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1
Atkinson, Devan, and Thorsten Hermann Becker. "Stereo Digital Image Correlation in MATLAB." Applied Sciences 11, no. 11 (May 26, 2021): 4904. http://dx.doi.org/10.3390/app11114904.
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Digital Image Correlation (DIC) has found widespread use in measuring full-field displacements and deformations experienced by a body from images captured of it. Stereo-DIC has received significantly more attention than two-dimensional (2D) DIC since it can account for out-of-plane displacements. Although many aspects of Stereo-DIC that are shared in common with 2D DIC are well documented, there is a lack of resources that cover the theory of Stereo-DIC. Furthermore, publications which do detail aspects of the theory do not detail its implementation in practice. This literature gap makes it difficult for newcomers to the field of DIC to gain a deep understanding of the Stereo-DIC process, although this knowledge is necessary to contribute to the development of the field by either furthering its capabilities or adapting it for novel applications. This gap in literature acts as a barrier thereby limiting the development rate of Stereo-DIC. This paper attempts to address this by presenting the theory of a subset-based Stereo-DIC framework that is predominantly consistent with the current state-of-the-art. The framework is implemented in practice as a 202 line MATLAB code. Validation of the framework shows that it performs on par with well-established Stereo-DIC algorithms, indicating it is sufficiently reliable for practical use. Although the framework is designed to serve as an educational resource, its modularity and validation make it attractive as a means to further the capabilities of DIC.
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Suswanto, Budi, Data Iranata, and Yanisfa Septiarsilia. "Analysis of Steel Material Characteristics using Digital Image Correlation (DIC) Method." MEDIA KOMUNIKASI TEKNIK SIPIL 30, no. 1 (September 16, 2024): 95–104. http://dx.doi.org/10.14710/mkts.v30i1.59491.
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The use of steel materials in building construction opens new opportunities for sustainable development, as steel exhibits corrosion resistance, durability, and reliability in terms of strength and ductility. Digital Image Correlation (DIC) is non-contact technique in which digital images of the surface of a test object are captured using high-resolution cameras. This study conducted measurements of strain distribution on the specimen's surface using the DIC method throughout the entire tensile testing process. The study particularly focuses on examining changes in strain distribution during the melting phase and the local deformation phase leading to fracture. In this research, a comparison will be made between the load-displacement curves obtained from experimental laboratory testing and the results analyzed using the DIC method for SS400-grade steel material. Based on the results of the tensile test and DIC analysis that have been conducted, conclusions have been drawn in the research. The tensile test results of SS400 steel material with a thickness of 6 mm, 8 mm, 10 mm, and 12 mm meet the quality requirements in the tested specification standards, and the results of the force-displacement curve between the experimental test results and the DIC method obtained a minimum deviation with a value below 10%,. Therefore, it can be concluded that the DIC method exhibits a reasonably good level of accuracy, making it suitable for validating the results of experimental tests.
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Jarrett, Steven R., Thinh Q. Thai, Lindsey J. Rowley, Weston D. Craig, and Ryan B. Berke. "The Effect of Bit Depth on High-Temperature Digital Image Correlation Measurements." Journal of Sensors 2022 (June 2, 2022): 1–19. http://dx.doi.org/10.1155/2022/6554128.
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Digital Image Correlation (DIC) is a camera-based method of measuring displacement and strain. High-temperature DIC is challenging due to light emitted from the sample which can saturate the image. This effect can be mitigated using optical bandpass filters, but the maximum sample temperature range of DIC remains dependent on the camera and camera settings. Among camera settings, bit depth, also referred to as color depth or number of bits, has received insufficient attention in high-temperature DIC literature. In this work, the effect of bit depth on DIC measurements is investigated both analytically and experimentally. It is shown that if image noise is sufficiently low, then increasing bit depth reduces DIC random error. A new metric, the effective number of bits, is presented to determine the appropriate number of bits for DIC images. Using increased bit depth, reduced exposure time, and low-noise images, the maximum sample temperature for DIC measurements was shown to increase without negatively impacting random error.
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Chen, Jiangping, and Weijun Tao. "Gradient-Based Automatic Exposure Control for Digital Image Correlation." Sustainability 15, no. 2 (January 7, 2023): 1149. http://dx.doi.org/10.3390/su15021149.
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Digital image correlation (DIC) is widely used in material experiments such as ores; the quality of a speckle image directly affects the accuracy of the DIC calculation. This study aims to acquire high-quality speckle pattern images and improve the calculation accuracy and stability. A gradient-based image quality metric was selected to evaluate the image quality, and its validity was verified by a rigid body experiment and a numerical experiment. Based on the maximum image quality metric, an automatic exposure control algorithm and the control procedure were proposed to obtain the optimal exposure time. Finally, nine sets of images with different poses and illuminations were captured, and displacement and strain fields were calculated at the fixed exposure time and the optimized exposure time. The results of the rigid-body motion experiment show that the calculated data at the optimized exposure time is smoother and less noisy, and the error is smaller, which verifies the effectiveness of the exposure control procedure and its algorithm and improves the accuracy and stability of DIC calculation.
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Bailey, Daniel. "Using Digital Image Correlation to Measure Full Field Strain." AM&P Technical Articles 172, no. 10 (October 1, 2014): 23–24. http://dx.doi.org/10.31399/asm.amp.2014-10.p023.
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Abstract Existing strain measurement techniques do not offer enough information about how failures occur, so alternative methods are needed. One technique involves using digital image correlation (DIC) to measure full field strain over the entire material surface. DIC works by capturing a series of images throughout a test and analyzing them afterwards.
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Zhang, Rui. "Elastic Parameters Measurement of Rubber by Digital Image Correlation." Applied Mechanics and Materials 444-445 (October 2013): 1532–35. http://dx.doi.org/10.4028/www.scientific.net/amm.444-445.1532.
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Application of Digital image correlation method (DIC) to measure the elastic modulus and Poisson ratio of rubber under compression is investigated in this paper. Surface images of the rubber surface subjected to various loading were captured using a CCD camera. DIC is subsequently used to obtain displacement field by correlating the images captured before and after deformation, and then the average compression strain is obtained by fitting the displacement using linear plane. The slope of each set of applied stress versus measured strain data is calculated by least-squares linear regression. The elastic modulus and Poisson ratio obtained from DIC, are compared to that determined from the dial gauge, which shows that they are in good accordance with existing data. Experimental results clearly show that DIC is suitable for accurate measurement the elastic modulus of rubber.
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Uzun, Fatih, and Alexander M. Korsunsky. "Digital Image Correlation for Elastic Strain Evaluation during Focused Ion Beam Ring-Core Milling." Journal of Manufacturing and Materials Processing 8, no. 4 (July 4, 2024): 144. http://dx.doi.org/10.3390/jmmp8040144.
