Rotordynamic Faults

8/12/2019 Rotordynamic Faults

1/13

Hindawi Publishing CorporationInternational Journal o Rotating MachineryVolume , Article ID ,pageshttp://dx.doi.org/.//

Review ArticleRotordynamic Faults: Recent Advances inDiagnosis and Prognosis

Ryan Walker, Sureshkumar Perinpanayagam, and Ian K. Jennions

Integrated Vehicle Health Management Centre, University o Craneld, Bedordshire MK AL, UK

Correspondence should be addressed to Ryan Walker; [email protected]

Received October ; Revised January ; Accepted January

Academic Editor: Arthur Lees

Copyright Ryan Walker et al. Tis is an open access article distributed under the Creative Commons Attribution License,which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

Diagnosis and condition monitoring in rotating machinery has been a subject o intense research or the last century. Recentdevelopments indicate the drive towards integration o diagnosis and prognosis algorithms in uture integrated vehicle healthmanagement (IVHM) systems. With this in mind, this paper concentrates on highlighting some o the latest research on commonaults in rotating machines. Eightkey aults havebeen described; the selected aults include unbalance, misalignment, rub/looseness,uid-induced instability, bearing ailure, shaf cracks, blade cracks, and shaf bow. Each o these aults has been detailed with regardto sensors, ault identication techniques, localization, prognosis, and modeling. Te intent o the paper is to highlight the latesttechnologies pioneering the drive towards next-generation IVHM systems or rotating machinery.

1. Introduction

Te topic o diagnosing and prognosing aults in rotatingmachinery is an ongoing subject o research, with manydevelopments published in a range o conerences and jour-nals annually. Tis research has the potential to become evenmore relevant in the coming years due to the rise o IVHM,in which the drive towards condition-based maintenance andwhole vehicle monitoring plays a vital role. Tis paper intendsto survey some o the recent developments in the eld,with the aim o summarizing some o the more promising

studies and trendswith relevance to uture IVHM systems orrotating machinery.

Modern day rotating machines operate with a high levelo reliability, and yet the drive or ever increased operationand decreased unscheduled maintenance is providing addi-tional challenges or industry. Te airline industry provides acurrent example o this desire, with airlines pushing manuac-turers to enable shorter turnaround times and to keep aircrafin the air longer, increasing cost benet. Despite the highlevelo reliability, the rotordynamic aults detailed in this paperremain aspects which require consideration in this drive orincreased reliability and improved maintenance procedures[].

In order to ully understand and summarize the trendsand developments in this area, several hundred recentconerence and journal papers have been studied. Overalltrends have been highlighted and discussed alongside specicpapers o relevance. It is intended that the work should pro-

vide a broad reerence and summary or working engineerson some o the latest developments in rotordynamic aultdiagnosis and prognosis, with specic application to paperso industrial relevance or the drive towards uture IVHMsystems.

In order to ully study the diagnosis and prognosis o

rotordynamic aults, it has been deemed necessary to breakdown the topic o rotordynamic aults into sections denedas ollows:

Sensors: sensors commonly used or diagnosis o spe-cic aults.

Fault Identication: diagnosis and root cause detec-tion.

Localisation : locating a specic ault within a complexsystem.

Prognosis: prognosis o components and remaininguseul lie.

Modelling: simulation o rotordynamic aults.


2/13

International Journal o Rotating Machinery

Trough the study o the topics listed, it is useul to placethe research conducted in this paper into context with regardto real-world applications. Further to this, it is intended toidentiy potential areas where more research is required inorder to push some o the recent technologies highlighted orthis study into industry.

Anderson [] provides a summary o maintenance timebreakdown or a collection o military aircraf. Tis indicatesthat as much as % o on-aircraf maintenance time (whichin turn accounts or % o total maintenance operations) isconsumed with inspection alone. Te techniques addressedin this paper enable the maintenance to be more inormedand targeted, with inventory ready when needed, providinga signicant contribution to reducing maintenance time andcost.

As the topic o rotordynamic aults is very large areao research, the scope o this paper has to be limited. Techoice o aults has been made afer considering the worksby Muszynska [] and Bently [], both o whom consider theundamentals o common aults in much detail. Out o thewide range o possible rotordynamic aults, eight have there-ore been selected. Due to the general reliability o the currentgeneration o gas turbines, aults alling outside o the eightlisted have been classed as uncommon or the purposes othis study. Tis decision was made by assessing the severityo each ault, dependences on other aults, and the level oresearch dedicated to diagnosis o each ault.

Te scope o this paper is thereore conned to the ol-lowing aults:

(i) unbalance,

(ii) misalignment,

(iii) rub and looseness,

(iv) uid-induced instability,

(v) bearing aults,

(vi) shaf cracks,

(vii) blade cracks,

(viii) rotor bow.

Each o these aults is varied, and some are more commonthan others. Te consensus rom the works reviewed withinthis paper is that unbalance is the most commonly occur-ring, in part due to the ne tolerances applied to modernmachinery and also due to the links between unbalance andother aults. Misalignment can also be identied as another

common ault. Te particular importance o these two aultsis highlighted by Domes [] who discusses common aultsrom the perspective o Rolls Royce.Bearing ailure is perhapsthe most diverse ault here and has the highest concentrationo research in various areas. Te decision has also been madeto separate aults occurring on the shafs o a system to thoseoccurring on rotors, as these can be classied as distinctaultsparticularly with regards to localization and mainte-nance. Despite these conclusions, quantiying the aults withregards to the rate o occurrence was not possible due to thelack o commercially available data, and each o the eightaults hasthereore beeninvestigatedto an equal level o detailin this paper.

It should be noted that although the aults have beenseparated into eight categories they are by no means mutuallyexclusive. Dependencies exist between many o the aults. Acommon example o this is the interaction between unbal-ance and misalignment (outlined by Bently []). Fault chainscan become even more complex, misalignments leading to an

unbalance which causes a rub or an example. Some workscontained herein detail single ault analysis, and a ew reerto two or more aults. Such ault dependencies are one o thelimiting actors when moving technologies rom the lab intoindustry. An example o this would be a system capable odiagnosing unbalance aults, without consideration or mis-alignment as a root cause may render such a system ineffec-tive when applied to a real-world scenario.

Te selected papers have been urther rened based uponrelevance to aeroengine gas turbines and publication date(with works rom the last three years preerred).

As research into the diagnosis and prognosis o aults inrotating machines is a developing topic, the application osuch technologies in industry has not yet reached a stagewhere there are common solutions, or even a set o estab-lished procedures to ollow. Tis holds particularly true withregards to the broader elds o IVHM. aking the state-o-the-art Joint Strike Fighter (JSF) program as one example othe current level o technology in circulation, although theautonomic logistics proposed by Hess et al. [] or the vehicleis undeniably impressive, it is still a long way rom imple-menting some o the recent technologies claimed to besuccessul in a lab-based environment.

