Tesi: "Digital image correlation"

1

Mosayebi, Mahshad. "Digital Laser Speckle Image Correlation". OpenSIUC, 2017. https://opensiuc.lib.siu.edu/theses/2131.

Abstract (sommario):

This thesis examines the feasibility of combining Digital Image Correlation (DIC) with laser speckle based methods to form a new hybrid deformation measurement method called Digital Laser Speckle Image Correlation (DilSIC). Consequently, this method does not require any sample preparation and allows for the measurement of displacement of micro structures in addition to large displacements. In this technique, a coherent 30mW-632nm laser beam is expanded with 40X lens and then illuminated on the target surface to produce a fine, homogenous laser speckle pattern. Images were captured before and after deformation due to external load and the whole field displacement and strain were determined by the DIC method. This technique could measure displacement less than 30-μm with high accuracy when a 120mm × 80mm area of the surface was inspected. Up to 10% strain was measured by this technique with high accuracy during the whole range. Eventually the sub-surface crack was located successfully, which is a revolutionary achievement in NDT optical methods. This method was tested in different material, with different roughness. Aluminum sheet and rubber material were used mostly. This method could broaden the capability of displacement measurement and subsurface crack detection in wide range of materials.

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2

Hartley, David Andrew. "Image correlation using digital signal processors". Thesis, Liverpool John Moores University, 1991. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.304465.

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3

Newberry, Shawn. "Laser Speckle Patterns with Digital Image Correlation". OpenSIUC, 2021. https://opensiuc.lib.siu.edu/theses/2885.

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Abstract (sommario):

Digital Laser Speckle Image Correlation (DiLSIC) is a technique that utilizes a laser generated speckle pattern with Digital Image Correlation (DIC). This technology eliminates the need to apply an artifact speckle pattern to the surface of the material of interest, and produces a finer speckle pattern resulting in a more sensitive analysis. This investigation explores the parameters effecting laser speckle patterns for DIC and studies DiLSIC as a tool to measure surface strain and detect subsurface defects on pressure vessels. In this study a 632.8 nm 30 mW neon-helium laser generated the speckle pattern by passing through the objective end of an objective lens. All experiments took place in a lab setting on a high performance laminar flow stabilizer optical table.This investigation began with a deeper look at the camera settings that effect the effectiveness of using laser speckles with DIC. The first studies were concentrated on the aperture size (f-stop), shutter speed, and gain (ISO) of the camera. Through a series of zero-correlation studies, translation tests, and settings studies, it was discovered that, much like white light DIC, an increased gain allowed for more noise and less reliable measurements when using DiLSIC. It was shown that the aperture size and shutter speed will largely depend on the surface composition of the material, and that these factors should be investigated with each new sample of different surface finish.To determine the feasibility of using DiLSIC on pressure vessels two samples were acquired. The first was a standard ASTM filament wound composite pressure vessel (CPV) which had an upper load limit of 40 psi. The second was a plastic vessel that had internal subsurface defects added with the use of an air pencil grinder. Both vessels were put under a pressure load with the use of a modified air compressor that allowed for multiple loading cycles through the use of a pressure relief valve. The CPV was mapped out in 10-degree increments between the 90° and 180° markings that were on the pressure vessel, occurring in three areas, each one inch apart. The CPV had a pressure load applied to at 10, 20, 30,and 40 psi. DiLSIC was able to measure increasing displacement with increased loading on the surface of the CPV, however with a load limit of 40 psi no strains were detected. The plastic vessel had known subsurface defects, and these areas were the focus of the investigation. The plastic vessel was loaded with a pressure load at 5, 10, 12, 15, 17, and 20 psi. The 5 psi loaded image was used as a reference image for the correlation and decorrelation consistently occurred at 20 psi. This investigation proved that DiLSIC can detect and locate subsurface defects through strain measurement. The results were verified with traditional white light DIC, which also showed that the subsurface defects on pressure vessels were detectable. The DIC and DiLSIC results did not agree on maximum strain measurement, with the DiLSIC prediciting much larger strains than traditional DIC. This is due to the larger effect out-of-plane displacement has on DiLSIC. DiLSIC was able to detect subsurface defects on a pressure vessel. The median measured hoop strain was in agreement for DiLSIC, DIC and the predicted hoop strain for a wall thickness of 0.1 inches. However, DiLSIC also produced unreliable maximum strain measurements. This technique shows potential for future applications, but more investigations will be needed to implement it for industrial use. A full investigation into the parameters surrounding this technique, and the factors that contribute the most to added noise and unreliability should be conducted. This technology is being developed by multiple entities and shows promising results, and once further advanced could be a useful tool for rapid surface strain measurement and subsurface defect detection in nondestructive evaluation applications. Therefore, it is recommended to continue further investigations into this technology and its applications.

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4

Liang, Yiming. "Analysis of Paperboard Performance using Digital Image Correlation". Thesis, KTH, Hållfasthetslära, 2020. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-277799.

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The performance of paperboard materials in packaging application has been investigated and evaluated for a long time. This is because it plays a decisive role for product protection and decoration in packaging applications. Potential damages during transportation sometimes affect the consistency of the performance. Therefore, the capability of the material to resist these external disturbances was of interest. A multiply paperboard was chosen as the experimental material. The analysis conducted in this thesis aimed to reveal the tensile behavior in the cross-machine direction (CD) of the material against various kinds of local or global changes. The changes included global and local climate variations, cutouts, and regional weakening and strengthening, which were applied during the intervals between preloading and reloading. The digital image correlation (DIC) analysis computed the time-varying strain fields from the gray level information contained in the recorded videos of loading processes. The generated strain fields were imported to post analysis. Comparison between comparable stages (two stages with the same average strain value from different loading sections) was considered as the scheme of isolating the influences of the changes and investigating them individually. The cosine image similarity method and the eigenface algorithm were used to validate this scheme, while the directional average calculation and the strain field compensation method were introduced to realize the isolation. The differences between the front and back outer plies of the paperboard sheets were detected as individual. Moreover, both global and local climate changes were affecting the strain distributions of the specimens proportionally on account of the moisture ratio within the material. In addition, the invisible mechanical weakening and strengthening were captured evidently with the analysis, which caused strain concentrations due to the uneven distribution of expansion capability. The relaxation and bending in unloading processes were two of the primary disturbing factors within all the deformed specimens, which were related to time and bending direction, correspondingly.
Egenskaperna hos kartongmaterial för förpackningstillämpningar har varit ett ämne att undersökning under lång tid. Detta för att dessa egenskaper spelar en avgörande roll som produktskydd och dekorativ utformning i mängde av tillämpningar. Potentiella skador under transport påverkar bland annat materialets tillförlitlighet och prestandard. Därför är det aktuellt att undersöka samt förstå materialets förmåga att motstå yttre störningar. Experimentmaterialet som användes bestod av en typ av flerskiktskartong. Analyser som utfördes i denna avhandling har syfte att identifiera de mekaniska förändringarna i materialets dragegenskaper i tvärsmaskin-riktningen (CD) på grund av olika lokala eller globala förändringar. Förändringarna innefattar både globala och lokala klimatvariationer, utskärningar, och lokala försvagningar samt förstärkningar. Dessa förändringar infördes vid intervallet mellan på- och avlastning. Den digital bildkorrelations analys (DIC) användes för att beräknade de tidsvarierande töjningsfälten från den grånivåinformationen i som registrerades med hjälp av inspelade videor under belastningen Den genererade töjningsfälten importerades för vidare analys. Två tillstånd med liknande medelvärde av töjningsnivån från olika delar av belastningen jämfördes, detta för att isolera påverkan av förändringarna och undersöka dem individuellt. Två olika metoder för jämförelse av bilderna (cosine image similarity och eigenface algorithm) användes för att validera analysschemat, där riktning-medelvärdesberäkningar och töjningsfälts kompensations-metoden användes för att realisera dessa isoleringar. Enstaka skillnader upptäcktes mellan de främre och bakre ytskikten på kartongarken. Dessutom påverkades töjningsfördelningarna för proverna både av den globala och lokala klimatförändringar på grund av fukttillståndet i materialet. Vidare kan de osynliga mekaniska försvagningar och förstärkningar tydligt fångas med de utförda analyserna, vilket ledde till töjningskoncentrationers uppkomst på grund av det inhomogena expansions-förmåga hos arket. Relaxationen och böjningen vid avlastning relaterade till tid och böjningsförmåga var två av de primära faktorerna som påverkade analysens kvalité.

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5

Nageswaran, Ashok R. "Deformation Analysis of Soft Tissues by Digital Image Correlation". University of Cincinnati / OhioLINK, 2009. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1233614556.