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The utilization of the focused ion beam digital image correlation (FIB-DIC) technique for measuring in-plane displacements and the employment of the height digital image correlation (hDIC) technique as two-step DIC for determining both in-plane and out-of-plane displacements within the region of interest are detailed in this paper. Consideration is given to the microscopy data’s measurement scale and resolution to confirming the capability of both techniques to conduct micro-scale correlations with nano-scale sensitivity, thereby making it suitable for investigating the residual elastic strains formed due to processing. The sequential correlation procedure of the FIB-DIC technique has been optimized to achieve a balance between accuracy and performance for correlating sequential scanning electron microscope images. Conversely, the hDIC technique prioritizes the accurate correlation of SEM images directly with the reference state without a sequential procedure and offers optimal computational performance through advanced parallel computing tools, particularly suited for correlating profilometry data related to large-scale displacements. In this study, the algorithm of the hDIC technique is applied as two-step DIC to evaluate the elastic strain relaxation on the surface of a ring-core drilled using focused ion beam. Both techniques are utilized to correlate the same scanning electron microscope images collected during the monitoring of the ring drilling process. A comparison of the correlation results of both techniques is undertaken regarding the quantification of the near-surface residual elastic strains, with the analysis conducted to discern the superior accuracy of the hDIC algorithm. Furthermore, the distinctions between the two techniques are delineated and discussed.
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Giancane, Simone, Riccardo Nobile, Francesco W. Panella, and Vito Dattoma. "Damage Evolution of Composite Laminates with Digital Image Correlation." Key Engineering Materials 452-453 (November 2010): 377–80. http://dx.doi.org/10.4028/www.scientific.net/kem.452-453.377.
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DIC (Digital Image Correlation) based methodology gives full field measure of the displacement using a well defined algorithm for matching the images of loaded and load free component, so that displacement in a plane can be evaluated for a certain number of grid reference points on the analysed surface. In this work, the authors present an application of DIC technique to analyse fatigue damage phenomena in two notched GFRC laminates under tensile load. Damage analysis based on optical DIC technique has been performed to detect the damaged areas on the specimen surface. The damage evolution and failure mechanism has been followed monitoring two parameters: the local hysteresis area of stress-strain cycles, the local stiffness variation.
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Mousa, Mohammed Abbas, Mustafasanie M. Yussof, Lateef N. Assi, and SeyedAli Ghahari. "A Pre-Process Enhanced Digital Image Correlation Approach for Smart Structure Monitoring." Infrastructures 7, no. 10 (October 18, 2022): 141. http://dx.doi.org/10.3390/infrastructures7100141.
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This research provides a practical guideline for Digital Image Correlation (DIC) data variations minimization in structural engineering through simple image processing techniques. The main objective of this research is to investigate the Pixel Averaging (P.A.) effect on the differential strain Diff(εx) variations. Three concrete arches were tested with three-point bending using the DIC technique for strain measurements. The measured strains are obtained through two virtual horizontal extensometers in the middle of each arch. The Diff(εx) was selected to avoid other 2D-DIC issues, such as the sample-camera out-of-plane movement. Three image cases, namely, one, ten, and twenty averaged images, were used for DIC analysis of each arch. The conditions of each image case are assessed by computing the Diff(εx) variance and the linear least square criterion (R2) between the two extensometers. The second objective is to examine the speckles’ dilation effects on the speckle pattern density and surface component quality utilizing the Image Erode (I.E.) technique. The (P.A.) technique provided consistent differential strain Diff(εx) values with a variance reduction of up to (90%) when averaged images were used. The (R2) has considerably increased (from 0.46, 0.66, 0.91 to 0.90, 0.96, 0.99), respectively, for the three samples. Moreover, the (I.E.) technique provided qualitatively denser speckles with a highly consistent DIC surface component.
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Lim, Chhoung, Yeongseok Jeong, Suchart Limkantanyu, and Minho Kwon. "Strain Measuring of Composite Grid Using Digital Image Correlation." Advances in Materials Science and Engineering 2022 (April 14, 2022): 1–12. http://dx.doi.org/10.1155/2022/6041887.
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Digital Image Correlation (DIC) is a new advanced technique for measuring the deformation of a specimen using high-resolution images. It has been used by numerous researchers since it can measure the deformation of specimens without interference because it is contactless. Moreover, the DIC technique can be applied to any materials to which normal measuring equipment is difficult to attach such as Fiber-Reinforced Polymer (FRP) grid in this paper, undulated and small surfaces. The DIC technique is easy to set up and provides reliable results compared to conventional equipment like a strain gauge. Although it is good, its associated equipment is too expensive to be readily affordable. Hence, this paper uses an open-source DIC program called Ncorr that works in MATLAB to analyze deformations of six FRP grids from direct tensile tests by comparing their results to the results from a strain gauge. Young’s modulus—calculated from ASTM 3039, ACI 440-3R-04, and regression analysis—of each specimen will be used for comparison. The results show that the difference between Young’s modulus from DIC and strain gauge is <5% if the stress–strain graph of data from the strain gauge is perfectly linear without straying.
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Crammond, G., S. W. Boyd, and Janice M. Dulieu-Barton. "Speckle Pattern Characterisation for High Resolution Digital Image Correlation." Applied Mechanics and Materials 70 (August 2011): 261–66. http://dx.doi.org/10.4028/www.scientific.net/amm.70.261.
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Digital image correlation (DIC) is an optical technique for full field deformation measurement. The spatial resolution and precision of the measurements are limited by the number of pixels within the image. The use of magnifying optics provides greater spatial resolution images, enabling smaller displacements to be observed with greater accuracy. Increasing the magnification of an image significantly changes the appearance of the non-periodic, stochastic speckle pattern which provides the grey scale contrast necessary for the image correlation method. In the paper a methodology is developed to evaluate the properties of different speckle pattern types under a range of resolutions up to 705 pixel / mm. Numerical deformation of the patterns is also undertaken to evaluate how the changes in the pattern properties affect the accuracy of the DIC measurements.
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Wang, Lu, Guangyan Liu, Tongzhen Xing, Haibin Zhu, and Shaopeng Ma. "Boundary Deformation Measurement by Mesh-Based Digital Image Correlation Method." Applied Sciences 11, no. 1 (December 23, 2020): 53. http://dx.doi.org/10.3390/app11010053.
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Digital image correlation (DIC) is a popular photomechanics method for deformation measurement. The conventional subset-based DIC method obtains the displacement vectors at the subset centers, but cannot calculate the deformation on the specimen edges, which may contain very useful information because specimens usually have greater deformation on edges, especially on curved edges due to stress concentration. In this study, the capability of a mesh-based DIC method using 8-node quadrilateral elements (Q8-mesh-DIC) in boundary deformation measurement was investigated and highlighted for specimens with non-uniform deformation. The results were compared with those obtained by some conventional subset-based DIC methods, and the accuracy of the boundary deformation measurement was verified through simulated and real experiments. The Q8-mesh-DIC appears to be more suitable for the boundary deformation measurement of non-uniform deformation fields.
