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Laser-Ultrasonic Measurement of Single-Crystal Elastic Constants from Polycrystalline Samples by Measuring and Modeling Surface Acoustic Wave Velocities

Du, Xinpeng
http://orcid.org/0000-0002-4816-7227
http://rave.ohiolink.edu/etdc/view?acc_num=osu1524177819455643

Abstract Details

2018, Doctor of Philosophy, Ohio State University, Materials Science and Engineering.
Elastic constants Cij are one of the essential properties to understand mechanical behaviors of materials. They are indispensable inputs for physics-based models of microstructural evolution and constitutive/micro-mechanistic simulations of properties. Young’s modulus, bulk modulus, shear modulus and Poisson’s ratio are just different combinations of elastic constant components and they only describe mechanical behavior under specific conditions. Elastic constants Cij are the intrinsic parameters fully describing the elastic mechanical behavior under any given condition. Several experimental methods have been developed to measure elastic constants of materials but most of them require single-crystal samples, which are time-consuming to grow. Many compounds are not even possible to grow single crystals. As a result, only about 1% (roughly 1500 out of 160,000 kinds) of distinct solid compounds have experimental values of the elastic constants. To change this scenario, an innovative experimental method has been developed to measure single-crystal elastic constants directly from polycrystalline samples, without the need of growing single crystals. The new method is based on measuring and modeling femtosecond laser-generated surface acoustic waves (SAWs) that only propagate on the sample surface and decay with the distance from the surface into the sample exponentially. An elastodynamic model has been developed to predict the SAW phase velocities along any general direction at given full elastic constants and density. A femtosecond laser-based experimental set-up was applied to generate and detect SAW velocities along any specific direction. To enable measuring narrow-band SAW velocities along a single direction without any interference from multiple modes, an organic PDMS (polydimethylsiloxane) film of 1-D grating was placed on top of the sample surface to guarantee only one SAW mode survives to be detected. With modeling predictions and experimental measurements, either a forward simulation algorithm or a neural network machine learning method has been applied to extract the full elastic constants. Polycrystalline samples of Ni, Al, Ta, Nb, Fe (bcc), Co (hcp) and ß-Sn (tetragonal) have been used to benchmark the measurement accuracy. The extracted elastic constants from our method are within 6.8% of the corresponding values obtained from single-crystal samples for all seven pure metals. This new method completely frees us from growing single crystals. The high spatial resolution feature (~20 microns) in tests makes it highly applicable in obtaining high throughput composition-dependent elastic constants through localized measurements on a diffusion couple. The power and versatility of this new method are illustrated with five measurement examples: (1) composition-dependent elastic constants from an Fe-Ni diffusion couple; (2) full elastic constants of Sn from its powders; (3) key elastic constants of the intermetallic compound Ni3Sn4 of the monoclinic crystalline symmetry; (4) full elastic constants of a polycrystalline Ni-based superalloy René 88DT; and (5) Young’s moduli of inorganic glass materials. Several appendixes are provided and attached at the end of this dissertation, including bulk acoustic wave modeling, surface acoustic wave modeling, the transformation of coordinate systems among the sample coordinate system, the crystalline coordinate system and the PDMS based coordinate system, and MATLAB coding used in this dissertation.
Ji-Cheng Zhao (Advisor)
Wolfgang Windl (Committee Member)
Stephen Niezgoda (Committee Member)
199 p.
Acoustics; Materials Science; Mechanical Engineering
Laser-ultrasonics; Surface acoustic wave; Time domain thermoreflectance; Elastic constants; Electron backscatter diffraction

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Citations

  • Du, X. (2018). Laser-Ultrasonic Measurement of Single-Crystal Elastic Constants from Polycrystalline Samples by Measuring and Modeling Surface Acoustic Wave Velocities [Doctoral dissertation, Ohio State University]. OhioLINK Electronic Theses and Dissertations Center. http://rave.ohiolink.edu/etdc/view?acc_num=osu1524177819455643

    APA Style (7th edition)

  • Du, Xinpeng. Laser-Ultrasonic Measurement of Single-Crystal Elastic Constants from Polycrystalline Samples by Measuring and Modeling Surface Acoustic Wave Velocities . 2018. Ohio State University, Doctoral dissertation. OhioLINK Electronic Theses and Dissertations Center, http://rave.ohiolink.edu/etdc/view?acc_num=osu1524177819455643.

    MLA Style (8th edition)

  • Du, Xinpeng. "Laser-Ultrasonic Measurement of Single-Crystal Elastic Constants from Polycrystalline Samples by Measuring and Modeling Surface Acoustic Wave Velocities ." Doctoral dissertation, Ohio State University, 2018. http://rave.ohiolink.edu/etdc/view?acc_num=osu1524177819455643

    Chicago Manual of Style (17th edition)

osu1524177819455643
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This open access ETD is published by The Ohio State University and OhioLINK.