| Summary: | 碩士 === 國立臺灣大學 === 應用力學研究所 === 103 === This thesis studies the nonlinear response of piezoelectric MEMS energy harvesters. The analysis is based on several assumptions including linear piezoelectric constitutive relation, Euler-Bernoulli beam theory considering geometric nonlinearity, Rayleigh-Ritz approximations, and Hamiltonian variational principle.
The nonlinear frequency responses under various accelerations and loads are approximated based on Harmonic Balance Method. Through the parameters provided by experiment, the frequency response is found to be of hardening type of nonlinearity. The results are validated by carrying out a series of experiment on micro piezoelectric unimorphs. In addition, the points initiating jump phenomenon almost remain the same under different electric loads, showing the weak electromechanical coupling.
On the other hand, the softening frequency response was observed by other samples with different substrate materials and sizes. A further examination on these substrate materials shows the hardening type of nonlinearity if the piezoelectric layers are completely removed. The internal stresses generated during the MEMS fabrication are postulated for explanation and will be verified in the near future.
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