In-situ measurements of strain distribution by coupling digital image correlation and an optical microscope

2020 ◽  
Author(s):  
Chien-Ching Ma ◽  
Hsiang-Wei Ho ◽  
Wan-Hsuan Chou ◽  
Dong-Rong Chen ◽  
Ching-Yuan Chang
Keyword(s):  
Digital Image Correlation ◽  
Digital Image ◽  
Strain Distribution ◽  
Optical Microscope ◽  
In Situ Measurements ◽  
Image Correlation

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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