摘要
電子光斑干涉術(ESPI)與數位影像相關法(DIC)兩種光學量測方法屬於非接觸式的量測技術，可量測到待測物全域性的位移分布，改善應變規鑽孔法無法得到待測物表面全場位移分布的缺點。 PMMA試片楊氏模數較小，試片施加較小負荷即有較大的位移量，符合ESPI在較小負載下可有較小誤差與DIC需在較大的位移下有正確的應變分布，此兩種光學量測方法進行互補，進而得到較佳的位移分布，且在試片經過旋轉或鑽孔後，應力分佈穩定時間較快。因此，發展以電子光斑干涉術結合數位影像相關法，配合旋轉施力機構量測面內位移為本研究重點。 本研究使用一雙軸向施力機構，此機構特點在於額外設置了滑軌，使水平及垂直方向夾治具多一自由度，避免在對試片施予負載時，造成額外的剪應力影響，且施力機構可以旋轉，使得能利用單軸向光路系統來獲得u場與v場的位移。而當給予試片水平方向負荷時，垂直方向夾頭因滑軌作動而自由滑動，可降低因十字形試片拘束於夾頭造成扭曲並造成剪應力的影響。 本研究建立旋轉施力機構實驗流程，解決旋轉定位精度問題，與消除旋轉過程中，會對試片造成移位與應力影響的原因。並加入雷射位移計作為定位參考。成功得到實驗u、v場電子光斑圖之後，運用高斯低通濾波轉換將ESPI干涉條紋影像的雜訊降低後，再由Schmit五步相移法與細胞自制相位重建技術，獲得重建後的連續相位圖，進而得到ESPI量測的試片的位移分布。同樣以DIC分析鑽孔前後的試片面內位移與應變場，並將ESPI與DIC所量測的u、v場位移分布比較探討，互相驗證對於試片位移分布的正確性，確認利用旋轉施力機構所獲得之試片u、v場干涉條紋以及位移分佈是否正確。
並列摘要
Electronic speckle pattern interferometry (ESPI) and Digital image correlation (DIC) belong to non-contact measurement techniques. The both techniques can measure the Full-field displacement, and also can improve the hole-drilling strain gage method, with which only local field instead of full-field strain information on the component surface can be acquired. ESPI fringe patterns revealing in-plane displacement can be obtained on surface under loading. The Young's modulus of PMMA specimen is low, so the specimen exhibits large displacement under small loading. In the case of smaller load, the result of ESPI has smaller error. DIC method is better for larger displacement and strain distribution. Combining ESPI and DIC more accurate strain information can be obtained. After hole drilling, the stress distribution on the PMMA specimen reaches a stable stale easily. This research was therefore focused on developing a method using biaxial loading device and combining ESPI and DIC method to find in-plane displacement in cruciform specimen. This research applied a biaxial loading device. The feature of this device is that additional sliding mechanism provides the horizontal and vertical clamp fixtures with additional degree of freedom. As horizontal loading is applied on specimen, the vertical axial fixtures can move freely to avoid the cruciform specimen from distortion when it is constrained by the fixtures. The biaxial loading device together with integrated rotation device allows the in-plane two dimensions displacement by one biaxial ESPI optical system. This research established an experimental procedure of rotation loading device that allowed a rotational positioning accuracy. A laser displacement sensor was used as positioning reference for the biaxial loading device. After successfully obtained experimental u and v field of ESPI, a Gaussian low pass filter was used to reduce the noise. The continuous ESPI phase map was obtained by the application of Schmit’s Five-steps phase shifting algorithm and Cellular-automata phase unwrapping method. The u and v field displacements were determined by the relative phase change of ESPI. Also the in-plane displacement and strain of the specimen can be measured by DIC. Comparison on displacements obtained from ESPI and DIC were performed and discussed.
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