Applications of digital-image-correlation techniques to experimental mechanics
About: This article is published in Experimental Mechanics.The article was published on 1985-09-01. It has received 2002 citations till now. The article focuses on the topics: Digital image & Digital image correlation.
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TL;DR: In this article, a review of the 2D digital image correlation (2D DIC) technique for displacement field measurement and strain field estimation is presented, and detailed analyses of the measurement accuracy considering the influences of both experimental conditions and algorithm details are provided.
Abstract: As a practical and effective tool for quantitative in-plane deformation measurement of a planar object surface, two-dimensional digital image correlation (2D DIC) is now widely accepted and commonly used in the field of experimental mechanics. It directly provides full-field displacements to sub-pixel accuracy and full-field strains by comparing the digital images of a test object surface acquired before and after deformation. In this review, methodologies of the 2D DIC technique for displacement field measurement and strain field estimation are systematically reviewed and discussed. Detailed analyses of the measurement accuracy considering the influences of both experimental conditions and algorithm details are provided. Measures for achieving high accuracy deformation measurement using the 2D DIC technique are also recommended. Since microscale and nanoscale deformation measurement can easily be realized by combining the 2D DIC technique with high-spatial-resolution microscopes, the 2D DIC technique should find more applications in broad areas.
2,530 citations
TL;DR: The importance of surface chemistry and cell type for interpretation of nanoparticle cytotoxicity studies is illustrated and a relatively unusual live cell application with gold nanorods is described.
Abstract: Gold, enigmatically represented by the target-like design of its ancient alchemical symbol, has been considered a mystical material of great value for centuries. Nanoscale particles of gold now command a great deal of attention for biomedical applications. Depending on their size, shape, degree of aggregation, and local environment, gold nanoparticles can appear red, blue, or other colors. These visible colors reflect the underlying coherent oscillations of conduction-band electrons (“plasmons”) upon irradiation with light of appropriate wavelengths. These plasmons underlie the intense absorption and elastic scattering of light, which in turn forms the basis for many biological sensing and imaging applications of gold nanoparticles. The brilliant elastic light-scattering properties of gold nanoparticles are sufficient to detect individual nanoparticles in a visible light microscope with ∼102 nm spatial resolution. Despite the great excitement about the potential uses of gold nanoparticles for medical diag...
1,689 citations
TL;DR: Ncorr is an open-source subset-based 2D DIC package that amalgamates modern DIC algorithms proposed in the literature with additional enhancements and several applications of Ncorr that both validate it and showcase its capabilities are discussed.
Abstract: Digital Image Correlation (DIC) is an important and widely used non-contact technique for measuring material deformation. Considerable progress has been made in recent decades in both developing new experimental DIC techniques and in enhancing the performance of the relevant computational algorithms. Despite this progress, there is a distinct lack of a freely available, high-quality, flexible DIC software. This paper documents a new DIC software package Ncorr that is meant to fill that crucial gap. Ncorr is an open-source subset-based 2D DIC package that amalgamates modern DIC algorithms proposed in the literature with additional enhancements. Several applications of Ncorr that both validate it and showcase its capabilities are discussed.
1,184 citations
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TL;DR: In this article, a general presentation of the extraction of displacement fields from the knowledge of pictures taken at different instants of an experiment is given, and different strategies can be followed to achieve a sub-pixel uncertainty.
Abstract: The current development of digital image correlation, whose displacement uncertainty is well below the pixel value, enables one to better characterise the behaviour of materials and the response of structures to external loads. A general presentation of the extraction of displacement fields from the knowledge of pictures taken at different instants of an experiment is given. Different strategies can be followed to achieve a sub-pixel uncertainty. From these measurements, new identification procedures are devised making use of full-field measures. A priori or a posteriori routes can be followed. They are illustrated on the analysis of a Brazilian test.
772 citations
TL;DR: A general presentation of the extraction of displacement fields from the knowledge of pictures taken at different instants of an experiment is given, and different strategies can be followed to achieve a sub-pixel uncertainty.
Abstract: The current development of digital image correlation, whose displacement uncertainty is well below the pixel value, enables one to better characterise the behaviour of materials and the response of structures to external loads. A general presentation of the extraction of displacement fields from the knowledge of pictures taken at different instants of an experiment is given. Different strategies can be followed to achieve a sub-pixel uncertainty. From these measurements, new identification procedures are devised making use of full-field measures. A priori or a posteriori routes can be followed. They are illustrated on the analysis of a Brazilian test.
764 citations
Cites methods from "Applications of digital-image-corre..."
...The computation of a cross-correlation can be performed either in the original space [26, 35] or in the Fourier space [36–38] by using fast Fourier transforms (FFT) f g 1⁄4 lFFT 1 FFTðf ÞFFTðgÞ ; (8)...
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References
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01 Jan 1934
TL;DR: The theory of the slipline field is used in this article to solve the problem of stable and non-stressed problems in plane strains in a plane-strain scenario.
Abstract: Chapter 1: Stresses and Strains Chapter 2: Foundations of Plasticity Chapter 3: Elasto-Plastic Bending and Torsion Chapter 4: Plastic Analysis of Beams and Frames Chapter 5: Further Solutions of Elasto-Plastic Problems Chapter 6: Theory of the Slipline Field Chapter 7: Steady Problems in Plane Strain Chapter 8: Non-Steady Problems in Plane Strain
20,724 citations
TL;DR: An improvement of the resolution by one decimal wotild require a correction of the objective to four decimals, a practically hopeless task.
Abstract: IT is known that the spherical aberration of electron lenses sets a limit to the resolving power of electron microscopes at about 5 A. Suggestions for the correction of objectives have been made ; but these are difficult in themselves, and the prospects of improvement are further aggravated by the fact that the resolution limit is proportional to the fourth root of the spherical aberration. Tnus an improvement of the resolution by one decimal wotild require a correction of the objective to four decimals, a practically hopeless task.
3,899 citations
TL;DR: An improved digital correlation method is presented for obtaining the full-field in-plane deformations of an object by numerically correlating a selected subset from the digitized intensity pattern of the undeformed object.
1,788 citations
"Applications of digital-image-corre..." refers background in this paper
...As a final note, it should be clear to the numerical analyst that this 'two-parameter' iterative technique will not converge to the exact answers unless the problem is linear; the problem as stated is highly nonlinear due to the square root noted in eq ( 13 )....
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...Together, these four experiments illustrate how the six deformation variables in eq ( 13 ) can be computed to determine the quantities of interest....
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...via eq ( 13 ) to give the first estimates, ( OUoy " and I,-:~-) .Or...
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...In any case, only (u,v) are assumed to vary; then the values of (ul,vl) Computed by maximizing eq ( 13 ) on a subset are our first approximations for the translation of...
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TL;DR: In this paper, the surface displacement components in laser speckle metrology were measured using a digital image scanner interfaced to a computer. Butt et al. used a boundary integral equation method to calculate surface traction in the contour.
Abstract: Digital imaging techniques are utilized as a measure of surface displacement components in laser speckle metrology. An image scanner which is interfaced to a computer records and stores in memory the laser speckle patterns of an object in a reference and deformed configuration. Subsets of the deformed images are numerically correlated with the references as a measure of surface displacements. Discrete values are determined around a closed contour for plane problems which then become input into a boundary integral equation method in order to calculate surface traction in the contour. Stresses are then calculated within this boundary. The solution procedure is illustrated by a numerical example of a case of uniform tension.
1,617 citations