Double-camera video frequency large-deformation measurement method and video frequency extension device based thereon

Abstract

This invention provides a non-contact measurement method and device to multiple enlarge measurement range, which comprises: using two cameras to form the picture shoot part of the extensometer, ensuring some overlap area of the sight angles of two cameras; for tension test, when two index lines on sample within the first camera range together, using the first camera to acquire picture and determine the distance of lines; when the line move to overlap area, switching the picture; then, using the picture from the first/second camera to determine the distance between the lower/upper line and switch place, adding two distance values to determine the distance of two lines; when the lower line moves over the switch place, using the second camera to acquire picture and determine distance between lines.

Description

technical field [0001] The invention relates to a deformation measurement method and an instrument in a material mechanics test, more specifically a dual-camera video large deformation measurement method and a video extensometer using the method. technical background [0002] Some materials, such as rubber, plastic, etc., have a large amount of deformation. Measuring the deformation of such materials in tensile tests is a difficult problem that has not been well resolved for a long time. At present, the following measurement methods are used, and the most widely used method at home and abroad is the so-called contact measurement. [0003] 1. Contact measurement technology [0004] In contact measurement, two marking lines should be drawn on the sample to be tested, and then the two marking lines should be clamped with two clamps protruding from the measuring mechanism. When the two marking lines move during the tensile test, the chuck is driven to move together. When eac...

AI Technical Summary

Problems solved by technology

[0039] 3. Limitations of existing single-lens video extensometers in large deformation measurement

[0041] First, the resolution of the captured image decreases, which affects the measurement accuracy

Although higher-resolution lenses and image sensors can be used to make up for this loss, this will not only lead to a sharp increase in cost, but for high-resolution lenses and image sensors, the increase in price will be far greater than the doubling of the resolution. doubled and is also limited by device availability

[0042] Second, the increase of the distance will lead to the installation inconvenience and the increase of the size of the testing machine, which will be an obvious disadvantage compared with the contact measurement

[0043] In order to expand the measurement range without increasing the distance between the lens and the sample, the angle of view of the lens must be increased, but there is a certain limit to the increase of the angle of view

As the angle of view of the lens increases, the image quality of the off-center area will decrease significantly, the resolution will decrease, and the distortion will increase

As a result, the measurement accuracy is significantly reduced

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