美國(guó)無(wú)損檢測(cè)學(xué)會(huì)無(wú)損檢測(cè)技術(shù)簡(jiǎn)介

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 measuresome characteristic ofan object. i.e. Inspect or

2、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 Det

3、ection 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 pe

4、netrant indicationWhen are NDE Methods Used?To assist in product development To screen or sort incoming materialsTo monitor, improve or control manufacturing processesTo verify proper processing such as heat treatingTo verify proper assemblyTo inspect for in-service damageThere are NDE application a

5、t almost any stage in 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 observatio

6、n 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 and

7、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 penet

8、rant 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 partic

9、les 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 higher en

10、ergy (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 Penetrate

11、 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) will v

12、ary with the amount of radiation reaching the film through the test object.Radiographic ImagesConductive materialCoilCoils magnetic fieldEddy currentsEddy currents magnetic fieldEddy Current TestingEddy Current TestingEddy current testing is particularly well suited for detecting surface cracks but

13、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 soun

14、d 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 echoOscilloscope, or flaw detector screenUltrasonic Inspection (Pulse-Echo) Ultrasonic ImagingGray sc

15、ale 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-cont

16、rolled 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 Proce

17、ssing Cracking Corrosion Erosion/Wear Heat Damage etc.Inspection For In-Service DamagePower Plant InspectionProbeSignals produced by various amounts of corrosion thinning.Periodically, power plants are shutdown for inspection. Inspectors feed eddy current probes into heat exchanger tubes to check fo

18、r 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 chairlifts, cranes and other lifting devices. Storage Tank InspectionRobotic crawlers use ultrasound to inspect the wa

19、lls 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 Inspection Nondestructive testing is used extensively during the manufacturing of aircraft. NDT is also used to find cracks and

20、corrosion damage during operation of the aircraft. A fatigue crack that started at the site of a lightning strike is shown below. Jet Engine Inspection Aircraft engines are overhauled after being in service for a period of time. They are completely disassembled, cleaned, inspected and then reassembl

21、ed. 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 crash of United Flight 232. Crash of United Flight 232Pressure Vessel InspectionThe failure of a pressure vesse

22、l 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 thousands of miles of rail to find cracks that could lead to a derailment. Bridge I

23、nspection The 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 about every 2 years. Some bridges are fitted with acoustic emission sensors that “l(fā)isten” for sounds of cracks growing. NDT is used to inspect pipelines to prevent leaks that could damage the environment. Visual inspection, ra