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Dan, Xizuo, Junrui Li, Qihan Zhao, Fangyuan Sun, Yonghong Wang, and Lianxiang Yang. "A Cross-Dichroic-Prism-Based Multi-Perspective Digital Image Correlation System." Applied Sciences 9, no. 4 (February 16, 2019): 673. http://dx.doi.org/10.3390/app9040673.
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A robust three-perspective digital image correlation (DIC) system based on a cross dichroic prism and single three charge-coupled device (3CCD) color cameras is proposed in this study. Images from three different perspectives are captured by a 3CCD camera using the cross dichroic prism and two planar mirrors. These images are then separated by different CCD channels to perform correlation calculation with an existing multi-camera DIC algorithm. The proposed system is considerably more compact than the conventional multi-camera DIC system. In addition, the proposed system has no loss of spatial resolution compared with the traditional single-camera DIC system. The principle and experimental setup of the proposed system is described in detail, and a series of tests is performed to validate the system. Experimental results show that the proposed system performs well in displacement, morphology, and strain measurement.
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Réthoré, Julien, Jean-Philippe Tinnes, Stéphane Roux, Jean-Yves Buffière, and François Hild. "Extended three-dimensional digital image correlation (X3D-DIC)." Comptes Rendus Mécanique 336, no. 8 (August 2008): 643–49. http://dx.doi.org/10.1016/j.crme.2008.06.006.
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Barišić, Ivana, Tihomir Dokšanović, and Matija Zvonarić. "Pavement Structure Characteristics and Behaviour Analysis with Digital Image Correlation." Applied Sciences 13, no. 1 (January 3, 2023): 664. http://dx.doi.org/10.3390/app13010664.
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Digital image correlation (DIC) is a method of point displacement measurement by an optical system. If two cameras are used for capturing the same point displacement, three-dimensional data are obtained using the 3D-DIC method. The areas of application of this method in pavement construction are diverse, but it is mainly used for displacement monitoring during standard tests of the failure of specimens due to load application. Furthermore, DIC technology was used only for testing particular material characteristics and assuming their influence on the overall pavement system. Within this research, DIC was applied in two areas: defining material mechanical characteristics and analyses of pavement structure behaviour under cyclic loading. The scope of this research was to gain more insights into DIC’s potential application within pavement behaviour analyses, specifically on cement-bound granular material (CBGM) characterisation. Results from this study confirm the suitability of 3D-DIC technology for pavement material characterisation. Furthermore, it is shown that certain trends of material behaviour defined on the simple material level of each independent pavement layer will significantly differ when it is placed in the system, and this kind of complex analysis is possible by using 3D-DIC technology.
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Shadmehri, Farjad, and Suong Van Hoa. "Digital Image Correlation Applications in Composite Automated Manufacturing, Inspection, and Testing." Applied Sciences 9, no. 13 (July 5, 2019): 2719. http://dx.doi.org/10.3390/app9132719.
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Since its advent in the 1970s, digital image correlation (DIC) applications have been rapidly growing in different engineering fields including composite material testing and analysis. DIC combined with a stereo camera system offers full-field measurements of three-dimensional shapes, deformations (i.e., in-plane and out-of-plane deformations), and surface strains, which are of most interest in many structural testing applications. DIC systems have been used in many conventional structural testing applications in composite structures. However, DIC applications in automated composite manufacturing and inspection are scarce. There are challenges in inspection of a composite ply during automated manufacturing of composites and in measuring transient strain during in-situ manufacturing of thermoplastic composites. This article presents methodologies using DIC techniques to address these challenges. First, a few case studies where DIC was used in composite structural testing are presented, followed by development of new applications for DIC in composite manufacturing and inspection.
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Atkinson, Devan, and Thorsten Becker. "A 117 Line 2D Digital Image Correlation Code Written in MATLAB." Remote Sensing 12, no. 18 (September 8, 2020): 2906. http://dx.doi.org/10.3390/rs12182906.
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Digital Image Correlation (DIC) has become a popular tool in many fields to determine the displacements and deformations experienced by an object from images captured of the object. Although there are several publications which explain DIC in its entirety while still catering to newcomers to the concept, these publications neglect to discuss how the theory presented is implemented in practice. This gap in literature, which this paper aims to address, makes it difficult to gain a working knowledge of DIC, which is necessary in order to contribute towards its development. The paper attempts to address this by presenting the theory of a 2D, subset-based DIC framework that is predominantly consistent with state-of-the-art techniques, and discussing its implementation as a modular MATLAB code. The correlation aspect of this code is validated, showing that it performs on par with well-established DIC algorithms and thus is sufficiently reliable for practical use. This paper, therefore, serves as an educational resource to bridge the gap between the theory of DIC and its practical implementation. Furthermore, although the code is designed as an educational resource, its validation combined with its modularity makes it attractive as a starting point to develop the capabilities of DIC.
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Kang, Myung Soo, and Yun-Kyu An. "Adaptive Subset-Based Digital Image Correlation for Fatigue Crack Evaluation." Applied Sciences 10, no. 10 (May 21, 2020): 3574. http://dx.doi.org/10.3390/app10103574.
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This paper proposes a fatigue crack evaluation technique based on digital image correlation (DIC) with statistically optimized adaptive subsets. In conventional DIC analysis, a uniform subset size is typically utilized throughout the entire region of interest (ROI), which is determined by experts’ subjective judgement. The basic assumption of the conventional DIC analysis is that speckle patterns are uniformly distributed within the ROI of a target image. However, the speckle patterns on the ROI are often spatially biased, augmenting spatially different DIC errors. Thus, a subset size optimization with spatially different sizes, called adaptive subset sizes, is needed to improve the DIC accuracy. In this paper, the adaptive subset size optimization algorithm is newly proposed and experimentally validated using an aluminum plate with sprayed speckle patterns which are not spatially uniform. The validation test results show that the proposed algorithm accurately estimates the horizontal displacements of 200 μ m , 500 μ m and 1 mm without any DIC error within the ROI. On the other hand, the conventional subset size determination algorithm, which employs a uniform subset size, produces the maximum error of 33% in the designed specimen. In addition, a real fatigue crack-opening phenomenon, which is a local deformation within the ROI, is evaluated using the proposed algorithm. The fatigue crack-opening phenomenon as well as the corresponding displacement distribution nearby the fatigue crack tip are effectively visualized under the uniaxial tensile conditions of 0.2, 1.0, 1.4 and 1.7 mm , while the conventional algorithm shows local DIC errors, especially at crack opening areas.
