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Article information
2015 , Volume 20, ¹ 2, p.65-78
Panin S.V., Titkov V.V., Lyubutin P.S.
Automatic determination of subset size in the problem of estimation of material strain by digital image correlation method
An algorithm for the subset size (correlation kernel) estimation in construction of the displacement vector for application in digital image correlation method is offered. The algorithm is based on the calculation and subsequent analysis of the autocorrelation function that is determined for the central region of an image of n õ n pixels size. The value of n is changed from 2 up to 64. The algorithm estimates the following parameters of the autocorrelation functions: width of the autocorrelation function at the 0.5 level (in pixels), the number of low-contrast regions in the image, number of the peaks in the autocorrelation function above the 0.5 level. The algorithm was tested with the help of model and experimental optical images which are characterized by different texture. Six series of images, three of which were the model ones were investigated. Synthetic images were divided into two types: a model of multi-layer image and speckle pattern. Multilayer model image was generated from a predetermined quantity of layers of random numbers. Within this approach each layer corresponds to a specific spatial frequency. Synthetic image, simulating the speckle pattern was generated by random selection of circles with different radius and brightness (by normal distribution) that emulate the sprayed drop - speckle spots. The influence of the subset size and texture image on robustness for the estimation of displacements was investigated. It is shown that the proposed algorithm can determine the subset size that provides the minimum error for estimation of displacement and deformation. The subset size for the six series of images with different texture pattern that provides minimum error for strain calculation was estimated using the proposed algorithm. It is shown that the algorithm is efficient in estimating the deformation of materials with different relief, including the processing of both prepared (with sprayed speckle) and unprepared (low contrast) image surfaces.
[full text]
Keywords: subset size, displacement vector field, shear strain intensity, digital image correlation
Author(s):
Panin Sergey Viktorovich
Dr. , Professor
Position: Head of Laboratory
Office: Institute of Strength Physics and Materials Science of SB RAS, National Research Tomsk Polytechnic University
Address: 634021, Russia, Tomsk
Phone Office: (3822)286-904
E-mail: svp@ispms.tsc.ru
Titkov Vladimir Viktorovich
Position: Student
Office: Institute of Strength Physics and Materials Science of SB RAS
Address: 634021, Russia, Tomsk
Phone Office: (3822)286-899
E-mail: titkov.vladimir@mail.com
Lyubutin Pavel Stepanovich
PhD.
Position: Junior Research Scientist
Office: Institute of Strength Physics and Materials Science of SB RAS
Address: 634021, Russia, Tomsk
Phone Office: (3822)286-889
E-mail: psl@sibmail.com
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Bibliography link:
Panin S.V., Titkov V.V., Lyubutin P.S. Automatic determination of subset size in the problem of estimation of material strain by digital image correlation method // Computational technologies. 2015. V. 20. ¹ 2. P. 65-78
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