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dc.contributor.advisorJacobs, Laurence J.
dc.contributor.authorSchempp, Fabian
dc.date.accessioned2014-01-13T16:53:22Z
dc.date.available2014-01-13T16:53:22Z
dc.date.created2013-12
dc.date.issued2013-11-20
dc.date.submittedDecember 2013
dc.identifier.urihttp://hdl.handle.net/1853/50396
dc.description.abstractIt is well known that liquid coupling agents, which are commonly used in conventional ultrasonic testing to couple an ultrasonic transducer to a solid specimen, cause a number of problems including inconsistency in results and slowness of the inspection. This is especially true when the specimen surface is rough, such as those in field concrete structures; here the solution involves time-consuming surface preparation to polish every single point of inspection, making it impractical to inspect field structures with conventional, contact methods. To address this issue, this thesis proposes a new, fully non-contact, air-coupled measurement setup in the mid to high ultrasonic frequencies (50-150 kHz). This advanced setup and measurement technique is evaluated by calculating the signal to noise ratio for different numbers of signal averages. In addition, the effect of the lift-off distance of the transducer over the sample is also investigated. Ultrasonic waves are generated and detected in this frequency range with a sufficiently high signal to noise ratio (SNR), which enables performing a fast scan with a small number of signal averages. Using this setup, phase velocity and attenuation of Rayleigh surface waves in a concrete specimen are first measured. Then, the air coupled ultrasound technique is used to detect dicontinuities such as cracks at a concrete joint and reinforcement bars in a concrete block. Also, the capability of the proposed technique for measuring depths of surface-breaking cracks using air-coupled generated Rayleigh waves is demonstrated. Since this measurement setup directly generates Rayleigh waves, most of the disadvantages in the techniques based on the impact-echo method can be avoided and thus data processing is much simpler than that in the impact-echo based techniques. The results of the measurements show that this setup is highly promising and a big advancement towards the rapid ultrasonic nondestructive testing on large-scale field concrete structures.
dc.format.mimetypeapplication/pdf
dc.publisherGeorgia Institute of Technology
dc.subjectUltrasound
dc.subjectAir-coupled
dc.subjectConcrete
dc.subject.lcshUltrasonic testing
dc.subject.lcshConcrete
dc.titleFully non-contact, air-coupled generation and detection of ultrasound in concrete for nondestructive testing
dc.typeThesis
dc.description.degreeM.S.
dc.contributor.departmentCivil and Environmental Engineering
thesis.degree.levelMasters
dc.contributor.committeeMemberKim, Jin-Yeon
dc.contributor.committeeMemberDesRoches, Reginald
dc.date.updated2014-01-13T16:53:22Z


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