本論文透過自製的 P(VDF-TrFE) 線聚焦式超聲波換能器，配合所建立的超
聲波散焦(De-Focusing)量測系統，對具有週期性結構的聲子晶體平板進行量測，
觀測蘭姆波於聲子晶體平板中的波傳情形，並搭配有限元素模擬驗證實驗結果。
本論文自行製作的 P(VDF-TrFE) 線聚焦式超聲波換能器，工作頻率落在 20-
40 MHz，具有寬頻的特性，搭配散焦量測系統和 V( f, z )波形處理法，即可進行
寬頻的超聲波波速量測。所製作之 P(VDF-TrFE) 線聚焦式超聲波換具有製作成
本低廉且容易工作的優勢，可於低頻區段取代傳統超聲波顯微鏡來進行材料波速
量測。本論文的測試結果證明: 此套系統用於量測體型材料的表面波和板型材料
的蘭姆波均有相當高的準確度。
利用此套系統，本論文探討蘭姆波於聲子晶體平板中之波傳情形，對具有通
孔型和盲孔型週期結構的二維聲子晶體平板進行量測。經過量測和波形處理，得
到蘭姆波於聲子晶體平板中傳遞的頻率-波速圖，並將其與無結構平板的蘭姆波
進行比對，以得知週期結構對蘭姆波速的影響。除了實驗量測，本論文也對聲子
晶體平板進行有限元素模擬，以單位晶格為模型，搭配對稱和週期性的邊界條件
設置，達成二維聲子晶體平板模擬，最後將模擬結果和實驗結果進行對照，以確
認結果可信度。
關鍵字詞：線聚焦式換能器、散焦量測、聲子晶體

This thesis investigates Lamb waves propagating in phononic crystal plates with periodic hole microstructures. The measurement system is based on self-made P(VDFTrFE) line-focused transducer and its V(f, z) measurement system. Finally, theoretical simulation and analysis are carried out based on finite element method (FEM) to verify corresponding experiment results.
The self-made P(VDF-TrFE) line-focused transducers operate in frequency range of 20-40 MHz, which are quite broadband. The transducers can be used for ultrasound wave velocity measurement along with the V(f, z) measurement system and V(f, z) waveform processing method. The transducer is inexpensive and easy to fabricate is comparison with conventional acoustic microscopy, and hence can be a substitute of acoustic microscopy for weave velocity measurements in low frequency domain. The measurement system is applied to measure both surface waves of bulk materials and Lamb waves of plate materials. The experimental results show good accuracy in broadband wave velocity measurements.
The Lamb wave measurements are carried out on phononic crystal plates, which are stainless steel plates containing either arrayed through-holes or arrayed blind-holes. Dispersion curves of Lamb wave on these phononic crystal plates are experimentally determined through defocusing measurements and waveform processing. The effects on Lamb wave propagation caused by arrayed and periodic hole-structures in the plates are studied. Simulation model based on unit cell and symmetric/periodic boundary conditions is adopted to simulate Lamb waves in two-dimensional phononic crystal plates. In the end, the simulation results are compared with the experimental ones to for understanding the wave propagation characteristics of Lamb waves in photonic plates.
Keywords: line-focused transducer, de-focusing measurement, phononic crystal

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