Speckle Pattern Characterisation for High Resolution Digital Image Correlation

Crammond, G.; Boyd, Stephen; Dulieu-Barton, J.M.

doi:10.4028/www.scientific.net/amm.70.261

Cited by 10 publications

(7 citation statements)

References 9 publications

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“…The resulting speckle pattern analysis is meant to determine the quality of the displacement measurement calculated using the 3D-DIC algorithm. In this investigation speckle pattern analyses of the image histogram, a two-dimensional Discrete Fourier transform (2D-DFT), speckle size and distribution [10], mean intensity gradient [12], subset entropy [13], and regional descriptors [14] are calculated for each area of the applied speckle patterns. In the following analysis description, the row and column designation of each pattern shown in figure 2 is maintained.…”

Section: Discussionmentioning

confidence: 99%

“…To calculate a speckle size and distribution, an image morphology technique proposed by Crammond et al [10] is used. From this calculation, the mean size of the speckles in each speckle pattern area is determined and shown in table 2 below.…”

Section: B Quantitative Speckle Pattern Analysismentioning

confidence: 99%

“…It was found that the size of the measurement subset, for a given speckle pattern, influences the accuracy of the measured displacements. Crammond et al [10] examined the effects of image histogram, speckle size and distribution on the measurement error from numerically induced displacements. Schmidt et al [11] experimentally determined an optimal speckle size of 3-5 pixels for a 256 x 256 pixel image.…”

Section: Introductionmentioning

confidence: 99%

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Experimental Investigation of Dynamic out of Plane Displacement Error in 3D Digital Image Correlation

Ehrhardt

Beberniss

2013

54th AIAA/ASME/ASCE/AHS/ASC Structures, Structural Dynamics, and Materials Conference

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With the development and implementation of digital image correlation (DIC) in static and dynamic experimentation, a deeper understanding of the variation of measurement error due to the experimental setup is sought. In this investigation, dynamic rigid body motion is measured using two high speed digital CMOS cameras paired with 3D digital image correlation (3D-DIC), a single point laser vibrometer, and a single axis accelerometer. To determine measurement error, a comparison is made between the measured displacement, velocity, and acceleration in the frequency domain. Prior to dynamic testing, characterization experiments with no motion were performed to determine potential sources of noise in a static environment. It was shown that the camera cooling fans and source of lighting can contribute to measurement noise. Dynamic experiments were designed to investigate the potential effect camera angle, sampling rate, and shutter speed have on measurement error. In addition to the 3D-DIC setup, speckle patterns with varying size, distribution, and randomness were investigated. Results show that the 3D-DIC setup and speckle pattern characteristics can affect the measurement error and measurement quality

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Section: Discussionmentioning

confidence: 99%

Section: B Quantitative Speckle Pattern Analysismentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 1 more Smart Citation

Experimental Investigation of Dynamic out of Plane Displacement Error in 3D Digital Image Correlation

Ehrhardt

Beberniss

2013

54th AIAA/ASME/ASCE/AHS/ASC Structures, Structural Dynamics, and Materials Conference

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“…3. Although it is difficult to make such a uniform pattern that would cause an erroneous hit, it is worthwhile to make the pattern as random as possible [15,16,17].…”

Section: A) B)mentioning

confidence: 99%

Speckle pattern optimization for DIC technologies

Szalai

Dogossy

2021

Acta Tech. Jaurinensis

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This paper contains the relation between speckle pattern and Digital Image Correlation (DIC). The most important advance in experimental mechanics has been DIC since the strain gage. The deformation (strain) of an object can be visualized by DIC. Among all scientific fields, the DIC Technologies have seen a dynamic increase. The relationship between the paint and the sample - as the patterns mediate the deformation to the cameras - has been the most important technological issue. In this article the method developed for the detection of isolated particles in alloys is used to characterize the spots, which help the best speckle pattern has determined.

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“…However, most samples on which DIC is used are much smaller and it is necessary to apply dots of micron or submicron size in order to obtain strain pattern results of acceptable quality. Some possible techniques that have been utilized to apply speckle patterns include airbrushing dots of paint onto the specimen (the method ultimately used for this study); spray painting directly from a spray paint can 46 (as will be discussed, this method was tested and rejected for this work); using a straw to blow toner across the surface 47 (also tested and rejected); and printing of a speckle pattern directly onto the sample being tested. 48 There are numerous different ways to calculate the motion of pixels in a DIC problem, many of which can lead to nearly identical answers despite completely different mathematical approaches.…”

Section: Digital Image Correlation For Local Strain Measurementmentioning

confidence: 99%

Three-Dimensional Constitutive Relations of Aligned Carbon Nanotube Polymer Nanocomposites

Handlin

2013

54th AIAA/ASME/ASCE/AHS/ASC Structures, Structural Dynamics, and Materials Conference

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Variable and high volume fraction aligned carbon nanotube (CNT) polymer nanocomposites (A-PNCs) are fabricated by biaxial mechanical densification of the CNTs, followed by polymer infiltration via capillarity-assisted wetting using an aerospace-grade epoxy. These APNCs are mechanically tested in order to determine the full elastic constitutive relations of the material as a function of volume fraction. Prior to this work, only bulk compression or nanomechanical tests have been attempted due to the small size of the samples. Elastic stiffness results derived from optical strain mapping via digital image correlation are in agreement both with prior experimental nanoindentation measurements and finite element calculations that include the effects of waviness of the reinforcing CNT 'fibers'. Results from longitudinal, transverse, and shear directed testing are shown for 0 to ~20% volume fraction aligned CNT reinforcement. Imaging via scanning electron microscopy and micro-computed tomography is used to establish morphology for structure-property relations. These are the first full elastic constitutive relations for non-isotropic aligned-CNT PNCs. Such relations are needed for modeling and understanding hierarchical nanoengineered composite architectures. Recommended future work includes more comprehensive shear sample testing and concerted modeling efforts to relate this experimental work to computational/theoretical studies of the nanocomposite properties as a function of morphology. AcknowledgementsI have received a great deal of help from many individuals without whom it would not have been possible to complete this thesis.First and foremost, my advisor Professor Brian Wardle has been a fantastic mentor from day one at MIT. He is always available to answer my numerous questions and many times throughout my project offered a new avenue to explore when I felt like I had run into a wall with one approach or another. From familiarizing me with the literature and teaching me the methodology and mindset of a successful researcher and scientist, this project could not have been completed without his guidance.My colleagues in necstlab have been enormously helpful throughout my experiences. Sunny Wicks was always happy to share her enormous expertise in all aspects of the research process, whether dealing with curing epoxy, growing and densifying CNT forests, or more mundane matters like which classes to take or which of the bewildering array of forms at MIT actually need to be filled out. Ethan Parsons provided incalculable help in the aspects of digital image correlation and testing, and taught me a great deal about the mindset of a good scientist. He introduced me to the DIC literature and taught me to use Vic-2D as software that performs digital image correlation rather than a program where I press some buttons and hope that a black box process gives me a logical answer. He also helped to show me the importance of attention to detail-making sure that cameras are parallel to the ground, not 5 degrees from para...

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Speckle Pattern Characterisation for High Resolution Digital Image Correlation

Cited by 10 publications

References 9 publications

Experimental Investigation of Dynamic out of Plane Displacement Error in 3D Digital Image Correlation

Experimental Investigation of Dynamic out of Plane Displacement Error in 3D Digital Image Correlation

Speckle pattern optimization for DIC technologies

Three-Dimensional Constitutive Relations of Aligned Carbon Nanotube Polymer Nanocomposites

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