基於雷射散斑攝影與曝光評估演算法於複合材料損傷檢測

Abstract

本文提出使用非接觸式雷射散斑方法結合數位影像相關法對複合材料進行損傷檢測，為了優化本套方法，另外開發曝光評估演算法以及損傷定位法，藉此提高量測精度以及降低實驗架設時間成本。 在傳統的數位影像相關法上，通常都是使用人造散斑作為特徵點來進行分析，但這樣的佈設不僅破壞材料本身美感，在進行量測時更有可能會有散斑剝落的情況發生，本研究使用雷射散斑，透過雷射投射在材料表面，材料表面具有一定的粗糙度，使用攝影設備捕捉雷射從於粗糙表面上散射出的光線，形成的影像即是雷射散斑，本研究即是使用此雷射散斑作為特徵點進行分析。 另外，本研究為了獲得較佳散斑品質，在攝影設備的調控上撰寫一套曝光評估演算法，由於相機具有不同的參數會影響成像品質，透過此演算法協助使用者用最低的時間成本調整影像至最佳影像，藉此保證具有較佳的散斑可供分析，以得到較準確的位移應變場進行進一步的分析；而在判斷損傷位置上，為了避免影像噪點造成誤差帶來的影響，使用損傷定位法可去除誤差外，也可以避免使用者直接觀察應變場所帶來的誤判。本研究更對材料內部的損傷進行研究，探討損傷若是發生於材料內部，本系統是否能夠成功定位損傷位置，藉此擴大可檢測的損傷類型。

This study introduces a non-contact laser speckle method combined with digital image correlation for damage detection in composite materials. To optimize this approach, exposure and damage localization method were developed, aimed at enhancing measurement accuracy and reducing experimental setup time and costs. In traditional digital image correlation, artificial speckles are often used as features for analysis. However, such deployments not only compromise the aesthetics of the material but also increase the likelihood of speckle detachment during measurements. In this research, laser speckles are utilized. A laser is projected onto the material's surface, which possesses a certain level of roughness. The camera captures the laser light scattered from this rough surface, forming the laser speckle pattern used as feature points for analysis. Additionally, to improve speckle quality, this study developed an exposure evaluation algorithm for camera control. Considering different parameters influencing image quality, the algorithm aids users in swiftly adjusting images for optimal quality at minimal time cost. This ensures superior speckle patterns for accurate displacement and strain field analysis. For damage localization, a specialized method avoids noise and error impact, eliminating the need for direct user observation and potential misjudgments. The study also studies internal material damage, exploring the system's capability to localize damage within the material, broadening the range of detectable damage types.