Transducer characterization for Vibrothermography

dc.contributor.advisor Stephen D. Holland
dc.contributor.author Vaddi, Jyani Somayajulu
dc.contributor.department Aerospace Engineering
dc.date 2018-08-11T11:45:59.000
dc.date.accessioned 2020-06-30T02:26:18Z
dc.date.available 2020-06-30T02:26:18Z
dc.date.copyright Sat Jan 01 00:00:00 UTC 2011
dc.date.embargo 2013-06-05
dc.date.issued 2011-01-01
dc.description.abstract <p>Vibrothermography, also known as Sonic IR and Thermosonics, is an NDE technique for</p> <p>finding cracks and flaws based on vibration-induced frictional rubbing of unbonded surfaces.</p> <p>The vibration is usually generated by a piezoelectric stack transducer which transduces electri-</p> <p>cal energy into large amplitude mechanical vibrations. The purpose of this study is to develop</p> <p>an understanding of the excitation process for vibrothermography so that optimal parameters</p> <p>and transducers for the testing can be selected. The amplitude and impedance transfer charac-</p> <p>teristics of the transducer system control the vibration of the sample. Within a linear contact</p> <p>(no tip chatter) model, the interaction between the transducer system and the specimen can</p> <p>be characterized using the theory of linear time-invariant (LTI) systems and electro-mechanical</p> <p>Norton equivalence.</p> <p>This work presents quantitative measurements of the performance of piezoelectric stack</p> <p>transducers in a vibrothermography excitation system and the effect of transducer perfor-</p> <p>mance and specimen characteristics on the induced vibration in the specimen. We show that</p> <p>with compliant coupling, the specimen vibration is directly proportional to the transducer open</p> <p>circuit velocity and that the system resonances generated because of metal-metal contact of</p> <p>specimen and transducer are disconnected by adding a couplant between specimen and trans-</p> <p>ducer. We then give suggestions for transducer and couplant selection for vibrothermography</p> <p>and suggest methods to flatten the velocity spectrum of the transducer.</p> <p>We extend our analysis to high amplitude transducer behavior and elaborate on the effect</p> <p>of power amplifier saturation on the transducer behavior. The saturation effect negates the</p> <p>effect of adding an external inductance to flatten the transducer velocity spectrum. Finally,</p> <p>preliminary results are reported on the effect of transducer degradation phenomenon.</p>
dc.format.mimetype application/pdf
dc.identifier archive/lib.dr.iastate.edu/etd/10121/
dc.identifier.articleid 1026
dc.identifier.contextkey 2736122
dc.identifier.doi https://doi.org/10.31274/etd-180810-1734
dc.identifier.s3bucket isulib-bepress-aws-west
dc.identifier.submissionpath etd/10121
dc.identifier.uri https://dr.lib.iastate.edu/handle/20.500.12876/24355
dc.language.iso en
dc.source.bitstream archive/lib.dr.iastate.edu/etd/10121/Vaddi_iastate_0097M_12098.pdf|||Fri Jan 14 18:14:26 UTC 2022
dc.subject.disciplines Aerospace Engineering
dc.subject.keywords couplant
dc.subject.keywords degradation
dc.subject.keywords Transducer
dc.subject.keywords two port model
dc.subject.keywords Vibrothermography
dc.title Transducer characterization for Vibrothermography
dc.type article
dc.type.genre thesis
dspace.entity.type Publication
relation.isOrgUnitOfPublication 047b23ca-7bd7-4194-b084-c4181d33d95d
thesis.degree.level thesis
thesis.degree.name Master of Science
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