Types of NDT                                                                         •   Visual                           ...
Reflected (pulse-echo) Transmission       Through Transmission Mode                                                       ...
B-scan                                                         C-scan                                                     ...
D-scan                                                                                         D-scan          (defect dep...
Microfocus X-ray Equipment                                             Real Time X-ray Technique                          ...
CT Scan Images                                                           Restrictions                                     ...
Acoustic Emission Set-up     Acoustic Emission Technique                   ENG 4793: Composite Materials and Processes   3...
Eddy Current Applications                                                     Shearography                                ...
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Ndt

  1. 1. Types of NDT • Visual • Ultrasonic Non-Destructive Testing (NDT) • X-ray • Thermographic ver 1 • Acoustic Emission • Eddy Current • Shearography ENG 4793: Composite Materials and Processes 1 ENG 4793: Composite Materials and Processes 2 Visual Inspection Visual Inspection Equipment• Basic principle: – illuminate the test specimen with light • Magnifying Glass – examine the specimen with the eye • Magnifying Mirror• Used to: • Microscope – to magnify defects which can not be detected by the unaided eye • Borescope – to assist in the inspection of defects – endoscopes or endoprobes – to permit visual checks of areas not accessible to • Flexible Fiber Optic Borescope unaided eye – working lengths are normally 60 to 365 cm with• Most widely used of all the nondestructive tests. diameters from 3 to 12.5 mm• Simple, easy to apply, quickly carried out and usually • Video Imagescope low in cost. ENG 4793: Composite Materials and Processes 3 ENG 4793: Composite Materials and Processes 4 Borescopes Ultrasonic Testing • The use of ultrasonic waves to evaluate the condition of a material. • Anomalies absorb or deflect the sound waves, which are then detected as changes in the waves. – holes, delaminations, voids Rigid Flexible fiber optic – damage, debonds – resin-rich, -poor areas ENG 4793: Composite Materials and Processes 5 ENG 4793: Composite Materials and Processes 6 1
  2. 2. Reflected (pulse-echo) Transmission Through Transmission Mode Mode emitter - detector - transceiver emitterpart part reflector detector ENG 4793: Composite Materials and Processes 7 ENG 4793: Composite Materials and Processes 8 Ultrasonic Test Equipment A-scan C-scan (single pulse - ice pick) • Received pulse amplitude is represented as a displacement along one axis and the travel time of the ultrasonic pulse is represented as a displacement along the other axis. • A-scan displays are more complex because all reflections are displayed, so signals (back wall, waterpath) need careful interpretation. ENG 4793: Composite Materials and Processes 9 ENG 4793: Composite Materials and Processes 10 A-scan B-scan (cross section) • A two-dimensional graphical presentation, in rectangular coordinates, in which the travel time of an ultrasonic pulse is represented as a displacement along one axis, and transducer movement is represented as a displacement along the other axis. ENG 4793: Composite Materials and Processes 11 ENG 4793: Composite Materials and Processes 12 2
  3. 3. B-scan C-scan (defect location map) • A two-dimensional graphical presentation, in which the discontinuity echoes are displayed in a top view on the test surface. • This method is applied to pulse-echo and through transmission techniques. • Usually no indication of depth is given unless the complete scan represents the time of flight evaluation (D-scan).ENG 4793: Composite Materials and Processes 13 ENG 4793: Composite Materials and Processes 14 C-scan C-scansENG 4793: Composite Materials and Processes 15 ENG 4793: Composite Materials and Processes 163D C-scan C-scan test blockENG 4793: Composite Materials and Processes 17 ENG 4793: Composite Materials and Processes 18 3
  4. 4. D-scan D-scan (defect depth map)• A two-dimensional graphical presentation, in which the time-of-flight values are displayed in a top view on the test surface. This is a modified C- scan in which are amplitudes displayed. ENG 4793: Composite Materials and Processes 19 ENG 4793: Composite Materials and Processes 20 D-scan of Test Block Performance • 5-25 MHz typical • 0.2- 800 MHz possible • Trade-off between frequency (resolution) and depth of penetration – higher frequency, better resolution, lower depth of penetration ENG 4793: Composite Materials and Processes 21 ENG 4793: Composite Materials and Processes 22 X-ray Technique Microfocus X-ray Technique Film pack Film pack or X-ray imaging or X-ray imaging system system Test object X-ray source Test object Greatly enlarged Microfocus image X-ray source ENG 4793: Composite Materials and Processes 23 ENG 4793: Composite Materials and Processes 24 4
