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1、Introduction to Nondestructive TestingOutline Introduction to NDT Overview of Six Most Common NDT Methods Selected ApplicationsThe use of noninvasive techniques to determine the integrity of a material, component or structure or quantitatively measure some characteristic of an object. i.e. Inspect o
2、r measure without doing harm.Definition of NDTMethods of NDTVisualLiquid PenetrantMagnetic ParticleEddy CurrentUltrasonicX-ray MicrowaveAcoustic EmissionThermographyLaser InterferometryReplicationFlux LeakageAcoustic MicroscopyMagnetic MeasurementsTap TestingWhat are Some Uses of NDE Methods? Flaw D
3、etection and Evaluation Leak Detection Location Determination Dimensional Measurements Structure and Microstructure Characterization Estimation of Mechanical and Physical Properties Stress (Strain) and Dynamic Response Measurements Material Sorting and Chemical Composition Determination Fluorescent
4、penetrant indicationWhen are NDE 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 treating To verify proper assembly To inspect for in-service damageThere are NDE applica
5、tion at almost any stagein the production or life cycle of a component.Six Most Common NDT Methods Visual Liquid Penetrant Magnetic Ultrasonic Eddy Current X-rayMost basic and common inspection method.Tools include fiberscopes, borescopes, magnifying glasses and mirrors.Robotic crawlers permit obser
6、vation in hazardous or tight areas, such as air ducts, reactors, pipelines.Portable video inspection unit with zoom allows inspection of large tanks and vessels, railroad tank cars, sewer lines.Visual Inspection A liquid with high surface wetting characteristics is applied to the surface of the part
7、 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 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. The
8、penetrant used is often loaded with a fluorescent dye and the inspection is done under UV light to increase test sensitivity.Liquid Penetrant InspectionMagnetic Particle InspectionThe part is magnetized. Finely milled iron particles coated with a dye pigment are then applied to the specimen. These p
9、articles are attracted to magnetic flux leakage fields and will cluster to form an indication directly over the discontinuity. This indication can be visually detected under proper lighting conditions. Magnetic Particle Crack Indications RadiographyThe radiation used in radiography testing is a high
10、er 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 source. High Electrical PotentialElectrons-+X-ray Generator or Radioactive Source Creates RadiationExposure Recording DeviceRadiation Pene
11、trate 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 the radiation. Thicker and more dense area will stop more of the radiation. = more exposure= less exposureThe film darkness (density) w
12、ill vary with the amount of radiation reaching the film through the test object.Radiographic ImagesConductivematerialCoilCoils magnetic fieldEddy currentsEddy currents magnetic fieldEddy Current TestingEddy Current TestingEddy current testing is particularly well suited for detecting surface cracks
13、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.High frequency sound waves are introduced into a material and they are reflected back from surfaces or flaws.Reflected
14、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 pulsecrackechoback surfaceechoOscilloscope, or flaw detector screenUltrasonic Inspection (Pulse-Echo) Ultrasonic ImagingGray
15、scale image produced using the sound reflected from the front surface of the coinGray scale image produced using the sound reflected from the back surface of the coin (inspected from “heads” side)High resolution images can be produced by plotting signal strength or time-of-flight using a computer- c
16、ontrolled scanning system.Common Application of NDT Inspection of Raw Products Inspection Following Secondary Processing In-Services Damage InspectionInspection of Raw Products Forgings, Castings, Extrusions, etc. Machining Welding Grinding Heat treating Plating etc.Inspection Following Secondary Processing Cracking Corrosion Er
