Residual gray field calculation method of local digital image correlation method

A digital image and calculation method technology, applied in related application scenarios, crack detection, digital image correlation method in the field of defect detection, to achieve the effect of easy implementation, accurate positioning, and ensuring continuity

Pending Publication Date: 2022-01-04
BEIHANG UNIV
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Problems solved by technology

It is not suitable for the problems of crack identification and defect location in the mechanics of materials that this paper focuses on.

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  • Residual gray field calculation method of local digital image correlation method
  • Residual gray field calculation method of local digital image correlation method
  • Residual gray field calculation method of local digital image correlation method

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specific Embodiment 1

[0067] figure 2 It is the image of a test piece with cracks in a fatigue test before and after the test, and a crack is produced in the middle of the test piece. Note that the picture taken before deformation is F(x, y), and the image after deformation is G(x, y), where (x, y) is the pixel coordinate of the image.

[0068] According to the traditional method of directly using image subtraction to calculate the residual gray level field, the residual gray level field is as follows: image 3 shown. In order to make the result more vivid, the residual grayscale image is inverted. Its calculation formula can be expressed as:

[0069] D(x, y)=255-|F(x, y)-G(x, y)|

[0070] Because the picture is not registered, and the motion difference between the upper and lower parts of the image is relatively large, in the residual gray field, the upper part has a weak deformation, while the lower part has a large deformation, and a large amount of aliasing will occur, which will affect th...

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Abstract

The invention discloses a residual gray field calculation method of a local digital image correlation method. The residual gray field calculation method comprises the steps of calculation point grid construction, displacement field interpolation and gray interpolation, residual gray field calculation, and residual gray field after-processing. According to the method, on the basis of traditional residual gray field analysis, aliasing and other factors which are not beneficial to feature extraction in a traditional method are eliminated; compared with a traditional discrimination method using correlation coefficients of DIC, the method can provide more accurate positioning for features, can quantitatively and visually display matching results, and can prompt newly appearing image features, such as cracks, defects and the like; according to the method, on the basis of grid construction, displacement fields of discrete calculation points in the sub-region DIC can be organized, continuous interpolation of the displacement fields is achieved, continuity of the displacement fields is guaranteed, and ambiguity is avoided; the method is clear in process and easy to implement, not only can be implemented by using a CPU, but also can be implemented by using a shader of a GPU, and has extremely high calculation efficiency.

Description

technical field [0001] The invention relates to a digital image correlation method in experimental solid mechanics, in particular to the fields related to the digital image correlation method in defect detection and crack detection. Specifically, it is a method for calculating the residual gray field using the calculation results of the local digital image correlation method based on the image sub-region, and using it in related application scenarios such as defect detection and crack detection. Background technique [0002] In the traditional defect detection methods, most of them are realized based on image transformation and image registration. By registering the calculation target with the template through the overall transformation of the image, and doing the difference to obtain the residual gray field, and the residual gray field is Analysis to determine the size and location of flaws or cracks. [0003] Existing image registration algorithms often only consider the ...

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Application Information

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Patent Type & Authority Applications(China)
IPC IPC(8): G06T7/30G06T5/50
CPCG06T7/30G06T5/50
Inventor 潘兵池宇希
Owner BEIHANG UNIV
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