Although, as mentioned, an established and commonlyapplied set o procedures and standards or IVHM has notyet emerged, with regards to rotating machinery a numbero standards and procedures can be reerred to with regardsto detailing and quantiying the aults. Tese include suchaspects as covered by ISO :, which details correctbalancing procedures and levels o mechanical vibration.Another example would be in the UK Ministry o DeenceMilitary Aviation Authority (), JAP A-Militaryaviation engineering policy and regulation, where a mentionis made o procedures or debris and vibration monitoring.Tis indicates a gradual move towards common ground orprocedures and standards or IVHM systems. Despite thisresearch remains varied, and separating the research withpotential or moving beyond the lab-based environment intoindustry can be difficult to identiy at rst glance.

Te discussion contained herein thereore takes into

account the above detailed considerations and constraints,with the aims o the paper as ollows.

(i) Highlight key examples o the latest research in eightcommon rotordynamic aults.

(ii) Summarise current trends identied rom the study.

(iii) Detail the current state o the art and the uturework required or next generation IVHM systems orrotating machinery.

2. Rotordynamic Faults

Te ollowing section details the aorementioned commonrotordynamic aults with regard to recent physics-based


3/13


simulation work and traditional data-driven methods.Research in this area o rotordynamics is particularly wide-spread, and so this paper outlines only a ew recent areaso research. Although not being o mainstream interest, alist o commonly used sensors has been included. able represents a summary o the inormation collected and

detailed as a part o this paper.As discussed, a wide selection o papers have beenreviewed or consideration in this paper, o which it is notpossible to describe them all in detail. In an attempt tohighlight some o the common themes across many o worksreviewed, able has been created.able by no meansdetails all relevant methods and approaches currently beinginvestigated; however, it details themes which were oundto be common across many areas o current research. It isintended or the detailed table to compliment the importantworks described in more detail in the ollowing section o thepaper, separated by ault type.

.. Unbalance. Tis is one o the most common rotordy-namic aults []; every rotating machine has an inherent

degree o unbalance. Unbalance as a ault can, thereore,be dened as unbalance outside o a given tolerance level.A recent piece o research which demonstrates the ongoingdevelopment o data-driven techniques is that by Ganeriwalaet al. [], who tested a technique or measuring operatingdeection shapes (ODS) in order to detect unbalance cases.Tese studies were conducted on a machine ault simulator (aphysical simulator o common aults in rotating machines)such simulators have the advantage o recreating aulty con-ditions quickly and easily, enabling a new dimension to data-driven diagnostic techniques. It is, however, worth mention-ing that data or these experiments were collected using accelerometers, which are easy to apply to such a simulator,but it may be much more difficult to congure these manysensors on a complex system. Despite this, the paper achieveditsaim in proving thehypothesis when an operating machinebecomes unbalanced, its ODS will change.

Regarding physics-based simulation o unbalance as aault, the work by Sudhakar and Sekhar [] described amodel-based method or ault identication using a minimalsensor suite. Tis is achieved through the analysis o trans-

verse vibrations at a single location. Troughout the paper,three different approaches are studiedleast squares mini-mization, equivalent loads minimization, and vibrationmini-mization. A reduced error is ound to occur using a proposed

modication to the typical equivalent loads minimizationapproach. Te work is o note due to the authors requirementto both identiy and locate (localize) unbalance.

Localization and prognosis o unbalance pose a uniqueseto challenges andas a result, research is still somewhat lim-ited in these areas. One recent work which claims to localiseunbalance accurately is by Yang and Hsu []; the authorsuse trending data and reasoning systems to locate unbalanceand shaf bow across a system. Quick diagnosis is achievedby avoiding the study o all ault combinations, and theauthors claim the ability to localise shaf bow and unbalancein large rotating machines. Te techniques rely extensively onprevious searches and are limited to large, stable machines

operating at a specic RPM. Remaining useul lie o unbal-ance is difficult to predict due to complicating actors. Asdiscussed, the ault dependencies are such that in many casesthe unbalance itsel will not be the ailing actor, instead anunbalance may cause a rub which then leads to damagewhichcan be prognoses.Such combinations o aults and underlying

causes or unbalance lead to the need or remaining useullie predictions to be made based upon the exact nature o aspecic ault.

.. Misalignment. Tis is another common ault which canpotentially inict considerable damage in rotating machines.As with unbalance, misalignment in a whole system can becomplicated by secondary aults (e.g., a misalignment whichcauses a rub). El-Shaei et al. [] are an example o theongoing research in this area; in this case, a unique combina-tion o angular misalignment and oil whip/whirl is detailed.Te authors describe how small degrees o misalignment canbe utilized in order to prevent the onset o uid-induced

instabilities, tested through the use o a lab-based test rig.Such research presents a new dimension in looking atcommon rotordynamic aults, with aspects that could beapplied to uture design or IVHM systems.

El-Shaei et al. [] demonstrate interesting research intomisalignment rom the perspective o physics-based simula-tion. Te authors construct mathematical models o a simplerotorsystem witha misaligned coupling andcollect harmonicresponse data rom this to assess the severity o differentmisalignment cases. Such models are useul throughout thelie o rotating machinesrom design to implementation,although again successul validation with experimentallyobtained data is key. Te authors highlight the act thatalthough misalignment is a prevalent and serious ault, nocomprehensive research has been perormed or treating thisproblem. Te methodology applied includes deriving theenergy expressions applying the Ritz series method, con-structing the equations o motion and then using the har-monic balance method to look or multiharmonic responses.Te paper demonstrates the ongoing research to understandand model the undamentals o such aults, in order thatimproveddiagnosisand prognosis methods can be built uponsuch knowledge.

As with unbalance, localization and prognosis o mis-alignment is a complex topic to research. Studies such as El-Shaei et al. [] can make accurate predictions or misalign-ment in a simple system with one coupling. However, real

systems (e.g., aircraf gas turbines) have many potential loca-tions o misalignment. Tis is an area where ew researchershave made an impact. Remaining useul lie predictions ormisalignment is complicated or the same reasons as withunbalance. Villa et al. [] discuss statistical diagnosis omisalignment aults, with reerence to prognosis. Te authorsuse the example o a wind turbine or their studies, butstress the applicability to other systems. Differentiation withunbalance aultsis also covered (as these two aultsare closelylinked). Unlike the work by El-Shaei et al. [], emphasis isgiven to the machine in question operating over a wide rangeo operating speeds and conditions. Tis is achieved throughthe use o an angular resampling method. Prognosisis tackled


4/13


: Rotordynamic ault table.