  5. 5. Microfocus X-ray Equipment Real Time X-ray Technique Fluorescent screen TV Monitor camera scope Intensifier Image X-ray source processor Test object ENG 4793: Composite Materials and Processes 25 ENG 4793: Composite Materials and Processes 26 X-ray Images X-ray Images IC chip Computer mouse Cooling lines in turbine blade Porosity in weld ENG 4793: Composite Materials and Processes 27 ENG 4793: Composite Materials and Processes 28 CT Scan CT Scanner• CT produces 3-dimensional images of objects using x-rays.• The scanner, made in the shape of a ring, contains an x-ray tube that circles the object. The object in the scanner is bombarded by x- rays from various angles and resulting information signals are then processed by a computer, yielding cross sectional slices which then make up images. ENG 4793: Composite Materials and Processes 29 ENG 4793: Composite Materials and Processes 30 5
  6. 6. CT Scan Images Restrictions • Radio opaque penetrant sometimes needed, as many composites are transparent even to low energy X-rays 15 - 25 kV – zinc iodide – tetrabromoethane – diiodobutane • Cannot detect fiber breaks ENG 4793: Composite Materials and Processes 31 ENG 4793: Composite Materials and Processes 32 Thermographic Principle Thermographic Technique• Heat flow in a material is altered by the presence of some types of anomalies.• These changes in heat flow cause localized temperature differences in the material.• Slow heating of part reveals these Heat anomalies. source Part IR camera ENG 4793: Composite Materials and Processes 33 ENG 4793: Composite Materials and Processes 34 Thermography Images Acoustic Emission Principle • Sounds made by a material, structure, or machine in use or under load are heard and analyzed to determine its "state of health". • One or more ultrasonic microphones are attached to the object and the sounds are analyzed using computer based instruments. • Noises may arise from: – friction (including bearing wear) PC board – crack growth Aircraft wing – material changes (such as corrosion) ENG 4793: Composite Materials and Processes 35 ENG 4793: Composite Materials and Processes 36 6
  7. 7. Acoustic Emission Set-up Acoustic Emission Technique ENG 4793: Composite Materials and Processes 37 ENG 4793: Composite Materials and Processes 38 Acoustic Emission Advantages Acoustic Emission Applications• Entire structure can be monitored from a few locations. • pipelines• Structure can be tested in use. • storage tanks (above and below the ground)• Continuous monitoring with alarms is • fiberglass structures possible. • rotating machinery• Microscopic changes can be detected if • weld monitoring sufficient energy is released. • biological and chemical changes• Source location is also possible using multiple sensors. ENG 4793: Composite Materials and Processes 39 ENG 4793: Composite Materials and Processes 40 Eddy Current Principle Eddy Current Technique• When an energized coil is brought near to the surface of a metal or conducting component, eddy currents Eddy current field Probe are induced into the specimen. These currents set-up magnetic field that tend to oppose the original magnetic field. The impedance of coil in close proximity to the specimen is affected by the presence of the induced eddy currents in the specimen. Defect• When the eddy currents in the specimen are distorted by the presence of the flaws or material variations, the impedance in the coil is altered. This change is measured and displayed in a manner that indicates the type of flaw or material condition. ENG 4793: Composite Materials and Processes 41 ENG 4793: Composite Materials and Processes 42 7
  8. 8. Eddy Current Applications Shearography • The object under study is illuminated by laser light,• Range from crack detection, to the rapid and a camera produces two sheared images that sorting of small components for either interfere with each other, causing a speckle pattern. flaws, size variations, or material • When the object is deformed (sheared), the speckle pattern changes. variation. • The two speckle patterns interfere to produce a fringe• Commonly used in aerospace, pattern that depicts the surface gradient of the automotive, marine, and manufacturing deformed object. industries. • Though the images obtained are good, this method is time-consuming. ENG 4793: Composite Materials and Processes 43 ENG 4793: Composite Materials and Processes 44 Shearography Technique Shearography Images Laser Part Shearography head Shear and detector motion Debonds ENG 4793: Composite Materials and Processes 45 ENG 4793: Composite Materials and Processes 46 Summary• Optical and Ultrasonic most widely used techniques.• Each has different principles and uses. ENG 4793: Composite Materials and Processes 47 ENG 4793: Composite Materials and Processes 48 8

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