Evaluation and improvement of digital image correlation uncertainty in dynamic conditions

Even though Digital Image Correlation (DIC) is a widely used optical full field measurement method, it still needs further performance investigations, when it comes to dynamic conditions. In dynamics, dealing with a moving target, causes a motion effect (i.e. blurring) on the acquired images. This factor is an important source of uncertainty that needs to be quantified. Therefore, the present study aims to evaluate and improve DIC’s uncertainty in dynamic conditions. The study focuses on 2D DIC. In the case of 3D DIC similar problems will arise and therefore, a complete understanding of two dimensional conditions will be of great help to further studies which deal with 3D conditions. The whole work can be divided in to two main parts. In the first part, two different methods to simulate the motion effect on a reference image are proposed, discussed and validated. These methods allow simulating the acquired images in a real dynamic test and estimating the measurement uncertainty caused by the motion effect. The validation was performed by conducting several harmonic vibration tests. The results show good agreement between the experiments and the simulations, proving the proposed technique to be an effective method for motion induced uncertainty estimation. In the second part of the study a numerical technique was proposed to estimate the motion effect present in an acquired image. This technique gives two main advantages. First of all, since the motion effect itself has a known influence on the uncertainty of measurement (first part of the study), we will be able to predict the DIC’s uncertainty by just having the acquired image and the static one. Furthermore, this numerical technique will be used to improve the uncertainty of DIC in dynamic applications. In this way the bias error and the uncertainty of the measurements will be considerably decreased.