Developing digital image correlation techniques for using water immersion to improve strain field measurement in micro-scale

Light reflection on the surface of test specimen leads to analyse error of strain measurement by using digital image correlation (DIC) technique in micro-scale test. In this study, water immersion is firstly proposed to combine with DIC technique to reduce the influence of light reflection on the surfaces of measured sample in a micro-scale experiment. Then, all test images are transformed into two dimensional K-space to compare the influence degree of light reflection on the various configurations of test specimens. Furthermore, the effects of light projection direction and the angle of light source are investigated into the analysis accuracy of strain measurement for the various configurations of test specimens. The test and analysis results from K-space indicate that the frequency signals of images, measured from test samples, observed in air are higher than the results from this proposed method. Otherwise, no matter how the variation of the light projection direction and the angle of light source are, the standard deviations of strain from this proposed method are diminished, reduced to below 0.001. The analysis accuracies of strain analysis for using water immersion method have been verified.