An Optical Measurement Method of In-plane Strain Rate Field Based on Velocity Linear Fitting

Abstract

The invention proposes an optical measurement method of in-plane strain rate field based on velocity linear fitting, which belongs to the technical field of object strain rate field measurement. The invention collects multiple images during the loading process of the measured object, and obtains triangular pixels in the image According to the coordinates of each measuring point of the block, the velocity field of the measuring point is obtained according to the interval time of the image, and the fitting data points of each triangular pixel block are obtained according to the coordinates and velocity of each measuring point in each triangular pixel block, and then each The coefficients of the fitting plane of the triangular pixel blocks, and finally obtain the strain rate field in the plane of the measured object according to the relationship between the obtained coefficients and the velocity partial derivative; the present invention is based on the idea of ​​data fitting, which is superior to the existing related methods. The process is simple, the steps are convenient and easy to understand, and the result can be obtained only by solving the coefficients of the fitting plane equation. The present invention considers the information of the internal measuring points of the discrete pixel blocks, improves the accuracy and credibility of the final result, and increases the Flexibility in measuring point selection.

Description

technical field [0001] The invention belongs to the technical field of object strain rate field measurement, and in particular relates to an optical measurement method of an in-plane strain rate field based on velocity linear fitting. Background technique [0002] Object deformation measurement is an important part of experimental mechanics; compared with other measurement methods, optical measurement methods play an irreplaceable role in experimental mechanics due to their advantages of non-contact, full-field, high spatial resolution and high measurement accuracy. role; in practical applications, object deformation measurement often refers to the measurement of deformation in the object plane; [0003] The digital image correlation method is an important method in the optical measurement method, which is to correlate two images (speckle fields) of the object surface collected before and after the deformation, so as to realize the deformation measurement of the object; Def...

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Problems solved by technology

[0006] 1) The digital image correlation method based on the Newton-Raphson (N-R) method can obtain the displacement and strain in the object plane at the same time, but the error of the strain calculation result is relatively large;

[0007] 2) The digital image correlation method based on the central difference method obtains the strain field by performing central difference on the displacement field, but the noise contained in the displacement field will reduce the credibility of the strain calculation results;

[0008] 3) The digital image correlation method based on the finite element smoothing method uses the finite element method to smooth the displacement field to obtain the strain field, but the mathematical form and programming execution are complicated, which is not conducive to popularization and application

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