Li Chenzhuo, Luo Haojian, Pan Bing
Institute of Solid Mechanics, School of Aeronautic Science and Engineering, Beihang University, Beijing 100191, China.
Rev Sci Instrum. 2020 Oct 1;91(10):105106. doi: 10.1063/5.0013496.
High-throughput measurement of thermal deformation and determination of coefficient of thermal expansion (CTE) using a high-resolution digital single lens reflex (DSLR) camera and digital image correlation (DIC) is described. To mitigate the mosaic effect caused by the Bayer filter of DSLR cameras, a color image pre-processing method, which adjusts the brightness and equalizes the color channels of the raw image, is carried out. In addition, a Gaussian pre-filtering step is adopted for denoising the images captured with DSLR cameras to enhance the subpixel registration accuracy. Then, by processing the recorded images using the state-of-the-art DIC algorithm, full-field displacements and strains can be determined. Compared with conventional industrial cameras, a DSLR camera offers not only portability, compactness, and economy but also much higher resolution of recorded images, allowing CTE characterization with higher throughput. Real experiments, including a verification experiment of the color image pre-processing technique, a benchmark CTE determination of Al alloy, and a high-throughput CTE determination of 15 samples of three different metals, validated the feasibility and accuracy of the proposed technique. The proposed method is cost-effective and time-saving, showing great potential in the high-throughput CTE measurement and other high-throughput strain measurement scenarios.
本文描述了使用高分辨率数码单反（DSLR）相机和数字图像相关（DIC）技术对热变形进行高通量测量以及热膨胀系数（CTE）的测定。为减轻DSLR相机拜耳滤镜造成的马赛克效应，采用了一种彩色图像预处理方法，该方法可调整原始图像的亮度并均衡颜色通道。此外，采用高斯预滤波步骤对DSLR相机拍摄的图像进行去噪，以提高亚像素配准精度。然后，通过使用先进的DIC算法处理记录的图像，可以确定全场位移和应变。与传统工业相机相比，DSLR相机不仅具有便携性、紧凑性和经济性，而且记录图像的分辨率更高，从而能够以更高的通量进行CTE表征。实际实验，包括彩色图像预处理技术的验证实验、铝合金的基准CTE测定以及三种不同金属的15个样品的高通量CTE测定，验证了所提技术的可行性和准确性。所提方法具有成本效益且节省时间，在高通量CTE测量和其他高通量应变测量场景中显示出巨大潜力。