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Lin, Zhe, Tian Cai, and Yanfeng Wang. "Parallel reliability-guided algorithm for digital image correlation." Insight - Non-Destructive Testing and Condition Monitoring 61, no. 12 (December 1, 2019): 729–37. http://dx.doi.org/10.1784/insi.2019.61.12.729.
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Digital image correlation is a non-contact optical method for measuring the displacement and strain on the surface of a material. The existing reliability-guided digital image correlation (RG-DIC) method is stable and reliable for a single image but it still needs a large calculational resource for a sequence of images. Due to the decorrelation effect, the reference image must be replaced several times to correct the measurement results for an image sequence involving a large deformation or a discontinuous deformation. Since the process must be executed sequentially, image by image, the total time required is often unacceptably large when the image sequence is long. The challenge is to find a way of improving the speed while retaining calculational reliability and measurement accuracy, which are important for the practical application of DIC. To address this problem, an improved method is proposed in this paper. The parallel bottleneck caused by the decorrelation effect is solved through improving the parallelism to increase the processing speed. This approach can be used to calculate the strain field of the surface of the material in cases of discontinuous deformation, such as in the area near to a crack. Compared with existing methods, this method not only retains the calculational reliability but also greatly improves calculation speed, especially on current multi-core computing platforms.
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Lee, Junhwa, Eun Kim, Seongwoo Gwon, Soojin Cho, and Sung-Han Sim. "Uniaxial Static Stress Estimation for Concrete Structures Using Digital Image Correlation." Sensors 19, no. 2 (January 15, 2019): 319. http://dx.doi.org/10.3390/s19020319.
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This paper proposes a static stress estimation method for concrete structures, using the stress relaxation method (SRM) in conjunction with digital image correlation (DIC). The proposed method initially requires a small hole to be drilled in the concrete surface to induce stress relaxation around the hole and, consequently, a displacement field. DIC measures this displacement field by comparing digital images taken before and after the hole-drilling. The stress level in the concrete structure is then determined by solving an optimization problem, designed to minimize the difference between the displacement fields from DIC and the one from a numerical model. Compared to the pointwise measurements by strain gauges, the full-field displacement obtained by DIC provides a larger amount of data, leading to a more accurate estimation. Our theoretical results were experimentally validated using concrete specimens, demonstrating the efficacy of the proposed method.
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Khoo, Sze-Wei, Saravanan Karuppanan, and Ching-Seong Tan. "A Review of Surface Deformation and Strain Measurement Using Two-Dimensional Digital Image Correlation." Metrology and Measurement Systems 23, no. 3 (September 1, 2016): 461–80. http://dx.doi.org/10.1515/mms-2016-0028.
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Abstract 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 2DDIC 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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Livens, Pieter, Enis Ukshini, and Joris J. J. Dirckx. "Measuring the motion of the eardrum using Digital Image Correlation." Journal of Physics: Conference Series 2698, no. 1 (February 1, 2024): 012024. http://dx.doi.org/10.1088/1742-6596/2698/1/012024.
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Abstract The human eardrum is a translucent curved membrane and is in direct contact with the middle ear bones. Studying this complicated biomechanical system remains challenging. Digital image correlation (DIC) is an optical technique that allows measuring the shape and displacement of curved surfaces in 3D. In this work, we discuss the advantages and disadvantages of using DIC to study the eardrum at frequencies around 1 kHz. Special attention is given to the application of speckle patterns required to perform DIC on the translucent eardrum. Additionally, we detail an alternative approach to high-speed cameras: phase-locked light pulses. Using light pulses synced to the phase of the sound, regular DIC cameras can be used at their full resolution. This enables a high spatial resolution to thoroughly investigate the motion of the eardrum at the relevant frequencies.
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Masthan Reddy, V. V., and S. Vidhyalakshmi. "Critical Evaluation of Reinforced Concrete Beams Using Digital Image Correlation Technique." IOP Conference Series: Earth and Environmental Science 1086, no. 1 (September 1, 2022): 012001. http://dx.doi.org/10.1088/1755-1315/1086/1/012001.
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Abstract Digital Image Correlation technique (DIC) is a non-contact optical method for rapid structural health monitoring of critical infrastructure. DIC is used to extract Moment (M) – Curvature (κ) relationships using random speckle patterns. The random speckle pattern is evaluated for 2D DIC measurements and shows an improved correlation with conventional measurements. Characteristics of random speckle patterns are quantified and their applicability to DIC is explored. The ultimate moment-curvature values computed from the random speckled pattern are found to be in good agreement with conventional measurements.
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Tambusay, Asdam, Benny Suryanto, and Priyo Suprobo. "Digital Image Correlation for Cement-based Materials and Structural Concrete Testing." Civil Engineering Dimension 22, no. 1 (May 19, 2020): 6–12. http://dx.doi.org/10.9744/ced.22.1.6-12.
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This paper presents the application of a low-cost digital image correlation (DIC) system for automated crack mapping. The system employed makes use of a conventional digital camera, a remote image recording controller, and an open-source digital image correlation MATLAB software Ncorr. To showcase the potential of the proposed system, two case studies involving general structural and material testing were undertaken. In the first series, the DIC system was used to study the fracture processes in a reinforced concrete beam and to investigate the influence of key input parameters on the spatial quality of strain maps obtained from the DIC analysis. In the second series, the application of the DIC method was expanded to assist in the study of complex multiple micro-crack formations in ductile cement composite testing. It is shown that the strain maps obtained from the DIC technique have a close resemblance to the actual crack patterns
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Koga, Norimitsu, and Osamu Umezawa. "Visualization of Strain Distribution on Deformed Steels Using Digital Image Correlation Method." Key Engineering Materials 741 (June 2017): 138–43. http://dx.doi.org/10.4028/www.scientific.net/kem.741.138.
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Digital image correlation (DIC) method is a convenient strain analysis method calculating strain from the difference of images between before and after deformation and shows an advantage to apply to any deformation mode or materials as long as significant contrast. We reviewed basic principles of DIC method and then demonstrated strain distribution in tensile deformed ferritic steel and cyclic deformed tempered martensitic steel. Strain distribution in tensile deformed ferritic steel becomes inhomogeneous with lowering temperature due to restriction of slip systems at low temperature. Strain distribution around a fatigue crack in cyclic deformed tempered martensitic steel was visualized by DIC analysis for replica film and strain concentrated on crack tip same as previous report in DIC analysis for specimen surface, which suggests that strain distribution obtained from replica film has an enough reliability. From these results, it can be concluded that DIC analysis is effective method to investigate local deformation and relation between local deformation and fracture behavior in metal materials.
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Périé, Jean-Noël, and Jean-Charles Passieux. "Special Issue on Advances in Digital Image Correlation (DIC)." Applied Sciences 10, no. 4 (February 24, 2020): 1530. http://dx.doi.org/10.3390/app10041530.
