A measurement method of crack tip opening displacement based on high temperature image processing
A technology of crack tip and opening displacement, which is applied in the field of engineering materials, structural deformation and mechanical experiments, and can solve problems such as being easily affected by human operation, unable to measure crack tip opening displacement, and complicated installation and use of high temperature extensometers.
Active Publication Date: 2016-09-28
TSINGHUA UNIV
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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.
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[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, an observation hole with a diameter of 12mm is opened 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 to obtain a picture of the notch crack expansion of the test piece;
[0046] d. Use the image edge detection technology to obtain the edge of the crack tip, and calculate the...
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The invention discloses a crack tip opening displacement measurement method based on high-temperature image processing, which belongs to the technical fields of engineering materials, structural deformation and mechanical experiments. The technical feature of the present invention is that by carrying out the high-temperature mechanical loading experiment on the test piece with prefabricated cracks, the camera equipped with a filter device is used to shoot the crack expansion process on the surface of the test piece, and the test piece is detected by using the method of edge detection for the obtained image. The notch crack is located and detected and the opening displacement of the crack tip is calculated, so as to obtain the crack tip opening displacement (crack-tip opening displacement, CTOD) of the material under high temperature environment. This method directly calculates the opening displacement of the crack tip through image processing technology. Compared with the conventional method of calculating the opening displacement of the material crack tip through the stress-displacement curve, this method is simple and direct, and the result can be directly obtained through software-assisted calculation, reducing Human judgment of errors in conventional stress-displacement curves.
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 ...
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IPC IPC(8): G01N3/00G01N3/06G01B11/02
Inventor 冯雪方旭飞张长兴
Owner TSINGHUA UNIV