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AAE552-Session22

AAE552-Session22 - 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 22 – 4 March 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 22 4 March 2009 Last Time: Radiography applications Safety issues Summary Today: Wrap up radiography X-ray diffraction Start Ultrasonics 4 Assignment Please read Textbook : Chapter 12 – Ultrasonics Webpage powerpoint references “Ultrasonic Testing, ” collaboration for NDT education Exam #1 – Session 29 (Friday, 27 March 2009) 5 X-Ray Applications 6 X-Ray Diffraction Diffraction of x-rays off rows of atoms Bragg’s law determines lattice spacing d Identify material, residual stresses Reference: P. J. Shull, Nondestructive Evaluation, Marcel Dekker, 2002, p 551 Bragg’s Law η λ = 2 d sin θ η = order of refraction λ = wave length d = atomic spacing θ = diffracted angle
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AAE 552 Spring 2009 – A. F. Grandt 2 7 X-Ray Diffraction Incident/scattered x-rays constructively interfere under certain conditions Determine lattice spacing Identify materials, residual stress, etc. θ Incident X-rays Scattered X-rays d 8 Bragg’s Law Ray B travels distance XYZ farther than A XY = YZ = d sin θ Bragg’s law describes constructive interference when η λ = 2 d sin θ η = order of refraction, λ = wave length d = atomic spacing, θ = diffracted angle X Y Z A B θ d 9 Bragg’s Law Use known wavelength, angle of incidence, to find lattice spacing Energy Wave length λ λ min or E max Intensity of x-ray Characteristic x-rays 10 Radiation Safety Radiographic NDE requires strict safety considerations 11 Radiography Safety Issues X-rays and gamma rays are dangerous and require special precautions Protect personnel Monitor radiation dosage Safety principles based on Distance – keep people away Absorption – shield radiation Time – plan minimum time of human exposure to radiation Safety important – but Adequate precautions are possible NDE can be conducted safely 12 Summary Radiography - Pros Detect internal and external damage Applicable to a wide variety of solid materials Can examine complex shapes and wide range of thickness Permanent record of inspection obtained Minimal part preparation Real time viewing possible Three-dimensional imaging possible with Computerized Tomography (CT)
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AAE 552 Spring 2009 – A. F. Grandt 3 Advantages of Radiography Technique is not limited by material type or density.
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