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AAE552-Session19

AAE552-Session19 - 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 19 – 25 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 19 25 February 2009 Last Time: Start radiography Today: Continue radiography Neutron Radiography Image Formation Computed Tomography 4 Chapter 11: Radiography Use penetrating power of x-rays or gamma rays to locate internal anomalies 5 Chapter 11: Radiography Topics Overview Absorption/Scatter Radiation sources Image formation Image quality Examples Computed Tomography Safety issues Summary 6 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)
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AAE 552 Spring 2009 – A. F. Grandt 2 Absorption and Scatter 7 8 Radiation Absorption Differential absorption of radiation by different materials is key to NDE I o = intensity on surface I x = intensity distance x from surface μ = coefficient of linear absorption (1/length) = function of material, energy level source I x I o x object I x = I o e - μ x (Eq. 11.3) 9 Linear Absorption Coefficients for Aluminum, Iron and Lead (Fig. 11.3) Note optimum energy for minimum λ λλ and max penetration X-ray Energy (MeV) Total linear absorption coefficient (cm -1 ) Lead Iron Aluminum I x = I o e - μ x I x I o x 10 Absorption/Scattering Mechanisms Several mechanisms for absorption and or scattering of radiation energy that passes through object Depend on energy of radiation Raleigh Scattering (E < 0.1 MeV) Photoelectric Effect (E < 0.5 MeV) Compton Scattering (0.1 MeV < E < 3 MeV) Pair Production (E > 1.02 MeV) 11 Components of Absorption Coefficient in Iron (Fig. 11.4) Note optimum energy for minimum μ and max absorption X-ray Energy (MeV) Rayleigh Photoelectric Pair production Compton Total I x = I o e - μ x Radiation sources 12
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AAE 552 Spring 2009 – A. F. Grandt 3 13 Sources of Radiation (Section 11.4) X-rays X-ray tubes (~ 450 kV max) High-energy (E > 1 MeV) Tuned transformers (1 –2 MeV) Van de Graaf Generators (1 – 8 MeV) Betatrons (1-30 MeV) Linear electron Accelerators (1 – 25 MeV) Gamma rays (~0.06 – 1.8 MeV) Neutrons Radiation Sources Two of the most commonly used sources of radiation in industrial radiography are x-ray generators and gamma ray sources. Industrial radiography is often subdivided into “X-ray Radiography” or “Gamma Radiography”, depending on the source of radiation used. 15
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AAE552-Session19 - AAE 552 Spring 2009 A F Grandt AAE 552...

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