Faults Sensors Fault identication

techniques Localisation o ault Prognosis

Work o note in aultmodelling

UnbalanceAccelerometer

Velocity transducer

Proximity transducer

Operating deectionshapesime-requency

analysis and manyothers

Neural-networkmodelling and

time-requencyanalysis

FCM-Markov model

Unbalance in ull-engineFEA model,Early detection inaeroengines

High radialloads andmisalignment

AccelerometerTermocoupleDisplacement

transducerAngular sensor

Bearing temperatureobservation advancedSofware-drivenltering methods

Various vibrationanalysis techniques

Prognosticmodelling usingsimulated vibrationdata

Modelling therelationship betweenmisalignment and otheraultsHarmonic balancemethod

Rub andlooseness

AccelerometerVelocity transducer

Optical sensor

Single valuedecompositionime-requencyanalysis

Least-squares ttingapproach

Adaptive waveletdenoising orprognostics

Rob and looseness usingFEA models Wholeengine modellingtechniques

Fluid-inducedinstability

Proximity probesKeyphase transducer

Full spectrum plotsLarge amplitudesubsynchronousvibrationDetection

Blade tip clearanceand loadingdistribution

Cross-coupledstiffness anddirect-dampingstudies

Nonlinear modellingaccuracy o model basedDiagnostics numericalmodelling

Bearing ailure

AccelerometerVelocity transducer

Displacementtransducer

Proximity probes

Postailure analysis oruture ailure diagnosisDynamictime-requency analysis

Statistical change inthe bispectraldomain

Numericalmodelling oaeroengine bearingsModel-basedprediction oremaining useul lieOn-boardprognostics

High and low delitydynamic systemmodellingComparisons oalgorithms tounderstand bearingvibration phenomena

Shaf cracks

Keyphase transducer

Proximity probes

Higher order spectra

Neural networksGrid support vectors

Forced response

measurements

Nonintrusive

torsion vibrationmonitoring

Statistical analysis FEA

modelling

Blade cracks Keyphase transducer

Proximity probes

Hilbert-HuangtransormationModel-baseddiagnosticsMorletwavelet/quantumtechniques

Novel bearingstructures

Active magneticactuator

Global and localasymmetry modellingFinite element modelling

Rotor BowKeyphase transducer

Proximity probesSeismic transducer

Examination o slowroll dataModel-baseddiagnostics

Partial mathematicalmodelling

Statistical symptomsanalysis

Advantages o aultmodelling oridenticationNonlinear modellingtechniques

through the use o a statistical diagnosis algorithm based onthe signicance level o the aults in question.

.. Rub and Looseness. Rub is always a secondary ault (i.e.,a product o another ault such as looseness) and can leadto atigue and wear. Rub and looseness can create com-plex vibration signals which are difficult to diagnose usingtraditional methods. Modeling and simulation o rub andlooseness aults have been considered in several recentworks.

Tis includes Ngolah et al. [], which detail the moni-toring and diagnosis o common aults (including rub and

looseness) based upon a three-layer Articial Neural Net-work (ANN). A series o key perormance indicators wereidentied and used as training. Te authors test the systemin a lab environment, but stress the applicability to industrialapplications. Te research indicates one o the latest methodso research which enables the implementation o diagnosistechniques. It is a useul tool or rub and looseness studies,as it incorporates a variety o aults which could underliesuch a ault. Despite this, the research relies on clear eaturesor each ault, which can be much easier to identiy in a labenvironment as opposed to noisy industrial applications.


5/13


Lu et al. [] have perormed several studies into rub andlooseness,including thisexamplein which a exibly mountedshaf has an induced rub due to a range o contact rings.Te study ocusses on the potentially dangerous effects o rubin causing excessive nonsynchronous and chaotic vibrations.Te links with unbalance and misalignment are discussed

and detailed. Te considerations or real-world cases in thedescribed research are considerable, as part o the drivetowards ull understanding o the nonlinear effects o rub andlooseness.

Localization o rub and looseness across whole systemsis relatively lightly studied in the literature. Many works(including those already cited) look at single or dual-rotorsystems where localization o such aults is not an issue. Inan industrial setting, complex systems may comprise manyrotors in several compressor and turbine stages, signicantlycomplicating diagnosis o such aults. Research into progno-sis o rotor-stator rubs lies mostly within the domain o data-driven techniques. Modeling and simulation research can beused to support data-driven techniques or prognosis andcondition-based monitoring. Han et al. [] is an example othis; the authors use nite element modeling to construct adual rotor model. Various types o rub-impact are then stud-ied. Such studies can provide a wide range o inormation,which can then be combined with data obtained rom livesystems, potentially with seeded aults, in order to constructaccurate remaining useul lie predictions. As pointed out bythe authors, one key advantage o simulation is the abilityto study more complex systems with a higher number orotors, which is used throughout this research. Tis presentsa different approach to identiying eatures or identicationo rub and looseness.

.. Fluid-Induced Instability. Fluid-induced instabilities(ofen reerred to as whip and whirl) are potentially veryserious aults which can result in wear, atigue, and extensivedamage to machine components. Such instabilities can beound in interstage seals, uid lubricated bearings, andblade-tip clearances. Research into simulating and modelinguid-induced instability has produced several works ointerest to ault diagnosis o rotating machines in the lastew years. De Castro et al. [] are a good example, wherenonlinear mathematical models are prepared or a rotor-bearing system. Te models are then used to predictinstability thresholds. Te authors consider a test case againsta power plant turbine and a test rig, thereore validating the

simulations. Te case o unbalance aults causing whip andwhirl phenomena is also considered. Te main conclusionthereore drawn rom the work is that the authors concludedthat nonlinear hydrodynamic journal bearing models enablesufficiently accurate simulations or predicting instabilitythresholds. Fan et al. [] represent an example o work romthe perspective o aeroengine turbines. In this case, startupconditions are studied using a ull Hilbert spectrum. Te aimbehind the paper is to accurately predict the point at whichwhip and whirl occur, thus enabling this to be avoided at thedesign stage. Such ndings could potentially also be used toidentiy whip and whirl as the case o a ault afer a period owear in the operating machine.

Prognosing uid-induced instability is a relatively lightlyresearched topic. Fluid instabilities can be covered as part oextensive research into remaining useul lie o bearings. Tepotential exists or modeling and simulation techniques suchas those detailed above to become a part o prognosis oruid-induced instabilities due to the act that it can be very

difficult to seed such aults into live systems or testing andevaluation. As with other aults detailed in this paper, manystudies have been perormed with the aim o describing uid-induced instabilities based on the measurement or simulationo single (or occasionally dual) rotor setups. Physics-basedsimulation with the aim o localising uid instability aultsacross a whole system can be limited by the complexity oboth the ault and the system, hence, the simplication tosingle rotor-stator bearing systems.

.. Bearing Failure. An area where data-driven techniquesare still providing the basis o much research in the eld orotordynamics is that o bearing ailure. Te title bearingailure can cover a wide range o potential issues whichcontinue to be studied in detail. Faults can occur in all kindso engine bearingsthe inner andouter case, the cage andtherolling elements, uid-induced instabilities (addressed in aseparate section), lubrication, and the complexities o activemagnetic bearings to name some examples. All types obearing relevant to rotating machinery are the subject oongoing research, and this subject has the potential to ormseveral separate papers. As a brie highlight, some recentexamples are discussed as ollows.

