High-Accuracy and High-Efficiency Compensation Method in Two-Dimensional Digital Image Correlation

The traditional two-dimensional (2D) digital image correlation (DIC) method often leads to results without enough accuracy due to the out-of-plane motions of the specimens in the deformation measurements of plate specimens. To remove the effects of the out-of-plane motions, a compensation method for the 2D DIC method has been developed. The compensation method sharply improves the measuring accuracy of the 2D DIC method. However, the existing compensation method often deduces compensation parameters with strong fluctuations. To solve these problems, an improved compensation method is proposed. The proposed method employs an extra single camera calibration to determine the distortion parameters so that the corresponding coefficient matrix is not affected by the experimental noise. For simplicity, the extensometer line measurement is taken as an example to compare the measuring accuracy of the two compensation methods. Static experiments have been carried out to analyze effects of different measuring parameters. Tensile experiments indicate that the measuring results of the improved compensation method are not only comparative with the results measured by the 3D DIC method but also accord with the results of the strain gage. Besides, a real-time extensometer measuring system with a measurement accuracy of 5 mu epsilon at a rate of 28 fps, has been developed.