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6

Shrestha, Shashi Shekhar. "Evaluation of Composite Adhesive Bonds Using Digital Image Correlation". OpenSIUC, 2015. https://opensiuc.lib.siu.edu/theses/1648.

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Abstract (sommario):

Advanced composite materials are widely used for many structural applications in the aerospace/aircraft industries today. Joining of composite structures using adhesive bonding offers several advantages over traditional fastening methods. However, this technique is not yet employed for fastening the primary structures of aircrafts or space vehicles. There are several reasons for this: There are not any reliable non-destructive evaluation (NDE) methods that can quantify the strength of the bonds, and there are no certifications of quality assurance for inspecting the bond quality. Therefore, there is a significant need for an effective, reliable, easy to use NDE method for the analysis of composite adhesive joints. This research aimed to investigate an adhesively bonded composite-aluminum joints of variable bond strength using digital image correlation (DIC). There are many future possibilities in continuing this research work. As the application of composite materials and adhesive bond are increasing rapidly, the reliability of the composite structures using adhesive bond should quantified. Hence a lot of similar research using various adhesive bonds and materials can be conducted for characterizing the behavior of adhesive bond. The results obtained from this research will set the foundation for the development of ultrasonic DIC as a nondestructive approach for the evaluation of adhesive bond line.

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7

Karimian, Seyed Fouad. "Evaluation of Adhesive Joints with Ultrasonic Digital Image Correlation". OpenSIUC, 2016. https://opensiuc.lib.siu.edu/theses/2054.

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Abstract (sommario):

Increasing use of composite materials in industry brings the need for newer and more practical methods to evaluate them. Widespread use of composite materials heavily depends on the manufacturer’s ability to unquestionably ensure its safety, given how much the user trusts them. Non-Destructive Evaluation (NDE) can be used to evaluate adhesive bondline health. This thesis employs Digital Image Correlation (DIC) method, one of the known methods in NDE, and combines it with an embedded speckle pattern in order to obtain valuable information from within the adhesive bondline. By recording the movement of the speckles and analyzing their behavior according to DIC algorithms, a strain map of the adhesive is drawn. An adhesive strain map helps find defects that might be out of sight using conventional NDE methods. This thesis discusses different possible materials to be used as the speckle pattern and chooses the one shows better results based on different criteria. Then employing the material, it records the speckle pattern using optical and ultrasonic methods to draw a strain map. By analyzing the obtained strain maps, defects within the bondline are revealed.

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8

Sapounas, D. "A novel approach to rotation invariant correlation". Thesis, Cranfield University, 1994. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.283306.

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9

Gubbels, Wade. "3-D Digital Image Correlation using a single color-camera". Thesis, University of British Columbia, 2014. http://hdl.handle.net/2429/50491.

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Digital Image Correlation (DIC) is an optical and numerical method capable of accurately providing full-field, two-dimensional (2-D) and three-dimensional (3-D) surface displacements and strains. 3-D DIC is typically done using two cameras that view the measured object from differing oblique directions. The measured images are independent and must be spatially connected using a detailed calibration procedure. This places a large demand on the practitioner, the optical equipment and the computational method. A novel approach is presented here where a single color-camera is used in place of multiple monochrome cameras. The color-camera measures three independent Red-Green-Blue (RGB) color-coded images. This feature greatly reduces the scale of the required system calibrations and spatial computations because the color images are physically aligned on the camera sensor. The in-plane surface displacements are obtained by performing traditional 2-D DIC in a single color. The out-of-plane information is obtained by a second 2-D DIC analysis and triangulation using oblique illumination from a differently colored light source. Further, the camera perspective errors associated with out-of-plane displacements can independently be measured during this second DIC analysis of the oblique illumination pattern. The 3-D Digital Image Correlation is completed by combining the 2-D correlations for each color. The design and creation of an example apparatus is described here. Experimental results show that the single-camera method can measure 3-D displacements with to within 1% error, with precision of the in-plane and out-of-plane measurements being consistently less than 0.04 and 0.12 pixels, respectively.
Applied Science, Faculty of
Mechanical Engineering, Department of
Graduate

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10

Adapa, Sujatha. "Evaluation of friction stir weld samples using digital image correlation /". Available to subscribers only, 2006. http://proquest.umi.com/pqdweb?did=1136092291&sid=5&Fmt=2&clientId=1509&RQT=309&VName=PQD.

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Thesis (M.S.)--Southern Illinois University Carbondale, 2006.
"Department of Mechanical Engineering and Energy Processes." Includes bibliographical references (leaves 70-74). Also available online.

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11

Bingleman, Luke. "Enhancing the robustness of ESPI measurements using digital image correlation". Thesis, University of British Columbia, 2010. http://hdl.handle.net/2429/27540.

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Electronic Speckle Pattern Interferometry (ESPI) provides a sensitive technique for measuring surface deformations. The technique involves comparison of the speckle phase angles within surface images measured before and after material deformation. This phase angle comparison requires that the speckle positions be consistent in all images. A lateral shift between images by just one pixel substantially degrades ESPI measurements, while a shift of two or more pixels typically causes complete speckle decorrelation and compromises the measurement entirely. To prevent such lateral motions, the specimen and the optical system must be rigidly fixed. This requirement typically prevents use of the ESPI method in applications outside laboratories or where it is necessary to remove the specimen from the optical setup between ESPI measurements. Here, Digital Image Correlation (DIC) is used to track speckle motion caused by specimen displacement between ESPI measurements. The measured images can then be mathematically shifted to restore the original speckle locations, thereby recorrelating the ESPI measurements. Examples are presented where ESPI measurements are successfully made with specimen shifts in excess of 60 pixels. A novel ESPI measurement technique where the specimen is removed in between ESPI measurements is also developed and validated.

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12

LYLES, ALBERT Anthony. "AN ADVANCED APPROACH VERIFICATION TO DIGITAL LASER SPECKLE IMAGE CORRELATION". OpenSIUC, 2018. https://opensiuc.lib.siu.edu/theses/2458.

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This research project on the campus of Southern Illinois University Carbondale is an extension to the inquiry into the feasibility and reliability of the technology known as Digital Laser Speckle Image Correlation (DiLSIC). This is a hybrid approach of combining two existing technologies. The first being Digital Image Correlation (DIC) which is a nondestructive evaluation commonly used to find displacement, in-plane strain, as well as deformation. The second being the of laser speckle patterns. This hybrid has achieved level of resolution measured to be 3.4μ. DiLSIC increases the application ability of the DIC technique to situations that generally would not be an option to use. DiLSIC needs no artifact speckle patterns to be applied to the specimen as a preparation for nondestructive testing. In DIC testing, the surface of a specimen must artifact speckles applied to the subject surface. Often the application of artifact speckles is not desirable or possible. DiLSIC is an acceptable alternative to the previously discussed industry-wide practice. This method broadens the usage of the DIC technique to situations which previously were not possible. This technology can identify, quantify, and detect the distribution of strain and stress concentrations in composite structures. For this study, a honeycomb-backed glass fiber reinforced polymer (GFRP) panel from a Cessna aircraft exterior luggage door was obtained and a defect panel is created. The panel is constructed with one area containing a repair compliant with manufacturer standardized methods and a repair area is not compliant and consists of multiple incorrect repair steps. An area with no repair is also tested to act as a control for comparison and quantification. The results for the inspected areas showed a linear strain increase in the noncompliant repair. The data plot for the compliant repair showed a trend of following the same basic curve as the no repair area. A verification process follows the DiLSIC testing consisting of using Infrared Thermography, Air-coupled ultrasonic, and white light artifact speckle DIC. These tests show DiLSIC is a viable alternative to the testing that is available in the industry. DiLSIC can detect defect location, size, geometry and map strain to determine the difference between compliant and noncompliant repairs when compared to a base level non-repair area

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13

Webster, Kelly Eileen. "Quantifying Renal Swelling during Machine Perfusion using Digital Image Correlation". Thesis, Virginia Tech, 2017. http://hdl.handle.net/10919/78244.

