A two-step three-dimensional Fourier transform method for measuring three-dimensional deformation field inside an object

Abstract

The invention provides a method for measuring a three-dimensional displacement field and a strain field inside an object by using two three-dimensional Fourier transforms. Using micro-focus computer tomography, micro-nuclear magnetic resonance or laser scanning confocal microscopy to obtain three-dimensional images of objects with natural or artificial speckle structures inside before and after deformation. The three-dimensional images before and after deformation are divided into several sub-blocks of the same size, and the corresponding pairs of sub-blocks are subjected to the first three-dimensional Fourier transform one by one, and the synthetic spectrum is obtained by numerical interference in the spectral domain. In the second step, the three-dimensional Fourier transform obtains the extended impulse function containing displacement information, obtains the displacement vector of the corresponding sub-block by calculating the peak position, and obtains the three-dimensional deformation field inside the object from the displacement vectors of all sub-blocks. Subvoxel accuracy of displacements is obtained by interpolation. From the relationship equation between strain and deformation, the strain field inside the object is obtained.

Description

technical field [0001] The invention relates to the measurement of a three-dimensional deformation field inside an object, and belongs to the field of solid experimental mechanics. Background technique [0002] Digital speckle correlation method or digital image correlation method (Digital Image Correlation, DIC) has been widely used in the measurement of two-dimensional plane deformation and strain. Digital volume correlation method (Digital Volume Correlation, DVC) is an extension of digital image correlation method to three-dimensional deformation measurement inside the object. This method uses micro-focus CT, micro-focus nuclear magnetic resonance or laser scanning confocal microscope to obtain the three-dimensional volume of the object before and after deformation. Image, directly search the corresponding points in the deformed body image in the deformed volume image, and obtain the displacement vector of the point, because it needs to be searched one by one in the sear...

AI Technical Summary

Problems solved by technology

Digital volume correlation method (Digital Volume Correlation, DVC) is an extension of digital image correlation method to three-dimensional deformation measurement inside the object. This method uses micro-focus CT, micro-focus nuclear magnetic resonance or laser scanning confocal microscope to obtain the three-dimensional volume of the object before and after deformation. Image, directly search the corresponding points in the deformed body image in the deformed volume image, and obtain the displacement vector of the point, because it needs to be searched one by one in the search area, resulting in a large calculation time consumption, especially when the object appears Large deformation, the search area increases, the time spent will be greatly increased, and the calculation efficiency will be reduced

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