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Zhu, Pingan, Chao Zhang, and Jun Zou. "Digital image correlation for sensing kinematic fields in manufacturing processes: a review." Journal of Intelligent Manufacturing and Special Equipment 2, no. 2 (December 10, 2021): 37–62. http://dx.doi.org/10.1108/jimse-09-2021-032.
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PurposeThe purpose of the work is to provide a comprehensive review of the digital image correlation (DIC) technique for those who are interested in performing the DIC technique in the area of manufacturing.Design/methodology/approachNo methodology was used because the paper is a review article.Findingsno fundings.Originality/valueHerein, the historical development, main strengths and measurement setup of DIC are introduced. Subsequently, the basic principles of the DIC technique are outlined in detail. The analysis of measurement accuracy associated with experimental factors and correlation algorithms is discussed and some useful recommendations for reducing measurement errors are also offered. Then, the utilization of DIC in different manufacturing fields (e.g. cutting, welding, forming and additive manufacturing) is summarized. Finally, the current challenges and prospects of DIC in intelligent manufacturing are discussed.
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SANTOS, A. H. A., R. L. S. PITANGUEIRA, G. O. RIBEIRO, and E. V. M. CARRASCO. "Concrete modulus of elasticity assessment using digital image correlation." Revista IBRACON de Estruturas e Materiais 9, no. 4 (August 2016): 587–94. http://dx.doi.org/10.1590/s1983-41952016000400007.
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Abstract This paper presents the use of the technique of digital image correlation for obtaining the elasticity modulus of concrete. The proposed system uses a USB microscope that captures images at a rate of five frames per second. The stored data are correlated with the applied loads, and a stress-strain curve is generated to determine the concrete compressive modulus of elasticity. Two different concretes were produced and tested using the proposed system. The results were compared with the results obtained using a traditional strain gauge. It was observed a difference in the range of 4% between the two methods, wherein this difference depends on some parameters in the case of the DIC results, as focal length and a video capture resolution, indicating that DIC technique can be used to obtain mechanical properties of concrete.
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Grant, B. M. B., H. J. Stone, P. J. Withers, and M. Preuss. "High-temperature strain field measurement using digital image correlation." Journal of Strain Analysis for Engineering Design 44, no. 4 (May 1, 2009): 263–71. http://dx.doi.org/10.1243/03093247jsa478.
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A method is presented for obtaining good images of sample surfaces at high temperatures, suitable for strain measurement, by digital image correlation (DIC) without the use of surface markers or speckles. This is accomplished by suppressing black-body radiation through the use of filters and blue illumination. Using only relatively low levels of illumination the method is demonstrated to be capable of providing accurate DIC measurements up to 1100 °C, and the potential to monitor strains to 1400 °C is identified. The capability of the method is demonstrated by measuring the Young's modulus and coefficient of thermal expansion of a nickel-base superalloy at temperatures from ambient to 1000 °C; two parameters that are well established in the literature and that require high strain sensitivity for their reliable determination.
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Górszczyk, Jarosław, Konrad Malicki, and Teresa Zych. "Application of Digital Image Correlation (DIC) Method for Road Material Testing." Materials 12, no. 15 (July 24, 2019): 2349. http://dx.doi.org/10.3390/ma12152349.
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The theoretical part of the paper presents the framework of the digital image correlation (DIC) method as well as its advantages and limitations. The DIC technique that can be used in static and fatigue tests is a non-contact, non-interferometric optical method for measuring the surface deformation of structural elements, and material samples. In the experimental part of the paper, the implementation of the DIC method for the selected laboratory tests of building materials is described. The results of the tests on the samples of the materials used in road construction, i.e., asphalt mixtures (HMA), stone, soil stabilized with a hydraulic binder, and geosynthetics are discussed. The conducted research pointed out the possibilities of using the DIC method to evaluate the deformation of road materials in laboratory tests, taking into account their specificity. The variety of samples of tested material allowed to indicate the areas in which the DIC method and the algorithms used to evaluate the results give a significant advantage compared to tensometric measurement methods.
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Huang, Wanghua, Kang Chen, Wei Wei, Jianbin Xiong, and Wenhao Liu. "Fast and Robust Digital Image Spearman's Rho Correlation for Displacement Measurement." Information Technology and Control 51, no. 4 (December 12, 2022): 661–77. http://dx.doi.org/10.5755/j01.itc.51.4.30866.
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The robustness and computational efficiency of digital image correlation (DIC) are two key influencing factors for displacement field measurement applications. Especially when the speckle images are contaminated by salt-and-pepper noise, it is difficult to obtain reliable measurement results using traditional DIC methods. Digital image Spearman’s Rho Correlation (DISRC), as a new DIC technique, has certain robustness to salt-and-pepper noise, but incurs a high computational load when computing subset ranks. It is found that the DISRC can tolerate up to 15% noise level theoretically by analyzing the mean character of Spearman’s Rho. Meanwhile a fast scheme is proposed in which parallelization is adopted for precomputing subset rank and computing for displacement field to accelerate the DISRC. The simulation results indicate that the fast DISRC is about 60 times faster than the original one, and the displacement field results are almost the same between them. The DISRC not only gives as well results as zero-mean normalized cross-correlation (ZNCC) without any noise, but also can tolerate 20% noise level in simulations. A case study also verifies that the result by DISRC is better than ZNCC when contaminated by smaller amounts of noise. The conclusion is that the DISRC is a strong anti-interference DIC technique, which is very important in application under complex environment, and the fast scheme is an effective way to accelerate the DISRC.
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Safavizadeh, S. A., A. Wargo, and Y. Richard Kim. "Utilizing Digital Image Correlation (DIC) in Asphalt Pavement Testing." Journal of Testing and Evaluation 46, no. 3 (November 10, 2017): 20160262. http://dx.doi.org/10.1520/jte20160262.
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Hammer, J. T., T. J. Liutkus, J. D. Seidt, and A. Gilat. "Using Digital Image Correlation (DIC) in Dynamic Punch Tests." Experimental Mechanics 55, no. 1 (August 21, 2014): 201–10. http://dx.doi.org/10.1007/s11340-014-9924-9.
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Chien, Chi-Hui, Ting-Hsuan Su, Chao-Jian Huang, Yuh-Jin Chao, Wei-Li Yeh, and Poh-Sang Lam. "Application of digital image correlation (DIC) to sloshing liquids." Optics and Lasers in Engineering 115 (April 2019): 42–52. http://dx.doi.org/10.1016/j.optlaseng.2018.11.016.
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Gupta, Sachin, Venkitanarayanan Parameswaran, Michael A. Sutton, and Arun Shukla. "Study of dynamic underwater implosion mechanics using digital image correlation." Proceedings of the Royal Society A: Mathematical, Physical and Engineering Sciences 470, no. 2172 (December 8, 2014): 20140576. http://dx.doi.org/10.1098/rspa.2014.0576.