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While machine perfusion of explanted kidneys is theoretically superior to standard cold storage, it may damage potential transplants unless machine-associated swelling is controlled. This thesis presents the effects of perfusate tonicity on renal swelling during hypothermic machine perfusion. Phosphate buffered solution (PBS) and PBS supplemented with 5% w/v mannitol were used as isotonic (289 mOsm/kg) and hypertonic (568 mOsm/kg) perfusates, respectively. Porcine kidney pairs were procured then flushed and machine perfused; the right and left kidneys were assigned opposite perfusates. An experimental methodology was developed to image porcine kidneys undergoing hypothermic machine perfusion (5 deg C) for 15 minutes followed by 120 minutes without perfusion to quantify surface displacement (renal swelling) with digital image correlation (DIC). Surface displacement and size (thickness) were compared between the right and left kidneys of each pair. In addition, discharged renal fluids (i.e., filtrate and venous outflow) and biopsies were collected. On average, kidneys perfused with the mannitol solution were smaller in size than the kidneys perfused with PBS (p < 0.05) at the start and end of each experiment; however, there was no significant difference between the renal sizes at the end of the 15 minute perfusion interval (p > 0.05). Thus, hypertonic and isotonic perfusates yielded different renal swelling outcomes (i.e., physical size and surface displacement), which suggests that perfusate tonicity influences renal swelling. These experiments are the first time ex vivo renal surface displacement measurements have been collected during machine perfusion.
Master of Science

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14

Kunchum, Shilpa. "Embedded Digital Image Correlation in a Full-Field Displacement Sensor". University of Akron / OhioLINK, 2012. http://rave.ohiolink.edu/etdc/view?acc_num=akron1346171486.

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15

Curt, Jordan. "Damage detection for wind turbine towers with Digital Image Correlation". Thesis, université Paris-Saclay, 2021. http://www.theses.fr/2021UPAST008.

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La technologie des éoliennes est mature et le marché est avec le temps devenu compétitif. Un levier pour diminuer les coûts de l’exploitation des éoliennes réside dans l’optimisation de la maintenance des turbines. Dans ce contexte, cette étude se focalise sur l’état de la tour de l’éolienne. La durée de vie de la tour est influencée par des paramètres incertains liés à l’environnement et les aléas matériaux. Ceci rend très difficile la prédiction de la durée de vie d’un mât et des marges importantes sont prises lors de son dimensionnement. Cependant des éoliennes se sont déjà effondrées dans le monde, à chaque fois lors d'épisodes climatiques violents. Les deux phénomènes de ruine identifiés sont le flambement local de la tour et l'arrachement de sa partie supérieure. Des sources académiques ou industrielles ont également rapporté la découverte de fissures sur quelques turbines aux interfaces soudure-matériau. Une réflexion concernant la criticité d'une fissure vis à vis du flambement et de sa propagation brutale a été menée dans le cas où la tour est soumise à des chargements violents. Des simulations éléments finis ont permis de montrer que la propagation brutale de fissure était le phénomène dimensionnant pour la prolongation de durée de vie d'une tour d'éolienne fissurée.Pour s'assurer de l'intégrité des structures des techniques de suivi de santé ont été développées. Celles-ci sont en général réalisées à partir de capteurs extrapolant un état de santé global à partir de données locales (accéléromètres, jauges de déformations). Le risque est qu'un défaut reste invisible mais soit tout de même critique pour la structure. Il est donc essentiel de revisiter les outils de prédiction à partir de données de sites relatives à l’endommagement de la tour et des structures les supportant. Dans le cadre de ce travail de thèse des méthodes basées sur l'imagerie et plus particulièrement la Corrélation d'Images Numériques (CIN) ont été développées. Pour aborder le problème, deux approches à différentes échelles ont été considérées.La première, à l’échelle structurale, consiste à reconstruire le champ de déplacement de l'éolienne vue comme une structure unidimensionnelle. La présence d'un défaut induira une perte de raideur latérale, et donc une (quasi-)discontinuité dans le champ de rotation. Les défis relatifs à cette partie sont doubles : l'absence de contraste sur la tour et la prise de photos en extérieur sur une grande structure. Une technique de CIN intégrée a été utilisée afin de diminuer le nombre d'inconnues du problème et réduire les incertitudes de mesures. Il a été montré que l'influence d'un défaut, plus particulièrement d'une fissure, serait trop faible par rapport aux incertitudes de mesures. Cependant, suivant cette approche, une méthode innovante d'analyse modale de tour d'éolienne a été développée et les deux premières fréquences propres ont pu être déterminées avec précision.La seconde est une stratégie de contrôle de la structure à l'échelle mésoscopique. Celle-ci se base sur un dispositif de caméras bon marché à l'intérieur de l'éolienne couvrant les soudures circonférentielles au niveau des zones de plus fortes contraintes. L'idée est d'établir pour chaque caméra lorsque la structure est considérée comme saine une base modale de déplacement caractéristique de cet état grâce à des techniques de réduction de modèle. Au cours du temps, si un défaut sous-jacent ou traversant apparait, celui-ci induira une perturbation du champ de déplacement qui pourra être détectée à l'aide d'indicateurs globaux tels que l'écart en déplacement ou les résidus de corrélation.Afin de déterminer si la détection d'un défaut aux deux échelles est faisable ou non, la prise en compte de l'incertitude de mesure en regard de l'influence d'un défaut est primordiale. Alors, un cadre mathématique de la CIN optimale à N champs a été proposé et validé
Wind turbine technology is mature and the market has become very competitive over time. A lever to reduce the costs of wind turbine operation lies in optimizing turbine maintenance. In this context, this study focuses on the wind turbine tower. The lifetime of the tower is influenced by uncertain parameters related to the environment and material hazards. This makes it very difficult to predict the tower lifetime, and large safety factors are used when dimensioning it. However, around the world, a few wind turbines have already collapsed, each time during extreme climatic episodes. The two identified ruin causes are the local buckling of the tower and the tearing off of its upper part. Academic and industrial sources have also reported the discovery of cracks on some turbines at the weld-material interfaces. An investigation of the criticality of a crack with respect to buckling and its fatal propagation has been carried out in the case where the tower is subjected to violent loads. Finite element simulations showed that the fatal crack propagation was the limiting phenomenon for the life extension of a cracked wind turbine tower.To ensure structural integrity, health monitoring techniques were developed over time. These are generally carried out using sensors extrapolating a global state of health from local data (accelerometers, strain gauges). The risk is that a defect remains invisible but is nevertheless critical for the structure. It is therefore essential to revisit the prediction tools based on site data. Within the framework of this work, methods based on imagery and more particularly Digital Image Correlation (DIC) have been developed. To address the problem, two approaches at different scales have been considered.The first, at structural scale, consists in reconstructing the wind turbine displacement field considered as a one-dimensional structure. The presence of damage will induce a loss of lateral stiffness, and thus a (quasi-)discontinuity in the field of rotation. The challenges for this part are twofold: the lack of contrast on the tower and the capture of outdoor photographs on a large structure. An integrated DIC technique was used in order to reduce the number of unknowns in the problem and to lower the measurement uncertainties. It was shown that the influence of a damage, especially a crack, would be too small regarding the measurement uncertainties. However, an innovative method of wind turbine tower modal analysis was developed and the first two natural frequencies could be determined accurately.The second strategy is focused on a mesoscopic scale. It is based on a low-cost camera system, inside the wind turbine, covering the circumferential welds in the regions of highest stress. The idea is to establish for each camera, when the structure is considered sound, a displacement modal basis using model reduction techniques. Over time, if an underlying or through defect appears, it will induce a disturbance in the displacement field which can be detected using global indicators such as displacement deviation or DIC residuals.In order to determine whether the detection of damage at both scales is feasible or not, it is essential to take into account the measurement uncertainty. Therefore, a mathematical framework of the optimal CIN with N fields has been proposed and validated

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16

Deshmukh, Prutha. "Damage Detection Of a Cantilever Beam Using Digital Image Correlation". University of Cincinnati / OhioLINK, 2021. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1623169831665585.

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17

Vullaganti, Anoop. "Mechanical Parameter Characterization of Thin Polymer Films Using Digital Image Correlation". Thesis, Blekinge Tekniska Högskola, Institutionen för maskinteknik, 2021. http://urn.kb.se/resolve?urn=urn:nbn:se:bth-21653.

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Mechanical parameter characterization of very thin polymer films using digital im- age correlation is performed in this work. At present days DIC is widely used in the construction, food industries, and aviation. Despite advantages when compared to other conventional methods, but users still face difficulties with the analysis of thin polymers like low-density polyethylene (LDPE) and polyethylene terephthalate (PET) thin polymer films. For the application of sprays to obtain the best pattern quality as well as the potential of thin-film material properties tempering from the stochastic pattern paint. This research work will investigate the effect of several spray paints on the material response of thin polymer film. It also shows how to achieve good surface traction, time effect, and the type of spray to be used for DIC analysis. Finally, this research also studies how the width of the specimen affects the wrinkling effect, which is a common phenomenon while testing the thin polymer films and exhibits the appropriate width for reducing wrinkles on thin polymer films.

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18

Eckstein, Adric. "Development of Robust Correlation Algorithms for Image Velocimetry using Advanced Filtering". Thesis, Virginia Tech, 2007. http://hdl.handle.net/10919/36338.

