| Summary: | 碩士 === 國立臺灣大學 === 機械工程學研究所 === 101 === This thesis studies the improved vibration isolation design of the brake-assist-vacuum-pump mounting on the vehicle using FEM analysis. One of the critical factors in achieving accurate dynamic predictions is the dynamic characterization of the rubber vibration isolators. In this study, fixtures are proposed to use the impact test for measuring both the axial and radial dynamic behavior of rubber vibration isolators. The test instruments include an impact hammer, an accelerometer, a spectrum analyzer and a force sensor. The input force, blocked force, axial and radial acceleration are then analyzed using the NI 9234 spectrum analyzer. Therefore, the dynamic characteristics of rubber vibration isolators can be obtained. Structural dynamics measurements have also been employed to determine the vibration characteristics such as natural frequencies, mode shapes and transmissibility of the vibration isolation system. Using the NI 9234 spectrum analyzer and Star modal analysis software, the modal parameters are acquired and compared with the simulated results, where the simulation is done based on the rubber dynamic characterization results. Most of the simulated natural frequencies achieve good consistence with the measured natural frequencies. As a result, the FEM model was validated and used in the improved vibration isolation design afterward. Adopting the mounting inclination angle and mounting position of vibration isolators as design parameters, improved vibration isolation design was then carried out. The prototype of improved vibration isolation design was manufactured, and the structural dynamic measurement was employed. It can be observed in the structural dynamic measurement that the transmissibility at pump excitation frequency of the new design has an obvious declination. This validates the feasibility of the improved vibration isolation design.
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