Sound radiation behavior and design of sandwich plates

• Main Authors: Shih, Senrithu, 施恩寶
• Other Authors: Kam, Tai-Yan
• Format: Others
• Language: zh-TW
• Published: 2012
• Online Access: http://ndltd.ncl.edu.tw/handle/02765755132145068401

碩士 === 國立交通大學 === 機械工程學系 === 100 === Flat-panel loudspeaker has become an attractive device for generating sound in the audio industry. The capability of producing smooth frequency response and high sound pressure level is vital to such loudspeaker. Higher bending strength can make frequency response smoother and light-weight panel improve sound pressure level. The thesis applies honeycomb core to fabricate sandwich panel for the loudspeaker. Plain papers of different weights are used to make sandwich plates which can be comparable with the light-weight balsa wood. Execute three point bending test of sandwich beams made of paper to identify the Young’s modulus of face plate and shear modulus of core material. Also execute compression test to identify the Young’s modulus of core material. Substitute the identified material constants into the 2D and 3D finite element models of the sandwich plate to construct the sound pressure level (SPL) curves in the audible frequency domain. Compare the theoretical results with the experiment results to check the correctness of the 2D and 3D models. Then discuss the suitability of two simplified 2D finite element models in predicting accurate SPL curves. The 2D models can greatly shorten the computing time when compared with the 3D model. The thesis discusses how to adjust the parameters of the sandwich plate to produce smoother frequency response and higher sound pressure level. It has been found that the thickness of core material can greatly affect the effective shear modulus Gyz of the sandwich plate. The thickness of core layer can greatly affect the bending strength per unit density and the equivalent density of the plate. An increase of the equivalent density and reduction of strength could be recovered by an increase of thickness of core layer. The thesis studies how to choose the proper design of the honeycomb sandwich panel that can improve the SPL curve of the plate via a numerical simulation approach. Finally, the cause of the local sound valley in the 3000 to 20000Hz range is investigated via the use of one equivalent layer plate model and the elimination of the sound valley is performed via the use of non-hexagonal honeycomb cells.