Title page for etd-0627117-211756


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URN etd-0627117-211756
Author Jau-Cho Lin
Author's Email Address No Public.
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Department Mechanical and Electro-Mechanical Engineering
Year 2016
Semester 2
Degree Ph.D.
Type of Document
Language English
Title Design and Experimental Research of Acoustic Cloak in the Air
Date of Defense 2017-07-07
Page Count 166
Keyword
  • acoustic metamaterial
  • acoustic invisibility
  • metamaterial
  • acoustic cloaks
  • transformation acoustic
  • Abstract The issue of random controlling wave propagation is very popular in the research literature. The techniques for controlling wave propagation can avoid unwanted wave disturbance, help control a specific wave to randomly propagate, and hide the object free from detection. The sound insulation performances of a traditional sound proof industrial element are based on the mass density of the object. Therefore, high sound insulation elements always come at the high cost, great volume, and heavy weight. The theories of acoustic cloak and metamaterials driven by new discoveries in recent decades have supplied the potential for developing novel strategies and new technologies in the control of acoustic noise. This study investigated the cloak of air borne acoustic wave based on the recently proposed theories of coordinate transformation and researches the design, fabrication and experimental analysis of acoustic cloak shell for meta-composite material in air applications.
      The material properties of three-dimensional (3D) cloak shell were developed according to the spatial transformation in three directions of a geometry coordinate system. Depending on the derived material properties, the anisotropic material properties of a cloak shell could be obtained. To realize the acoustic cloak, the designed tube-cavity meta-composite structure formulized the layered structure for the cloak shell. Cloak shell structures provide the anisotropic material properties of a cloak shell and control the acoustic wave propagation through its structural geometric design. Both elliptical and circle cloak shells were designed and numerically evaluated herein.
     The analysis of plane waves passing through the elliptical cloak shell explains the effectiveness of the meta-composite material in its acoustic cloaking performance over a frequency range of 800 to 1250 Hz in 1/3 octave band. The results demonstrated that anisotropic properties of the proposed cloak make it possible to alter the direction of acoustic waves propagating from the original path and direct them to travel along a pre-determined path. In addition, the circle cloak shell also provides acoustic invisibility in 1000 Hz. According to the dimension parameters of the cloak shell structure, the full 3D diagram of a meta-composite cloak circle shell was plotted and the real cloak shell specimen was manufactured by the 3D print technique for experimental evaluation. The experiment analyzed the acoustic cloak effect of a circle cloak shell in a semi-anechoic room under a free field environment. Experimental results demonstrate the effectiveness of the circle cloak shell in the air at a design frequency of 1000 Hz. The research results present a way to comply with anisotropic cloak shell for acoustic purposes. These research findings provide new strategies and coating structure design for the physical realization of an invisibility cloak in the air.
    Advisory Committee
  • Jao-Hwa Kuang - chair
  • Mei-Ling Wu - co-chair
  • Shao-Yi Hsia - co-chair
  • Wei-Chih Lin - co-chair
  • Bor-Tsuen Wang - co-chair
  • Jyin-Wen Cheng - co-chair
  • Chi-Hui Chien - co-chair
  • Shiuh-Kuang Yang - advisor
  • Files
  • etd-0627117-211756.pdf
  • Indicate in-campus at 5 year and off-campus access at 5 year.
    Date of Submission 2017-08-10

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