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The physical processes associated with the implosion of cylindrical tubes in a hydrostatic underwater environment were investigated using high-speed three-dimensional digital image correlation (3D DIC). This study emphasizes visualization and understanding of the real-time deformation of the implodable volume and the associated fluid–structure interaction phenomena. Aluminium 6061-T6 cylindrical tubes were used as the implodable volumes. Dynamic tourmaline pressure transducers were placed at selected locations to capture the pressure history generated during each implosion event. A series of small-scale calibration experiments were first performed to establish the applicability of 3D DIC for measuring the deformation of submerged objects. The results of these experiments indicated that the effects of refraction due to water and the optical windows can be accounted for by evaluation of the camera's intrinsic and extrinsic parameters using a submerged calibration grid when the surface normal of the optical windows is collinear with the camera's optical axis. Each pressure history was synchronized with its respective high-speed DIC measurements. DIC results showed that the highest rate of increase in contact area correlates to the largest pressure spike during the implosion process. The results also indicated that, for a given diameter, longer implodable volumes generated higher pressure spikes.
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Zhang, Chuang, Cong Liu, and Zhihong Xu. "High-Accuracy Three-Dimensional Deformation Measurement System Based on Fringe Projection and Speckle Correlation." Sensors 23, no. 2 (January 6, 2023): 680. http://dx.doi.org/10.3390/s23020680.
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Fringe projection profilometry (FPP) and digital image correlation (DIC) are widely applied in three-dimensional (3D) measurements. The combination of DIC and FPP can effectively overcome their respective shortcomings. However, the speckle on the surface of an object seriously affects the quality and modulation of fringe images captured by cameras, which will lead to non-negligible errors in the measurement results. In this paper, we propose a fringe image extraction method based on deep learning technology, which transforms speckle-embedded fringe images into speckle-free fringe images. The principle of the proposed method, 3D coordinate calculation, and deformation measurements are introduced. Compared with the traditional 3D-DIC method, the experimental results show that this method is effective and precise.
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Meng, Xin, Andy Pullen, Xi Guo, Xiang Yun, and Leroy Gardner. "Applications of 3D scanning and digital image correlation in structural experiments." ce/papers 6, no. 3-4 (September 2023): 1674–79. http://dx.doi.org/10.1002/cepa.2543.
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AbstractThe primary aim of the present study is to explore the use, advantages and potential of two advanced data acquisition techniques – 3D scanning and digital image correlation (DIC), in the testing of metallic structures. 3D scanning is a novel method for capturing the full outer geometry of an object. It is being increasingly used in experimental studies for the determination of dimensional parameters and the characterisation of local and global imperfections, examples of which are given and discussed. Digital image correlation (DIC) is a rapidly evolving technology for the full‐field measurement of the displacements and strains over a surface. A brief introduction to DIC and its workflow is firstly provided. Example applications of DIC in various scales of experiments, including material tests, structural element tests and full‐scale structural system tests, are subsequently discussed. These new‐generation data acquisition techniques enable structural researchers to gain a deeper insight into the behaviour of metallic structures in experimental research.
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Fíla, Tomáš, Petr Zlámal, Jan Falta, Tomáš Doktor, Petr Koudelka, Daniel Kytýř, Marcel Adorna, et al. "Testing of Auxetic Materials Using Hopkinson Bar and Digital Image Correlation." EPJ Web of Conferences 183 (2018): 02045. http://dx.doi.org/10.1051/epjconf/201818302045.
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In this paper, a split Hopkinson pressure bar (SHPB) was used for impact loading of an auxetic lattice (structure with negative Poisson’s ratio) at a given strain-rate. High strength aluminum and polymethyl methacrylate bars instrumented with foil strain-gauges were used for compression of an additively manufactured missing-rib auxetic lattice. All experiments were observed using a high-speed camera with frame-rate set to approx. 135.000 fps. High-speed images were synchronized with the strain-gauge records. Dynamic equilibrium in the specimen was analyzed and optimized pulse-shaping was introduced in the selected experiments. Longitudinal and lateral in-plane displacements and strains were evaluated using digital image correlation (DIC) technique. DIC results were compared with results obtained from strain-gauges and were found to be in good agreement. Using DIC, it was possible to analyze in-plane strain distribution in the specimens and to evaluate strain dependent Poisson’s ratio of the auxetic structure.
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Chen, Hao, Hao Li, Guohua Liu, and Zhenyu Wang. "A Novel Simulation Method for 3D Digital-Image Correlation: Combining Virtual Stereo Vision and Image Super-Resolution Reconstruction." Sensors 24, no. 13 (June 21, 2024): 4031. http://dx.doi.org/10.3390/s24134031.
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3D digital-image correlation (3D-DIC) is a non-contact optical technique for full-field shape, displacement, and deformation measurement. Given the high experimental hardware costs associated with 3D-DIC, the development of high-fidelity 3D-DIC simulations holds significant value. However, existing research on 3D-DIC simulation was mainly carried out through the generation of random speckle images. This study innovatively proposes a complete 3D-DIC simulation method involving optical simulation and mechanical simulation and integrating 3D-DIC, virtual stereo vision, and image super-resolution reconstruction technology. Virtual stereo vision can reduce hardware costs and eliminate camera-synchronization errors. Image super-resolution reconstruction can compensate for the decrease in precision caused by image-resolution loss. An array of software tools such as ANSYS SPEOS 2024R1, ZEMAX 2024R1, MECHANICAL 2024R1, and MULTIDIC v1.1.0 are used to implement this simulation. Measurement systems based on stereo vision and virtual stereo vision were built and tested for use in 3D-DIC. The results of the simulation experiment show that when the synchronization error of the basic stereo-vision system (BSS) is within 10−3 time steps, the reconstruction error is within 0.005 mm and the accuracy of the virtual stereo-vision system is between the BSS’s synchronization error of 10−7 and 10−6 time steps. In addition, after image super-resolution reconstruction technology is applied, the reconstruction error will be reduced to within 0.002 mm. The simulation method proposed in this study can provide a novel research path for existing researchers in the field while also offering the opportunity for researchers without access to costly hardware to participate in related research.
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Adorna, Marcel, Stefan Brodner, Jan Falta, Petr Zlámal, and Tomáš Fíla. "EVALUATION OF HOPKINSON BAR EXPERIMENTS USING MULTIPLE DIGITAL IMAGE CORRELATION SOFTWARE TOOLS." Acta Polytechnica CTU Proceedings 25 (December 6, 2019): 1–5. http://dx.doi.org/10.14311/app.2019.25.0001.
