Intuitive Interface for the Quantitative Evaluation of Speckle Patterns for Use in Digital Image and Volume Correlation Techniques

Abstract

Digital image correlation (DIC) and digital volume correlation (DVC) are powerful means of resolving local kinematic descriptions of material deformation fields across a variety of material and testing platforms. Their spatial resolution, sensitivity, and accuracy depend in large part on the quality of the intrinsic material speckle pattern. Traditional evaluation of speckle pattern quality, or subset intensity distribution, relies on a set of wellcharacterized experimental measurements including rigidbody translation and rotation. In order to provide a significantly faster quantitative evaluation process on whether a particular speckle pattern is suitable for DIC or DVC purposes, we present a simple, intuitive DIC and DVC speckle pattern graphical user interface (GUI) tool programmed in matlab. This tool assesses the DIC and DVC robustness of usersupplied speckle patterns via a twostep procedure: The first step involves warping the specific image according to a set of analytically prescribed deformation functions. The second step involves correlating the analytically warped and reference image pairs to recover the prescribed displacement field and its quantitative comparison to the prescribed warping function. Since the accuracy and precision of the recovered solution depend on the characteristics of the intensity distributions encoded in the image, this approach allows for a simple, yet effective, quantification procedure of the correlation suitability in the supplied image speckle pattern. In short, this procedure allows for fast and quantitative evaluation of the quality and suitability of a given speckle pattern to be used in DIC and DVC applications without the need of performing timeconsuming experimental measurements. As such, we hope that this free tool will benefit anyone interested in performing DICor DVCbased kinematic measurements.