| Summary: | 碩士 === 中原大學 === 機械工程學系 === 87 === The resonator is stimulated by piezoelectric ceramics to produce oscillations with frequencies in the ultrasonic region for the ultrasonic motor application. The steady-state temperature rise due to the heat generated by this actuation and its effects on the dynamic behavior of the resonator are investigated. The effect of three different geometry shapes of the resonator is also studied for the resonator design. The piezothermoelasticity theory is applied to model the complex coupled phenomenon of interaction among the mechanical deformation, electric field and temperature distribution. The extended Hamilton's principle is used for formulation and the finite element method is used to approximate the governing equations for numerical simulation. From the simulation results, it is found that the resonator expands axially by this temperature rise and thus the trajectory of the resonator tip has an offset. This offset is large compared to the axially moving range of the tip trajectory, although the trajectory shape is not changed at all. This will greatly degrade the performance of an ultrasonic motor. The shape of the resonator can change a little bit of the temperature distribution in the resonator, but it may have large impact on the natural frequencies of the resonator.
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