Data-driven techniques have enabled accurate bearingdiagnostics and prognostics to be described or a rangeo rotordynamic systems. Despite the prevalence o data-driven research in this area, research rom a physics-basedsimulation perspective has also recently produced someinteresting papers o relevance to condition monitoring andhealth management o rotating machinery.

Tis includes Kappaganthu and Nataraj [], in whichrolling element bearings have been studied through the useo nonlinear models. Te included nonlinearity in this caseis clearance, and the model is then used in order to studychaotic motions, in particular the regions o chaotic response.Te research orms a part o an ongoing drive to develop anaccurate model-based diagnostic technique or rolling ele-ment bearings, taking into account clearance nonlinearitiesand chaotic responses.

Guptaetal.[] demonstrate another example o thelatestresearch into instability and chaos in rolling element bearingsthrough high-delity simulations. Tis detailed and complexstudy involves the application o a novel scheme to analyzethe quasiperiodic response o the system combined with anonautonomous shooting method. Tis workhighlights thelevel o detail to which nonlinearities and complex nonlinearmotions in bearings are beginning to be understood andaccurately modeled. Again, such work presents the potentialor design o IVHM in uture evolutions o the research.

As so much research hasbeen perormed (and is ongoing)into bearing aults across a wide variety o mechanicalsystems, both prognostics and localization o bearing aults


6/13


have been researched in somewhat more detail than someo the other aults detailed here. Despite this, much workstill needs to be perormed in order to translate some othis core research into industrial applications. Research suchas that detailed above has made signicant advances intodetermining bearing ailure as the root cause o malunction.

Detecting which bearing is ailing across a complex systemhas received somewhat less research. Bearing prognostics isanother area with much ongoing research being perormedboth in the simulation and data-driven domains. o givean example, Hong et al. [] combined grade lie andextensive mathematical modeling techniques in order to pro-duce prognostic models or aeroengine bearings. Te resultsare described by the authors as practical and veriable.Although a number o similar recent studies exist,this work iso note or the extent o the studies perormed which includebearing test stand run-to-ailure validation. Te lab resultsappear impressive; this research has yet to be applied andtested in real lie applicationsindicating that despite thenumber o parameters considered, it is still not possible tomodel naturally occurring phenomena sufficiently.

A large body o work in this area also exists romBorghesani et al. [], where several examples o data driventechniques can be seen applied to a wide variety o bearingtypes. An example o recent developments involves the use ocepstrum prewhitening in order to remove sufficient noiseor accurate bearing diagnosis and prognosis. Tis work isparticularly noteworthy due to the emphasis on real-worldapplications, where the traditional lab-based techniques oorder tracking and synchronous averaging do not providesufficient noise removal or harsh industrial environments.Te addition o such techniques is a crucial step in developingthe current generation o diagnosis and prognosis algorithmsor use in uture IVHM systems.

.. Shaf Cracks. Another potentially serious ault in rotat-ing machinery is shaf cracks, and so early detection o anysuch ault is highly important. Methods o crack ormationandpropagation canbe diverse, andrange rom highand low-cycle atigue to stress corrosion. Simulation and modelingo shaf cracks can have signicant advantages over data-driven methods. Perhaps the most obvious advantage is therelative simplicity o inserting a ault into, orexample, a niteelement model as opposed to seeding a ault in a workingindustrial machine. As such, research into shaf cracks has

been progressing steadily with the corresponding increasesin computing power.

A clear synergy between data-driven and physics-basedsimulation research can be implied by a number o recentworks o research. An example o recent advances rom a datacollection perspective is Li et al. [], which details statisticalmodels based on historical data or condition monitoringpurposes. Tis unique work uses the human auditory systemas inspiration or enriching methods o mechanical aults andeatures extraction. Te results indicated by the paper areperhaps not as convincing as some other methods discussedin this paper, it describes an interesting outside the boxmethod o tackling common problems.

From a modeling perspective, Bachschmid et al. []cover a wide range o vibration phenomena in order todevelop a model-based identication and severity procedure.Tis work is noted or its thoroughness in modeling pro-cedure, including accurate modeling o the crack breathingmechanism. A combination o high and low delity models

is validated through experimental study, and excellentaccuracy is claimed by the authors in detecting crack positionand depth through the use o the proposed model-baseddiagnostics.

Te nature o shaf cracks has resulted in a wide variety oresearch beingperormed intoboth localization and prognos-tics o these aults (indeed, the two topics can be consideredrelated). Recent examples o work in this area include Inoueetal.[], who detail crack localization using orced responsemodeling. In this case, a test rig was constructed consistingo a circular shaf supported by two bearings. Frequency-domain data was used to create a localization algorithm,designed in combination with an FE model. Although thisresearch provides good accuracy o localization in a labenvironment, it remains untested in a more complex system(e.g., a ull gas turbine).

Sonnichsen [] describes nite element modeling ocrack propagation, with validation against experimentalresults provided to demonstrate the validity o such modelingtechniques. Te paper concentrates on natural requenciesand resonance curves. Whilst the authors claim improve-ments in the ability to understand such aults, again thesystem in question is quite simpleand such FEA models aredifficult to scale up to ull size applications.

.. Blade Cracks. Blade cracks, i allowed to develop, canresult in serious consequences. Cracks can orm due to highcentriugal stresses across operational cycles (in the case oan aircraf gas turbine, or example, start up, and take offthrough landing and taxi). As excessive crack growth canlead to catastrophic rotor/blade ailure, early detection andprognosis o such aults are essential. As with shaf cracks,physics-driven simulation o blade cracks is an area o sig-nicant research. Tis varies rom high-delity nite elementmodels to low-delity system and mathematical models. Terecent work demonstrated by Green and Casey []is agoodexample o recent mathematical modeling rom a diagnosisperspective. In this paper, the authors concentrate on earlydetection using global and local asymmetry crack models. X

harmonic components are identied as key areas or the earlydetection o blade cracks, however again this paper suffersrom being applied and tested on a relatively simple systemwhich may not scale up to a ull size turbine.

Sonnichsen [] demonstrated high-delity modeling,the authors used FEA to model crack growth, making com-parisons and validating against an experimental rig. Tiswork is particularly interesting as it outlines the advantagesand drawbacks with the latest state-o-the-art modelingtechniques.

Localization and prognosis o blade cracks have alsobenetted rom recent advances in simulation and modeling.Sawicki et al. [] contains details o work on a novel active


7/13


magnetic bearing system or use in the early detection, local-ization and prognosis o blade cracks. Again the emphasis ison early detection, with the bearings used to excite the systemin order to obtain optimum response vibrations or analysis.Te authors admit the approach hassome merit in diagnosingblade cracks; however, it is in the early stages o development

and work are ongoing. FEA has also been used extensivelyto support blade crack prognostic tools; Xiang et al. [] arean extensive example o recent work. In this case, a numbero advanced FEA methods are applied to produce accurateFEA solutionsthese include surace-tting techniques andthe contour-plotting method. Te authors experimentally

validate their work and suggest that it can be applied toprognosis and quantitative diagnosis o blade cracks. Despitethe claimed advances, again the scalability o such research toull size turbines is an issueparticularly with regard to thecomplexity o the FEA models.

