Cross Correlation of Eddy Current Images for Detection of Fatigue Crack Propagation
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Begun in 1973, the Review of Progress in Quantitative Nondestructive Evaluation (QNDE) is the premier international NDE meeting designed to provide an interface between research and early engineering through the presentation of current ideas and results focused on facilitating a rapid transfer to engineering development.
This site provides free, public access to papers presented at the annual QNDE conference between 1983 and 1999, and abstracts for papers presented at the conference since 2001.
There is a need within the NDE industry to evaluate the growth of damage such as fatigue cracking and plastic deformation over the life of a structure. To accomplish this aim, data collected over a period of time must be compared spatially while quantitative measures must be developed to determine the extent of crack propagation in a damaged region. To facilitate automated inspection and characterization of defects in metals, the application of cross-correlation techniques and frequency mixing to sequential eddy current images of fatigued welds and fatigue cracks in compact tension and reduced section specimens has been investigated. Results indicate that cross-correlation techniques can be used to align scan images to provide a history of damage development and that frequency mixing can enhance the signal-to-noise ratios of fatigue cracks in welded steel. Localized damage was detected by segmenting the images into smaller cross-correlation regions for improved resolution. The technique may be used to examine magnetic eddy current data from ferrous welds and seams and to identify cracks or regions of cold working in transportation and energy-generation systems.