| Summary: | 碩士 === 淡江大學 === 機械與機電工程學系碩士班 === 104 === This thesis attempted to provide an optimal design of semi-elliptic sound absorption coefficient on the surface of corrugated foam mixed with saturated fluid. Biot’s poroelastic theory was integrated into the study of frequency domain, Galerkin type finite element approach was employed to derive the rigid matrix as well as the force vector of two-dimensional quadrilateral elements, and with the given material parameters and boundary conditions, the mean displacement of fluids and solids on the surface of foam were obtained. Based on the results stated above, the complex dynamic stiffness (CSD) and sound absorption coefficient (SAC) were obtained.
Firstly, analysis method was validated to make sure it was appropriate for this study. The results indicated that the complex dynamic stiffness and sound absorption coefficient on the surface of elliptic border were exactly the same as the results released by previous researchers. Apparently, the finite element frequency domain analysis (FEFDA) employed by this study was sufficient to simulate porous materials’ sound absorption coefficient precisely. Secondly, sequential quadratic programming (SQP) was employed to analyze the optimization of semi-elliptic sound absorption coefficient on the surface of corrugated foam, attempting to find out the optimal sound absorption coefficient of different sectional width ratios (MWR) at low frequency (0~2000Hz), medium frequency (1000~3000Hz), and high frequency (2000~4000Hz), respectively. According to the analysis results, optimal sound absorption coefficient was gained when foam was restricted by same area in which MWR was 0.33, 0.34, and 1.31 at low frequency, medium frequency, and high frequency, respectively.
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