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AAE552-Session20 - AAE 552 Spring 2009 A F Grandt AAE 552...

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AAE 552 Spring 2009 – A. F. Grandt 1 1 AAE 552: Nondestructive Evaluation of Structures and Materials A. F. Grandt, Jr. Professor of Aeronautics and Astronautics Purdue University W. Lafayette, IN 47907 Session 20 – 27 February 2009 2 Contact Information Alten F. (Skip) Grandt, Jr. Email: [email protected] Telephone: Office: 765-494-5141 Home: 765-463-4276 FAX: 765-494-0307 Course webpage accessed at: http://www.itap.purdue.edu/tlt/blackboard 3 AAE 552 Session 20 27 February 2009 Last Time: Neutron Radiography Image Formation Computed Tomography Today: Finish CT Backscatter X-ray Image Quality Applications 4 Chapter 11: Radiography Topics Overview Absorption/Scatter Radiation sources Image formation Image quality Examples Computed Tomography Safety issues Summary 5 Assignment Please read Textbook : Chapter 11 Webpage powerpoint references “Radiographic Testing” – collaboration for NDT education Paper #1 – Due Session 21 (2 March 2009) Exam #1 – Session 29 (Friday, 27 March 2009) Final Exam – Wednesday, 6 May 2009 (comprehensive) 6 Neutron Radiography Alternate energy source complements materials that can be inspected by x-rays or gamma-rays Some low density materials that are transparent to x- rays absorb neutrons Hydrogen, lithium, boron Some high density materials that are opaque to x- rays pass neutrons Lead, Bismuth, Uranium Applications Rubber O rings Metal jacketed explosives (ordnance devices Corrosion products Residual core for investment cast turbine blades doped with Bd 2 O 2
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AAE 552 Spring 2009 – A. F. Grandt 2 7 X-ray and Neutron Mass Attenuation Coefficients vs Atomic Number Fig. 11.8 Mass Attenuation Coefficient ( μ m/ ρ ) Atomic Number X-rays Imaging Modalities Several different imaging methods are available to display the final image in industrial radiography: Film Radiography Real Time Radiography Computed Tomography (CT) Digital Radiography (DR) Computed Radiography (CR) Computed Tomography 9 10 Computed Tomography (CT) Special imaging technique that provides cross sectional view Can be used with variety of energy beams (ultrasonic, x-rays, etc) Mathematical principle described in 1917 by Radon Any 2-d distribution can be reconstructed from infinite set of line integrals thru distribution Practical applications 1960’s and 70’s Early applications in medical field Conventional radiography compresses 3-d into 2-d view Can’t specify flaw shape/location Interpretation difficult Tomogram provides 3-d view by combining results of multiple images from different directions 11 Reconstructed cross sectional image of object Scans (thin slice) taken at different angles Source Reconstruction algorithm Test object Scan image
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AAE552-Session20 - AAE 552 Spring 2009 A F Grandt AAE 552...

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