| Summary: | 碩士 === 國立成功大學 === 土木工程學系碩博士班 === 101 === This research is to refine the Thin Film Shaker (TFS) device to measure mechanical properties of materials, such as Young’s modulus, shear modulus and loss tangent. The classical Euler-Bernoulli beam model works well to extract the Young’s modulus of the thin film from the first resonant frequency, and the measured Young’s modulus are 64.8 GPa for aluminum, 106.1 GPa for titanium, 7.4 GPa for PET, separately. However, in order to obtain both elastic constants of isotropic, homogeneous materials, the resonant frequency associated to the torsional mode is identified experimentally. And, by solving the inverse problems with the COMSOL finite element software through optimization procedures, multiple elastic constants can be determined through one frequency-scan experiment with multiple identified resonant frequencies. For stainless steel, Young’s modulus 194 GPa and shear modulus 70 GPa are measured simultaneously. Attempts to extract linear viscoelastic properties of materials through fitting the shape of a resonant peak are conducted. The measured loss tangent is 0.069 for PET. Furthermore, by using the similar technique for the inverse problem, defects, such as cracks, in the thin film can be identified through TFS frequency sweep experiments. In addition, to better model the electric-mechanical system of the TFS apparatus, the finite element method is adopted to model the behavior of the bimorph piezo actuator.
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