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Elastic Stiffness Characterization of Anisotropic Materials by Line-focus Ultrasound Transducer

LI, QIUYAN (2019) Elastic Stiffness Characterization of Anisotropic Materials by Line-focus Ultrasound Transducer. Doctoral Dissertation, University of Pittsburgh. (Unpublished)

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Elastic stiffness constants are critical parameters to evaluate mechanical property of solid materials, and it is of great importance to develop convenient and accurate methods that can characterize material stiffness constants in industrial applications. Line-focus ultrasound transducer has been used as one of the methods to generate surface wave in isotropic and anisotropic materials because of its accurate control on transducer-sample alignment. However, little work has been found to employ this transducer to systematically characterize stiffness constants of anisotropic solids due to the absence of the mathematic model that describes the relationship between stiffness constants and surface wave velocity. The purpose of this dissertation is to develop a new approach that enables a lens-less line focus ultrasound transducer to characterize stiffness constants of anisotropic materials through simultaneously measurement of both Rayleigh surface wave and longitudinal bulk wave. Firstly, a lens-less line focus PVDF (Polyvinylidene fluoride) ultrasound transducer and corresponding testing system have been established. This inhouse developed testing system is then experimentally calibrated using metal alloys made by both conventional and additive manufacturing methods. The comparison results demonstrate reasonably good accuracy to characterize elastic constants of isotropic materials. Secondly, mechanistic models for the relationship of wave propagation with stiffness constants are developed for more complicated Cubic and Trigonal anisotropic materials. Again, the model validation is conducted by comparing model prediction and experimental measurement using single crystal silicon and quartz as examples. Additionally, a generalized form of model development process is summarized in the end, and this form can be used as a guideline to develop numerical model for surface wave propagating along any direction on any types of crystallographic structures. As an example, the generalized model development process is utilized to develop the mechanistic model for orthorhombic materials. Based on the theoretical and experimental studies in this dissertation, a novel elastic stiffness constant characterization method is developed and characterized, which largely simplified the measurement procedure and minimized the sample used for fully characterization of stiffness constants of different types anisotropic solids.


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Item Type: University of Pittsburgh ETD
Status: Unpublished
CreatorsEmailPitt UsernameORCID
ETD Committee:
TitleMemberEmail AddressPitt UsernameORCID
Date: 11 September 2019
Date Type: Publication
Defense Date: 19 July 2019
Approval Date: 11 September 2019
Submission Date: 23 July 2019
Access Restriction: No restriction; Release the ETD for access worldwide immediately.
Number of Pages: 139
Institution: University of Pittsburgh
Schools and Programs: Swanson School of Engineering > Mechanical Engineering and Materials Science
Degree: PhD - Doctor of Philosophy
Thesis Type: Doctoral Dissertation
Refereed: Yes
Uncontrolled Keywords: Elastic stiffness, Line-focus ultrasound transducer, Anisotropic material, longitudinal bulk wave, Rayleigh surface wave
Date Deposited: 11 Sep 2019 15:12
Last Modified: 11 Sep 2019 15:12

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