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Eddy current measurements are sensitive to variation in the dimensions of probe. This paper presents the results of a parametric study conducted via simulation to determine the effects of varying dimensions on the split D differential eddy current probe response. Details about the study design, the numerical model and major results are presented. The results provide practical guidance on the sensitivity of certain probe dimensions on eddy current probe response. [ABSTRACT FROM AUTHOR]

A comprehensive approach to NDE characterization error evaluation is presented that follows the framework of the 'ahat-versus-a' model evaluation process for probability of detection (POD) assessment. Before characterization error model building is performed, an intermediate step must evaluate the presence and frequency of several possible classes of poor characterization results. A case study is introduced based on the estimation the length, depth and width of surface breaking cracks using bolt hole eddy current (BHEC) NDE. This study highlights the importance of engineering and statistical expertise in the model-building process to ensure all key effects and possible interactions are addressed. [ABSTRACT FROM AUTHOR]

While parametric uncertainty quantification for NDE models has been addressed in recent years, the problem of stochastic field parameters such as spatially distributed electrical conductivity has only been investigated minimally in the last year. In that work, the authors treated the field as a one-dimensional random process and Karhunen-Loeve methods were used to discretize this process to make it amenable to UQ methods such as ANOVA expansions. In the present work, we will treat the field as a two dimensional random process, and the eigenvalues and eigenfunctions of the integral operator will be determined via Galerkin methods. The Karhunen-Loeve methods is extended to two dimensions and implemented to represent this process. Several different choices for basis functions will be discussed, as well as convergence criteria for each. The methods are applied to correlation functions collected over electron backscatter data from highly micro textured Ti-7Al. [ABSTRACT FROM AUTHOR]

A sensitivity analysis was performed for a pit characterization problem to quantify the impact of potential sources for variation on the performance of inverse methods. Certain data processing steps, including careful feature extraction, background clutter removal and compensation for variation in the scan step size through the tubing, were found to be critical to achieve good estimates of the pit depth and diameter. Variance studied in model probe dimensions did not adversely affect performance. [ABSTRACT FROM AUTHOR]

A model-assisted approach for the design and execution of probability of detection (POD) studies is proposed. General agreement was achieved between experimental and full-model assisted results for eddy current inspection of cracks at fastener sites located at both the first and second layers. The accuracy of the POD results was found to be dependent upon the NDE model and assumptions in the model-assisted POD evaluation. Insight is presented for improving the quality of future studies. [ABSTRACT FROM AUTHOR]

To improve the ability of eddy current nondestructive evaluation to characterize fatigue cracks in multilayer structures, a model-based image processing approach is presented that fits approximate models based on first-principles to image data. Model refinements are also presented that address error associated with adjacent holes and poor hole centering due to cracks. Using this approach, improvements in the visual representation of image data for crack detection and the potential for characterization were demonstrated. [ABSTRACT FROM AUTHOR]

This paper explores improving crack detection capability for Giant Magnetoresistive (GMR) measurements through simulation and development of automated data analysis algorithms. Simulated studies were performed that highlight differences in the measurements for varying fastener material properties and indicate potential locations for greater sensitivity to cracks. Automated algorithms were demonstrated to register fastener locations and extract crack features. To address the particular challenge of crack detection at fasteners near part edges, a model-based approach is introduced. [ABSTRACT FROM AUTHOR]

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 is 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. © 2007 American Institute of Physics [ABSTRACT FROM AUTHOR]

This paper explores feature extraction and signal classification for crack characterization in eddy current inspection of fastener sites. Using simulated studies, a promising feature extraction method with broad noise invariance is presented associated with changes in the eddy current response in the circumferential direction. An experimental study is also presented demonstrating the ability of this measure to improve the capability to detect and potentially size cracks around fasteners while maintaining a low false call rate. © 2006 American Institute of Physics [ABSTRACT FROM AUTHOR]