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A Weak Form-Based Digital Image Correlated Strain Field Calculation Scheme

A technology for digital images and calculation schemes, applied in the field of weak-form-based digital image-related strain field calculation schemes, can solve problems such as precision and narrow application range, and achieve the effect of wide application range, clear guidance, and suppression of the influence of noise.

Active Publication Date: 2020-05-05
BEIHANG UNIV
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Problems solved by technology

[0006] The purpose of the present invention is to provide a weak form-based method that can suppress the influence of noise, has a wider range of use, and has a clearer parameter selection for the existing digital image correlation (DIC) method that has a narrow range of accuracy and narrow application range in terms of strain calculation. Digital Image Correlation Strain Calculation Scheme for

Method used

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  • A Weak Form-Based Digital Image Correlated Strain Field Calculation Scheme
  • A Weak Form-Based Digital Image Correlated Strain Field Calculation Scheme
  • A Weak Form-Based Digital Image Correlated Strain Field Calculation Scheme

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Experimental program
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Effect test

Embodiment 1

[0040] Such as figure 1 Shown is the flow chart of the present invention, embodiment 1 adopts the situation that the displacement field U(x, y) changes gently, taking the constant strain displacement field as an example, its specific implementation steps are as follows:

[0041] Step (1): First, make artificial speckle on the test piece, or directly use the clear texture on the surface of the test piece;

[0042] Step (2): Then load the test piece on the experimental machine;

[0043] Step (3): In the process of loading, use a CCD camera to shoot images before and after deformation;

[0044] Step (4): Store the images before and after deformation in the computer, and then use a search algorithm to find the displacement field, for example, Newton-Raphson method (NR) and iterative least squares (ILS) can be used to find the displacement field;

[0045] Step (5): According to the calculated displacement field, directly select the strain field formula (5), select the appropriate...

Embodiment 2

[0056] Embodiment 2 adopts the situation that the displacement field U(x, y) changes sharply, taking the sinusoidal displacement field as an example. Its implementation steps are consistent with the implementation steps of Embodiment 1.

[0057] Similarly, in order to verify the precision effect of the present invention on the strain field calculated based on the rapidly changing displacement field, based on a simple and reliable numerical simulation method, we implemented the above method with a computer program to illustrate the results of the present invention. Use the NR method to calculate the displacement field, and then obtain the strain field according to the calculation scheme of the present invention; as a contrast, we have calculated the strain obtained by the Newton-Raphson method (NR) and the pointwise least square method (PLS) simultaneously field.

[0058] In the case where U(x,y) changes sharply, the displacement field is taken as Add 2% Gaussian noise to it...

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Abstract

The invention relates to a digital image correlation strain field calculating scheme based on a weak form; the scheme comprises the following steps: setting a digital image correlation measuring system including a to-be-tested piece, a light source, a camera and a computer; using the CCD camera to gather images before and after deformation; using certain searching method to solve a displacement field; using a parse strain field expression derived by employing a weak form method to process the displacement field to directly calculate the strain field. On the basis of the digital image correlation method, the calculating scheme uses the weak form method to transfer the discrete displacement differential to an examination function differential, thus converting a value differential operation into integration operation, and effectively inhibiting noise influences in the displacement field. Compared with the prior art, the calculating scheme can suit the conditions in which the displacementfield rapidly changes, thus providing a wider application scope; the calculating scheme is clear in parameter selection guiding.

Description

technical field [0001] The invention belongs to the fields of digital image processing technology, photometric mechanics, engineering material mechanical performance test, component deformation measurement, etc., and specifically relates to a digital image correlation strain field calculation method based on a weak form. Background technique [0002] Engineering structures or materials are widely used in aerospace, construction engineering and many other fields. Testing of structural and material properties and physical parameters is very important. The measurement of deformation is an essential link in the testing of structural and material properties and physical parameters, including the measurement of displacement and strain. Displacement and strain are not only an important basis for understanding the bearing capacity, work performance and safety of engineering structures or materials, but also important parameters for engineering construction control, monitoring and q...

Claims

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Application Information

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Patent Type & Authority Patents(China)
IPC IPC(8): G01B11/16G06T7/00
CPCG01B11/16G06T7/001
Inventor 董雷霆杨秋红贺双新
Owner BEIHANG UNIV