.. Rotor Bow. Rotor bows can be a primary source ounwanted vibration in gas turbines. Te main cause o arotor bow (rotor bows do not include bows due to gravity) isthermal differences in a system caused by operating con-ditions. It is noted by Domes [] that this nonsymmetricalthermal distribution can cause excessive unbalance to theextent where a gas turbine will not start correctly. Such rotorbows are common on start up or shut down, and are ofenaccounted or in operational procedures. However, i thermalhot spots exceed a given tolerance level, they can causepermanent unbalances due to rotor deections. Such rotorbows can lead to other aults, includingrubbing andloosenesswhich complicate isolation and localization.

raditional data-driven techniques or detecting rotorbows involve combinations o slow roll and vibration data[]. More recently, mathematical modeling techniques suchas that detailed by Meagher et al. [] have been used inorder to diagnose residual rotor bows and differentiate theseaults rom other sources o unbalance. Te authors o thispaper build upon established methods or the models and areunique in that they concentrate on response at the bearingpoints. Tis is perhaps more useul orindustrial applications,as vibration inormation is more readily available at bearingpoints rather than intrusive proximity probes, which are ofenused in lab work.

Te little work that exists on attempting to localise rotorbows across complex systems tends to be data-driven in

nature; see Gaka and abaszewski [], where the authorsused statistical symptoms based on known data as a methodo diagnosing and prognosing a number o aults, includingrotor bows and unbalance. Tis paper attempts to address theirregularities and uctuations that occur over a long servicelie. In order to achieve this, a modied energy processormodel is created, using data drawn rom large steam turbinesover long periods o lie.

Prognosing rotor bows is a complex subject. As rotorbows are ofen caused by temperature deections, makingpredictions or remaining useul lie and potential utureproblems lies not only in the realm o mechanical rotor-dynamics but also to some extent in thermodynamics. Te

recent work detailed by Sinha [] is o note or detailingdiagnosis and quantication o various rotordynamic aultsand describing the advantages o mathematical modelingover traditional vibration-based approaches. Te topic oscalability regarding FEA models is discussed, including anargument or the use o partial (simplied) mathematical

models or large, complex systems.Another two works which are o interest with regard to

modeling o rotor bows include Shen et al. [], where theauthors modeled a rotor-bearing system with a permanentrotor bow, looking at the impact o secondary aults such asrub. Te study o ault combinations in this paper is useulor ault differentiation studies; however, the authors studya permanent, initial rotor bow. Tis thereore does not takeinto account developing or worsening aults and the different

vibration phenomena that are observed as such aults aredeveloping.

Lees et al. [] describe the importance o model-basedault identication techniques and outline recent research in

the area, providing a good reerence paper or more researchon this specic ault.

3. Discussion

.. Sensor Suites. Te subject o sensor suites is o greatimportance with regard to uture industrial applications. Onone hand, advanced and complex sensor suites generallyenable improved ault localization and diagnosis; however,the added complexity and cost has resulted in many o thesesystems being omitted rom the latest generations o rotatingmachinery in industrial applications. From an industrialperspective, the cost benet o additional sensors needs to

be signicant in order to justiy this approach. In response, anumber o works listed, including [] as a good example, takethe approach o achieving the same objectives using a greatlyreduced sensor suite. In many ways, the required sensor suiteor many o the currently researched ault diagnosis andprognosis techniques provides an indication o the ability othe techniques to be used practically in industrial situations.A complex suite may return a very high success rate on alab-based rig; however, the impracticalities o mounting suchsuites on a real-world application negate the advantages.

Further to this, the consideration orsensor position mustbe considered. Te use o proximity probes and keyphasortransducers has very clear advantages in a number o situ-

ations; however, the intrusive nature o the sensor preventsapplication in a number o complex systems. With this inmind, a number o the more promising studies listed rely onthe simple suiteo an accelerometer placed in positions whichare relatively remote rom the sources o vibration, potentiallywith a noisy transer path.

.. Diagnosis. It can be seen rom the research outlined inthe previous section that the diagnosis o aults in rotatingmachinery is a subject o much ongoing research. Tisinvolves the improvement and development o traditional

vibration monitoring techniques, development o new data-driven technologies, and novel research into physics-based


8/13


simulation and modeling. In many cases, these topics oresearch are dependent on one another or reasons o vali-dation, verication, and speed o analysis. In several cases,it can be seen that multiple aults have been modeled orthe purposes o identication and isolation. However, nostudies have yet been perormed which deal with all o the

aorementioned aults. All o these aults are intrinsicallyrelated to one another. Complex combinations o aults havebegun to be analyzed with the emphasis on developing newdiagnosis techniques. Physics-based modeling has proven toprovide signicant advances with regard to specic aults,notably shaf and blade cracks, where techniques such as FEAenable much easier, aster, and cheaper test data then seedingaults into live systems.

It can be noted, however, that both high and low-delitymodeling techniques are being applied to cutting edgeresearch or all o the listed rotordynamic aults (and othersnot detailed in this paper). In addition to the advantages inthe speed o obtaining test results, physics-based simulationis providing another dimension to data-driven techniques.System models are being used as part o logic and reasoningsuites in the identication and differentiation o variousaults. High-delity models enable simulations o ault com-binations, which are not possible practically or are pro-hibitively expensive in live systems.

Nevertheless, results obtained rom modeling studies stillneed to be validated against proven data-driven techniquesbeore implementation in industrial applications is possible.It is also o note rom the literature reviewed or this paperthat almost all modeling or the diagnosis o aults involvesextensive simplication, ofen reducing potentially complexsystems down to one or two disc/shaf/bearing models.Adapting the claimed results rom such research to systemswith many discs/bearings/shafs is important in improvingexisting rotating machinery diagnostic techniques.

Te inclusion o nonlinear effects is notable amongstmany authorsas the understanding o the complex aultsand interactions continues to progress. Such research opensthe potential or promising new avenues into areas o designor IVHM.

Finally, it is o note that despite the wide variety oadvanced research here, a consensus or the most efficienttechniques and algorithms has yet to emerge in order or thenal adaption to industrial application to be achieved. How-ever, the consideration or industrial application taken bymany o the authors detailed in this paper provides promise

or next generation IVHM systems.

.. Localisation. Fault localization in rotating machinery isan important topic o research or uture condition-basedmonitoring systems. Knowing not only what type o aulthas occurred, but also where in the system is an importantconsideration which can inuence maintenance proceduresin complex machinery. It is worth noting rom the literaturesurveyed or this paper that many studies have ocusedon diagnosis and prognosis o single rotor/bearing systems.Ofen or legitimate reasonssimplication or computingspeed, or example. Few studies, however, have taken intoaccount the localization o aultsacross whole systems. Oneo

the more extensive examples highlighted in this paper (Hanet al. []) provides extensive analytical studies relevant tolocalization on a duel disk setup, utilizing Hilbert-Huangransorms; however, in this example comprehensive valida-tion is lacking, thus limiting the potential applicability o theresearch.

