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Title: Global and local coordinates in digital image correlation

Abstract

Digital image correlation (DIC) is commonly used to measure specimen displacements by correlating an image of a specimen in an undeformed or reference configuration and a second image under load. To establish the correlation between the images, numerical techniques are used to locate an initially square image subset in a reference image. In this process, choosing appropriate coordinates is of fundamental importance to ensure accurate results. Both global and local coordinates can be used in shape functions. However, large rigid body rotations and deformations are accurately obtained by using global rather than local shape functions. In addition, points located after displacement may not be at an integer pixel distance from the original position. Hence subpixel displacement estimation methods such as interpolation or fitting of correlation coefficients are essential. A solution using the least-squares method is employed by choosing proper coordinates, and the feasibility of using local coordinates is demonstrated and validated with a mathematical model. Both simulated and experimental results show that the proper choice of coordinates does ensure the reliability and improve the accuracy of measurements in DIC.

Authors:
; ; ;
Publication Date:
OSTI Identifier:
20929660
Resource Type:
Journal Article
Resource Relation:
Journal Name: Applied Optics; Journal Volume: 46; Journal Issue: 7; Other Information: DOI: 10.1364/AO.46.001050; (c) 2007 Optical Society of America; Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSICS; ACCURACY; COORDINATES; CORRELATIONS; DEFORMATION; FUNCTIONS; IMAGE PROCESSING; IMAGES; INTERPOLATION; LEAST SQUARE FIT; MATHEMATICAL MODELS; MORPHOLOGY; RELIABILITY; ROTATION; SIGNALS

Citation Formats

Sun Wei, Quan Chenggen, Tay, C.J., and He Xiaoyuan. Global and local coordinates in digital image correlation. United States: N. p., 2007. Web. doi:10.1364/AO.46.001050.
Sun Wei, Quan Chenggen, Tay, C.J., & He Xiaoyuan. Global and local coordinates in digital image correlation. United States. doi:10.1364/AO.46.001050.
Sun Wei, Quan Chenggen, Tay, C.J., and He Xiaoyuan. Thu . "Global and local coordinates in digital image correlation". United States. doi:10.1364/AO.46.001050.
@article{osti_20929660,
title = {Global and local coordinates in digital image correlation},
author = {Sun Wei and Quan Chenggen and Tay, C.J. and He Xiaoyuan},
abstractNote = {Digital image correlation (DIC) is commonly used to measure specimen displacements by correlating an image of a specimen in an undeformed or reference configuration and a second image under load. To establish the correlation between the images, numerical techniques are used to locate an initially square image subset in a reference image. In this process, choosing appropriate coordinates is of fundamental importance to ensure accurate results. Both global and local coordinates can be used in shape functions. However, large rigid body rotations and deformations are accurately obtained by using global rather than local shape functions. In addition, points located after displacement may not be at an integer pixel distance from the original position. Hence subpixel displacement estimation methods such as interpolation or fitting of correlation coefficients are essential. A solution using the least-squares method is employed by choosing proper coordinates, and the feasibility of using local coordinates is demonstrated and validated with a mathematical model. Both simulated and experimental results show that the proper choice of coordinates does ensure the reliability and improve the accuracy of measurements in DIC.},
doi = {10.1364/AO.46.001050},
journal = {Applied Optics},
number = 7,
volume = 46,
place = {United States},
year = {Thu Mar 01 00:00:00 EST 2007},
month = {Thu Mar 01 00:00:00 EST 2007}
}
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