Importance of Exposure Time on DIC Measurement Uncertainty at Extreme Temperatures

Thai, Thinh; Hansen, Robert S.; Smith, A. G. R.; Lambros, John; Berke, Ryan

doi:10.1007/s40799-019-00313-3

Cited by 28 publications

(29 citation statements)

References 23 publications

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“…For comparison purposes, a sixth speckle pattern (RANDOM) was produced using a toothbrush speckling method as advised by Thai 16 and Berke 20 in the documentation above. For this pattern, a wooden craft stick of the same size, shape, and material as the text-patterned specimens was spray painted with white paint to produce a solid white background.…”

Section: Methodsmentioning

confidence: 99%

“…As recommended by Reu, 12 all patterns have at least 50 grayscale values between a “typical” dark speckle and “typical” bright speckle. In this case, the “typical” grayscale values are selected based on the recommendation by Thai 16 that this grayscale metric include the median 90% of all pixels. Thus, the typical dark pixel is found by integrating from 0% to 5% of the area under the histogram, and similarly the typical light pixel grayscale value is found by integrating up to 95% of the area under the histogram.…”

Section: Methodsmentioning

confidence: 99%

“…There should be at least 50 gray levels between the light and dark pixels. 16 An ideal speckle pattern has equally sized and distributed light and dark speckle areas. 17 Ideal speckle patterns adhere well enough to the surface of the sample so that they deform with the sample as the sample moves.…”

Section: Introductionmentioning

confidence: 99%

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Using text as a native speckle pattern in digital image correlation

Craig

Leeuwen

Jarrett

et al. 2021

The Journal of Strain Analysis for Engineering Design

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In certain applications, native surface patterns can be used in place of speckle patterns in digital image correlation (DIC). This paper explores the feasibility of using text as a native speckle pattern in DIC. Five text speckle patterns are tested in three different scenarios: a rigid body translation test, a rigid body rotation test, and an out of plane bending test. The patterns are benchmarked against a sixth, random speckle pattern applied using traditional DIC speckling methods. Rigid body translation tests are additionally performed on text patterns with varying font types and line spacings. In general, text patterns have good contrast, but low density as line spacing increases. Measurement uncertainty for the text patterns was comparable to measurement uncertainty in the random speckle pattern. Results from these tests show that while text patterns cannot be expected to perform better than a traditional DIC speckle pattern, text patterns can be effective speckle patterns in situations where already present on a specimen and applying a traditional speckle pattern is difficult.

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Section: Methodsmentioning

confidence: 99%

Section: Methodsmentioning

confidence: 99%

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Using text as a native speckle pattern in digital image correlation

Craig

Leeuwen

Jarrett

et al. 2021

The Journal of Strain Analysis for Engineering Design

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“…Having the capability to perform measurements at high-temperature test objects, DIC has shown itself to be a very attractive technique for measuring strain and deformation at high spatial resolution as a noncontact, imager-based technique that can potentially be used to measure strain and deformation in two or three dimensions. In a typical DIC measurement, a speckle pattern is applied to the structure being tested and is observed as it undergoes deformation loading using imagers [39]. In the case of the microreactor core block, the speckle pattern will be applied to the test article using high-temperature paint.…”

Section: Digital Image Correlationmentioning

confidence: 99%

Advanced Measurement and Visualization Techniques for High-Temperature Heat Pipe Experiments

Qin

Nuñez

Sellers

et al. 2022

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This report conducts a preliminary investigation of the available literature and summarizes some potential advanced measurement and visualization techniques for operating high-temperature heat pipe (HP) that can be implemented to support the United States (U.S.) Department of Energy (DOE) Microreactor Program (MRP). The primary objective for the extensive literature research is to investigate the possibilities and feasibility for the design and construction of an advanced experimental test facility with the aim of producing high-fidelity high-resolution heat pipe data during its operation.Based on the existing HP test facilities at Idaho National Laboratory (INL)including the Single Primary Heat Extraction and Removal Emulator (SPHERE) and the Microreactor Agile Non-Nuclear Experimental Test Bed (MAGNET)further efforts will be made to examine the technical feasibility to HP measurements and support the research, development, and demonstration (RD&D) process for an HP-cooled microreactor. Continuing collaborations with the Nuclear Energy Advanced Modeling and Simulation (NEAMS) program, other research institutes and universities are considered to be extremely important so that the experimental facility and resultant database can satisfy the validation needs of advanced heat pipe modeling codes being developed under DOE NEAMS program. vii

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“…For legibility in this paper, the contrast was artificially improved using Matlab's histogram equalization function, but only the un-altered versions were used in DIC calculations. The contrast of the un-altered images is also reported, defined as the span of the median 90% of pixel gray levels [50] consistency within each image. Because there is no strain or deformation in this rigid body translation test, the applied motion is nominally uniform and ideal measurement would yield zero variation.…”

Section: Rigid Body Translation Testmentioning

confidence: 99%

Super Resolution Digital Image Correlation (SR-DIC): an Alternative to Image Stitching at High Magnifications

et al. 2021

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Background High-resolution Digital Image Correlation (DIC) measurements have previously been produced by stitching of neighboring images, which often requires short working distances. Separately, the image processing community has developed super resolution (SR) imaging techniques, which improve resolution by combining multiple overlapping images. Objective This work investigates the novel pairing of super resolution with digital image correlation, as an alternative method to produce high-resolution full-field strain measurements. Methods First, an image reconstruction test is performed, comparing the ability of three previously published SR algorithms to replicate a high-resolution image. Second, an applied translation is compared against DIC measurement using both low- and super-resolution images. Third, a ring sample is mechanically deformed and DIC strain measurements from low- and super-resolution images are compared. Results SR measurements show improvements compared to low-resolution images, although they do not perfectly replicate the high-resolution image. SR-DIC demonstrates reduced error and improved confidence in measuring rigid body translation when compared to low resolution alternatives, and it also shows improvement in spatial resolution for strain measurements of ring deformation. Conclusions Super resolution imaging can be effectively paired with Digital Image Correlation, offering improved spatial resolution, reduced error, and increased measurement confidence.

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Importance of Exposure Time on DIC Measurement Uncertainty at Extreme Temperatures

Cited by 28 publications

References 23 publications

Using text as a native speckle pattern in digital image correlation

Using text as a native speckle pattern in digital image correlation

Advanced Measurement and Visualization Techniques for High-Temperature Heat Pipe Experiments

Super Resolution Digital Image Correlation (SR-DIC): an Alternative to Image Stitching at High Magnifications

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