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Digital Particle Image Velocimetry (DPIV) is a planar measurement technique to measure the velocity within a fluid by correlating the motion of flow tracers over a sequence of images recorded with a camera-laser system. Sophisticated digital processing algorithms are required to provide a high enough accuracy for quantitative DPIV results. This study explores the potential of a variety of cross-correlation filters to improve the accuracy and robustness of the DPIV estimation. These techniques incorporate the use of the Phase Transform (PHAT) Generalized Cross Correlation (GCC) filter applied to the image cross-correlation. The use of spatial windowing is subsequently examined and shown to be ideally suited for the use of phase correlation estimators, due to their invariance to the loss of correlation effects. The Robust Phase Correlation (RPC) estimator is introduced, with the coupled use of the phase correlation and spatial windowing. The RPC estimator additionally incorporates the use of a spectral filter designed from an analytical decomposition of the DPIV Signal-to-Noise Ratio (SNR). This estimator is validated in a variety of artificial image simulations, the JPIV standard image project, and experimental images, which indicate reductions in error on the order of 50% when correlating low SNR images. Two variations of the RPC estimator are also introduced, the Gaussian Transformed Phase Correlation (GTPC): designed to optimize the subpixel interpolation, and the Spectral Phase Correlation (SPC): estimates the image shift directly from the phase content of the correlation. While these estimators are designed for DPIV, the methodology described here provides a universal framework for digital signal correlation analysis, which could be extended to a variety of other systems.
Master of Science

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19

Salvati, Peter. "The Examination of Fracture Behavior in Anisotropic Rock with Digital Image Correlation". Thesis, University of Louisiana at Lafayette, 2017. http://pqdtopen.proquest.com/#viewpdf?dispub=10287221.

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Modern hydraulic fracturing designs assume that drilled formations are both isotropic and homogeneous, and fractures are linear and symmetrical. However, unconventional resources are often obtained from formations that are both anisotropic and heterogeneous, resulting in complex fracture behavior. The objective of this study is to evaluate fracture behavior based on the influence of anisotropy and water saturation. Isotropic and homogeneous Austin Chalk, Berea Sister Gray Sandstone, and Silurian Dolomite, laminated anisotropic and heterogeneous Parker Sandstone, Nugget Sandstone, and Winterset Limestone Carbonate, and fully anisotropic and heterogeneous Edwards Brown Carbonate cores were ordered for testing. Brazilian discs were cut according the ISRM and ASTM standards, and prepared as dry, brine saturated, and fresh water saturated samples. All samples were fractured by the Brazilian test, and laminated anisotropic samples were tested at various loading angles (0?, 15?, 30?, 45?, 90?). Tensile strengths were calculated using the peak load of the primary fracture of each sample, and the fractures were observed for geometrical trends. Additionally, the strain development of each fracture was analyzed through the application of Digital Image Correlation (DIC) software. The results determined that anisotropy and saturation can decrease the tensile strength of a formation. The fracture geometries were influenced by planes of anisotropic lamination, and fully anisotropic rocks produced winding, erratic fractures. DIC allowed for closer 101 examination of fracture development, and identified that saturation can cause failure along lamination planes subjected to less than the maximum, load induced stress. This research can be utilized to improve the hydraulic fracturing design models to optimize formation fractures, and increase revenue for the oil and gas industry.

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20

Mekky, Waleed Nicholson P. S. "Fracture toughness of the nickel-alumina laminates by digital image-correlation technique". *McMaster only, 2005.

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21

Ajmal, Osman Z. "The use of digital image correlation to monitor delaminations in composite structures". Thesis, University of Surrey, 2018. http://epubs.surrey.ac.uk/849052/.

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The range of applications for composite materials is growing, but understanding of the effect of defects is limited, as is the ability to detect them. Versatile non-destructive testing (NDT) techniques, that can be deployed rapidly and reliably, to detect and monitor damage in composite components are vital to the continued growth of this sector. This research investigates the application of Digital Image Correlation (DIC) as an NDT technique for monitoring delamination defects in Fibre Reinforced Polymer (FRP) composites. The research has matched physical experiments with Finite Element (FE) modelling. Four types of glass-fibre reinforced epoxy matrix composite structural elements were designed and manufactured to assess this application of DIC. The first two types of structural elements were flat coupons containing fully embedded delaminations, artificially introduced using two different methods. It was found that by placing these specimens in three-point bending, near surface delaminations, one ply below the surface being monitored, would cause a plateau in the surface strains. This plateau in strains was used to measure the embedded defect sizes. The size of the delamination was consistently overestimated from the interpretation of the strain fields. This was improved with the assistance of FE modelling to identify the relationship between the feature and the delamination. Pulse thermography was found to be a better technique for measuring the size of these defects. The third type of specimen was a flat coupon containing a milled-slot, which was fatigued to grow a delamination at the foot of the milled slot, and the delamination measured visually. For this specimen, the DIC results showed good correlation with the visually determined delamination lengths with an empirical fit applied to the strain results. Both lock-in thermography and pulse thermography were used to measure the delamination size of the same specimens and showed reasonable correlation with the visually determined delamination lengths. Finally, tubular specimens containing embedded PTFE delamination-defects were fatigued at different ratios of tension and torsion. DIC of the specimens loaded at the fatigue load ratio at which the delaminations were grown could not be used to quantify the size of the delaminations. The work has shown that DIC can be used to monitor delaminations in some structural elements, however the type of loading needs to be considered to ensure sufficient influence on the surface strains to enable strain features that can be used to measure the size of delamination.

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22

Buck, Nicole V. "Implementation of an Open-Source Digital Image Correlation Software for Structural Testing". DigitalCommons@CalPoly, 2020. https://digitalcommons.calpoly.edu/theses/2215.

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This thesis investigates the appropriateness of a simplified, open-source digital image correlation (DIC) software for use in quasi-static, structural testing utilizing two-dimensional (2D) DIC measurements. DIC is a non-contact optical measurement technique that uses computer vision to track unique attributes on the surface of an object. For structural testing, traditional instrumentation such as displacement sensors and strain gages are impractical for full field measurements due their limited ability to capture large amounts of data. However, over the past decade, DIC has proven a successful method for full-field kinematics measurements, making it an appealing tool for collecting high densities of accurate data. This thesis specifically studies the accuracy and limitations of the DIC software, MODEM, for various test specimens and loading conditions. This research work is part of an experimental program comprised of three phases. The first stage was conducted by another investigator on aluminum coupons tested in pure tension. These results were used to calibrate parameters (speckle pattern density, lighting, and camera settings) used with the DIC software. The second stage included pure compression tests on concrete cubes and concrete cylinders to compare the difference in results between: (i) surface curvature, (ii) camera distance, (iii) surface treatment, and (iv) speckle pattern color. The final stage involved analysis of a tension test of a concrete prism completed at the University of Auckland in an effort to assess how MODEM could be utilized to accurately detect onset and propagation of concrete cracking. Results showed the most accurate DIC strains were within 5% error when compared to traditional instrumentation for aluminum loaded in tension and within 6% error for concrete loaded in compression/tension. This level of accuracy is comparable to existing open source and commercial DIC software utilizing 2D DIC analysis. Therefore, MODEM can be used to provide accurate 2D DIC strain measurements for small and medium scale structural test specimens when using the following parameters: (i) the surface of the specimen is planar, (ii) the camera is placed accordingly so the maximum amount of zoom can be used, (iii) the surface of a test specimen is free of debris or imperfections, and (iv) a high contrast and evenly distributed speckle pattern is used. Computational analysis of the results showed that known material properties can be used to calibrate, or remove errors from, the DIC results when traditional instrumentation is not available. Additionally, results showed MODEM strain contours can be used for initial detection of cracks in concrete loaded in tension while MODEM tracking performance can be used to characterize the centerline and orientation of cracks. The experimental tests provide critical information on how to set up, run, and analyze DIC results when using MODEM. The full field measurements are of value in providing accurate data for structural testing to develop a better understanding of material response and structural performance, since large-scale tests are typically limited by a sparse number of data points when using traditional instrumentation.

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Jiang, Yanxia. "MEASUREMENT OF J-INTEGRAL VALUES OF DENTAL CERAMICS BY DIGITAL IMAGE CORRELATION". Case Western Reserve University School of Graduate Studies / OhioLINK, 2016. http://rave.ohiolink.edu/etdc/view?acc_num=case1453880114.

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24

Wang, Dezhi. "Kriging regression in digital image correlation for error reduction and uncertainty quantification". Thesis, University of Liverpool, 2015. http://livrepository.liverpool.ac.uk/2029379/.