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Three different tools for Digital Image Correlation (DIC) were used for evaluation of dynamic experiments performed using custom Open Hopkinson Pressure Bar (OHPB) apparatus. High strain-rate measurements were performed on specimens of advanced cellular materials with predefined structure and negative Poisson’s ratio. Low impedance polymethyl methacrylate (PMMA) bars instrumented with foil strain-gauges were used for dynamic loading of the specimens. Experiments were observed using a pair of high-speed cameras for imaging of loading process in sufficient quality. Custom developed evaluation DIC tool implemented in Matlab, open-source Matlab tool (NCorr) and commercial DIC software (ISTRA 4D) were all used for evaluation of image sequences recorded by high-speed cameras. Comparison of results obtained using all three different DIC tools and results of complementary strain-gauge measurement are shown in this paper. Verification of reliability of custom made DIC software tool is presented.
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Tewari, Kavita, and R. K. Kulkarni. "Locating Cracks in 1050 Aluminium Alloy by Digital Image Correlation." SAMRIDDHI : A Journal of Physical Sciences, Engineering and Technology 13, no. 02 (December 25, 2021): 104–8. http://dx.doi.org/10.18090/samriddhi.v13i02.8.
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In this paper deformation of commercial 1050 grade aluminum alloy is studied by digital image correlation (DIC) technique using open-source software, Ncorr. For this purpose, samples of aluminum alloy were subjected to uniaxial deformation under a scanning electron microscope (SEM) till the initiation of crack. Intermittently images were captured during deformation and by using DIC technique, variations in the microstructure of the deformed samples were identified in terms of displacement. Using these displacements, normal strains Exx, Eyy, and Exy shear strain were estimated to subpixel accuracy. By superimposing the region of crack and distribution of strains in the microstructures, it was possible to show that near the crack, strains not only attain high values but also show large fluctuations. Various aspects relating to the nature of strain distribution are discussed in the paper.
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Hermle, Doris, Markus Keuschnig, Michael Krautblatter, and Valentin Tertius Bickel. "Systematic Quantification and Assessment of Digital Image Correlation Performance for Landslide Monitoring." Geosciences 13, no. 12 (December 3, 2023): 371. http://dx.doi.org/10.3390/geosciences13120371.
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Accurate and reliable analyses of high-alpine landslide displacement magnitudes and rates are key requirements for current and future alpine early warnings. It has been proved that high spatiotemporal-resolution remote sensing data combined with digital image correlation (DIC) algorithms can accurately monitor ground displacements. DIC algorithms still rely on significant amounts of expert input; there is neither a general mathematical description of type and spatiotemporal resolution of input data nor DIC parameters required for successful landslide detection, accurate characterisation of displacement magnitude and rate, and overall error estimation. This work provides generic formulas estimating appropriate DIC input parameters, drastically reducing the time required for manual input parameter optimisation. We employed the open-source code DIC-FFT using optical remote sensing data acquired between 2014 and 2020 for two landslides in Switzerland to qualitatively and quantitatively show which spatial resolution is required to recognise slope displacements, from satellite images to aerial orthophotos, and how the spatial resolution affects the accuracy of the calculated displacement magnitude and rate. We verified our results by manually tracing geomorphic markers in orthophotos. Here, we show a first generic approach for designing and optimising future remote sensing-based landslide monitoring campaigns to support time-critical applications like early warning systems.
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Cheng, Xuanshi, Shibin Wang, Huixin Wei, Xin Sun, Lipan Xin, Linan Li, Chuanwei Li, and Zhiyong Wang. "Application of Stereo Digital Image Correlation on Facial Expressions Sensing." Sensors 24, no. 8 (April 11, 2024): 2450. http://dx.doi.org/10.3390/s24082450.
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Facial expression is an important way to reflect human emotions and it represents a dynamic deformation process. Analyzing facial movements is an effective means of understanding expressions. However, there is currently a lack of methods capable of analyzing the dynamic details of full-field deformation in expressions. In this paper, in order to enable effective dynamic analysis of expressions, a classic optical measuring method called stereo digital image correlation (stereo-DIC or 3D-DIC) is employed to analyze the deformation fields of facial expressions. The forming processes of six basic facial expressions of certain experimental subjects are analyzed through the displacement and strain fields calculated by 3D-DIC. The displacement fields of each expression exhibit strong consistency with the action units (AUs) defined by the classical Facial Action Coding System (FACS). Moreover, it is shown that the gradient of the displacement, i.e., the strain fields, offers special advantages in characterizing facial expressions due to their localized nature, effectively sensing the nuanced dynamics of facial movements. By processing extensive data, this study demonstrates two featured regions in six basic expressions, one where deformation begins and the other where deformation is most severe. Based on these two regions, the temporal evolutions of the six basic expressions are discussed. The presented investigations demonstrate the superior performance of 3D-DIC in the quantitative analysis of facial expressions. The proposed analytical strategy might have potential value in objectively characterizing human expressions based on quantitative measurement.
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Marcińczak, Dorota. "Metoda DIC." BUILDER 259, no. 2 (February 1, 2019): 66–68. http://dx.doi.org/10.5604/01.3001.0013.3444.
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DIC (DIGITAL IMAGE CORRELATION) METHOD IN THE RESEARCH OF RC BEAMS STRENGTHENED WITH PBOFRCM MATERIALS. The article presents tests of a reinforced concrete beam strengthened in a shear with PBO-FRCM composite materials. Measurement of the deformation of the composite was carried out using two methods - with strain gauges and the optical DIC method (Digital Image Correlation). The DIC method consists in taking a series of photographs of the tested object before and during loading. The surface of the tested element must have randomly spaced spots that are applied to the object before measurement. During the study, the cameras monitor the shifting of spots against each other, which in comparison to the reference image before loading gives information about strains and stresses of the tested element. Measurements of deformation of composite materials using strain gauges are difficult to clearly analyze, because the strain gauge is in a specific, limited place, which does not correspond to the work of the entire composite. In addition, the strain gauge tends to break at the place of crack. The article discusses this problem by presenting the results of deformation of PBO-FRCM composite meshes measured in two mentioned ways, their comparison and discussion of results.
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Cunha, Filipa G., Telmo G. Santos, and José Xavier. "In Situ Monitoring of Additive Manufacturing Using Digital Image Correlation: A Review." Materials 14, no. 6 (March 19, 2021): 1511. http://dx.doi.org/10.3390/ma14061511.
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This paper is a critical review of in situ full-field measurements provided by digital image correlation (DIC) for inspecting and enhancing additive manufacturing (AM) processes. The principle of DIC is firstly recalled and its applicability during different AM processes systematically addressed. Relevant customisations of DIC in AM processes are highlighted regarding optical system, lighting and speckled pattern procedures. A perspective is given in view of the impact of in situ monitoring regarding AM processes based on target subjects concerning defect characterisation, evaluation of residual stresses, geometric distortions, strain measurements, numerical modelling validation and material characterisation. Finally, a case study on in situ measurements with DIC for wire and arc additive manufacturing (WAAM) is presented emphasizing opportunities, challenges and solutions.
