization and Levenberg–Marquardt algorithms slightly outperforms RF.

Parametric Evaluation on the Response of Damaged Simple Supported Structure Under Transit Mass

2017 ◽  
Author(s):  
Shakti P. Jena ◽  
Dayal R. Parhi ◽  
B. Subbaratnam
Keyword(s):  
Finite Element Analysis ◽  
Integral Method ◽  
Critical Speed ◽  
Crack Depth ◽  
Element Analysis ◽  
Simply Supported ◽  
Crack Location ◽  
Integral Converge ◽  
Duhamel Integral ◽  
Ansys Workbench

In the present article, the responses of a double cracked simply supported beam have been investigated. The responses of the structure are determined using Duhamel integral method numerically and validated with finite element analysis (FEA) using ANSYS WORKBENCH 2015 along with experimental verifications. The mass is moving on the structure in terms of critical speed of the structure. The normalized deflections of the structure at different damaged configurations are calculated. The influences of speed, mass, crack depth and crack location on the structures response are investigated. It is observed that the results obtained from Duhamel integral converge well with FEA and experimental verifications.

Fatigue failure analysis of ceramic tools in intermittent cutting harden steel based on experiments and finite element method

2019 ◽  
Vol 234 (4) ◽  
pp. 692-700 ◽  
Author(s):  
Xiuying Ni ◽  
Jun Zhao ◽  
Feng Gong ◽  
Gang Li
Keyword(s):  
Finite Element ◽  
Fatigue Crack ◽  
Fatigue Failure ◽  
Cutting Tools ◽  
Temporal Distribution ◽  
Crack Model ◽  
Rake Face ◽  
Element Simulation ◽  
Fracture Area ◽  
Intermittent Turning

The major concern of this article is the fatigue failure mechanisms of ceramic cutting tools with the help of intermittent turning experiment and simulation. Finite element simulation was adopted to analyze the spatial and temporal distribution of the stress on the cutting tools. The crack initiation and expansion life in the different positions was researched based on the fatigue crack model. The experiment results showed that the fracture area of flank face reduced with the increase in feed rates, while the fracture area and damage depth of rake face both increased. Through the simulation of fatigue crack, it could be inferred that fatigue fractures were caused by coalescence of cracks. When the feed rate was greater than or equal to 0.2 mm, tool failure was mainly manifested as fatigue fracture of the rake face. And the results of fatigue crack propagation simulation well predicted the cutting tool life. A novel research method for tool fatigue failure was provided.

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