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A Dynamic Poisson's Ratio Measurement Method for Brittle Materials

A technology of brittle materials and measurement methods, which is applied in the direction of testing the strength of materials, measuring devices, and analyzing materials using one-time impact force. It can solve problems such as high cost, damage, and rapid rock failure process, and achieve accurate, reliable and adaptable results. , enhance the effect of authenticity and reliability

Active Publication Date: 2020-10-27
CENT SOUTH UNIV
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Problems solved by technology

However, the measurement of the displacement extensometer and the strain gauge is limited to a fixed measurement length and a specific sticking point, respectively, and the rock-like brittle material itself is a heterogeneous material, and the deformation measurement at one point or one direction on the sample surface cannot accurately reflect the test results. Deformation of the sample as a whole
However, if you want to obtain more deformation data, you need to arrange a large number of strain gauges or extensometers, which is expensive
Especially for the dynamic Poisson's ratio measurement of rock brittle materials under high strain, under the action of impact load, the rock damage process is rapid and severe, and the surface will undergo large local deformation or crack expansion, and the displacement extensometer and strain gauge are easy to measure. Major issues such as misalignment, detachment and damage occur

Method used

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  • A Dynamic Poisson's Ratio Measurement Method for Brittle Materials
  • A Dynamic Poisson's Ratio Measurement Method for Brittle Materials
  • A Dynamic Poisson's Ratio Measurement Method for Brittle Materials

Examples

Experimental program
Comparison scheme
Effect test

Embodiment 1

[0083]The sample is a cuboid sample of blue sandstone, the size is: h×w×d=60mm×60mm×25mm; the angle α between the lenses of two high-speed cameras is 15°, and the lens with a focal length of 90mm is used, and the end surface of the lens is distanced from the sample for observation The distance to the surface is about 2000mm, the shooting resolution is set to 128×256pixels, and the shooting speed is 150,000 frames per second.

[0084] The method for measuring the dynamic Poisson's ratio of blue sandstone in this embodiment comprises the following steps: first, the blue sandstone rock sample is processed into a cuboid sample whose size is h×w×d=60mm×60mm×25mm, and then the sample is observed on the surface of the sample. To create an artificial speckle field, first clean the observation surface of the sample and then evenly spray white paint on it, and then use a special speckle stamp to make black speckle spots after it dries, such as Figure 4 shown; then according to the oper...

Embodiment 2

[0098] The sample is a marble cuboid sample, the sample size and test implementation steps are the same as in Example 1, and the loading rate is 1865GPa / s. The angle α between the lenses of the two high-speed cameras is 18°. A 100mm focal length lens is used. The distance between the lens end face and the sample observation surface is about 1200mm. The shooting resolution is set to 256×256pixels, and the shooting speed is 79161 frames per second. The measured elastic segment time (μs) on the dynamic stress-strain curve of the sample is (69, 109), and thus the digital image range (sheets) of the elastic segment is (5, 8); the starting and ending states of the elastic segment The full-field X-direction mean strain e under x-a =1.197×10 -3 、e x-b =5.638×10 -3 ; The average strain e in the Y direction y-a =-2.881×10 -5 、e y-b =-1.385×10 -3 ; Substituting the data, the sample dynamic Poisson's ratio μ=|e y-b -e y-a | / |e x-b -e x-a |=0.305.

Embodiment 3

[0100] The sample is a granite cylinder sample with a diameter of D = 50mm and a height of h = 50mm. The sample is placed between the SHPB horizontal impact devices by means of axial loading. The loading rate is 1747GPa / s. The test system is set and Implementation steps are the same as in Example 1. The measured elastic segment time (μs) on the dynamic stress-strain curve of the sample is (61, 112), and thus the digital image range (sheets) of the elastic segment is (9, 17); the starting and ending states of the elastic segment The full-field X-direction mean strain e under x-a =2.328×10 -3 、e x-b =4.875×10 -3 ; The average strain e in the Y direction y-a =-1.424×10 -4 、e y-b =-7.753×10 -4 ; Substituting the data, the sample dynamic Poisson's ratio μ=|e y-b -e y-a | / |e x-b -e x-a |=0.248.

[0101] As can be seen from the above description, the advantages of the dynamic Poisson's ratio measurement system and method for brittle materials of the present invention are:...

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Abstract

The invention relates to the field of material mechanical performance test, and discloses a system for measuring a dynamic Poisson ratio of a brittle material. The system comprises an SHPB (Split Hopkinson Pressure Bar) horizontal impact device, a high-speed camera, a synchronous trigger, an ultra dynamic strain acquisition device and a digital image receiving device, wherein the ultra dynamic strain acquisition device is connected with the SHPB horizontal impact device, so as to acquire dynamic strain signals of incident waves, reflected waves and transmitted waves output by the SHPB horizontal impact device in real time; the synchronous trigger is electrically connected with the ultra dynamic strain acquisition device and the high-speed camera, so as to control the ultra dynamic strain acquisition device and the high-speed camera to achieve synchronous triggering and real-time measurement; and the digital image receiving device is electrically connected with the high-speed camera. The invention also provides a method for measuring a dynamic Poisson ratio of a brittle material. Through adoption of the system and the method of the invention, authenticity and reliability of dynamicPoisson ratio measurement of the brittle material can be effectively improved; and a novel method with good adaptability as well as accurate and reliable results is provided for measuring the dynamicPoisson ratio of a rock brittle material under the function of impact load.

Description

technical field [0001] The invention relates to the field of testing mechanical properties of materials, in particular to a method for measuring dynamic Poisson's ratio of brittle materials. Background technique [0002] Poisson's ratio refers to the ratio of the absolute value of the transverse normal strain to the axial positive strain when the material is under unidirectional tension or compression, also called the transverse deformation coefficient, which is an elastic constant reflecting the transverse deformation of the material. The accurate measurement of Poisson's ratio can provide a reliable basis for the calculation of parameters such as the elastic modulus of rock-like brittle materials, and play an important role in the deformation control and stability evaluation of engineering rock mass. [0003] At present, the methods commonly used to test the Poisson's ratio of rock-like brittle materials are mainly contact methods, mainly including the strain gauge method ...

Claims

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Application Information

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Patent Type & Authority Patents(China)
IPC IPC(8): G01N3/30G01N3/06
CPCG01N3/066G01N3/068G01N3/30G01N2203/001G01N2203/0075G01N2203/0617G01N2203/0647
Inventor 朱泉企李地元周亚楠杜少华韩震宇肖鹏
Owner CENT SOUTH UNIV