DWTT (Drop Weight Tear Test) specimen fracture imaging method

An imaging method and fracture technology, which can be used in measurement devices, material analysis by optical means, instruments, etc., can solve the problems of poor imaging effect of DWTT fractures, and achieve the effect of improving the imaging effect.

Inactive Publication Date: 2017-08-04
HARBIN INST OF TECH
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Problems solved by technology

[0011] Aiming at the existing problem of poor imaging effect on DWTT fract

Method used

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  • DWTT (Drop Weight Tear Test) specimen fracture imaging method
  • DWTT (Drop Weight Tear Test) specimen fracture imaging method
  • DWTT (Drop Weight Tear Test) specimen fracture imaging method

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specific Embodiment

[0056] According to the actual situation, the measurement field of view is better than 100mm×50mm, which can meet all application requirements.

[0057] Due to the uneven surface of the specimen fracture 4 to be detected, the peak-to-valley difference of the specimen fracture surface can reach 30mm, and the crystal grain size in the brittle fracture zone is 100-200μm. For the situation where the fracture of the tested specimen is not on the same surface, the depth of field of ordinary industrial lenses Difficult to meet requirements. In order to meet the requirements of precise measurement, a telecentric lens is used. Because of its unique parallel optical path design and field of view resolution, it is generally higher than ordinary lenses, and the depth of field is more than 10 times larger than ordinary lenses, and the distortion rate is very small. The parameters of the selected telecentric lens should meet the following comprehensive considerations: the depth of field △d...

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Abstract

In allusion to the problem of a poor DWTT (Drop Weight Tear Test) fracture imaging effect in the prior art, the invention provides a DWTT specimen fracture imaging method, and belongs to the field of image measurement. A specimen fracture is placed on a moving platform, and a camera is postponed above the specimen fracture. The DWTT specimen fracture imaging method comprises the following steps: adjusting a normal incident light source and an inclined incident light source, irradiating onto the surface of the specimen fracture, and acquiring a preliminary image of the specimen fracture by the camera; segmenting the preliminary image by an image segmenting method to obtain a fracture area; dividing the net section of the fracture area into N parts, controlling the moving platform to move up and down, obtaining focusing evaluation values of the parts respectively, and finding a maximum focusing evaluation value for each part; controlling the moving platform to move up and down, and when the focusing evaluation values of the N parts are high than a% of the respective maximums, stopping movement of the moving platform, and acquiring a focal plane image of the specimen fracture by the camera. By the DWTT specimen fracture imaging method, the imaging depth of field and the imaging resolution are ensured, and a tough fracture area and a brittle fracture area can be effectively distinguished.

Description

technical field [0001] The invention relates to an imaging method and belongs to the field of image measurement. Background technique [0002] DWTT (Drop Weight Tear Test) is currently the main method for testing the strength and toughness of metal materials. DWTT has been included in the international standard (API 5L / ISO (International organization forstandardization) 3183, "Recommended Practice for Pipeline Drop Weight Tear Test" (API RP 5L3) and the national standard "Ferritic Steel Drop Weight Tear Test Method" (GB / T8363-2007). DWTT can evaluate the strength, toughness and ductile-brittle transition temperature of materials. The drop weight tearing test of pipeline steel is to simulate the loading and fracture of pipeline steel in the laboratory and characterize its fracture characteristics, so as to define its safety in use Effective means. Usually, the area percentage of the ductile section (shear section) in the effective area of ​​the fracture, that is, p SA To c...

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Application Information

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IPC IPC(8): G01N21/84
CPCG01N21/84
Inventor 刘国栋陈凤东周立富周立民张轶鑫
Owner HARBIN INST OF TECH
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