Investigating The Effect Of A Speckle Pattern On Measurement Uncertainty In A Three-Dimensional Digital Image Correlation (3D-Dic) System

Three-dimensional digital image correlation (3D-DIC) is an imaging technique that uses cameras to measure the surface displacement of a speckled specimen under test loading from which surface strains can be derived. This study aims to investigate the effect of the speckle pattern on the uncertainty in the measurement system. A Monte-Carlo experimental approach is used by uniformly displacing a known speckle pattern by a prescribed amount. This allows the coupled influence of the image collection system, processing and post-processing to be investigated. To minimize the uncertainty of a speckle pattern, it was determined that uniform speckle size of 5-pixel diameter speckles at a density of one speckle per 20 square-pixels is optimal. The methods used to measure and analyze the speckle pattern effects on measurement uncertainty are presented.