In-situ 3D shape and recession measurements of ablative materials in an arc-heated wind tunnel by UV stereo-digital image correlation

2019 ◽  
Vol 116 ◽  
pp. 75-81 ◽  
Author(s):  
Yali Dong ◽  
Bing Pan
Keyword(s):  
Wind Tunnel ◽  
Digital Image Correlation ◽  
Digital Image ◽  
Image Correlation ◽  
3D Shape ◽  
Stereo Digital Image Correlation

Experimental Study on Flow-Induced Full-Field Vibration of a Flexible Splitter Plate Behind a Cylinder Using Stereo-Digital Image Correlation

2020 ◽  
Vol 143 (3) ◽  
Author(s):  
Ruili Xie ◽  
Liping Yu ◽  
Weidong Zhu ◽  
Bing Pan
Keyword(s):  
Wind Tunnel ◽  
Digital Image Correlation ◽  
Digital Image ◽  
Plane Deformation ◽  
Splitter Plate ◽  
Image Correlation ◽  
Full Field ◽  
Out Of Plane ◽  
Stereo Digital Image Correlation ◽  
Deformation Measurements

Abstract The flow-induced vibration of a flexible splitter plate behind a circular cylinder is investigated experimentally in this study. Unlike previous studies that mainly devoted to flow dynamics, the full-field three-dimensional (3D) dynamic deformation of a splitter plate behind a cylinder in the wind tunnel is measured with an easy-to-implement, compact but practical single-camera high-speed (SCHS) stereo-digital image correlation (DIC) system. The system parameters of the wind tunnel, the configuration of the SCHS-DIC system, and the measurement principles are introduced first. Then, the effectiveness, accuracy, and stability of the SCHS stereo-DIC system are verified by the deformation measurements of the high-stiffness fixed cylinder. Finally, the full-field dynamic 3D deformation measurements of different splitter plates are carried out under different wind speeds. Results of the polyvinyl chloride (PVC) splitter plate show that the out-of-plane deformation is much larger than in-plane deformation. The maximum deformation occurs at the tip region of the plate, the position of which can move non-periodically along the free-end edge. The full-field deformation of the plate presents the characteristics of complex vortex distribution with high and low fluctuations, and exhibits an asymmetric and non-periodic oscillation in the out-of-plane direction. The comparison results reveal how the wind load and material type of the plate affect the oscillation characteristics.

scholarly journals A Simple and Practical Single-Camera Stereo-Digital Image Correlation Using a Color Camera and X-Cube Prism

Sensors ◽  
2019 ◽  
Vol 19 (21) ◽  
pp. 4726 ◽  
Author(s):  
Bo Dong ◽  
Fancang Zeng ◽  
Bing Pan
Keyword(s):  
Digital Image Correlation ◽  
Digital Image ◽  
High Speed ◽  
Image Correlation ◽  
Single Camera ◽  
Full Field ◽  
3D Shape ◽  
Stereo Digital Image Correlation ◽  
Deformation Measurements ◽  
Dic Technique

A simple and practical full-frame single-camera stereo-digital image correlation (stereo-DIC) technique for three-dimensional (3D) shape, displacement, and deformation measurements is proposed. The technique uses a compact X-cube prism-based color separation device and a color camera to capture images of blue and red colors from different optical paths, and then extracts the surface 3D shape and deformation information of a test sample by processing the captured two sub-channel color images using regular stereo-DIC algorithm. Compared with the existing full-frame single-camera stereo-DICs, the proposed one eliminates the need for a beam splitter and two bandpass filters to capture images, and offers more simple, compact, and easy-to-use optical arrangement. This novel single-camera stereo-DIC technique was validated by a series of baseline experiments involving 3D surface reconstructions, translation tests, and full-field deformation measurements, which provide a new flexible and practical avenue for measuring surface 3D shape and deformation, particularly in microscopic and high-speed applications.

scholarly journals Accurate 3D Shape, Displacement and Deformation Measurement Using a Smartphone

Sensors ◽  
2019 ◽  
Vol 19 (3) ◽  
pp. 719 ◽  
Author(s):  
Liping Yu ◽  
Ran Tao ◽  
Gilles Lubineau
Keyword(s):  
Digital Image Correlation ◽  
Digital Image ◽  
Cost Effective ◽  
Image Correlation ◽  
Correlation Technique ◽  
3D Shape ◽  
Resource Limited ◽  
3D Deformation ◽  
Stereo Digital Image Correlation ◽  
Deformation Measurements