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Digital Image Correlation (DIC) is a widely used full-field measurement technique in the field of experimental mechanics because of its simplicity and ease of implementation. However, owing to the inherent complexity of DIC error sources, the problem of DIC error reduction and uncertainty quantification is still unsolved and has received considerable attention in recent years. The existing work on DIC error reduction is usually focused on specific error sources, e.g. local smoothing techniques are normally applied to reduce errors due to image acquisition noise. Moreover, DIC uncertainty quantification methods are usually derived from a subset-based DIC framework with an assumption of Gaussian image noise. Established methods are normally subject to an ad-hoc choice of parameterisation and might only be able to achieve a local optimum. On the other hand, originally developed in geo-statistics, Kriging is known as optimal interpolation to predict interpolated values using random variables as a realization of a Gaussian process. The Kriging technique has the excellent capability in global optimisation and uncertainty quantification. It is advisable to make an attempt to introduce the Kriging method to DIC to facilitate the solution of error and uncertainty issue. The main purpose of this thesis is to offer a generic and global method that can reduce general DIC errors and quantify measurement uncertainty for displacement and strain results based on Kriging regression from Gaussian Process (GP) and Bayesian perspective. Firstly, a new global DIC approach known as Kriging-DIC was developed through incorporating the Kriging regression model into the classical global DIC algorithm as a full-field shape function. The displacement field of the Region of Interest (RoI) is formulated as a best linear unbiased realisation that contains correlations between all the samples. The measurement errors of control points are accounted for through a global regularisation technique using a global error factor. With the aid of the Mean Squared Error (MSE) determined from the Kriging model, a self-adaptive updating strategy was developed to achieve an optimal control grid without artificial supervision. The developed Kriging DIC method was compared with subset-based DIC, FE-DIC and B-Spline DIC by using synthetic images and open-access experimental data. The effectiveness and robustness of Kriging DIC was verified by numerical examples and an experimental I-section beam test. Secondly, a Kriging-based DIC uncertainty quantification method was proposed to quantify uncertainty of displacement and strain results of the subset-based DIC through a post-processing analysis based on Kriging regression. The subset-by-subset uncertainty was estimated through the subset-based DIC framework and derived as a function of the inverse of the Hessian matrix and residual of Sum of Squared Difference (SSD). This local subset-based uncertainty was then integrated into Kriging regression formula allowing uncertainty quantification of displacement field from a global sense. Based on Cholesky decomposition and covariance matrix solved by the Kriging formula, a multivariate normal sampling process was used to quantify the strain uncertainty whereas displacement gradients were calculated by a Finite Difference technique. Both numerical case studies and an experimental cantilever beam test were employed to test the method, which was found to be able to improve the accuracy of displacement and strain results and quantify corresponding uncertainties. Furthermore, a new approach was developed to calculate strain results by means of Kriging gradients, which was also compared with a state-of-the-art PLS local fitting algorithm. In summary, the main contribution of this thesis is the development of a global DIC algorithm (i.e. Kriging-DIC) and a Kriging-based DIC uncertainty quantification approach. These two methods provide great potential to globally improve DIC measurement accuracy and quantify uncertainties of displacement and strain results.

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Lim, WeiChiang Eric. "EMBEDDED SPECKLE BONDLINE DEFECT DETECTION USING ULTRASONIC DIGITAL IMAGE CORRELATION (UT-DIC)". OpenSIUC, 2018. https://opensiuc.lib.siu.edu/theses/2391.

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The primary objective of this research is to conduct further evaluation of ultrasonic digital image correlation (UT-DIC) on strain map analysis and defect detection of adhesive joints with embedded speckle pattern. UT-DIC is a non-destructive evaluation method that utilized ultrasonic C-scan images for whole field strain and displacement analysis. Acrylic glass, epoxy resin system and metal shavings with high acoustic impedance of a specific weight were used to create the samples which were loaded under tension. Defects with varying shapes and sizes were implemented by surface preparation to understand the limits of this approach. UT-DIC and optical DIC strain map results were compared, and it was found that each approach detected certain shapes of defect better than the other.

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26

Mamand, Heman. "The assessment of deteriorated concrete structures using extended digital image correlation (EDIC)". Thesis, University of Portsmouth, 2015. https://researchportal.port.ac.uk/portal/en/theses/the-assessment-of-deteriorated-concrete-structures-using-extended-digital-image-correlation-edic(91a6f1a9-6c0b-4b5c-8715-8edb4194ccac).html.

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Concrete structures in marine environments frequently experience long-term deterioration due to environmental exposure. This exposure results in surface damage with the subsequent spalling of concrete, which has a significant effect on the long-term durability of the structure. The reinforced concrete jetty investigated in this study suffered similar problems. The concrete jetty is located on the South East England coast. The jetty consists of a deck that is part precast and part in-situ cast, which is supported by steel, concrete and a sheet pile wall. Five decades after its construction, erosion by sea water is the most serious problem facing the jetty structure and has resulted in significant deterioration and surface damage. This project was established to evaluate the damage level of the jetty using an extended non-destructive measurement approach with an FEA simulation. The basic non-destructive measurement technique used in this investigation is a digital image correlation (DIC) optical system. The current DIC technique is limited to detecting macro cracks; thus, this investigation aims to develop an Extended Digital Image Correlation (EDIC) method to extend the capability of the current DIC from measuring the strain field to detecting multiscale cracks and predicting micro crack propagation. There is an industrial necessity to enhance the damage assessment level based on micro-crack detection. The EDIC study was performed empirically and demonstrated an important role in detecting damaged zones and multiscale cracks, including micro- and macro-cracks of the concrete surface. The EDIC can be used for further studies on detailed damage mechanisms in concrete and other engineering materials, such as timber or masonry structures. The assessment provide information on the current structural degradation, load bearing capacity and safety margin of the damaged jetty. To simulate the ageing jetty numerically, a material model of the ageing concrete was created in terms of the tested core samples obtained from the jetty structure, and the model was implemented in an UMAT subroutine in ABAQUS for FEA simulation. The mechanical properties of the ageing jetty obtained from the experimental tests proved to be suitable, with a compressive and tensile strength of approximately 67 MPa and 4.2 MPa, respectively, and the elastic modulus was 38728 MPa. Using the DIC in situ assessment and FEA simulation, the damage evaluation was completed. The results indicated a considerable decrease in the structural stiffness of the damaged jetty of approximately 40%. The load bearing capacity of the damaged jetty reported was approximately 240 tonnes. Despite the significant damage, the safety margin under the current practical loading condition (162 tonnes) is still high, i.e., approximately 1.48. However, due to the severe condition of the damaged jetty located in an aggressive marine environment and the loading impacts, it is highly recommended that the cracks and corrosion be immediately stopped and controlled. Furthermore, for safety reasons, any additional loads in conjunction with the current practical load (162 tonnes) should be avoided.

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Thai, Thinh Quang. "Importance of Exposure Time on Digital Image Correlation (DIC) at Extreme Temperatures". DigitalCommons@USU, 2018. https://digitalcommons.usu.edu/etd/7067.

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Extreme temperatures have increasingly played an important role in engineering applications, including leading edges during hypersonic flight, spacecraft re-entry, and propulsion systems. In order to design for such thermo-mechanical conditions, materials must be characterized using suitable measurement methods. DIC is a popular and versatile method in full-field measurement. In brief, DIC compares images of a sample between its undeformed and deformed state in order to get displacement and strain field maps. Since the images are acquired from digital cameras, it is important to have high contrast images for meaningful correlation. Exposure time is a pivotal camera setting relating to camera sensitivity. Alteration in exposure time results in variation of image contrast, thereby affecting DIC correlation. Also, it is well known that at extreme temperatures, materials emit light which can saturate DIC camera sensors, but the light can be mitigated using optical bandpass filters. In previous work, many have shown that blue bandpass filters can effectively extend the temperature range of DIC, and our lab has shown that ultraviolet (UV) filters can extend the range further. In this thesis, four different temperatures: room temperature, 1300°C, 1450°C, and 1600°C were tested by rigid-motion experiments. At each temperature level, UV images were acquired in order to examine the variation of DIC error over the whole range of exposure time. UV images were acquired at exposure times ranging from 500μs to 61,000μs, which are the minimum and maximum possible values for the cameras used in this thesis. The results showed that there were higher errors of UV-DIC at extremely dark or bright exposure times where as errors were generally insignificant at intermediate exposure times. In order to perform meaningful DIC up to 1600oC, the exposure time for the camera used in this thesis is suggested to be set between 10,000μs and 40,000μs.

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Barhli, Selim Matthias. "Advanced quantitative analysis of crack fields, observed by 2D and 3D image correlation, volume correlation and diffraction mapping". Thesis, University of Oxford, 2017. https://ora.ox.ac.uk/objects/uuid:d6240241-8a1e-4a8e-aff0-4a2ef14b0da7.

