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- Volume 17 (1998)
- Number 1 - June 1998
- Measurements of orientation in a discretized space by Fourier transform: automatic investigation of fiber orientation in a reinforced concrete
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Measurements of orientation in a discretized space by Fourier transform: automatic investigation of fiber orientation in a reinforced concrete
Abstract
Usual algorithms implemented on many automatic analyzers to establish the roses of directions are too sensitive to digitization, which can lead to biased results. With usual methods indeed, measurements are conducted at the local 3 x 3 pixel scale. Moreover at that local scale, only 0°, ± 26.5°, ± 45°, ± 63.5° and 92° directions can be selected. As measurements are performed at the scale of the whole image (256 x 256 or 512 x 512 pixels), the incidence of digitization artefacts is considerably decreased. In such a manner it appears that the (Fast) Fourier Transform (FFT) algorithm, whose procedures are described, is a well suited method to give an actual estimate of orientation. Moreover, depending on the accuracy required, a larger number of orientations can be investigated and without any bias. Automatic length measurements are done at a local 3 x 3 pixel scale. The direct use of the FFT can only contribute to reduce the error of length measurements. The examples given in this paper are concerning a civil engineering material: global fiber arrangement was quantified in a concrete reinforced with metallic glass ribbons.