碩士 / 國立臺灣海洋大學 / 輪機工程學系 / 106 / In this thesis we apply the problem of designing passive constrained layer (PCLD) of sandwich structures and the radiation of underwater vehicles. Sandwich structure was first used for the reinforced material of aircraft. Light weight and high strength are characteristics of sandwich structures. And the viscoelastic layer has the features of reducing noise and vibration, insulating heat, absorbing sound, and isolating vibration. Underwater vehicles have the limit of space and weight, so the reinforced material cannot be installed on the entire structure. Therefore, this paper discusses the design and basic characteristics of sandwich materials. First we verify the accuracy and stability of physical characteristics, and then install materials on full-scale underwater vehicles to verify the purpose of reducing vibration efficiency. And this article shows that install damping materials on suitably locations have obvious effect. Further, use numerical methods to compute the coupling of the responses. In order to verify the numerical accuracy and stability, we compared finite element method (FEM) solutions with boundary element method (BEM) solutions. The finite element method has an advantage in computation efficiency of calculate the sound field radiation over boundary element. For solving the inverse of matrix, the coefficient matrix of finite element method is sparse matrix, and the boundary element method is a full matrix. For the analysis sound field characteristics of complex geometric, finite element method has its powerful characteristics. It can simulate the characteristics of waves realistically at low frequencies; Boundary element method have advantage of solving infinite domain problem. Due to the Helmholtz equation automatically satisfies the Sommerfeld radiation condition, boundary element method provide the benefit of dealing with the infinite domain problem. Therefore, the boundary element method and the finite element method are used to solve the frequency of full band in engineering application. Finally, the numerical results show that new sandwich structure has excellent damping characteristics. It can reduce vibration and sound radiation efficiency. Hence, the numerical results have value and its engineering application.
| Identifer | oai:union.ndltd.org:TW/106NTOU5484011 |
| Date | January 2018 |
| Creators | Cheng, Hao-Ting, 鄭皓庭 |
| Contributors | Chen, Yung-Wei, 陳永為 |
| Source Sets | National Digital Library of Theses and Dissertations in Taiwan |
| Language | zh-TW |
| Detected Language | English |
| Type | 學位論文 ; thesis |
| Format | 71 |
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