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This thesis is concerned with the evaluation, in-situ, of the elastic strain energy release rate of cracks. This can define the criteria for crack propagation, and it is usually necessary to obtain this via calculation from the geometry and applied load. A new method is proposed, based on the conjoint use of digital image correlation to measure full-field displacements and finite element to extract the strain energy release rate of surface cracks. It has been extended to 3-D datasets with the use of digital volume correlation and tomographic imaging. A finite element model with imported full-field displacements measured by DIC/DVC acting as boundary conditions is solved and the J-integral is calculated. For linear elastic materials, modal contributions can be separated via the interaction integral. The method has been benchmarked using synthetic datasets to assess its sensitivity to noise and experimental uncertainties. It is very robust to experimental noise and can be used without knowledge of the specimen geometry and applied loads. The application of the method in 2-D is demonstrated in an analysis of experimental data for a mode I fatigue crack, introduced to an aluminium alloy compact tension specimen. Analysis of mixed-mode cracks in 2-D is shown on a PMMA sample with the Arcan geometry. In 3-D, static loading of a fatigue crack in nodular graphite cast iron is studied and the results from the method are compared with those obtained via a field-fitting approach. Diffraction analysis of polycrystalline materials can determine the full tensor of the elastic strains within them. Maps of elastic strains can thus be obtained typically using synchrotron X-rays or neutrons. A method is presented to calculate the elastic strain energy release rate of a crack from 2-D diffraction strain maps. The diffraction data is processed via a finite element approach to obtain the parameters required to calculate the $J$-integral. A validation is presented using a synthetic dataset from a finite element model. Its experimental application is demonstrated in an analysis of synchrotron X-ray diffraction strain maps of a propagating fatigue crack in a bainitic steel, before and after an overload. Finally, a complex case study of stable fracture propagation in polygranular isotropic nuclear graphite is presented. Synchrotron X-ray tomography and strain mapping by diffraction were combined with DVC and image analysis to extract the full-field displacements and elastic crystal strains. The displacement fields have been analysed using the developed methods to extract the critical strain energy release rate for crack propagation. Non-linear properties described the effect of microcracking on the elastic modulus in the fracture process zone. The analysis was verified by comparison of the predicted and measured elastic strain fields.

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Lan, Yusha. "Macroscale Analysis of Strain Path Change Effects in AA3104 by Digital Image Correlation". Thesis, Université d'Ottawa / University of Ottawa, 2014. http://hdl.handle.net/10393/31350.

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Cold rolled aluminum is a widely used metal in industry. The forming limit diagram (FLD) which is commonly used to predict safe deformation parameters currently fails to predict the uniform elongation after non-proportional strain path often found in industrial operations. In this work, a non-proportional strain path change in aluminum alloy 3104 going from plane strain tension to uniaxial tension was investigated. Plane strain tensile tests have been carried out to various pre-strains (3%, 6% and 9%), followed by uniaxial tensile tests at various orientation with respect to the tensile direction (0°, 45° and 90°). Digital image correlation (DIC) was employed to analyze the strain distribution in the sample during deformation. The mechanical response was studied as a function of pre-strain and reloading angle to quantify the effect of strain path change on AA3104.

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Gustafson, Hannah Marie. "Quantifying the response of vertebral bodies to compressive loading using digital image correlation". Thesis, University of British Columbia, 2016. http://hdl.handle.net/2429/59416.

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Understanding vertebral mechanics is of interest for identifying persons at risk of fracture, whether that is due to everyday loading such as in osteoporotic fracture or as a result of dynamic loading leading to a traumatic fracture. Vertebral fractures negatively impact the quality life of patients and represent a large financial burden on the healthcare system. A powerful but underutilized tool that can be used to study vertebral loading and fracture is digital image correlation (DIC). DIC is a non-contact optical method for measuring the displacement on the surface of materials, including bone. In this thesis, DIC was used in a laboratory setting to provide a more complete understanding of the response of vertebral bodies to compressive loading. The first investigation compared measurements from DIC with strain gages, a commonly accepted experimental method for measuring the bone surface response. For porcine vertebral bodies, the agreement was strong between the strain gages and DIC-measured strains indicating that DIC can be successfully used on bone. Based on those findings, experimental studies were performed using DIC to identify fracture of the anterior cortex and to quantify rate-dependency of the vertebral body response. For the fracture study, high DIC strains on the anterior cortex of vertebral bodies corresponded well with the locations of damage identified by observation of the video. For the rate-dependency study, the DIC displacement patterns were similar for the slow and fast rate tests, but the displacements from the slow rate tests had higher magnitudes, as expected for viscoelastic materials such as bone. Finally, specimen-specific finite element (FE) vertebral body models were created and DIC was used to validate the displacement and stiffness response. The FE models were predictive of the experimental stiffnesses measured using DIC on the surface of the vertebrae. This thesis demonstrates the utility of DIC for experimental vertebral body investigations and for validation of FE models. Through these studies and future work, DIC has advanced and will continue to advance the understanding of vertebral mechanics under everyday loads as well as in simulated osteoporotic and healthy bone trauma.
Applied Science, Faculty of
Graduate

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Gadepalli, Prasanna Chaitanya. "USING THREE-DIMENSIONAL DIGITAL IMAGE CORRELATION TO FIND STRAINS IN STRUCTURAL POLYMER FOAM". University of Akron / OhioLINK, 2020. http://rave.ohiolink.edu/etdc/view?acc_num=akron1595947881930553.

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Shrestha, Sulochana Shrestha. "STUDY OF FATIGUE CRACK PROPAGATION ON METALS USING ACOUSTIC EMISSION AND ELECTRIC RESISTIVITY IN CORRELATION WITH DIGITAL IMAGE CORRELATION". University of Akron / OhioLINK, 2018. http://rave.ohiolink.edu/etdc/view?acc_num=akron1525705916102737.

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Aswad, Mohsin Abbas. "Residual stress and fracture in high temperature ceramics". Thesis, University of Manchester, 2012. https://www.research.manchester.ac.uk/portal/en/theses/residual-stress-and-fracture-in-high-temperature-ceramics(2d617cd5-ac5c-4927-8b87-cae0fdcee6da).html.

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Recrystallised alumina is used as a high performance crucible material. Its thermal shock resistance is known to be affected by component shape, and also by processing variables, since the defects and internal stress at both the microscale (i.e. between grains due to anisotropic crystal properties) and macroscale (i.e. due to differential shrinkage during sintering) influence the fracture strength. The aim of this thesis is to study the nucleation and growth of defects in pure alumina and Cr-doped alumina, and to investigate how their behavior is affected by residual stresses, such those introduce by thermal expansion of the crystal grains. In this thesis, digital image correlation is applied to polycrystalline aluminas (i.e. Cr-doped alumina and pure alumina with average grain 3.6 µm and 1.5 µm respectively) that are stressed in an optical microscope. The defect size and the surface crack opening displacement were measured using digital image correlation. The distribution and population of crack nucleating defects were obtained by in-situ observation of the stressed surface and by analysis with digital image correlation. These data are then compared with independent measurements of the defect population using Hertzian indentation, from which defect populations are derived for the pure and Cr-doped alumina samples. Grain boundary plane and grain orientations in the vicinity of crack nuclei were characterised by electron microscopy. Crack nuclei were shown to develop at boundaries predicted to have high tensile thermal strains, caused by the orientation of the grain boundary plane relative to the adjacent grains, such as basal plane grain facets. The techniques of focused ion beam (FIB) milling and electron backscatter diffraction (EBSD) characterization of the crystallographic orientations and structure of cracked grain boundaries were used to provide data for a model to explain the cracking of these boundaries as a result of the thermal strains and the anisotropic thermal expansion behaviour of alumina.

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Keller, Jürgen. "Micro- and nanoscale characterization of polymeric materials by means of digital image correlation techniques". kostenfrei, 2005. http://deposit.ddb.de/cgi-bin/dokserv?idn=975021079.

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35

Khennouf, Djallal. "Assessing the feasibility of using digital image correlation to monitor deformation in historical tapestries". Thesis, University of Southampton, 2011. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.538985.

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36

Liutkus, Timothy James. "Digital Image Correlation in Dynamic Punch Testing and Plastic Deformation Behavior of Inconel 718". The Ohio State University, 2014. http://rave.ohiolink.edu/etdc/view?acc_num=osu1397751677.

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37

Lee, Dong Gun. "Strain measurement of flip-chip solder bumps using digital image correlation with optical microscopy". Diss., Online access via UMI:, 2009.

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Abstract (sommario):

Thesis (M.S.)--State University of New York at Binghamton, Thomas J. Watson School of Engineering and Applied Science, Department of Mechanical Engineering, 2009.
Includes bibliographical references.

