楔形體導波於具缺陷陵線傳播上模態轉換行為探討

楔形體導波(wedge wave, WW)是沿著楔形體(wedge)尖端傳播的一種彈性波。ASF模態(Antisymmetric Flexural Mode)是楔形體導波最常被研究，其能量集中在頂端大約一個波長的範圍內，本論文設計各種缺陷狀況假設並以超音波探頭量測WW波經過缺陷會有多少振幅反射或穿透，並將係數做個系統化的整理，並探討當ASF接觸到缺陷時，此時模態轉換也會發生，本論文也將探討波在缺陷中的行進速度和性質以及模態轉換的特性，將會設計各種的缺陷大小參數來一一比較。本研究利用FEM動態分析模擬不同缺陷形狀之波傳行為，實驗與有限元素分析的結果發現反射係數隨著缺陷深度增大而上升，穿透係數則隨之下降。得知缺陷深度與反射係數成正比，與穿透係數成反比。

關鍵字

楔形體導波；模態轉換；雷射超音波；缺陷

並列摘要

This study is focused on the propagation conducts of elastic wedge waves (WW) propagating along the tips. Employing a laser ultrasound technique (LUT) and finite element method (FEM) is used to characterize the more specifically, reflection coefficient and transmission coefficients is obtained between the modeled and measured coefficients are modeled and measured for several of defect depths on the wedge tip. In this study, mode conversion phenomenon commonly known in plates are also observed in ASF modes. When ASF modes are partially reflected and partially transmitted, with the RC and TC highly depending on the defect depth.

並列關鍵字

wedge wave ； laser ultrasound technique ； mode conversion

參考文獻

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[5] J. R. Chamuel, “Edge waves along immersed elastic elliptical wedge with range dependent apex angle,” IEEE Ultrasonics Symposium 313-318, 1993.

[7] M. de Billy and A. C. Hladky-Hennion “The effect of imperfections on acoustic wave propagation along a wedge waveguide,” Ultrasonics 37, 413-416 (1999)

[8] M. J. S. Lowe and O. Diligent “Low-frequency reﬂection characteristics of the s0 Lamb wavefrom a rectangular notch in a plate,” J. Acoust. Soc. Am. 111 (1), Pt. 1, Jan. 2002

國際替代計量

楔形體導波於具缺陷陵線傳播上模態轉換行為探討

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