PERFORMANCE EVALUATION OF THE CORRELATION AND SMOOTHING METHODS OF THE DIGITAL IMAGE CORRELATION AND ITS APPLICATION TO THE OPENING SPECIMENS

摘要

Digital Image Correlation (DIC) has been known as one of the non-intrusive experimental methods in solid mechanics. This method has several advantages such as full-field examination, robustness of the algorithms, and the instantaneous visualization of the results. The key of this method is to find the displacement vectors by using a certain correlation method. In this paper, two correlation methods are performed and evaluated, i.e. cross-correlation and FFT (Fast Fourier Transformation) correlation. Performance of these methods in term of error analysis and processing time wre evaluated. Error analysis was performed by using self-generated artificial images with several desired parameters. The results showed that the cross-correlation has less fluctuation results and more constant accuracy. The average processing time of FFT technique is 64% of the cross correlaton. Smoothing algorithms are applied to the displacement results. The results of the smoothing process are compared to the original one to verify the effect of the algorithms. This smoothing process is the important step if the derivative parameters of the displacements such as stress and strain distribution need to be obtained. The complete DIC algorithms are then applied to measure the displacements of the plate with circular and rectangular opening specimens by using experimental images. The result showed that this technique can produce displacement field with good accuracy.