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Introduction ofIntroduction of Non-Destructive Test
ENCE710 – Advanced Steel StructuresENCE710 Advanced Steel Structures
C. C. Fu, Ph.D., P.E.Department of Civil & Environmental Engineering
University of MarylandCollege Park, MDCollege Park, MD
Definition of NDT
The use of noninvasive techniques to determine qthe integrity of a material, component or structure
or quantitatively measuresome characteristic ofsome characteristic ofan object.
i.e. Inspect or measure without doing harm.2
What are Some Uses of NDE Methods?
Flaw Detection and Evaluation
Leak DetectionLeak Detection
Location Determination
Dimensional Measurements Fluorescent penetrant indication
Structure and Microstructure Characterization
Estimation of Mechanical and Physical Properties y p
Stress (Strain) and Dynamic Response Measurements
Material Sorting and Chemical Composition Determination
3
When are NDE Methods Used?
There are NDE application at almost any stage in the production or life cycle of a component
To assist in product development To screen or sort incoming materialsTo monitor, improve or control manufacturing processesT if i h h tTo verify proper processing such as heat treatingTo verify proper assemblyTo verify proper assemblyTo inspect for in-service damage
4
Nondestructive Testing
• AdvantagesCan test in service structures– Can test in-service structures
– Evaluate surface and internal conditions
– Cost efficient• Disadvantages
l b l ( d d l )– Reliability (measurements are made indirectly)– Qualitative
Requires a skilled professional for– Requires a skilled professional for interpretation of results
5
Destructive Testing• Advantages
– Reliable (direct measurements)– Quantitative– Directly relates to material properties
Di d t• Disadvantages– Cannot test in-service structures
Requires a model– Requires a model• Costly & Time Consuming
– Multiple tests are sometimesprequired
6
Six Most Common NDT Methods
• Visual• Liquid Penetrant
M ti• Magnetic • Ultrasonic• Eddy Currenty• X-ray
7
Most basic and common
Visual InspectionMost basic and common inspection method.
Tools include fiberscopes,Tools include fiberscopes, borescopes, magnifying glasses and mirrors.
Portable video inspectionPortable video inspection unit with zoom allows
inspection of large tanks and vessels, railroad tank
Robotic crawlers permit b ti i h d
,cars, sewer lines.
observation in hazardous or tight areas, such as air ducts, reactors, pipelines. 8
Liquid Penetrant Inspection• A liquid with high surface wetting characteristics is
applied to the surface of the part and allowed time to seep into surface breaking defects.
Liquid Penetrant Inspection
seep into surface breaking defects.• The excess liquid is removed from the surface of
the part. • A developer (powder) is applied to pull the• A developer (powder) is applied to pull the
trapped penetrant out the defect and spread it on the surface where it can be seen.
• Visual inspection is the final step in the process• Visual inspection is the final step in the process. The penetrant used is often loaded with a fluorescent dye and the inspection is done under UV light to increase test sensitivity.g y
9
Liquid PenetrationProcess:
Clean surfaceApply liquid penetrantRemove excess penetrantRemove excess penetrantApply developerInspectPost-cleaning
10
DYE PENETRANTS
These are an aid to visual inspectioninspection
Will only find surface defects
Use correct type
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DYE PENETRANTSDYE PENETRANTS
12
DYE PENETRANTSTypes
Red Flouresant
CAUTIONOil basedW t h blWater washable
13
Dye Penetrant Test
• Dye penetrant testing locates minute surface cracks and porosity
• Dye types that may be used include:
Color contrast dye - which shows up under ordinary light
Fluorescent dye – which shows up under black light
14
Fluorescent dye which shows up under black light
• The dye is normally applied by spraying it directly on the weld
(AISC & NISD 2000)
Magnetic Particle InspectionThe part is magnetized. Finely milled iron particles coated with a dye pigment are then applied to the specimen. These particles are attracted to magnetic flux leakage fields and will cluster to form an g gindication directly over the discontinuity. This indication can be visually detected under proper lighting conditions.
15
Magnetic ParticleProcess:Process:
Magnetize surfaceDi ti iti tDiscontinuities create amagnetic flux
Sprinkle magnetic particlesInspectp
16
Magnetic Particle Crack Indications
17
MAGNETIC PARTICLEMainly for surface defectsSome sub surface defects can be foundfoundOnly ferrous metal
18
Magnetic Particle Inspection
• Magnetic particle inspection uses powdered magnetic particles to indicatedefects in magnetic materials
• A magnetic field is induced in the part
19
• The magnetic powder is attracted to and outlines cracks within the material
(AISC & NISD 2000)
RadiographyThe adiation sed in adiog aph testing is a
High Electrical Potential
X-ray Generator or Radioactive Source Creates
Radiation
The radiation used in radiography testing is a higher energy (shorter wavelength) version of the electromagnetic waves that we see as visible light. The radiation can come Electronsgfrom an X-ray generator or a radioactive source.