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38

Ferreira, Catarina Duarte Barros. "Digital Image Correlation for Vibration Analysis". Master's thesis, 2021. https://hdl.handle.net/10216/136673.

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Hung, Po-Chih. "Strain analysis by digital image correlation /". Diss., 1998. http://gateway.proquest.com/openurl?url_ver=Z39.88-2004&rft_val_fmt=info:ofi/fmt:kev:mtx:dissertation&res_dat=xri:pqdiss&rft_dat=xri:pqdiss:9914246.

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40

Ceng, Shun-Long, e 曾舜隆. "Digital image correlation for large deformation measurement". Thesis, 2014. http://ndltd.ncl.edu.tw/handle/13662027928882515729.

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碩士
國立中興大學
機械工程學系所
102
The present study has developed a plane displacement measurement system based on a digital image correlation method. For these purposes,the strain of large deformation was defined as 40%. A series of analyses was performed on the images before and after deformation, including correlational analysis, connected component labeling, and shape interpolation function analysis. Furthermore, optimizations were made employing displacement equations and brightness of transformation models, in conjunction with Newton’s method. Iterative methods were used to find the underwent displacement of an object after deformation,finally determining the surface displacement field and the strain field. However, the use of Newton’s method iteration methods requires inputting an initial value. These values must first be derived by marking each connected area with connected component labeling, then constructing a grid with this data and corresponding the before-after images based on this grid. The methods of this study were to print prepared images onto the object being tested, then to record digital images of the object before and after deformation. Analysis was conducted with software based on digital image correlation theory and shape function, to determine the displacement field of the object’s surface,concluding with a discussion of the displacement field derived from analysis, and possible improvements to be made for future investigations.

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Chen, Yu-Hsiang, e 陳鈺翔. "Strain Measurement Using Digital Image Correlation Method". Thesis, 2011. http://ndltd.ncl.edu.tw/handle/10901417533429290795.

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碩士
國立中興大學
機械工程學系所
99
Digital image correlation method is a non-contact, non-destructive optical measuring method, the principle is the second image by comparing each pixel with the first image (reference image) in the fixed point of reference pixel correlation to find images from the second image with the first reference pixel has a maximum correlation of the pixels, the point that this reference in the second pixel of the image of the corresponding points in the statistics there are several kinds of method used to calculate the correlation coefficient, used in digital image correlation method is the most common use of Pearson''s correlation coefficient for correlation matching of operations. In this study, obtained by deformation of the surface before and after images, and image distortion as a reference image before using the digital image correlation method to find the reference image of each pixel in the deformed image of the integer corresponding to the point, and by a simple displacement equation and the brightness of the transformation model with the theory of the Newton equation of motion optimization, and then obtained through iteration after the surface displacement and strain in the deformation of sub-pixel part, and then calculate the displacement and strain by filtering the of smoothing, and then obtain the deformed surface in the global displacement field and strain field.

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Jiang, Jei-Wei, e 江偉傑. "Digital Image Correlation Applied in Strain Measurement". Thesis, 2004. http://ndltd.ncl.edu.tw/handle/85723835291767600728.

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Abstract (sommario):

碩士
國立雲林科技大學
機械工程系碩士班
92
This text presents a new numerical conception of digital image correlation to measure full-field strain in planar specimen which is suffering external force. This new method can afford strain information on entire field of specimen surface by processing two digital images which were respectively caught from the unforced and forced specimen. The new numerical procedures here aim at making this method a widely applicatory strain measuring method. It means that ideally this method can be applied in various conditions. Two numerical iterative methods are used to conclude the whole optimized strain solution in this research. Both two numerical methods can appropriately be called “selectively exhaustive optimization”.This is because each iterative method is an exhaustive optimization method with techniques of reducing time consumption. While all numerical procedures finished, the optimized strain solutions are verified and compared with the experimental results from MTS.

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Botha, Theunis R. "Digital Image Correlation : applications in Vehicle Dynamics". Thesis, 2015. http://hdl.handle.net/2263/45956.

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Abstract (sommario):

Except for aerodynamics forces, all vehicle excitation forces are generated at the tyre-road interface. Considering low speed applications, such as terramechanics where the aerodynamics force are negligible, the road-tyre interaction is of extreme importance. Crucial variables which govern the forces generated at the tyre-road interface are tyre side-slip angle, tyre longitudinal slip ratio and terrain pro le. Solutions to measure these variables exist for smooth hard roads but the solutions experience challenges on rough and o -road terrain. Digital Image Correlation is concerned with tracking the changes of a scene in a sequence of images or in images obtained from multiple viewpoints. These methods are frequently used in micro and nano-scale mechanical testing due to its ease of implementation and use as well as its non-contact approach. As a result these techniques are being implemented in many elds from material testing, physics, lm animations and engineering. The aim of this thesis is to investigate the applications of Digital Image Correlation in vehicle dynamics using cost e cient o -the-shelf digital cameras and lenses. The following three vehicle dynamic problems are investigated: The measurement of the vehicle side-slip angle, longitudinal slip-ratio of a pneumatic tyre and high delity terrain pro ling. The vehicle side-slip angle can be used as a measure of the vehicle stability and therefore be used to improve the e ectiveness of vehicle stability controllers. The tyre side-slip angle is also a vital measurement in characterising the lateral force characteristics of pneumatic tyres. A planar measuring method using Digital Image Correlation is shown to accurately measure the side-slip angle. The method is expanded by developing two additional algorithms which can measure all translational and rotational velocities. These methods are validated on both smooth surfaces and rough o -road terrain. A method is also implemented whereby the longitudinal slip ratio of a tyre can be measured using a single camera. Therefore, doing away with the conventional method of using three independent measurement systems. Features in the contact patch, encompassing both the tyre and the road, are tracked in a sequence of images. The features are classi ed into features lying on the tyre, road and outliers using a clustering algorithm. This enables the system to determine the tyre and road velocities from which the slip ratio is determined. High delity terrain pro ling is performed using a calibrated stereographic rig to obtain a three dimensional point cloud of the scene which is being viewed. The point cloud generated at one sample contains a grid of points encompassing a large area with points spaced both laterally and longitudinally. Overlapping point clouds are generated and joined using various registration techniques. The joined point clouds are sub-sampled to obtain a regularised grid of point containing a single point cloud of non overlapping points. The proposed techniques create new possibilities in the eld of vehicle dynamics. Enabling the side-slip angle to be measured in rough of road conditions while providing additional measurements. The longitudinal slip ratio which is measured directly at the contact patch could pave the way for better understanding the mechanism of the longitudinal tyre force generation. The inexpensive road pro ling systems enables multiple sensors to be used in terramechanics tests to determine the impact of a vehicle on the environment. The thesis presents the mere tip of the ice berg concerning digital image correlation used in vehicle dynamics with many more possibilities waiting to be discovered.
Thesis (PhD)--University of Pretoria, 2015.
tm2015
Mechanical and Aeronautical Engineering
PhD
Unrestricted

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44

Yang, Jin. "Fast Adaptive Augmented Lagrangian Digital Image Correlation". Thesis, 2019. https://thesis.library.caltech.edu/11233/1/Yang_Jin_2019.pdf.

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Digital image correlation (DIC) is a powerful experimental technique for measuring full-field displacement and strain. The basic idea of the method is to compare images of an object decorated with a speckle pattern before and after deformation in order to compute the displacement and strain fields. Local Subset DIC and finite element-based Global DIC are two widely used image matching methods; however there are some drawbacks to these methods. In Local Subset DIC, the computed displacement field may not satisfy compatibility, and the deformation gradient may be noisy, especially when the subset size is small. Global DIC incorporates displacement compatibility, but can be computationally expensive. In this thesis, we propose a new method, the augmented-Lagrangian digital image correlation (ALDIC), that combines the advantages of both the local (fast and in parallel) and global (compatible) methods. We demonstrate that ALDIC has higher accuracy and behaves more robustly compared to both Local Subset DIC and Global DIC.

DIC requires a large number of high resolution images, which imposes significant needs on data storage and transmission. We combined DIC algorithms with image compression techniques and show that it is possible to obtain accurate displace- ment and strain fields with only 5 % of the original image size. We studied two compression techniques – discrete cosine transform (DCT) and wavelet transform, and three DIC algorithms – Local Subset DIC, Global DIC and our newly proposed augmented Lagrangian DIC (ALDIC). We found the Local Subset DIC leads to the largest errors and ALDIC to the smallest when compressed images are used. We also found wavelet-based image compression introduces less error compared to DCT image compression.

