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Title |
Application of Image Processing Method to Evaluate Ultimate Strain of Rebar
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DOI |
http://dx.doi.org/10.11112/jksmi.2016.20.3.111 |
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Keywords |
이미지 프로세싱 ; 한계상태변형률 ; 변형률 분포 ; 변형률 계측 ; 인장시험 Image processing method ; Ultimate strain ; Strain distribution ; Strain measurement ; Uniaxial tensile test |
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Abstract |
In this study, measurements were conducted by image processing to do an in-depth evaluation of strain of rebar in a uniaxial tension test. The distribution of strain and the necking region were evaluated. The image processing is used to analyze the color information of a colored image, so that the parts consistent with desired targets can be distinguished from the other parts. After this process, the image was converted to a binary one. Centroids of each target region are obtained in the binary images. After repeating such process on the images from starting point to the finishing point of the test, elongation between targets is calculated based on the centroid of each target. The tensile test were conducted on grade 60 #7(D22) and #9(D29) rebars fabricated in accordance with ASTM A615 standards. Strain results from image processing were compared to the results from a conventional strain gauge, in order to see the validity of the image processing. With the image processing, the measuring was possible in not only the initial elastic region but also the necking region of more than 0.5(50%) strain. The image processing can remove the measuring limits as long as the targets can be video recorded. It also can measure strain at various spots because the targets can easily be attached and detached. Thus it is concluded that the image processing helps overcome limits in strain measuring and will be used in various ways.
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