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JournalAuthors:FrancRAVNIKandJanez GRUM
Presentedby:GlennGilTamayo
ForCE297 NonDestructiveTesting
INTRODUCTION ThepaperpresentsaNonDestructiveTestMethod
usingACOUSTICEMISSIONduringQUENCHINGProcess.
QUENCHING QUENCHINGPROCESS 1.HEATINGTHEMETAL
Heatingofthematerialtotherequiredtemperature(815900C)
Soakingcanbedonebyair(airfurnace)orliquid(bath)
2.WETTINGPROCESS
Materialis
immediately
plunged
in
liquid
media e.g.
air,
brine,waterandoil
THISRESULTSINANEXTREMELYHARDBUTBRITTLEMATERIAL.
DURINGTHEWETTINGPROCESS Formationofbubbles,whichoscillatesandeventually
disappearintheliquid.
Thisprocessgeneratenoise.
Theseemittedsoundsignalsaredetectedandanalyzedtoprovideusefulinformationduringthequenchingprocess.
EXPERIMENTALSETUP
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SPECIMENMATERIALANDFORM LowalloyCrMoheat
treatablesteel(EN42CrMo4)
Thisformischosentoachievecrackingofthespecimenduringthequenchingprocess
QUENCHINGMEDIAPUREWATER SALTSOLUTION Toensurepropermodeof
quenching Toensurehighercoolingrate
thanthecriticalcoolingrate
Ahighercoolingratewillcausethespecimentocrackaxially
PROCEDURE Preheatingto~600C
Progressiveheatingto600C
Theinitialquenchingmediumtemperatureis18C
Thefinalquenchingmediumtemperaturevariesbetween25Cand30C
Theconstant
volume
of
the
quenching
medium
is
14
liters
Thesoundsignalprocessing programcalledSpectraLABwasrunningontheIBMnotebook
RESULTSTHESPECIMENBEFOREANDAFTERQUENCHING
RESULTSTIMESERIESDIAGRAMOFSOUNDPRESSURESIGNAL
RESULTSSPECTROGRAMOFSOUNDPRESSURESIGNAL
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RESULTSAVERAGESPECTRUMOFSAMPLES
RESULTS3DSURFACEVIEW
CONCLUSIONS Thearticlepresenteddescribesthesignalscapturedby
measuringacousticemissioncausedduringquenching
Thesoundpressuresignalwascapturedusingahydrophone
Achangeinsignalshapeappearscorrespondingtothe
formationof
avapors
around
the
specimen
Significantchangeofthesignalfollowedwhenthespecimencracks.
Significantchangeofthesignalisverymuchaudible(visible)andrecognizable.
CONCLUSIONS Itcouldbeconcludedfromtheexperimentalresults
thatthecapturingoftheacousticemissionwasreliableandhasgivensufficientresults.
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