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dc.contributor.authorYoo, Byungseoken
dc.date.accessioned2014-03-14T20:50:30Zen
dc.date.available2014-03-14T20:50:30Zen
dc.date.issued2006-12-12en
dc.identifier.otheretd-12202006-112642en
dc.identifier.urihttp://hdl.handle.net/10919/36335en
dc.description.abstractThe ultrasonic NDE technique to characterize the ultrasonic nonlinear response of the cyclically load 7075-T6 aluminum is described in this thesis. In order to estimate the nonlinear relation of the ultrasonic waves due to material fatigue damage or degradation, the spectral analysis techniques such as the power spectrum, bispectrum, and bicoherence spectrum are applied. The ultrasonic nonlinearity parameters by Cantrell and Jhang are introduced and presented as a function of the material fatigue growth, the number of fatigue cycles. This thesis presents the effectiveness of the bispectral analysis for evaluating the nonlinear aspects of the ultrasonic wave propagation. The results show that the nonlinearity parameters by Cantrell and Jhang are responsive to the output amplitude of the received signal and vary for the various materials, and independent of the input frequency and the ultrasonic wave propagation distance. By using the bispectral analysis tools, particularly the bicoherence spectrum, the increase of the coupling levels between the fundamental, its harmonic, and subharmonic frequency components is presented as the number of fatigue cycles is increased. This thesis suggests that the application of the bicoherence spectrum based on the nonlinear wave coupling relations be more effective for estimating the level of the material fatigue life.en
dc.publisherVirginia Techen
dc.relation.haspartByungseok_Yoo_MS_Thesis.pdfen
dc.rightsIn Copyrighten
dc.rights.urihttp://rightsstatements.org/vocab/InC/1.0/en
dc.subjectUltrasonicen
dc.subjectNDEen
dc.subjectNonlinearity Parameteren
dc.subjectPower Spectrumen
dc.subjectBispectrumen
dc.subjectBicoherence Spectrumen
dc.titlePractical Aspects of Assessing Nonlinear Ultrasonic Response of Cyclically Load 7075-T6 Aluminumen
dc.typeThesisen
dc.contributor.departmentEngineering Science and Mechanicsen
dc.description.degreeMaster of Scienceen
thesis.degree.nameMaster of Scienceen
thesis.degree.levelmastersen
thesis.degree.grantorVirginia Polytechnic Institute and State Universityen
thesis.degree.disciplineEngineering Science and Mechanicsen
dc.contributor.committeechairDuke, John C. Jr.en
dc.contributor.committeememberKriz, Ronald D.en
dc.contributor.committeememberHajj, Muhammad R.en
dc.identifier.sourceurlhttp://scholar.lib.vt.edu/theses/available/etd-12202006-112642/en
dc.date.sdate2006-12-20en
dc.date.rdate2007-01-09en
dc.date.adate2007-01-09en


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