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A Method for Measuring Plastic Strain Ratio During Metal Tensile Testing

A technology of plastic strain ratio and tensile test, which is applied in the direction of measuring device, using stable tension/pressure to test material strength, strength characteristics, etc., can solve the problems of measurement accuracy error and mechanical property influence, and achieve small influence and high precision The effect of high and good application prospects

Active Publication Date: 2021-10-01
NANJING UNIV OF AERONAUTICS & ASTRONAUTICS
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Problems solved by technology

In the actual measurement of the plastic strain ratio (r value), contact measurement is often used, that is, the extensometer is installed at both ends of the gauge length of the sample, and the elongation of the sample is measured by the deformation of the extensometer. Although the extensometer The use of the extensometer can improve the measurement accuracy, but it will inevitably affect its mechanical properties when it is in direct contact with the sample, and the change in the width direction cannot be measured by the extensometer, and it needs to rely on traditional measurement tools such as vernier calipers, which leads to the measurement accuracy. There is a certain error

Method used

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  • A Method for Measuring Plastic Strain Ratio During Metal Tensile Testing
  • A Method for Measuring Plastic Strain Ratio During Metal Tensile Testing
  • A Method for Measuring Plastic Strain Ratio During Metal Tensile Testing

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Embodiment 1

[0025] The device platform used in this embodiment is as figure 1 and figure 2 As shown, the symmetrical light source 2 is projected on the surface of the sample to be tested, and the CCD industrial camera 3 is aimed at the gauge area where speckle spots are arranged in the center of the tensile sample 1 , and the image data collected by the CCD industrial camera 3 is stored in the data collector 4 .

[0026] The method for measuring the plastic strain ratio in the metal tensile test process of the present embodiment comprises the following steps:

[0027] The first step is to uniformly spray a layer of white spray paint on one side of the surface of the metal sample as the base, and after the white spray paint dries, arrange a plurality of black speckle spots on the base of the gauge area, thereby making tensile sample 1.

[0028] Usually, the stamp tool can be used to arrange speckle spots in the gauge area of ​​the metal sample, and the size of each speckle spot is about ...

Embodiment 2

[0054] This embodiment is a further improvement on the basis of Embodiment 1, and the difference from Embodiment 1 is:

[0055] 1) In the third step, multiple images of the gauge length region in the uniform plastic deformation stage of the tensile specimen are collected, and a uniform plastic deformation image sequence is formed in time order, and then the first image in the uniform plastic deformation image sequence is taken as the second image ;

[0056] 2) After the sixth step is executed, the first image remains unchanged, and the next image in the uniform plastic deformation image sequence is used as the second image, and then the fourth to sixth steps are repeated until the calculation of the uniform plastic deformation is completed All images in the image sequence, resulting in multiple plastic strain ratios;

[0057] 3) Take the average value of all the plastic strain ratios as the plastic strain ratio of the metal sample.

[0058] In order to ensure that the test r...

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Abstract

The invention relates to a method for measuring the plastic strain ratio in the metal tensile test process, comprising the following steps: arranging speckle spots in the gauge length region of the surface of the metal sample to make a tensile sample to be tested; pulling the tensile sample Stretch test, the image of the initial state is obtained as the first image, and the image of the uniform plastic deformation stage is used as the second image; the correlation matching of the gray field of the first image and the second image can be obtained for all pixels of the first image Displacement field; the differential calculation of the displacement field is carried out to obtain the real plastic strain in the length and width directions in the gauge area; according to the principle of volume invariance in the stretching process, the plastic strain ratio of the metal sample is obtained. The invention has the advantages of non-contact, little influence on the mechanical properties of the sample, high precision and reliable results, and provides a new idea and means for accurately measuring the plastic strain ratio (r value) in the metal tensile test process.

Description

technical field [0001] The invention relates to a method for measuring the plastic strain ratio in the metal tensile test process, belonging to the technical field of material mechanics. Background technique [0002] Plastic strain ratio (r value) is an important mechanical parameter to measure the formability of metal sheets, reflecting the ability of metal sheets to resist thinning or thickening when they are subjected to tension or compression in a certain plane. A larger r value indicates that the material is easily deformed in the width direction during stretch forming to resist thinning in the thickness direction, and thickness reduction is one of the main reasons for material fracture during the stamping process. [0003] Since the plastic strain ratio (r value) characterizes the ratio of the true plastic strain in the width direction and the true plastic strain in the thickness direction of the material under uniaxial tension, the deformation of the length is easier ...

Claims

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Application Information

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Patent Type & Authority Patents(China)
IPC IPC(8): G01N3/08G01N3/06
CPCG01N3/068G01N3/08G01N2203/0017G01N2203/0075G01N2203/0282G01N2203/0647G01N2203/0682
Inventor 金霞蔡顺陈樱利胡俊聪惠昊翀赵亮潘劲伟王耀武王建政任朝东胡鹏宋云鹤卞玉新袁锡康肖叶鑫赵怀勇王鹏刘艳杰张浩伟
Owner NANJING UNIV OF AERONAUTICS & ASTRONAUTICS