-+
Radiation Penetrate the Sample
Exposure Recording Device
p
20
Fil R di hFilm RadiographyThe part is placed between the radiationThe part is placed between the radiation source and a piece of film. The part will stop some of the radiation. Thicker and
d ill t f thmore dense area will stop more of the radiation.
The film darkness
X-ray film
(density) will vary with the amount of radiation reaching the film through X ray film
= less exposure
g gthe test object.
Top view of developed film
= more exposureess e posu e
21
Radiographic Images
22
RADIOGRAPHICX-RAYGAMMA RAYElectro magnetic
radiation of short duration
Both of these methods are a danger to health
23
Radiographic Inspection
• Radiographic inspection, or X-ray, can also be used to detect flaws inside welds
• Invisible rays penetrate the metal and reveal flaws on an x-ray film orfluorescent screen (above)
24
fluorescent screen (above)
• This is the most costly of the inspection methods
(AISC & NISD 2000)
X- RAY
25
X- RAY
26
27
X-RAY VIEWERPictures taken are
viewed as negatives
will only give flat i i himage not in three dimensional
d k d tdarkened area must be used for viewingviewing
28
Eddy Current Testing
Coil's
Eddy Current Testing
Coil magnetic field
Eddy current's
Eddy
ymagnetic field
Conductive
ycurrents
Conductivematerial
29
Eddy Current TestingEddy current testing is particularly well suited for detecting surface cracks but can also be used to make electrical conductivity and coating thickness measurements. Here a small surface probe is scanned over the part surface in an attempt to detect a crack.
30
High frequency sound waves are introduced into a material
Ultrasonic Inspection (Pulse-Echo) High frequency sound waves are introduced into a material and they are reflected back from surfaces or flaws.Reflected sound energy is displayed versus time, and inspector can visualize a cross section of the specimen
finspector can visualize a cross section of the specimen showing the depth of features that reflect sound.
initial pulsepulse
crackecho
back surfaceecho
plate
crack
0 2 4 6 8 10
echo
Oscilloscope, or flaw detector screen 31
Ultrasonic ImagingHigh resolution images can be produced by plotting signal strength or time-of-flight using a computer-controlled scanning system.
Gray scale image produced using the sound reflected from the front surface of the coin
Gray scale image produced using the sound reflected from the back surface of the coin (inspected from “heads” side) 32
ULTRASONIC TESTINGThis uses high pitched
soundThe sound will not
pass through an air b b kgap so bounces back
and is picked up on a receiverreceiver
The reader is a oscilloscopeoscilloscope
33
ULTRA SONIC Device
34
35
Ultrasonic Inspection
• Ultrasonic inspection can be used to detect flaws inside welds
• High frequency sound waves are directed into the metal with a probe held at a• High frequency sound waves are directed into the metal with a probe held at aspecific angle
• The flaws reflect some energy back to the probe
36
• Flaws show up as indications on a screen (above) and are subject tointerpretation by an inspector
(AISC & NISD 2000)
Ultrasonic
37
Usage: Inspection of Raw ProductsForgings,Castings,Extrusions,etc.
38
Usage: Inspection FollowingUsage: Inspection Following Secondary Processing
MachiningWeldingGrindingHeat treatingPlatingPlatingetc.
39
Usage: Inspection ForUsage: Inspection For In-Service Damage
CrackingCorrosionErosion/Wear/Heat Damageetc.
40
Usage: Power Plant InspectionUsage: Power Plant InspectionPeriodically, power plants are h td f i tishutdown for inspection.
Inspectors feed eddy current probes into heat exchanger tubes to check for corrosion damageto check for corrosion damage.
Probe
Signals produced by various
Pipe with damage
amounts of corrosion thinning.
41
Usage: Storage Tank InspectionUsage: Storage Tank Inspection
Robotic crawlers use ultrasound to inspect the walls of large b d t kabove ground tanks
for signs of thinning due to corrosion.
Cameras on long articulatingarticulating arms are used to inspect underground
kstorage tanks for damage.
42
Usage: Pressure Vessel InspectionUsage: Pressure Vessel InspectionThe failure of a pressure vessel can result in the rapid release of a plarge amount of energy. To protect against this dangerous event, the tanks are inspected using radiography and ultrasonic testing.
43
Usage: Pipeline InspectionNDT is used to inspect pipelines to prevent leaks that could damage the en i onment Vis al inspection
Usage: Pipeline Inspection
environment. Visual inspection, radiography and electromagnetic testing are some of the NDT methods used.
Remote visual inspection using a robotic crawlera robotic crawler.
Magnetic flux leakage inspection. This device, known as a pig, is
Radiography of weld joints.
s de ce, o as a p g, splaced in the pipeline and collects data on the condition of the pipe as it is pushed along by whatever is being transported. 44