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1、Introduction to Nondestructive Testing For IPPSAgendaIntroduction to NDTOverview of Seven Most Common NDT MethodsApplicationsThe use of nondestructive techniques to determine the integrity of a material, component, or structure.To inspect or measure without doing harm.Definition of NDTMethods of NDT
2、VisualMagnetic ParticleX-rayLiquid PenetrantUltrasonicEddy CurrentChemical CompositionWhat are Some Uses of NDT Methods?Flaw Detection and EvaluationLeak Detection Location DeterminationDimensional Measurements Estimation of Mechanical and Physical Properties Fluorescent penetrant indicationWhen are
3、 NDT Methods Used?To assist in product development To screen or sort incoming materials *To monitor, improve or control manufacturing processes *To verify proper processing such as heat treatingTo verify proper assemblyTo inspect for in-service damageThere are NDT application at almost any stageTher
4、e are NDT application at almost any stage in the production or life cycle of a component. in the production or life cycle of a component.Seven Most Common NDT Methods Visual Liquid Penetrant Magnetic Particle X-ray Eddy Current Ultrasonic Chemical CompositionMost basic and common inspection method.T
5、ools include fiberscopes, borescopes, magnifying glasses and mirrors.Visual InspectionA liquid dye is applied to the surface of the part and allowed time to seep into surface breaking defects.The excess liquid is removed from the surface of the part. A developer (powder) is applied to pull the trapp
6、ed penetrant out the defect and spread it on the surface where it can be seen. 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.Liquid Penetrant InspectionMagnetic Part
7、icle 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 indication directly over the discontinuity. This indication can be visually detect
8、ed under proper lighting conditions. Magnetic Particle Crack Indications RadiographyThe 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 from an X-ray generator or a radioactive sou
9、rce. High Electrical PotentialElectrons-+X-ray Generator or Radioactive Source Creates RadiationExposure Recording DeviceRadiation Penetrate the SampleFilm RadiographyTop view of developed film X-ray filmThe part is placed between the radiation source and a piece of film. The part will stop some of
10、the radiation. Thicker and more dense area will stop more of the radiation. = more exposure= less exposureThe film darkness (density) will vary with the amount of radiation reaching the film through the test object.Radiographic ImagesConductive materialCoilCoils magnetic fieldEddy currentsEddy curre
11、nts magnetic fieldEddy Current TestingEddy Current TestingEddy current testing is particularly well suited for detecting surface Eddy current testing is particularly well suited for detecting surface cracks but can also be used to make electrical conductivity and cracks but can also be used to make
12、electrical conductivity and coating thickness measurements.coating thickness measurements. Here a small surface probe is Here a small surface probe is scanned over the part surface in an attempt to detect a crack.scanned over the part surface in an attempt to detect a crack.High frequency sound wave
13、s 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 showing the depth of features that reflect sound. fplatecrack0246810initial pulsecrack echoback surface ech
14、oOscilloscope, or flaw detector screenUltrasonic Inspection (Pulse-Echo) Chemical Composition orPositive Material Identification (PMI)Optical emission systems (OES), also called arc/spark, uses an arc or a spark to vaporize the sample, exciting the atoms and ions into emission of radiation. This emi
15、tted radiation then passes through an optical fiber and is dispersed into its spectral components. A photo-multiplier tube (PMT) measures the range of wavelengths emitted x-ray fluorescence (XRF) uses X-rays emitted from an X-ray tube or a radioisotope to excite the atoms of the sample material. An
16、electron is ejected, causing a second to fall into its void and energy is released. A detector within the instrument uses the energy level to determine the element. Common Application of NDTInspection of Raw MaterialInspection Following Secondary ProcessingIn-Services Damage InspectionInspection of
17、Raw ProductsForgingsCastingsExtrusionsPlateMachiningWeldingGrindingHeat treatingPlatingInspection Following Secondary ProcessingCrackingCorrosionErosion/WearHeat DamageInspection For In-Service DamagePower Plant InspectionProbeSignals produced by various amounts of corrosion thinning.Periodically, p
18、ower plants are shutdown for inspection. Inspectors feed eddy current probes into heat exchanger tubes to check for corrosion damage.Pipe with damageWire Rope InspectionElectromagnetic devices and visual inspections are used to find broken wires and other damage to the wire rope that is used in chai
19、rlifts, cranes and other lifting devices. Storage Tank InspectionRobotic crawlers use ultrasound to inspect the walls of large above ground tanks for signs of thinning due to corrosion.Cameras on long articulating arms are used to inspect underground storage tanks for damage. Aircraft InspectionNond
20、estructive testing is used extensively during the manufacturing of aircraft. NDT is also used to find cracks and corrosion damage during operation of the aircraft.A fatigue crack that started at the site of a lightning strike is shown below. Jet Engine InspectionAircraft engines are overhauled after
21、 being in service for a period of time. They are completely disassembled, cleaned, inspected and then reassembled. Fluorescent penetrant inspection is used to check many of the parts for cracking. Sioux City, Iowa, July 19, 1989A defect that went undetected in an engine disk was responsible for the
22、crash of United Flight 232. Crash of United Flight 232The 17 year old disk had undergone routine maintenance and six times had been subjected to flourescent penetration inspections. Investigators concluded that human error was responsible in improperly identifying the fatigued area before the accide
23、nt.United Flight 232Pressure Vessel InspectionThe failure of a pressure vessel can result in the rapid release of a large amount of energy. To protect against this dangerous event, the tanks are inspected using radiography and ultrasonic testing.Rail InspectionSpecial cars are used to inspect thousa
24、nds of miles of rail to find cracks that could lead to a derailment. Bridge InspectionThe US has 578,000 highway bridges.Corrosion, cracking and other damage can all affect a bridges performance.The collapse of the Silver Bridge in 1967 resulted in loss of 47 lives.Bridges get a visual inspection ab
25、out every 2 years.Some bridges are fitted with acoustic emission sensors that “listen” for sounds of cracks growing. NDT is used to inspect pipelines to prevent leaks that could damage the environment. Visual inspection, radiography and electromagnetic testing are some of the NDT methods used. Remot
26、e visual inspection using a robotic crawler. Radiography of weld joints. Magnetic flux leakage inspection. This device, known as a pig, is placed in the pipeline and collects data on the condition of the pipe as it is pushed along by whatever is being transported. Pipeline InspectionFor More Information on NDTThe Collaboration for NDT Education www.ndt-ed.orgThe American Society for Nondestructive Testing www.asnt.orgFor More Information on NDTFor More Information on NDTChinese Society for Non-destructive Testing (ChSNDT)
