Abstract
The deformation and strain measurements have always been one of the main issues in structural engineering. Measuring displacements accurately without damaging structures are an important aim in experimental analysis. For an example, the existing structures need to be evaluated whether they are still fit for purposes or not. To assess complex structures, we need an acceptable and enough amount of data Current strain measurement technologies are not capable of evaluating compounded structures. This paper investigates on an alternative method that uses digital images to provide a full displacement and strain field called Digital Image Correlation (DIC); This technique compares the digital images taken from digital cameras, before and after deformation. We also calculated the coefficient of plastic anisotropy. An aluminium 1050 specimen was loaded in tension according to ASTM E8 testing method while the Sony camcorder captured the video of the specimen being loaded. Once the video was captured, the images were snapshot from video strip using a built-in function of the camera. After that, the images were processed using the Matlab software. The results determined by the extensometer and the optical strain measurement method were compared to each other. This comparison shows that if the test’s setup could be configured in a good way, the error will be less than 2%.
Highlights
The Digital Image Correlation method has been used in the literature since the beginning of 1980s [4, 5] and takes different kinds of form
The method which will be concentrated in this paper, is known as two dimensional Digital Image Correlation (DIC) and includes the usage of an individual camera to Article published by EDP Sciences
The errors produced in displacement when using the DIC method, are deductions of a pixel commonly and while evaluating the strain, the consequence of this error can be decreased via applying a larger longitude for gage length to produce a smaller error in strain measurement
Summary
The Digital Image Correlation method has been used in the literature since the beginning of 1980s [4, 5] and takes different kinds of form. It has one significant disadvantage and that is all the displacements should befall within a single motionless measurement plane otherwise inaccurate results will be obtained Researchers have dominated this constraint by presenting 2.5-D [7] and 3-D DIC systems [8] that use several cameras to measure a 3-D displacement field. Hung and Voloshin [11] carried out a single axial test on a sheet made of aluminum and achieved an average of 5.8% error They didn’t give any specifics on the experimental equipments and subpixel interpolation code; so we cannot evaluate the possible causes which led to error, compared to their offered method. Evaluating the suitability of strain measurement of aluminium by MATLAB GUIs, comparing the results obtained by DIC with those obtained by a conventional mechanical transverse extensometer, and obtaining the coefficient of plastic anisotropy, are the main objectives of this paper
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