Tis problem is not limited to modeling and simulation-based research. Many newly developed data-driven tech-niques or diagnostics and prognostics claim good results byheavily instrumenting specic components o a test system.In many industrial cases, this is not possible, practical or cost-effective.

o give some examples, a keyphasor transducer can beparticularly useul in diagnosing aults such as rotor bow.However, this equipment requires the ability to cut a keyway or measurements to be perormed. Optical sensors haverecently been applied to detect rotor unbalance; yet such atechnology would be difficult to implement in a system withseveral rows o rotors (as in a gas turbine).

Whilst new diagnosis and prognosis techniques or aultsin rotating machinery are being continuously researched,the lack o corresponding studies into localization can beconsidered one o the many challenges in promoting recentcore research into live industrial applications.

.. Fault Differentiation. One promising development inrecent modeling and simulation o rotordynamic aults isthat o ault differentiation. Several researchers have movedon rom studies on individual aults in order to concentrateon combinations o aults. As stated, rotordynamic aultssuch as those listed in this paper are linked to each other.Such studies, thereore, concentrate on such topics as a

misalignment causing an unbalance or a looseness causinga rub. Findings rom reports such as these are important inunderstanding complex anomalies. In industrial applications,simply detecting and rectiying an unbalance does not pro-

vide a satisactory solution, i the root cause o the ault isa misalignment. Tis is a complex topic, as several aults canexhibit similar vibration characteristics, making traditionaldetection techniques inaccurate in some cases.

Making reerence to some o the aorementioned stud-ies, those such as Bachschmid et al. [] and Sonnichsen[] indicate some initial studies including several aults.Te results o such studies, indicate a high success rate indifferentiating the aults in the given conditions; however

a number o limitations still exist. Studies such as theseconsider unbalancein the aultchains. Tisis typically staticor simple unbalance applied to a single shaf/rotorin realityunbalance aults can be more complex than this. In addition,the simple systems used to study and differentiate aultsare very different rom the complexities o a ull turbine.However, urther work may enable such research to scale-up to this stage with the aid o urther validation and

verication.

.. Prognosis. It can be seen rom the examples o recentresearch described or common aults that prognostic tech-niques are a topic where much work is being perormed.


9/13


Some o this work would be very difficult or impossibleto implement in an industrial situation; others providepromising results o use to uture work in the area. Predictingthe remaining useul lie o components is critical in thedevelopment o condition-based monitoring strategies orindustrial implementation.

It can be noted that prognostic studies or certain rotor-dynamic aults are considerably more advanced than orothers. Te most obvious examples o the aults detailed inthis paper are bearing aults, shaf, and blade cracks. Teseare also areas where physics-driven simulations have hadan important impact. Te ability to design any ault type(or combinations o aults) into such simulations (to be itslow-delity mathematical models or high-delity nite ele-ment analysis) has provided researchers with many differentavenues to explore. Studies into the prognostics o otheraults can be complicated by various actors. An unbalance,or example, has had relatively little research perormed intoprognosis. Te act that unbalance is ofen the cause oanother underlying ault is one reason or the difficulty inresearching prognosis in detail or this ault. Te results ounbalance are also very dependent on the severity o the aultand the system in which it occurs.

It is worth noting that even or the aults where prognosisresearch is more advanced (e.g., shaf cracks); true develop-ment o the ault is not always studied. Fan et al. [], orexample, study sets o discrete cracks in order to prognosecrack growth. In act, thisstudy is more akinto detecting aultseverity with inerred effects on crack growth. In contrast, Liet al. [] consider the continual development o such cracks;however, the authors do admit this work is in its inancy.Such points limit the ability or true prognosis to be achievedwithout extensive operational data.

It is also worth noting that combinations o aults havebeen simulated extensively or the purpose o diagnostics;however, ew studies exist combining aultsor the purpose oprognostics. Such studies are, however, a logical progressionrom some o those already perormed. It may be that suchprognostic studies build upon some o the condition-basedmaintenance (CBM) or diagnostics. High-level studies suchas Jaw and Merrill [] indicate how prognosis and diagnosistechniques can be combined into a CBM system. Tis studyis designed or a military aeroengine, indicating the desire orsuch systems to be implementedalthough the architecturedescribed has the capability o including various algorithmsoraultprognosis, the amount o consideration orprognosis

o ault combinations is unclear.

.. Modelling. Te large number o works reviewed or thispaper which includes modeling techniques in order to aiddiagnosis and prognosis indicates the possibilities providedby modern computer power and sofware development.Broadly, the modeling studied in the aorementioned papersbreaks down into two categories: mathematical modeling andnite element analysis (FEA). Te mathematical models, suchasBorghesani etal. [], ofen provide a theoretical basis uponwhich data driven or FEA studies can build and validate.Mathematical models, despite being a traditional approach to

rotordynamic problems, thereore continue to be developedto tackle more advanced problems.

FEA techniques offer a constantly expanding area osimulation to explore. Tey are used or research as diverseas crack propagation to unbalance localization []. Moderncodes such as NASRAN and Ansys enable rotordynamics to

be studied beyond the traditional stress and modal analysis.Te ability to study the effects o rotation (e.g., throughCampbell diagrams and transient analysis) continues to driveresearch and innovation in this area. Te studies discussedin this paper indicate the power o FEA, with some highlyaccurate simulations having been perormed. However, thereis still a limitation o computer powerapplying some othe FEA techniques to whole engine models would proveto be too computationally expensive to be viable. As aresult, alternate methods such as model order reductionand system level modeling (and model-based reasoning orimplementation) are still required in order to make some othe FEA studies viable in an industrial environment.

Nonlinearities continue to orm an important part omany recent studies, with the complexity and detail o thespecied aults being continually expanded. Te depth omodeling has enabled in many cases accurate validationagainst experimental approaches. Despite this, completeunderstanding o the vibrational phenomena o rotatingmachinery is not currently possible, despite the drive towardsthis end.

.. Rotordynamics and IVHM. Te bulk o current researchinto rotordynamics rom the point o view o prognostichealth management (PHM) can be roughly divided intotwo types: initial single-ault diagnosis/prognosis techniquesand studies into the general requirements and limitationso current systems along with current and uture trends.An example o the latter is Pusey [] who provides agood summary overview o current diagnosis and prognosistechniques with regard to condition-based maintenance.

