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CTOD (crack-tip opening displacement) measurement method based on high-temperature image processing

A crack tip, opening displacement technology, applied in measuring devices, instruments, scientific instruments, etc., can solve the problems of complicated installation and use of high-temperature extensometers, inability to measure crack tip opening displacement, and inability to further reveal the real-time specific process of the specimen.

Active Publication Date: 2015-01-07
TSINGHUA UNIV
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Problems solved by technology

However, the disadvantages of using high-temperature extensometers are: on the one hand, high-temperature extensometers are very expensive; The online observation and recording of the specimen under the test conditions cannot further reveal the real-time specific process of the deformation and evolution of the specimen during the test
However, none of the above methods can accurately measure the crack tip opening displacement in a high temperature environment.

Method used

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  • CTOD (crack-tip opening displacement) measurement method based on high-temperature image processing
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  • CTOD (crack-tip opening displacement) measurement method based on high-temperature image processing

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Embodiment

[0042] This method carried out experiments at 600°C, 800°C, 1000°C, 1200°C, 1400°C and 1600°C respectively, among which the high temperature experiment results at 1200°C were selected for specific explanation:

[0043] a. The superalloy Nb521 is made into a unilateral notched beam specimen (the specific size details meet the requirements of GB / T 2358-94);

[0044] b. Carry out high-temperature three-point bending experiment on the prepared Nb521 specimen, and the experimental temperature is a constant temperature of 1200 °C;

[0045] c. In this example, there is an observation hole with a diameter of 12mm on the heating furnace wall of the high-temperature three-point bending experiment, and the whole experiment process is photographed by a high-speed camera equipped with a high-temperature filter system, and the picture of the notch crack expansion of the test piece is obtained;

[0046] d. Use the image edge detection technology to get the edge of the crack tip, and calculat...

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Abstract

The invention discloses a CTOD (crack-tip opening displacement) measurement method based on high-temperature image processing, and belongs to the technical field of engineering materials, structure deformation and mechanical experiments. The CTOD measurement method is technically characterized in that a test piece provided with precracks is subjected to high-temperature mechanical loading experiment, a camera equipped with a filter device is used for shooting the propagation process of cracks on the surface of the test piece, , cracks of a notch of the test piece are subjected to positioning detection with an edge detection method on an acquired image, and the open displacement of a crack tip is calculated, so that CTOD in the high-temperature environment of the material is acquired. According to the method, the CTOD is directly calculated through an image processing technology; and compared with a conventional method for obtaining the CTOD of the material through a stress-displacement curve, the method is simple and direct, a result can be directly obtained through auxiliary calculation of software, and conventional errors of the stress-displacement curve due to human judgment are reduced.

Description

technical field [0001] The invention relates to a method for measuring crack tip opening displacement based on high-temperature image processing, and belongs to the technical fields of engineering materials, structural deformation and mechanical experiments. Background technique [0002] Crack-tip opening displacement (CTOD) is an important index to measure the fracture toughness of engineering materials under elastic-plastic conditions, and it characterizes the ability of materials to resist crack cracking or propagation. The crack tip opening displacement refers to the displacement generated at the original crack tip along the direction perpendicular to the crack when the crack body is stressed. In 1965, Wells proposed the CTOD criterion for elastic-plastic fracture mechanics. The criterion can be expressed as: when the crack tip opening displacement δ reaches the critical value δ c When , the crack will open, that is, δ=δ c . The opening displacement of the crack tip ...

Claims

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Application Information

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Patent Type & Authority Applications(China)
IPC IPC(8): G01N3/00G01N3/06G01B11/02
Inventor 冯雪方旭飞张长兴
Owner TSINGHUA UNIV
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