Development of a pulsed eddy current instrument and its application to detect deeply buried corrosion

dc.contributor.author Ward, William
dc.contributor.department Electrical and Computer Engineering
dc.date 2018-08-22T16:17:41.000
dc.date.accessioned 2020-06-30T07:55:12Z
dc.date.available 2020-06-30T07:55:12Z
dc.date.copyright Wed Jan 01 00:00:00 UTC 1997
dc.date.issued 1997
dc.description.abstract <p>Eddy current techniques have historically been valuable to nondestructive evaluation and testing. They allow detection of cracks, corrosion, and other inhomogeneities in conducting materials. However, due to the fact that traditionally eddy currents only use one frequency to excite the coil, limited information about the detected flaw is available. Swept frequency eddy current methods, which sweep the frequency of excitation over a specified range, allow much more information about the flaw to be extracted from the data. This method is much slower due to the amount of time required to sweep the frequency. The pulsed eddy current method was developed to decrease the time required for swept frequency measurements while retaining the ability to extract more information from the data.;The technique is a broadband measurement which requires the coil to be excited by a step function and the response of the coil monitored. Since the coil is excited with a spectrum of frequencies contained in the step function, similar information content to the swept frequency method is available. In this thesis, the electronic hardware for a pulsed eddy current system with the ability to operate a probe in the absolute or reflection mode using a step voltage drive waveform was developed and demonstrated. The system consists of a portable computer with three expansion boards to control the probe drive and signal amplification, digitize the signal, and control the scanner.;The system is controlled by custom designed software based on the Windows[Superscript TM] operating system. The capabilities of the pulsed eddy current system were then extended to allow for a step current drive waveform. The experimental results for corrosion detection in a two-layer structure of 1 mm thick aluminum plates simulating an aircraft lap joint are compared with theory and are found to be in good agreement. The ability to use the instrument with a magnetic sensor capable of sensing the magnetic field threading the coil was also added to the instrument. Using theory and experiment, it is demonstrated that a magnetic sensor is superior to the coil sensor at detecting deeply buried corrosion in aluminum.</p>
dc.format.mimetype application/pdf
dc.identifier archive/lib.dr.iastate.edu/rtd/16795/
dc.identifier.articleid 17794
dc.identifier.contextkey 7406543
dc.identifier.doi https://doi.org/10.31274/rtd-180813-8033
dc.identifier.s3bucket isulib-bepress-aws-west
dc.identifier.submissionpath rtd/16795
dc.identifier.uri https://dr.lib.iastate.edu/handle/20.500.12876/70572
dc.language.iso en
dc.source.bitstream archive/lib.dr.iastate.edu/rtd/16795/ISU_1087633.pdf|||Fri Jan 14 21:06:03 UTC 2022
dc.subject.disciplines Other Materials Science and Engineering
dc.subject.disciplines Signal Processing
dc.subject.keywords Electrical and computer engineering
dc.subject.keywords Electrical engineering
dc.title Development of a pulsed eddy current instrument and its application to detect deeply buried corrosion
dc.type article
dc.type.genre thesis
dspace.entity.type Publication
relation.isOrgUnitOfPublication a75a044c-d11e-44cd-af4f-dab1d83339ff
thesis.degree.level thesis
thesis.degree.name Master of Science
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