To further speed up and improve the accuracy of DIC algorithms, especially in the study of complex heterogeneous strain fields at various length scales, we apply an adaptive finite element mesh to DIC methods. We develop a new h-adaptive technique and apply it to ALDIC. We show that this adaptive mesh ALDIC algorithm significantly decreases computation time with no loss (and some gain) in accuracy.

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45

ZHOU, YOU-LIANG, e 周祐諒. "Application of the digital image correlation method to image stitching". Thesis, 2016. http://ndltd.ncl.edu.tw/handle/17087065999970008153.

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碩士
國立高雄大學
土木與環境工程學系碩士班
104
Unmanned aerial vehicle (UAV) can be used to take aerial photographs, and it has been rapidly developed in many fields in recent years. This study uses digital image correlation method (DIC) to increase precision of image stitching and three-dimensional terrain model. DIC will be applied in two ways. Firstly, DIC is used to locate control points’ image positions in different photos, so that the precision of image stitching and three-dimensional terrain model will increase by raising control points’ precision. Secondly, DIC is used to match feature points which extracted by SURF algorithm and then these points are imported into Pix4dmapper to increase the precision of image stitching and three-dimensional terrain model. An experiment is carried out to compare the precision of various image matching methods, such as SIFT, SURF, BRISK as well as DIC. The results of different movements in x and y directions show that the precisions of SIFT、SURF and BRISK range from 0.1 to 1 pixel and the precision of DIC is 0.02pixel. It shows that DIC is more accurate than the other methods. Furthermore, this study compares two different methods adopted to obtain the image coordinates of control points. In one of the method, the control points’ image coordinates are positioned manually. The other method will use DIC method to improve the precision of manually positioned control points. Ladder specimen’s results show that the positioning precision by using DIC is 0.08 mm while the manual positioning precision is 0.201 mm, 3D model specimen’s results show that the positioning precision by using DIC is 0.48 mm while the manual positioning precision is 0.696 mm. It shows that applying DIC to positioning control points can improve the precision. Eventually, this study carries out two indoor experiments to evaluate the influence of different amounts of DIC connection points and SURF connection points on the precision of image stitching and three-dimensional terrain model. According to the altitude error of check points from ladder specimen and 3D model specimen, we can find that importing DIC connection points can increase the precision of image stitching and three-dimensional terrain model. The magnitude of improvement will be raised as the amount of connection points increases, and its effect is better than importing SURF connection points. Ladder specimen’s result shows that the altitude error is 0.08mm without connection points. The best result is 0.049mm while importing DIC connection points. The 3D model specimen’s result shows that the altitude error is 0.48mm without connection point. The best result is 0.27mm while importing DIC connection points. These results show that applying DIC to image stitching and three-dimensional terrain model establishment can actually improve the precision.

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46

Dutton, MICHAEL. "Digital Image Correlation for Evaluating Structural Engineering Materials". Thesis, 2012. http://hdl.handle.net/1974/7552.

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In the structural engineering community, a need exists for a non-contact two-dimensional measurement system which could provide information for field monitoring and greatly enhance the accuracy of numerical structural models. Recent advances have enabled the use of digital image correlation (DIC) to calculate the surface displacements of chosen targets in a series of digital images with a high degree of accuracy. Images are recorded during an experiment and are afterwards post-processed to find relevant information including, but not limited to, a) global displacement, b) relative displacement and c) changes in strain. In this research, a series of experiments were conducted to create measurement techniques for monitoring steel and reinforced concrete (RC) structures utilizing DIC. However, to ensure accurate DIC measurements, the addition of artificial texture from lightly applied spray paint on finished concrete was investigated and was determined to noticeably improve results. Furthermore, the placement of the digital camera relative to the structure being monitored was shown to control not only the desired field of view in the region of interest, but also the resulting image texture and DIC measurement accuracy. The DIC technique was applied to monitor and understand two important aspects of structural evaluation: a) the movement along shear planes and b) the evaluation of changes in strain due to curvature in beam elements. To monitor the change in crack width and slip, a method was created and validated on a series of artificial and reinforced concrete images for the cases of pure shear, pure flexure and combine flexure and shear. Curvature was found to impact the crack slip measurement, but its effect can be removed by using an innovative averaging technique. The curvature of a steel HSS and RC beams was found by using virtual DIC strain gauges and the horizontal strain profile. Results matched well with the curvature from electrical foil gauges and numerical models when the gauge length was maximized and selected so that the effects of cracking were accounted for.
Thesis (Master, Civil Engineering) -- Queen's University, 2012-09-28 09:36:04.274

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47

Dong, Zuo-Chun, e 董作群. "Using digital image correlation in triaxial stress sensor". Thesis, 2015. http://ndltd.ncl.edu.tw/handle/11275044670372839084.

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碩士
國立交通大學
機械工程系所
104
The present study aims to using DIC(Digital Image Correlation) in the development of a triaxial stress sensor system.The sensor can measure normal and shear stress at the same time. Toward this end, a standard operating procedure for manufacturing a novel triaxial stress sensor has been established. The sensor system includes a flexible and transparent material(PDMS), a series of image sensors as well as a data acquisition and processing system. Therefore, when the material deforms with external load, using image sensors and DIC algorithm to calculate the displacement of the material from the images. The stress-displacement relationship of the PDMS material, obtained by means of calibration experiments and numerical simulations, can then be incorporated to recover the normal and shear stress.In this thesis, according to normal and shear and both force, present recover result with overall system. the results will compare with numerical simulations.

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48

Liao, Jhan-Jhang, e 廖展章. "Digital Image Forensic Method Using Image Invariant Feature and Region Correlation". Thesis, 2012. http://ndltd.ncl.edu.tw/handle/9xum86.

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碩士
國立臺北科技大學
電機工程系研究所
100
With the coming of age of the digital era, it brings us a colorful digital life. However, the authenticity of digital image has become an important issue as the digital image is easily modified. Region duplication is a common and simple way to modify or tamper the digital image. The recent methods proposed in literature are based on spare image invariant feature (such as SIFT, SURF), and can effectively detect the geometric and brightness tampering. However, they fail to detect the tampering when the image invariant feature is inadequate, and often misclassify the original contents as the duplication tampering when the image contains the intrinsic repeated elements. Our method proposes a modified SIFT algorithm, an image invariant feature clustering analysis, and local outlier detection to improve the above problem. In order to locate the tampering region, we design an adaptive tampering locating method based on image local region correlation and image texture feature. We evaluate our proposed approach on tampered images with and without intrinsic repeated elements, and the geometry and brightness of the tampered duplicated region is further altered by an automatic forgery program. The experimental results and analyses demonstrate that our proposed method is robust and effective in region duplication detection.

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49

Shen, Min-Chien, e 沈旻建. "Strain and Morphology Measurement by Digital Image Correlation Method". Thesis, 2011. http://ndltd.ncl.edu.tw/handle/61983871064415332864.

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Abstract (sommario):

碩士
國立雲林科技大學
機械工程系碩士班
99
Digital image correlation (DIC) is a whole-field, non-contact and non-destructive strain measuring method. This method captures the surface image of a specimen before and after the deformation, and then the displacement as well as strain information about the surface of the specimen can be obtained by analyzing the change of the images. In this work, a two-step DIC is presented. In the first step, the coarse-fine iterative technique is used to search the displacement of an interested region of the specimen, and then the strain can be obtained by utilizing the finite element method in the second step. To verify the accuracy of this method, a rigid-body motion experiment which prevents the error from the CCD sensor, lighting or other experimental error resource is used. On the surface of the specimen, random specimen speckle pattern by spray paint have been tested. Strain gauges are adhered on the back of the specimen. Furthermore, to have a more stable light resource, we provide the Halogens light as well. By comparing the value from the strain gauge and the method, one can verify the accuracy of DIC. In addition, the effects of image filters (wiener2) and the adjacent images are considered. Also composite material specimens and polymer material specimens are tested to obtain their mechanical properties. Then, the development of three-dimensional digital Image correlation method is developed. The obtained morphology from the surface of a specimen is compared to those obtained from reversed engineering-3D optical scanning system.

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50

Cai, Shun-Ji, e 蔡舜吉. "Digital Image Correlation for analysis of cracked cylindrical pipes". Thesis, 2009. http://ndltd.ncl.edu.tw/handle/41222012644669684387.

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Abstract (sommario):

碩士
國立中興大學
土木工程學系所
97
Abstract The stress concentration at the tip of the crack in the penstock may ignite the fast crack growth and lead to the total failure of the penstock. In the study, the technique of Digital Image Correlation (DIC) is applied to detect the strain distribution around the crack tip in a penstock subjected to the pressure of water. With the experiment results, the DIC solutions are in very good agreement with that of finite element within the elastic range of the material. This shows the technique of Digital Image Correlation is feasible in use for strain measurement for penstock.

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