Digital image correlation strain measurement study based on smoothing displacement gradient field

Digital image correlation (DIC) technology has been widely used in engineering measurement. In the process of DIC strain measurement, the commonly used gradient method and the local least squares method for displacement field fitting often produce large errors. To reduce the strain measurement error and improve the measurement results, a method of local weighted regression smoothing and moving means smoothing for displacement gradient is proposed to measure strain. The simulated Gaussian speckle is generated by a computer, and the reference image is deformed to verify the effect of these two methods, then compared with the gradient and local least squares methods. The results show that the strain field obtained by smoothing the displacement gradient has a good denoising effect, a more accurate solution, a more stable result, and less error.