Abstract
Microscopic and Macroscopic Measurements of Poisson’s Ratio of ASTM B557M Using Digital Image Correlation and Local Search Algorithm
Highlights
The precision measurement of biaxial strain and Poisson’s ratio is crucial for monitoring the mechanical properties of a specimen under tensile testing
Conventional strain gauges mainly measure the elastic deformation and are unable to derive (a) biaxial strain or (b) Poisson’s ratio associated with plastic deformations.(1) In contrast, digital image correlation (DIC) is an optical metrology ideally suited to measurement in industrial applications.(2) The fact that DIC enables multiscale measurement has led to its wide adoption in experimental mechanics,(3) composite structures,(4) and reinforced concrete.(5) Advances in hardware and software have lowered the requirements for the execution of DIC calculations from clusters of highperformance computers to personal and laptop computers
Current electronic devices provide high performance and compact size. They can run multiple threads for parallel processing,(9) thereby facilitating the numerical computation [zero-mean normalized cross-correlation (ZNCC)] required for DIC.(10) Pioneering researchers have reduced the mathematical complexity of image correlation and enhanced the computational efficiency of image-tracking algorithms.(11) The DIC program developed in this study uses ZNCC for pixel resolution in conjunction with a numerical gradient to enable subpixel resolution
Summary
The precision measurement of biaxial strain and Poisson’s ratio is crucial for monitoring the mechanical properties of a specimen under tensile testing. Traditional metrologies use two strain gauges associated with the vertical and horizontal directions to measure biaxial strain, from which the Poisson’s ratio of deformed specimens is derived. Current electronic devices provide high performance and compact size They can run multiple threads for parallel processing,(9) thereby facilitating the numerical computation [zero-mean normalized cross-correlation (ZNCC)] required for DIC.(10) Pioneering researchers have reduced the mathematical complexity of image correlation and enhanced the computational efficiency of image-tracking algorithms.(11) The DIC program developed in this study uses ZNCC for pixel resolution in conjunction with a numerical gradient to enable subpixel resolution. We present a brief introduction regarding DIC and the features of precision measurement related to the biaxial strain and Poisson’s ratio of large deformations.
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