In-plane strain measurement by digital image correlation

Hung, Po-Chih; Voloshin, Arkady

doi:10.1590/s1678-58782003000300001

Cited by 160 publications

(94 citation statements)

References 13 publications

(16 reference statements)

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“…For a steep-strain gradient in a strain fields, smoothing can lead to erroneous results [19]. At a subset size of 81×81 pixels, local distortions and deviations in the speckle pattern (size and distribution) were considered to be the major contributions to the measurement errors [20]. A consequence of this was that the strain amplitude and gradients between phases may be affected.…”

Section: Dic Analysismentioning

confidence: 99%

Etching Method to create a Random Speckle Pattern on Semi-Solid Cast A356 Aluminium for DIC in-situ strain measurements

Segolle

Santos

Kasvayee

et al. 2017

jcme

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Aluminum semi-solid casting is constantly evolving, as it offers a combination of reduced shrinkage porosity and gas entrapment defects together with high productivity and an extended die-life. The relationship between the microstructure and stress-strain behavior is not well-understood due to its non-conventional microstructure. In-situ tensile testing, combined with optical microscope and Digital Image Correlation (DIC), has been used for local strain distribution measuements in cast irons. The critical capability was an etching technique to generate a micro-scale random speckle pattern with a sufficiently high speckle density to enable the sufficient spatial resolution of displacement and strain. The current paper focuses on the development of a pit etching procedure for the semi-solid cast A356 aluminum alloy to study local strain accommodation on the microstructure during tensile loading. The critical challenge of this procedure was the generation of homogeneously distributed pits on both the primary aluminum and eutectic regions. Therefore, a heated solution used for wet-etch aluminum in microfabrication was modified as well as a process adapted to generate pits with suitable characteristics. In-situ tensile tests were performed attached to an optical microscope to record the microstructure and displacements during loading. DIC software was used for analysis. The procedure was validated through a comparison between the resulting Young´s moduls using standard tensile testing and the DIC process on the speckle pattern generated. A good fit between the two methods for Young´s modulus was found. The spatial resolution obtained was, however, not sufficient to fully resolve the strain gradients in the microstructure, but it did reveal large strain variations in the microstructure.

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Section: Dic Analysismentioning

confidence: 99%

Etching Method to create a Random Speckle Pattern on Semi-Solid Cast A356 Aluminium for DIC in-situ strain measurements

Segolle

Santos

Kasvayee

et al. 2017

jcme

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“…In 2003, Hung et al [29] presented a peak-finding algorithm known as Fast and Simple (FAS) for measurement of the surface deformation in two dimensions. This algorithm was developed to reduce the computational time required by the Newton-Raphson method.…”

Section: Improvement Of 2d-dic Algorithms Regarding Their Computationmentioning

confidence: 99%

A Review of Surface Deformation and Strain Measurement Using Two-Dimensional Digital Image Correlation

Khoo¹,

Karuppanan²,

Tan³

2016

Metrology and Measurement Systems

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Among the full-field optical measurement methods, the Digital Image Correlation (DIC) is one of the techniques which has been given particular attention. Technically, the DIC technique refers to a non-contact strain measurement method that mathematically compares the grey intensity changes of the images captured at two different states: before and after deformation. The measurement can be performed by numerically calculating the displacement of speckles which are deposited on the top of object's surface. In this paper, the Two-Dimensional Digital Image Correlation (2D-DIC) is presented and its fundamental concepts are discussed. Next, the development of the 2D-DIC algorithms in the past 33 years is reviewed systematically. The improvement of 2D-DIC algorithms is presented with respect to two distinct aspects: their computation efficiency and measurement accuracy. Furthermore, analysis of the 2D-DIC accuracy is included, followed by a review of the DIC applications for two-dimensional measurements.

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“…There is a need for automated inspection techniques to interrogate structural components over time-dependent processes, with submillimetre accuracies while also adhering to safety concerns [3,4]. Digital Image Correlation (DIC) is an optical-based remote sensing technology in which digital images before and after loading are compared using automated computer algorithms in order to determine changes in position or deformation [5][6][7]. DIC has been regarded as a powerful technique in the field of experimental solid mechanics providing a low-cost approach for surface deformations, displacement field, strain and stress distributions [8][9][10].…”

Section: Introductionmentioning

confidence: 99%

Improved 2D Digital Image Correlation Method for Displacement and Deflection Measurements of Structural Beams

Oats¹,

Dai²

2017

MCSE

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Abstract. Digital imaging correlation (DIC) is an innovative approach for evaluating full-field mechanical deflections and time-dependent responses of structural members. An illustration of 2D DIC is shown for a rigid body translation of a small-scale steel beam. This paper presents improvements in deployment of 2D DIC for evaluating mechanical behaviors and responses of structural beam members. Improvement considerations regarding image resolution and speckle correlation design were emphasized for observing flexural behavior of steel and timber structural beams. A suggestive guideline for focal length configuration for observing displacements with 2D DIC and a contrasting speckle design emphasizing physical pixel sizing was presented. The DIC displacements were converted to physical scale measurements capturing within 1% error differences and subpixel accuracies when compared to traditional measuring devices and numerical modeling. DIC enabled detection of mid and full span deflection distribution in addition to time-dependent displacements advocating for DIC's versatility for structural beam evaluations.

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In-plane strain measurement by digital image correlation

Abstract: This paper presents a "fast and simple" (FAS) detection algorithm based on the digital

Cited by 160 publications

References 13 publications

Etching Method to create a Random Speckle Pattern on Semi-Solid Cast A356 Aluminium for DIC in-situ strain measurements

Etching Method to create a Random Speckle Pattern on Semi-Solid Cast A356 Aluminium for DIC in-situ strain measurements

A Review of Surface Deformation and Strain Measurement Using Two-Dimensional Digital Image Correlation

Improved 2D Digital Image Correlation Method for Displacement and Deflection Measurements of Structural Beams

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