As a result o this split, a clear gap exists between thecore research being perormed into rotordynamics rom acondition-based maintenance perspective and the identiedneeds o industry. aking a edgling piece o research andapplying it to a commercially-ready system (e.g., a gas turbineengine or an aircraf) is a long and complex task. It isnevertheless worth noting that technologies or automaticallydetecting an unbalance or misalignment in a gas turbine were

developed over years beore the latest commercial aircrafwere conceptualized, and yet these planes are still limited inthis capacity. Tis highlights the need or work which linksthe undamental research into individual ault diagnosis tolive systems in use in industry.

Physics-based simulation and modeling o rotordynamicparts is a well-researched eld. Such modeling has been usedas the basis o diagnosis and prognosis o aults by manyresearchers; several recent examples have been outlined inthis paper. Occasional pieces o work have been perormedinto modeling multiple aults, such as Jain and Kundra []who usea system model oronline identication o unbalanceand cracks. Beyond this, however, very limited research


10/13


Business case/cost benetanalysis

Live system

RubCracksBearingfailure

Rotor bowUnbalance

Fault differentiationLocalisation

Root cause analysis

Remaining useful life

Data driven analysis and physics-based simulation

Mis-alignment

Experimental/

eld data

F : Physics-based simulationrom research to industry.

exists. Te demands o PHM techniques in industry are suchthat any systemmust notonly be capable o detecting multipleaults, but must also be capable o detecting these aultsacrossa range o different systems. Other considerations includethe aorementioned ability to differentiate between multipleaults. Processing also needs to be taken into account, as theobjective o these systems is to implement efficient conditionmonitoring and condition-based maintenance procedures. Iprocessing data is a long, power-hungry process, then thisaim cannot be achieved.

Figure details a potential ramework required in order

to push core research, such as that detailed in this report,towards industrial applications. Many studies now exist onindividual rotordynamic aults across a wide range o condi-tions and applications. Some studies have taken this urther,with advanced prognostic models and diagnosis o dual aults(primary cause and secondary effect). Future research inthe area o rotordynamics rom a PHM perspective couldpotentially provide the bridge between these studies and livesystems, by combining physics-based simulations with data-driven techniques and validating against experimental data.

Although quantiying the success o the research studiedisdifficult,it ispossibleto dene the key areas in whicha tech-nique must excel in order to be considered viable. Te work

byWheeleretal.[] discussesin detailmetrics ordiagnosticand prognostic analysis, as does that by Vachtsevanos []and Saxena et al. []. Te conclusions drawn rom thesepapers and applied in practice to research like that covered bythis paper indicate that the ollowing metrics are importantwhen considering the potential o a given technique to diag-nose aults: coverage, alse positive rate, and alse negativerate. In the case o prognosis, probabilities, and lead timeto ailure are other important considerations. Tis criteriaenables research to be assessed in terms o its suitability orindustrial applications. Unortunately, inormation on these

metrics is not made readily available by the authors o mostpapers.

In terms o evaluating the effectivenesso theresearch dis-cussed in this paper, there are difficulties in recommending aspecic technique over others or general application. Mostpapers reviewed or this document (not just those reerencedand discussed in detail) take a technique (new or evolved),

validate or a given, specic system, and report success o theresearch. Despite this, some conclusions can be drawn romassessing common techniques applied across different studiesand different aults. Although it is not possible to dene themost common methods or diagnosing andprognosing aultsin terms o numbers (as it was not possible to cover all recent


11/13


rotordynamics research or this paper), as perceived by theauthors, the ollowing techniques have eatured prominentlyin the reviewed research.

(i)Sensors: accelerometers.

(ii)Teoretical studies: mathematical modeling.

(iii)Physics-based simulation: FEA.(iv)Data-driven: joint time/requency domain analysis.

(v)Implementation: neural networking.

Tese techniques appear to be among the most promisingcurrently under development, as they tend to eature numer-ous timesamongst some o the work with wider scope, acrossault types and with the most comprehensive validation.Tere are o course many subsections to these techniques;however, it shows one general direction o research and theclear possibilities posed in these areas.

Future developments in the eld o IVHM or rotat-ing machinery may incorporate these techniques alongsideextensive use o nonlinear modeling and multiple aultinteractions. Te eld o design or IVHM has only recentlyemerged; however, the potential exists or specic nonlinear-ities to be designed into a system in order to enable accuratediagnosis andprognosis o aults. Te development o currentalgorithms to include diagnosis, localization, and prognosiso a range o aults will provide a signicant advancement oruture generations o IVHM systems. Tis combined withcost-effective sensor suites indicates the potential or evolu-tions o some o the research detailed hereto orm part onextgeneration IVHM suites or rotating machinery.

4. Conclusion

Tis paper has reviewed some o the latest research around anumber o rotordynamic aults, namely unbalance, misalign-ment, rub and looseness, uid-induced instability, bearingaults, shaf cracks, blade cracks, and rotor bow. Each aultwas reviewed rom the perspective o sensors, diagnosis,prognosis, localization, and modeling.

Key examples o recent work into the eight describedaults have been detailed through works by a number oeminent authors. Additional work has been summarized andormatted or easy reerence. Some current trends amongstthe recent body o work include developments in the vastarea o modeling nonlinearities, combinations o high andlow delity modeling, and synergy between data driven and

physics-based simulation approaches.Despite the large volume o promising research reviewed,

urther development in a number o areas is required in orderto produce effective next generation IVHM systems. As such,uture developments may include usion o and/or devel-opment o current algorithms to encompass all eight aultsdetailed, consideration o prognosis, diagnosis, and localiza-tion achieved using a reduced, cost-effective sensor suite.

References

[] I. K. Jennions,Integrated Vehicle Health Management: Perspec-tives on an Emerging Field, .

[] G. Anderson, Providing best-value IVHM solutions or agingaircraf, inProceedings o the th Joint FAA/DoD/NASA AgingAircraf Conerence, vol. , pp. , .

[] A. Muszynska,Rotordynamics, aylor & Francis, st ed edition,.

[] D. E. Bently, Fundimentals o Rotating Machinery Diagnostics,

ASME Press, st edition, .[] B. Domes, Vibration phenomena in aero-engines, inProceed-ings o the th International Conerence on Vibrations in RotatingMachinery Exeter (IMechE ), vol. , pp. , September.

[] A. Hess, G. Calvello, and. Dabney, PHM a keyenabler or theJSF autonomie logistics support concept, inProceedings o theIEEE Aerospace Conerence Proceedings, pp. , March.

[] S. N. Ganeriwala, B. Schwarz, and M. H. Richardson, Operat-ing deection shapes detect unbalance in rotating equipment,Sound and Vibration, vol. , no. , pp. , .

[] G. N. D. S. Sudhakar and A. S. Sekhar, Identication o unbal-ance in a rotor bearing system,Journal o Sound and Vibration,

vol. , no. , pp. , .[] . Yang and M. W. Hsu, An efficient diagnosis technique or

variations o shaf-bow and unbalance, in Proceedings o theASME International Design Engineering echnical Conerencesand Computers and Inormation in Engineering Conerence(DEC ), pp. , San Diego, Cali, USA, September .

