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Ultrasonic Characterization of Polycrystals with Texture and Microtexture: Theory and Experiment

Li, Jia
http://rave.ohiolink.edu/etdc/view?acc_num=osu1418908225

Abstract Details

2015, Doctor of Philosophy, Ohio State University, Welding Engineering.
When an ultrasonic wave propagates in polycrystalline materials, the wave is scattered on grain boundaries and the scattered waves carry important information on material microstructure, e.g. grain size and texture. Using grain scattering information for nondestructive testing purposes can be useful as quality control in many manufacturing processes. In particular, measurement and interpretation of ultrasonic scattering can be very useful in the development of practical methods for nondestructive ultrasonic characterization of microtextured regions in titanium alloys that are widely used for aeroengine components. Ultrasonic scattering and scattering-induced ultrasonic attenuation are two measurable ultrasonic characteristics that can be employed for material microstructures characterization. Most past studies address ultrasonic attenuation and scattering in polycrystals with macroscopic isotropy or simple artificial textures and equiaxed grains of high crystallographic symmetry (cubic or hexagonal). However, most manmade materials, as a result of thermomechanical processing, exhibit nonequiaxed grains and complex forms of macroscopic texture. One objective of this dissertation is to provide a better understanding of ultrasonic propagation and scattering in textured polycrystyals. In this dissertation, general attenuation and scattering models are developed for polycrystals with arbitrary macrotexture and ellipsoidal grain shape with triclinic symmetry. The attenuation coefficients were derived in the Born approximation by generalizing previous theoretical models that were suitable for equiaxed grains and uniaxial hexagonal textures. The general scattering coefficients were obtained from the integrand of the attenuation coefficients. The second major objective is to ultrasonically characterize the microtextured regions (MTRs) in Ti alloys which is a result of orientation clustering of crystallites and leads to a reduction of dwell fatigue properties of the material. The models developed are extended to titanium alloys with those dual-scale microstructures. The third objective of this dissertation is to establish an inversion methodology to robustly reconstruct material characteristics from ultrasonic attenuation and backscattering measurements. By using a combination of the attenuation-to-backscattering ratios and directional backscattering ratios, an inversion procedure is developed for a complete reconstruction of MTR sizes and its effective elastic parameters. The experimental methodology and the system calibration method are described for the near field of the ultrasonic transducer measurements. Examples of measurements and application of inversion models to typical titanium alloy samples are given. It is shown that in general, the MTR sizes and the microtexture parameters determined by ultrasonic inversion models are in reasonable agreement with those measured by others on the same samples by destructive electron backscatter diffraction (EBSD) characterization methods.
Stanislav Rokhlin (Advisor)
Dave Farson (Committee Member)
Daniel Mendelsohn (Committee Member)
Adam Pilchak (Committee Member)
420 p.
Acoustics; Materials Science
ultrasound propagation and scattering; material characterization; macrotexture and microtexture

Recommended Citations

Citations

  • Li, J. (2015). Ultrasonic Characterization of Polycrystals with Texture and Microtexture: Theory and Experiment [Doctoral dissertation, Ohio State University]. OhioLINK Electronic Theses and Dissertations Center. http://rave.ohiolink.edu/etdc/view?acc_num=osu1418908225

    APA Style (7th edition)

  • Li, Jia. Ultrasonic Characterization of Polycrystals with Texture and Microtexture: Theory and Experiment. 2015. Ohio State University, Doctoral dissertation. OhioLINK Electronic Theses and Dissertations Center, http://rave.ohiolink.edu/etdc/view?acc_num=osu1418908225.

    MLA Style (8th edition)

  • Li, Jia. "Ultrasonic Characterization of Polycrystals with Texture and Microtexture: Theory and Experiment." Doctoral dissertation, Ohio State University, 2015. http://rave.ohiolink.edu/etdc/view?acc_num=osu1418908225

    Chicago Manual of Style (17th edition)

osu1418908225
441
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This open access ETD is published by The Ohio State University and OhioLINK.