Effect of High-Frequency Elastic Shearwave Emitted on the Plate with Blocker
碩士 === 國立成功大學 === 土木工程學系碩博士班 === 95 === High frequency shear wave on a flat plate can be an advance approach to improve the structure on the weld and release the residue stress of a machine part. However, the energy of the high frequency wave decays rapidly with increasing distance form the acting p...
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| Format: | Others |
| Language: | zh-TW |
| Published: |
2007
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| Online Access: | http://ndltd.ncl.edu.tw/handle/77289949657990614659 |
| Summary: | 碩士 === 國立成功大學 === 土木工程學系碩博士班 === 95 === High frequency shear wave on a flat plate can be an advance approach to improve the structure on the weld and release the residue stress of a machine part. However, the energy of the high frequency wave decays rapidly with increasing distance form the acting point of vibration actuator. Hence, how to transport the vibration energy to a given location is a problem needed to be solved.
The purpose of this research was to develop an effective method to focus the energy of plane shear wave at a pre-defined position on a flat plate. The behaviors of the high frequency (20kHz) plane shear wave were simulated by finite element analysis (ABACUS). The results show that a fixed reflector can focus the energy to a given location very will. The elliptic reflector focuses the wave energy best than the reflectors with other geometries. The sinusoidal simulation force gives the maximum energy density at the focus, while the rectangular and pulsed force give less energy. The results show the focusing effect by the elliptic reflector is very robust. Even the reflector is designed for a wave length of 7.1 times greater than the true wave length, the energy density at the focus still can be 400 times greater than that of a plate without the reflector.
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