The stereo-digital image correlation technique using two synchronized industrial-grade cameras has been extensively used for full-field 3D shape, displacement and deformation measurements. However, its use in resource-limited institutions and field settings is inhibited by the need for relatively expensive, bulky and complicated experimental set-ups. To mitigate this problem, we established a cost-effective and ultra-portable smartphone-based stereo-digital image correlation system, which only uses a smartphone and an optical attachment. This optical attachment is composed of four planar mirrors and a 3D-printed mirror support, and can split the incoming scene into two sub-images, simulating a stereovision system using two virtual smartphones. Although such a mirror-based system has already been used for stereo-image correlation, this is the first time it has been combined with a commercial smartphone. This publication explores the potential and limitations of such a configuration. We first verified the effectiveness and accuracy of this system in 3D shape and displacement measurement through shape measurement and in-plane and out-of-plane translation tests. Severe thermal-induced virtual strains (up to 15,000 με) were found in the measured results due to the smartphone heating. The mechanism for the generation of the temperature-dependent errors in this system was clearly and reasonably explained. After a simple preheating process, the smartphone-based system was demonstrated to be accurate in measuring the strain on the surface of a loaded composite specimen, with comparable accuracy to a strain gauge. Measurements of 3D deformation are illustrated by tracking the deformation on the surface of a deflating ball. This cost-effective and ultra-portable smartphone-based system not only greatly decreases the hardware investment in the system construction, but also increases convenience and efficiency of 3D deformation measurements, thus demonstrating a large potential in resource-limited and field settings.

scholarly journals Digital Image Correlation for Evaluation of Cracks in Reinforced Concrete Bridge Slabs

2021 ◽  
Vol 6 (7) ◽  
pp. 99
Author(s):  
Christian Overgaard Christensen ◽  
Jacob Wittrup Schmidt ◽  
Philip Skov Halding ◽  
Medha Kapoor ◽  
Per Goltermann
Keyword(s):  
Reinforced Concrete ◽  
Digital Image Correlation ◽  
Crack Initiation ◽  
Laboratory Test ◽  
Digital Image ◽  
Crack Detection ◽  
Image Correlation ◽  
In Situ Tests ◽  
Stop Criterion

In proof-loading of concrete slab bridges, advanced monitoring methods are required for identification of stop criteria. In this study, Two-Dimensional Digital Image Correlation (2D DIC) is investigated as one of the governing measurement methods for crack detection and evaluation. The investigations are deemed to provide valuable information about DIC capabilities under different environmental conditions and to evaluate the capabilities in relation to stop criterion verifications. Three Overturned T-beam (OT) Reinforced Concrete (RC) slabs are used for the assessment. Of these, two are in situ strips (0.55 × 3.6 × 9.0 m) cut from a full-scale OT-slab bridge with a span of 9 m and one is a downscaled slab tested under laboratory conditions (0.37 × 1.7 × 8.4 m). The 2D DIC results includes full-field plots, investigation of the time of crack detection and monitoring of crack widths. Grey-level transformation was used for the in situ tests to ensure sufficient readability and results comparable to the laboratory test. Crack initiation for the laboratory test (with speckle pattern) and in situ tests (plain concrete surface) were detected at intervals of approximately 0.1 mm to 0.3 mm and 0.2 mm to 0.3 mm, respectively. Consequently, the paper evaluates a more qualitative approach to DIC test results, where crack indications and crack detection can be used as a stop criterion. It was furthermore identified that crack initiation was reached at high load levels, implying the importance of a target load.

Methodology for in situ stress intensity factor determination on cracked structures by digital image correlation

2010 ◽  
Vol 1 (4) ◽  
pp. 344-357 ◽  
Author(s):  
V. Richter‐Trummer ◽  
P.M.G.P. Moreira ◽  
S.D. Pastrama ◽  
M.A.P. Vaz ◽  
P.M.S.T. de Castro
Keyword(s):  
Stress Intensity Factor ◽  
Stress Intensity ◽  
Digital Image Correlation ◽  
Intensity Factor ◽  
Digital Image ◽  
Strain Field ◽  
Image Correlation ◽  
Content Type ◽  
Cracked Structures

PurposeThe purpose of this paper is to develop a methodology for in situ stress intensity factor (SIF) determination that can be used for the analysis of cracked structures. The technique is based on digital image correlation (DIC) combined with an overdetermined algorithm.Design/methodology/approachThe linear overdeterministic algorithm for calculating the SIF based on stress values around the crack tip is applied to a strain field obtained by DIC.FindingsAs long as the image quality is sufficiently high, a good accuracy can be obtained for the measured SIF. The crack tip can be automatically detected based on the same strain field. The use of the strain field instead of the displacement field, eliminates problems related to the rigid body motion of the analysed structure.Practical implicationsIn future works, based on the applied techniques, the SIF of complex cracked plane stress structures can be accurately determined in real engineering applications.Originality/valueThe paper demonstrates application of known techniques, refined for other applications, also the use of stress field for SIF overdeterministic calculations.

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