[] A. El-Shaei, S. H. awck, and M. O. A. Mokhtar, Experi-mental investigation o the effect o angular misalignemt onthe instability o plain journal bearings, in Proceedings o theASME/SLE InternationalJointribology Conerence(IJC ),pp. , Memphis, enn, USA, October .

[] A. El-Shaei, S. H. awck, and M. O. A. Mokhtar, Misalign-ment modeling in rotating systems, in Proceedings o the ASMEurbo Expo, H. Bahaloo, A. Ebrahimi, and M. Samadi, Eds., vol.

, pp. , Orlando, Fla, USA, June .

[] L. F. Villaet al., Statistical diagnosisbased on vibration analysisor gear test-bench under non-stationary conditions o speedand load,Mechanical Systems and Signal Processing, vol. , pp., .

[] C. F. Ngolah et al., Intelligent ault recognition and diagnosisor rotating machines using neural networks,Sofware Scienceand Computational Intelligence, vol. , no. , pages, .

[] Y. Lu, Z. Ren, H. Chen, N. Song, and B. Wen, Study on loose-ness and impactrub coupling aults o a vertical dual-diskcantilever rotor- Bearing system, Key Engineering Materials,vol. , no. , pp. , .

[] Q. Han, Z. Zhang, and B. Wen, Periodic motions o a dual-

disc rotor system with rub-impact at xed limiter,Proceedingso the Institution o Mechanical Engineers, vol. , no. , pp., .

[] H. F. de Castro, K. L. Cavalca, and R. Nordmann, Whirland whip instabilities in rotor-bearing system considering anonlinear orce model,Journal o Sound and Vibration, vol. ,no. -, pp. , .

[] C. C. Fan et al., Mechanical systems and signal processing,Study o Start-Up Vibration Response or Oil Whirl and DryWhip, vol. , pp. , .

[] K. Kappaganthu and C. Nataraj, Nonlinear modeling andanalysis o a rolling element bearing with a clearance,Commu-nications in Nonlinear Science and Numerical Simulation, vol.,no. , pp. , .


12/13


[] . C. Gupta, K. Gupta, and D. K. Sehgal, Instability and chaoso a exible rotor ball bearing system: an investigation on theinuence o rotating imbalance and bearing clearance,Journalo Engineering or Gas urbines and Power, vol. , no. ,ArticleID , pages, .

[] J. Hong, X. Miao, L. Han, and Y. Ma, Prognostics model orpredicting aero-engine bearing grade-lie, inProceedings o theASME urbo Expo, vol. , pp. , Orlando, Fla, USA, June.

[] P. Borghesani, P. Pennacchi, R. B. Randall, N. Sawalhi, and R.Ricci, Application o cepstrum pre-whitening or the diagnosiso bearing aults under variable speed conditions,MechanicalSystems and Signal Processing, .

[] Y. Li, J. Zhang, L. Dai, Z. Zhang, and J. Liu, Auditory-model-based eature extraction method or mechanical aults diagno-sis, ChineseJournal o MechanicalEngineering (EnglishEdition),vol. , no. , pp. , .

[] N. Bachschmid, P. Pennacchi, and E. anzi, Cracked rotatingshafs: typical behaviors, modeling and diagnosis, IUAMSymposium on Emerging rends in Rotor Dynamics, vol. , pp.

, .[] . Inoue, N. Nagata, and Y. Ishida, Fem modelling and

experimental verication o a rotor system with a open crack,in Proceedings o the ASME International Design Engineeringechnical Conerences and Computers and Inormation in Engi-neering Conerence (DEC ), pp. , San Diego, Cali,USA, September .

[] H. E. Sonnichsen, Real-time detection o developing cracksin jet engine rotors, in Proceedings o the IEEE AerospaceConerence, pp. , March .

[] I. Green and C. Casey, Crack detection in a rotor dynamicsystem by vibration monitoringpart I: analysis, Journal oEngineering or Gas urbines and Power, vol. , no. , pp. , .

[] J. . Sawicki, M. I. Friswell, A. H. Pesch, and A. Wroblewski,Condition monitoring o rotor usingactive magnetic actuator,inProceedings o the ASME urbo Expo, pp. , Berlin,Germany, June .

[] J. Xiang, X. Chen, Q. Mo, and Z. He, Identication o crack ina rotor system based on wavelet nite element method, FiniteElements in Analysis and Design, vol. , no. , pp. ,.

[] M. G. Maalou,Slow speed vibrationsignal analysis:i you cantdo it slow, you cant do it ast, in Proceedings o the ASME urboExpo, pp. , Montreal, Canada, May .

[] J. Meagher, X. Wu, and C. Lencioni, Response o a warpedexible rotor with a uid bearing, International Journal o

Rotating Machinery, vol. , Article ID , pages, .

[] . Gaka andM. abaszewski, An applicationo statistical symp-toms in machine condition diagnostics, Mechanical Systemsand Signal Processing, vol. , no. , pp. , .

[] J. K. Sinha, Recent trands in ault quantication in rotatingmachines,Advances in Vibration EngIneerIng, vol. , no. , pp., .

[] X. Shen, J.Jia, andM. Zhao, Nonlinear analysis o a rub-impactrotor-bearing system with initial permanent rotor bow,Archiveo Applied Mechanics, vol. , no. , pp. , .

[] A. W. Lees, J. K. Sinha, and M. I. Friswell, Model-based identi-cation o rotating machines,Mechanical Systems and SignalProcessing, vol. , no. , pp. , .

[] L. C. Jaw and W. Merrill, CBM+ research environmentacilitating technology development, experimentation, andmaturation, inProceedings o the IEEE Aerospace Conerence(AC ), March .

[] R. Walker, S. Perinpanayagam, and I. K. Jennions, SimulatingUnbalance or Future IVHM Applications, in Proceedings o theSociety or Experimental Mechanics (IMAC ), vol. , pp. , May .

[] H. C. Pusey, urbomachinery condition monitoring and ail-ure prognosis,Sound and Vibration, vol. , no. , pp. ,.

[] J. R. Jain and . K. Kundra, Model based online diagnosiso unbalance and transverse atigue crack in rotor systems,Mechanics Research Communications, vol. , no. , pp. ,.

[] K. R. Wheeler, . Kurtoglu, and S. D. Poll, A survey o healthmanagement user objectives related to diagnostic and prognos-tic metrics, in Proceedings o the th Computers and Inor-mation Engineering Conerence, vol. , pp. , .

[] G. Vachtsevanos, Perormance metrics or ault prognosis o

complex systems, inIEEE Systems Readiness echnology Con-erence (AUOESCON ), pp. , September .

[] A. Saxena, J. Celaya, E. Balaban et al., Metrics or evaluatingperormance o prognostic techniques, in Proceedings o theInternational Conerence on Prognostics and Health Manage-ment (PHM ), pp. , October .


13/13

Submit your manuscripts at

http://www.hindawi.com

Rotordynamic Faults

Documents

Transcript of Rotordynamic Faults