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School of Civil and Environmental Engineering
Ph.D. Thesis Defense Announcement
Characterization of Early-Stage Material Damage in Cement-Based Materials using Nonlinear Ultrasound
By
Gun Kim
Advisor:
Dr. Laurence Jacobs ( CEE) and Dr. Kimberly E. Kurtis ( CEE)
Committee Members:
Dr. Jin-Yeon Kim (CEE), Dr. Karim Sabra (ME), and Dr. Yang Wang (CEE)
Date & Time: Wednesday, November 2nd, 2016, at 9:00am
Location: Jesse W. Mason Conference Room 2119
Quantitative nondestructive evaluation (NDE) of engineering materials requires the reliable sensing techniques capable of providing quantitative information on early stage damage. Nonlinear ultrasound (NLU) is a promising candidate because it provides a direct measure of the nonlinear elastic behavior of materials. NLU excels at the detection and characterization of damage that originates at or beneath the material's micro-scale. This thesis presents a procedure for second harmonic generation (SHG) using nonlinear Rayleigh surface waves. This SHG technique determines material nonlinearity by measuring the acoustic nonlinearity parameter, β. Specifically, microscale material characterization of physical/chemical phenomena including drying shrinkage, the role of shrinkage-reducing admixture (SRA) in mitigating shrinkage cracking, self-healing by carbonation, and sustained and cyclic loading in cement-based materials will be determined using β. The results reveal how the SHG technique with Rayleigh surface waves can provide the quantitative relationship between the acoustic nonlinearity parameter and the damage state of construction materials. Overall, with an integrated understanding of the early-age behavior in the cement-based materials, new strategies for the application of the SHG technique will be discussed with an emphasis on the assessment of in-service civil infrastructure and in-situ interrogation.
