Die Penetrant-English

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Discontinuities which can be revealed by penetrant inspection: opened - clean, without coating, and electroplating, hot and cold cracks, fatigue cracks, hardening cracks, pitting, porosity, shallow defects cause of fatigue cracks, minimum dimensions of detected defects (cracks): 1μm wide, 10 mm depth and 1 mm in length. it is possible to detect material discontinuities of semi- fnished and fnished products, with even the most complicated shapes Liquid Penetrant esting

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Transcript of Die Penetrant-English

•opened - clean, without coating, and electroplating,
•hot and cold cracks, fatigue cracks, hardening cracks, pitting, porosity,
•shallow defects cause of fatigue cracks,
•minimum dimensions of detected defects (cracks): 1μm wide, 10 mm depth and 1 mm in length.
•it is possible to detect material discontinuities of semi- fnished and fnished products, with even the most complicated shapes
Liquid Penetrant esting
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d) shrinking crack
i) shrinkage
high roughness (metals).
or developer) can not react with tested
workpieces (plastic).
the liquids %called penetrant& with low sur'ace tension, proper viscosity, wettability and low density $he wettability phenomena
a& ( ) *0+ - good wetting
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%a&() *0+ - capillary rise %b&( *0+ - no capillary
depression or rise. %c&( *0+ - capillary depression
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postemulsifiable penetrants
1./ur'ace preparation
surface (and other contaminantion)
. #enetration
- after cleaning operation penetrant is applied into the surface in the form of thin liquid !lm,
 - the !lm should remain on the surface depends of the penetration time called as a dwell time (recomendation of the penetrant
producer, mosty between " to #$min)%
!i"uid #enetrant $esting
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. 2emoval o' ecess penetrant
• e&cess penetrant must be removed from the surface, removing method depends of the type of
penetrant% • many penetrants easily removed with water'
others require the use of emulsi!ers (lipophilic or hydrophilic) or solventremover%
• removing of e&cessive penetrant is necessary for eective inspection, but overremoval must be avoided (no discontinuities will be revealed)%
!i"uid #enetrant $esting
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•  time of developing depends of the
developing agent used (mostly between " to #$min%)
!i"uid #enetrant $esting
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• after developing process the surface is visually
e&amined for indications o' penetrant which is visible like a colored stains%
• visible penetrant inspection is performed in white light,
• when the 5uorescent penetrant is used, inspection is performed in a dark room under ultraviolet light, (penetrant is shinning)%
!i"uid #enetrant $esting
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• !an be used on a wide range of material types.
• "arge areas or large volumes of parts#materials can be inspected rapidly and at low cost.
• $arts with comple% geometries are routinely inspected.
• &ndications are produced directly on surface of the part providing a visual image of the discontinuity.
• &nitial equipment investment is low.
• 'erosol spray cans can make equipment very portable.
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• equires relatively smooth nonporous material.
• $recleaning is critical. !ontaminants can mask defects. • equires multiple operations under controlled
• Metal smearing from machining, grinding and other operations inhibits detection. Materials may need to be etched prior to inspection.
• $ost cleaning is necessary to remove chemicals.
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6agnetic $esting %6$& 6789E$4 #72$4!E 49/#E$4;9
• *ethod of locating sur'ace and subsur'ace discontinuities in 'erromagnetic materials%
• +hen the material or part under test is magneti<ed, magnetic discontinuities that lie in a direction generally transverse to the direction o' the magnetic feld cause a leakage !eld to be formed at and above the surface of the part%
•  he discontinuity, is detected by the use of !nely divided ferromagnetic particles applied over the surface, with some of the particles being gathered and held by the leakage !eld%
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!imitation 'or 6agnetic #article $esting: •  he method can be used only on 'erromagnetic materials,
• or best results, the magnetic !eld must be in a direction that will intercept the principal plane o' the discontinuity' this sometimes requires two or more se"uential inspections with
dierent magnetiations, • Demagneti<ation following inspection is often necessary,
• #ostcleaning  to remove remnants o' the magnetic particles clinging to the surface may sometimes be required after testing and demagnetiation,
• .&ceedingly large currents are sometimes needed for very large parts,• /are is necessary to avoid local heating and burning of !nished parts or surfaces at the points of electrical contact
• 0lthough magnetic particle indications are easily seen, e&perience and skill are sometimes needed to 1udge their signi!cance%
6agnetic $esting %6$&
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6agnetic $esting %6$& =E22;6789E$4 67$E247!/ *etals which conduct magnetic !eld:
• elements:  iron,
Ferromagnetic Materials •  ' material is considered ferromagnetic if it can be
magnetized. Materials with a significant &ron, nickel or cobalt
content are generally ferromagnetic.
• *erromagnetic materials are made up of many regions in
which the magnetic fields of atoms are aligned. +hese regions are call magnetic domains.
• Magnetic domains point randomly in demagnetied material,
but can be aligned using electrical current or an external
magnetic field to magnetie the material.
-emagnetied Magnetied
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l o n g i t u d a l 
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6agnetic $esting %6$&Magnetizing current
• 0oth direct current "dc) and alternating current "ac) are suitable for
magnetiing parts for magnetic particle inspection.
• +he strength, direction, and distribution of magnetic fields are greatly affected by the type of current used for magnetiation.
• +he important difference with regard to magnetic particle inspection
is that the fields produced by direct current generally penetrate
the cross section of the part, while the fields produced by alternating current are confined to the metal at or near the
surface of the part, a phenomenon known as the skin effect.
+herefore, alternating current should not be used in searching for
subsurface discontinuities.
are commonly used for
0oth are hand held and
therefore quite mobile.
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Dry 6agnetic #articles 
*agnetic particles come in a variety of colors% 0 color that produces a high level of contrast against the background should be used%
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>et 6agnetic #articles Wet particles are typically supplied as visible or
fluorescent. 3isible particles are viewed under
normal white light and fluorescent particles are
viewed under black light.
@isible, Dry #owder 6ethod
7dvantages o' 6agnetic #article4nspection • /an detect both sur'ace and near sub-sur'ace defects%
• /an inspect parts with irregular shapes easily%
• Precleaning of components is not as critical as it is for
some other inspection methods% *ost contaminants within a 2aw will not hinder 2aw detectability%
• ast method of inspection and indications are visible directly on the specimen surface%
• /onsidered low cost compared to many other 34
methods% • 5s a very portable inspection method especially
when used with battery powered equipment%
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6/annot inspect non-'errous materials such as aluminum, magnesium or most stainless steels.
65nspection of large parts may require use of equipment with special power requirements%
67ome parts may require removal o' coating or plating to achieve desired inspection sensitivity%
6Limited subsurface discontinuity detection capabilities% *a&imum depth sensitivity is approimately 0.AB (under ideal conditions)%
6#ost cleaning, and post demagneti<ation is often necessary%
60lignment between magnetic 5u and de'ect is important