1ENG 4793: Composite Materials and Processes1Non-Destructive Testing (NDT)ver 1ENG 4793: Composite Materials and Processes2Types of NDT•Visual• Ultrasonic•X-ray• Thermographic• Acoustic Emission• Eddy Current• ShearographyENG 4793: Composite Materials and Processes3Visual Inspection• Basic principle:– illuminate the test specimen with light– examine the specimen with the eye• Used to:– to magnify defects which can not be detected bythe unaided eye– to assist in the inspection of defects– to permit visual checks of areas not accessible tounaided eye• Most widely used of all the nondestructive tests.• Simple, easy to apply, quickly carried out and usuallylow in cost.ENG 4793: Composite Materials and Processes4Visual Inspection Equipment• Magnifying Glass• Magnifying Mirror• Microscope• Borescope– endoscopes or endoprobes• Flexible Fiber Optic Borescope– working lengths are normally 60 to 365 cm withdiameters from 3 to 12.5 mm• Video ImagescopeENG 4793: Composite Materials and Processes5BorescopesRigidFlexible fiber opticENG 4793: Composite Materials and Processes6Ultrasonic Testing• The use of ultrasonic waves to evaluatethe condition of a material.• Anomalies absorb or deflect the soundwaves, which are then detected aschanges in the waves.– holes, delaminations, voids– damage, debonds– resin-rich, -poor areas2ENG 4793: Composite Materials and Processes7Through Transmission ModeemitterdetectorpartENG 4793: Composite Materials and Processes8Reflected (pulse-echo) TransmissionModeemitter - detector - transceiverpartreflectorENG 4793: Composite Materials and Processes9Ultrasonic Test EquipmentC-scanENG 4793: Composite Materials and Processes10A-scan(single pulse - ice pick)• Received pulse amplitude is represented as adisplacement along one axis and the traveltime of the ultrasonic pulse is represented asa displacement along the other axis.• A-scan displays are more complex becauseall reflections are displayed, so signals (backwall, waterpath) need careful interpretation.ENG 4793: Composite Materials and Processes11A-scanENG 4793: Composite Materials and Processes12B-scan(cross section)• A two-dimensional graphicalpresentation, in rectangular coordinates,in which the travel time of an ultrasonicpulse is represented as a displacementalong one axis, and transducermovement is represented as adisplacement along the other axis.3ENG 4793: Composite Materials and Processes13B-scanENG 4793: Composite Materials and Processes14C-scan(defect location map)• A two-dimensional graphical presentation, inwhich the discontinuity echoes are displayedin a top view on the test surface.• This method is applied to pulse-echo andthrough transmission techniques.• Usually no indication of depth is given unlessthe complete scan represents the time offlight evaluation (D-scan).ENG 4793: Composite Materials and Processes15C-scanENG 4793: Composite Materials and Processes16C-scansENG 4793: Composite Materials and Processes173D C-scanENG 4793: Composite Materials and Processes18C-scan test block4ENG 4793: Composite Materials and Processes19D-scan(defect depth map)• A two-dimensional graphicalpresentation, in which the time-of-flightvalues are displayed in a top view onthe test surface. This is a modified C-scan in which are amplitudes displayed.ENG 4793: Composite Materials and Processes20D-scanENG 4793: Composite Materials and Processes21D-scan of Test BlockENG 4793: Composite Materials and Processes22Performance• 5-25 MHz typical• 0.2- 800 MHz possible• Trade-off between frequency(resolution) and depth of penetration– higher frequency, better resolution, lowerdepth of penetrationENG 4793: Composite Materials and Processes23X-ray TechniqueX-ray sourceTest objectFilm packor X-ray imagingsystemENG 4793: Composite Materials and Processes24Microfocus X-ray TechniqueMicrofocusX-ray sourceTest objectFilm packor X-ray imagingsystemGreatly enlargedimage5ENG 4793: Composite Materials and Processes25Microfocus X-ray EquipmentENG 4793: Composite Materials and Processes26Real Time X-ray TechniqueX-ray sourceTest objectFluorescentscreenIntensifierTVcameraImageprocessorMonitorscopeENG 4793: Composite Materials and Processes27X-ray ImagesComputer mouseIC chipENG 4793: Composite Materials and Processes28X-ray ImagesCooling lines in turbine bladePorosity in weldENG 4793: Composite Materials and Processes29CT Scan• CT produces 3-dimensional images of objectsusing 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 resultinginformation signals are then processed by acomputer, yielding cross sectional sliceswhich then make up images.ENG 4793: Composite Materials and Processes30CT Scanner6ENG 4793: Composite Materials and Processes31CT Scan ImagesENG 4793: Composite Materials and Processes32Restrictions• Radio opaque penetrant sometimesneeded, as many composites aretransparent even to low energy X-rays15 - 25 kV– zinc iodide– tetrabromoethane– diiodobutane• Cannot detect fiber breaksENG 4793: Composite Materials and Processes33Thermographic Principle• Heat flow in a material is altered by thepresence of some types of anomalies.• These changes in heat flow causelocalized temperature differences in thematerial.• Slow heating of part reveals theseanomalies.ENG 4793: Composite Materials and Processes34Thermographic TechniqueHeatsourcePart IR cameraENG 4793: Composite Materials and Processes35Thermography ImagesAircraft wingPC boardENG 4793: Composite Materials and Processes36Acoustic Emission Principle• Sounds made by a material, structure, ormachine in use or under load are heard andanalyzed to determine its "state of health".• One or more ultrasonic microphones areattached to the object and the sounds areanalyzed using computer based instruments.• Noises may arise from:– friction (including bearing wear)– crack growth– material changes (such as corrosion)7ENG 4793: Composite Materials and Processes37Acoustic Emission TechniqueENG 4793: Composite Materials and Processes38Acoustic Emission Set-upENG 4793: Composite Materials and Processes39Acoustic Emission Advantages• Entire structure can be monitored from a fewlocations.• Structure can be tested in use.• Continuous monitoring with alarms ispossible.• Microscopic changes can be detected ifsufficient energy is released.• Source location is also