Drop-weight tear test sample fracture shearing area detection method

Abstract

The invention provides a drop-weight tear test sample fracture shearing area detection method. After a DWTT sample is shorn, a DWTT sample fracture is shot and imaged through a camera, the area of net sections and the area of brittle fracture regions are calculated through image analysis software, and therefore fracture shearing area percentage is worked out. The method is simple and easy to carry out, none equipment needs purchasing, funding is not needed, the brittle fraction regions, especially small brittle fraction regions facilitating brittle fraction region boundary recognition can be freely amplified in the image analysis software, and therefore accuracy of the area of the brittle fraction regions is guaranteed. Due to the adoption of the method that the thickness of the root portion of a sample image notch is measured in the interface of the image analysis software to determine the amplification factor, accuracy of the area of the net sections can be guaranteed, irregular shear lips are prevented from appearing on the hammered side of the sample after sample shearing, calculation accuracy of the area of the net sections is guaranteed, and accordingly scientific and reliable detection data bases are provided for pipeline steel pipe control and fraction prediction.

Description

technical field [0001] The invention belongs to the field of inspection and testing methods, in particular to a detection method for evaluating the percent shear area of ​​a drop-weight tear sample by using image analysis software. Background technique [0002] Since the test method of the drop weight tear test (DWTT for short) is closer to the use state of the material and reflects the real situation of its fracture, the evaluation results of the fracture of the DWTT sample are widely used to control and predict the fracture of pipeline steel pipes, and As one of the toughness indicators to measure the ability of pipeline steel pipes to resist brittle cracking, the accuracy of fracture evaluation results is of great significance. [0003] The evaluation result of DWTT specimen fracture refers to the percentage of shear area on the measured net section. For a sample with a thickness t≤19.0mm, the net section is to deduct one sample thickness from the root of the sample notc...

AI Technical Summary

Problems solved by technology

[0006] The disadvantages of the planimeter detection method are: the general graduation value of the ruler is 1mm, and the minimum resolution is 0.5mm. It is difficult to ensure the accuracy of the sample thickness on the drawing, so there will be errors in the division of the net section, resulting in net There will be deviations in the calculation of the cross-sectional area. At the same time, it is difficult to ensure that the ruler is parallel to the fracture of the drop weight specimen when taking pictures, which will also affect the accuracy of the calculation of the net cross-sectional area.

[0011] The disadvantage of this method is: GB / T 8363-2007 stipulates that the length of the DWTT sample is 305mm±5mm, and the tolerance is relatively large. Generally, it is processed to the length by a sawing machine.

After the sample is punched, because the height of the sample is not equal, the maximum height difference is 5mm. When doing the fracture analysis of the series of DWTT tests, it is difficult to use the same ruler to calibrate the geometric dimensions to ensure the accuracy of the test.

In addition, after the specimen is punched, only the notch does not undergo plastic deformation, and the rest of the specimen undergoes plastic deformation, especially the hammered side presents an irregular shear lip, and the boundary is difficult to confirm

However, the software uses the upper left point of the root of the notch to click the left button, place the mouse to the lower right point and press the right button at the same time to determine the net cross-sectional area, and the calculation of the net cross-sectional area has a large deviation

In addition, the image cannot be enlarged on the computer. When the area of ​​the brittle fracture area is small, the deviation of the drawn area is large, which affects the accuracy of the test results.

In addition, a large amount of money needs to be invested in purchasing a fracture image analyzer

Images