AAE552-Session13

AAE552-Session13 - 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 13 – 11 February 2009 2 Contact Information Alten F. (Skip) Grandt, Jr. Email: 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 13 11 February 2009 Last Time: Proof testing Today: Finish Proof testing Visual inspection 4 Assignment Please read Textbook : Chapter 10 Webpage powerpoint references “Visual inspection” – collaboration for NDT education “Endoscopes: The Borescope for Humans,” Christine Poulin AAE 552 term paper 5 Proof Testing as NDE Goal : interpret results in terms of initial crack size Approach : Assume structure cracked and “almost” fractures K proof = K c = σ proof ( π a p ) 1/2 β (a p ) Solve for a p = largest possible crack that could be present after proof test σ o σ proof = α σ o σ time σ a p 6 Sun Tzu: The Art of War (circa 500 B.C.) Defense vs Offense “Security against defeat implies defensive tactics; ability to defeat the enemy means taking the offensive ”

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AAE 552 Spring 2009 – A. F. Grandt 2 7 Proof Testing Applications Proof testing especially suited for simple structures and loading Pressure vessels Tension members Hooks Easy to load/interpret results surface cracks p 8 False Indication Reject Component Accept Component Evaluate Relevant Indication Relevant Indication Nonrelevant Indication Interpret Indication "Indication" obtained from Inspection Response to Stimulus Apply Stimulus to Component Figure 4.1 Proof Test Process Stimulus? Response? Indication? Interpret Relevant False Nonrelevant 9 Advantages – Proof Testing Structure readily screened for gross defects Previous inspections (ultrasonic, X- ray, etc.) are reliably checked Upper limit for the initial crack size is readily determined Proof test overload may “retard” subsequent fatigue crack growth (see Chapter 7). 10 Disadvantages – Proof Testing May fracture during proof test (i.e. the method is not “nondestructive”) Can be expensive for large components Difficult to proof all components to same level, or to accurately determine applied loads in certain areas Difficult to load structure similar to service Existing cracks may extend subcritically during proof cycle 11 Visual Inspection (Chapter 10) Visual inspection is first line of defense! James Stewart, “No Highway in the Sky,” 20 th Century Fox, 1951 12 Visual Inspection Scheduled visual inspection and hinge free play measurement of RAAF F/A-18 LEF idler Hinges Photo courtesy of FLTLT B. Main
AAE 552 Spring 2009 – A. F. Grandt 3 13 Visual Inspection (Fig. 10.1) Visual detection of

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AAE552-Session13 - AAE 552 Spring 2009 A F Grandt AAE 552...

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