Multi-mirror-aided digital image correlation for internal and external panoramic deformation measurement

This study developed a variable-attitude multi-mirror-assisted digital image correlation method for realizing the simultaneous measurement of panoramic deformation inside and outside a tubular structure. The setup consists of a co-axial imaging system containing three variable-attitude optical mirrors and the necessary cold light source. The arrangement and attitude adjustment of the mirrors are the key to realizing panoramic imaging, thus enabling simultaneous imaging of the interior and exterior surfaces of a pipe. The co-axial acquisition system ensures that both cameras can observe all areas of interest, thereby improving the comprehensiveness and accuracy of the measurements. The acquired images were used for calculations, which involved coordinate conversion, to provide for the panoramic morphology of the interior and exterior surfaces. Additionally, the images exhibit three-dimensional deformation distributions. To verify the effectiveness and accuracy of the proposed method, two experiments on morphology and deformation were performed. The experimental results show that the method can accurately measure the morphology and deformation of the interior and exterior surfaces of the pipe and effectively identify and quantify the strain concentration areas in the presence of defects. In addition, the experiments demonstrated the stability and repeatability of the system under different loading conditions, thus providing a powerful tool for the mechanical analysis and defect detection of tubular structures.