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This paper explores feature extraction algorithms for crack characterization in eddy current inspection of fastener sites. A novel feature extraction method fitting approximate models to data associated with geometric part features addressing adjacent fastener sites and panel edges are developed. Data classification methods in the circumferential direction around fastener sites are developed to better characterize fatigue cracks with improved noise invariance. Model-assisted probability of detection results are presented highlighting the benefit of automation in NDE., The original document contains color images. All DTIC reproductions will be in black and white. Submitted to be published in the Proceedings of the 33rd Annual Review of Progress in Quantitative Nondestructive Evaluation (QNDE) Conference 2006.

U.S. Air Force aircraft are managed by Damage Tolerance Assessment (DTA) and Nondestructive Evaluation (NDE) plays a critical role in insuring their flight safety. This paper provides an overview of current NDE capabilities for aircraft structures. The potential migration to Condition-Based Maintenance (CBM) will require NDE to evolve from detection of defects to characterization of their location and size. This represents multiple significant challenges as aircraft have many material and geometry factors that complicate this analysis. This paper provides a strategy to resolve these factors., The original document contains color images. All DTIC reproductions will be in black and white. Submitted for publication in the Proceedings of the 33rd Annual Review of Progress in Quantitative Nondestructive Evaluation (QNDE) Conference 2006.

This paper presents a model-assisted probability of detection (MAPOD) study for inspection of a two-layer airframe structure. Eddy current measurements for varying crack length around fastener holes in a two-layer aluminum structure are studied using both experimental and model-generated data. New statistical algorithms are used to calculate the probability of detection. Good agreement was achieved between empirical and model-assisted approaches., Prepared in collaboration with Computational Tools, Inc., Gurnee, IL and Statistical Engineering, Palm Beach Gardens, FL. 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.