Estimating the Distribution of the Sizes Of Flaws Remaining After an Inspection (Preprint)

The U.S. Air Force plans for maintenance and retirement of aircraft based in part on fatigue crack growth models. Periodic inspections are used to help assess airworthiness and plan for future inspections. Nondestructive inspections are not perfect so some cracks are missed and the likelihood that a...

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Bibliographic Details
Main Authors: Hovey, Peter W, Berens, Alan P, Knopp, Jeremy
Format: Report
Language:English
Subjects:
Aircraft
AIRFRAMES
AIRWORTHINESS
CRACKS
FATIGUE CRACK GROWTH MODELS
FLIGHT HOURS
MAXIMUM LIKELIHOOD ESTIMATION
Mechanics
NONINTRUSIVE INSPECTION
PE62102F
POD(PROBABILITY OF DETECTION)
SAMPLING PROCEDURE
Statistics and Probability
SYMPOSIA
Test Facilities, Equipment and Methods
WUAFRL43494105
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Summary:The U.S. Air Force plans for maintenance and retirement of aircraft based in part on fatigue crack growth models. Periodic inspections are used to help assess airworthiness and plan for future inspections. Nondestructive inspections are not perfect so some cracks are missed and the likelihood that an individual crack is detected is a function of the size of the crack when inspected. Additionally, the crack size distribution is related to the number of flight hours the aircraft has experienced, so not all inspection results come from the same distribution. In a recent study several models were compared that utilize the capability of the inspection system and the variation between aircraft and times of inspections to estimate the distribution of sizes of cracks that were missed during the inspection. This white paper summarizes those results and identifies some methods for extending them. Prepared in collaboration with the University of Dayton Research Institute, Dayton, OH and the Nondestructive Evaluation Branch, Air Force Research Laboratory, Wright-Patterson AFB, OH. Presented at the Annual Review of Progress in Quantitative Nondestructive Evaluation (33rd), QNDE 2006, held in Portland, OR on 30 Jul-4 Aug 2006. The original document contains color images. All DTIC reproductions will be in black and white.