Follow-up window and digital image-based non-contact real-time strain measurement method
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A strain measurement, non-contact technology, applied in the field of strain measurement, can solve problems such as unsatisfactory measurement results, high requirements for ambient light sources, complex strain algorithms, etc., to improve efficiency and anti-interference ability, improve calculation efficiency, and simple algorithm Effect
Active Publication Date: 2015-05-20
XIANGTAN UNIV
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The traditional deformation measurement methods mainly include contact measurement methods such as electronic extensometer method and electronic strain gauge method. Limitations, such as the weight of the extensometer itself will affect the stress state of the sample, and the embedded strain gauge will cause a certain degree of damage to the surface of the sample, especially when the sample is a flexible material (such as rubber, film material) , the measurement results are not ideal; and the existing digital speckle measurement system and video extensometer based on digital image technology, although non-contact, can measure the full-field deformation of the material, and the measurement results are accurate, but the equipment is expensive and The strain algorithm is complex and has high requirements for ambient light sources
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Embodiment 1
[0018] A non-contact real-time strain measurement method based on a follow-up window and a digital image, which is used to measure the axial line strain of a sample.
[0019] Step 1: Install the sample (2) on the loading machine, and make a pair of marks (3) along the loading direction of the axis;
[0020] Step 2 Control the camera to align with the sample and adjust the camera focus to make the image clearly visible.
[0021] Step 3 Collect the image before loading (1), add a pair of windows (4) to the image, each window contains a marker (3), such as figure 1 shown. Windows are
[0022] in, window A 0 the X and Y coordinates of the upper left corner, window A 0 The number of pixels contained in the horizontal and vertical directions of the image, similarly, the window B can be deduced 0 The meaning of the elements. Windows A 0 , B 0 Intercept and process the images separately to obtain the center point of the corresponding mark in the window image coordi...
Embodiment 2
[0028] A non-contact optical real-time strain measurement method based on a moving window and a digital image for measuring the axial strain of a sample and transverse strain And calculate the Poisson's ratio μ of the material.
[0029] Step 1 Make a pair of marks (3) on the sample (2) in the axial direction and transverse direction respectively, and install it on the loading machine.
[0030] Step 2 Control the camera to align with the sample and adjust the camera focus to make the image clearly visible.
[0031] Step 3 Collect the image before loading, add two pairs of windows (4) to the image, so that each window contains a marker (3), and the axial pair of windows is A 0 = [ X A 0 , Y A 0 , L A 0 ,...
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Abstract
The invention discloses a follow-up window and digital image-based non-contact real-time strain measurement method. The method comprises: step 1. making a pair of markers (3) on a sample (2) as along a preset direction, and installing the sample; step 2. controlling a camera in acquisition of an undeformed sample image (1), and adding windows (4) equivalent to the marks in quantity to the image, capturing sample images from the windows and carrying out analytical processing, identifying the marks in each window and extracting their initial center coordinates; and step 3. loading the sample, and simultaneously acquiring sample images at regular time, carrying out image capture and processing similar to those of step 2 on each of the acquired images in the windows, extracting the new center coordinate of each mark, and comparing the new center coordinates with the initial center coordinates, calculating the strain and visualizing it, and updating window positions according to center coordinate increments and making the windows automatically move along with the marks, and alternating the operations till the end of a test. The method provided in the invention is economic, simple and practical, and has strong interference resistance.
Description
technical field [0001] The invention relates to a strain measurement method, in particular to a non-contact real-time strain measurement method based on a follow-up window and a digital image. technical background [0002] The testing of mechanical properties of materials is usually inseparable from the measurement of deformation. The traditional deformation measurement methods mainly include contact measurement methods such as electronic extensometer method and electronic strain gauge method. Limitations, such as the weight of the extensometer itself will affect the stress state of the sample, and the embedded strain gauge will cause a certain degree of damage to the surface of the sample, especially when the sample is a flexible material (such as rubber, film material) , the measurement results are not ideal; and the existing digital speckle measurement system and video extensometer based on digital image technology, although non-contact, can measure the full-field deform...
Claims
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