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Aghdam, Milad Z., and Nasser Soltani. "Effect of speckle size on surface crack detection via digital image correlation." JUSTC 52 (2022): 1. http://dx.doi.org/10.52396/justc-2021-0160.
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Digital image correlation (DIC) is an experimental stress analysis technique used in nondestructive tests. The accuracy of DIC in crack detection depends on various factors such as the sizes of speckles and pixels. In the current study, a speckle pattern based on the spreading of nanoparticles with small speckles is compared with a conventional sprayed pattern to understand whether crack detection via DIC is improved by reducing the sizes of speckles and pixels. Owing to the small size of nanoparticles, an optical microscope is used for magnification. The spreading method for crack detection is first investigated experimentally. Results show that cracks can be detected easily when a 250 nm opening appears in the crack edges. Subsequently, the spreading method is compared with the conventional DIC, in which spraying method is used for patterning, in terms of crack detection. Results show that by reducing the speckle size and closely analyzing the speckle pattern, the DIC technique is considerably better than the conventional technique in detecting small cracks. Moreover, the conventional method is more suitable for detecting large cracks.
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Hu, Hao, Boxing Qian, Yongqing Zhang, and Wenpan Li. "Digital Image Correlation with a Prism Camera and Its Application in Complex Deformation Measurement." Sensors 23, no. 12 (June 13, 2023): 5531. http://dx.doi.org/10.3390/s23125531.
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Given the low accuracy of the traditional digital image correlation (DIC) method in complex deformation measurement, a color DIC method is proposed using a prism camera. Compared to the Bayer camera, the Prism camera can capture color images with three channels of real information. In this paper, a prism camera is used to collect color images. Relying on the rich information of three channels, the classic gray image matching algorithm is improved based on the color speckle image. Considering the change of light intensity of three channels before and after deformation, the matching algorithm merging subsets on three channels of a color image is deduced, including integer-pixel matching, sub-pixel matching, and initial value estimation of light intensity. The advantage of this method in measuring nonlinear deformation is verified by numerical simulation. Finally, it is applied to the cylinder compression experiment. This method can also be combined with stereo vision to measure complex shapes by projecting color speckle patterns.
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Murray, Chris A., W. Andy Take, and Neil A. Hoult. "Measurement of vertical and longitudinal rail displacements using digital image correlation." Canadian Geotechnical Journal 52, no. 2 (February 2015): 141–55. http://dx.doi.org/10.1139/cgj-2013-0403.
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Excessive rail displacements can result in reduced rail traffic speeds and increased risk of derailments. A number of methods exist for the measurement of vertical rail displacements, including using geophones, high-speed cameras, and rail vehicle mounted systems. The advantage of rail vehicle mounted methods is that large lengths of track can be assessed. However, there are some instances where the measurement of absolute rail deformations is essential, particularly in poor subgrade conditions where significant long-term settlements are possible. Vehicle-mounted monitoring strategies cannot capture the so-called “running rail” phenomena, where the passage of a train can push the rails longitudinally. Monitoring rail displacements using digital image correlation (DIC) has the potential to capture both of these phenomena unlike other technologies. The objectives of this paper are to evaluate the use of a system of synchronized high-speed cameras to measure absolute longitudinal and vertical rail displacements using DIC, to observe what factors influence the relative magnitudes of these displacements, and to investigate whether DIC measurements can be used to evaluate the stiffness and damping parameters required to develop the displacement–time response of a rail foundation system. The DIC system was evaluated at two sites: one with a high-quality subgrade and one with a peat subgrade. The DIC system was able to capture the absolute vertical and longitudinal displacements due to the passage of trains at both sites. The data from one of the sites, with the high-quality subgrade, were used to develop parameters for system stiffness and damping.
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Zhu, Kaiyu, and Bing Pan. "Panoramic/Dual-Surface Digital Image Correlation Measurement Using a Single Camera." Sensors 22, no. 9 (April 24, 2022): 3266. http://dx.doi.org/10.3390/s22093266.
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We propose a cost-effective and simple-to-implement mirror-assisted single-camera panoramic digital image correlation (DIC) method for panoramic/dual-surface profile and deformation measurement. Specifically, two planar mirrors and a single camera attached with a four-mirror adapter are used to capture stereo images of the front and rear surfaces of a test object. These stereo images can be processed by regular stereo-DIC to retrieve shape and kinematics fields of each surface. Further, with the speckle patterns prefabricated on the mirrors, reflection transformation matrices are obtained and applied to transform all reconstructed surfaces into a common world coordinate system. As such, panoramic/dual-surface shape and deformation measurements can be realized. For validation, a high-resolution smartphone camera and an industrial camera were, respectively, used to construct mirror-assisted single-camera panoramic DIC systems. Real experiments, including panoramic shape measurement of an aluminum cylinder, dual-surface shape measurement of an aluminum plate and uniaxial tensile tests of aluminum sheet specimens, were performed, confirming the feasibility and accuracy of the method. Since only a single camera and a few auxiliary reflective mirrors are required, the proposed method provides a cost-effective and convenient way for taking panoramic/dual-surface shape and deformation measurements of regular-sized cylindrical and bar samples.
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Zhu, Kaiyu, and Bing Pan. "Panoramic/Dual-Surface Digital Image Correlation Measurement Using a Single Camera." Sensors 22, no. 9 (April 24, 2022): 3266. http://dx.doi.org/10.3390/s22093266.
Full textAbstract:
We propose a cost-effective and simple-to-implement mirror-assisted single-camera panoramic digital image correlation (DIC) method for panoramic/dual-surface profile and deformation measurement. Specifically, two planar mirrors and a single camera attached with a four-mirror adapter are used to capture stereo images of the front and rear surfaces of a test object. These stereo images can be processed by regular stereo-DIC to retrieve shape and kinematics fields of each surface. Further, with the speckle patterns prefabricated on the mirrors, reflection transformation matrices are obtained and applied to transform all reconstructed surfaces into a common world coordinate system. As such, panoramic/dual-surface shape and deformation measurements can be realized. For validation, a high-resolution smartphone camera and an industrial camera were, respectively, used to construct mirror-assisted single-camera panoramic DIC systems. Real experiments, including panoramic shape measurement of an aluminum cylinder, dual-surface shape measurement of an aluminum plate and uniaxial tensile tests of aluminum sheet specimens, were performed, confirming the feasibility and accuracy of the method. Since only a single camera and a few auxiliary reflective mirrors are required, the proposed method provides a cost-effective and convenient way for taking panoramic/dual-surface shape and deformation measurements of regular-sized cylindrical and bar samples.