A noise-adding device for SHPB shaper and damage analysis method

Abstract

The present invention discloses a noise-adding device for an SHPB shaper and a damage analysis method, including a device body arranged between an incident bar of a true triaxial Hopkinson bar device and a high-pressure gas gun; the device body is a steel cylindrical closed cavity structure, and a number of steel balls with different particle sizes are arranged in the inner cavity of the device body; one end of the device body abuts against the high-pressure gas gun, and the other end abuts against the incident bar of the true triaxial Hopkinson bar device through a rubber gasket. The present invention enriches the components of each frequency band of the incident wave by designing a noise-adding device for a shaper, and later compares the amplitude changes of waves in different frequency bands of the incident wave and the transmitted wave through wavelet analysis, so as to analyze the damage conditions such as cracks and holes inside the specimen.

Description

Technical Field

[0001] The present invention relates to the technical field of rock mechanics tests, and specifically refers to an SHPB shaper noise adding device and a damage analysis method. Background Art

[0002] Materials such as rocks and concrete contain a large number of defects such as pores, cracks, and joints. Studying the damage and failure laws of materials such as rocks and concrete under dynamic impact loading can better analyze the dynamic characteristics of solid materials such as rocks and concrete. At the same time, understanding the dynamic damage evolution law of solid materials such as rocks and concrete will help to qualitatively and quantitatively analyze the influence of the dynamic damage evolution of solid materials on the propagation and attenuation laws of ultrasonic waves and stress waves. Currently, the research on the dynamic damage of materials such as rocks and concrete is mainly based on the dynamic impact or static-dynamic combined loading of the Hopkinson bar (SHPB bar), and then using CT scanning equipment or ultrasonic instruments to calibrate the dynamic damage of materials such as rocks and concrete. At the same time, as the diameter of the SHPB bar increases, the high-frequency components in the pulse and the wave dispersion will become more and more serious, and the failure effect of brittle concrete materials becomes smaller. In the conventional Hopkinson bar test, the rise time of the incident pulse rise edge is very short, which causes that before the concrete specimen has time to reach equilibrium, most of the units in the specimen have failed. To solve the above problems and make the Hopkinson bar test results more accurate, the pulse shaping technology came into being.

[0003] The existing technical methods for studying dynamic damage are to disassemble the specimen after the static-dynamic loading of the Hopkinson bar, and then use other equipment (such as CT scanning equipment or ultrasonic instruments) to detect the damage of the specimen. The existing methods separate the static-dynamic combined loading and the damage detection, and currently it is impossible to study the dynamic damage of materials such as rocks and concrete and its influence on the propagation and attenuation laws of ultrasonic waves in the in-situ pressure-holding state.

[0004] The existing pulse shaping technology device is to add gaskets of different materials with the same diameter as the incident bar (such as copper, brass, paper, rubber, etc.) between the impact bullet and the incident bar of the Hopkinson bar to achieve a smooth waveform, eliminate the high-frequency oscillation of the stress wave, and solve the problems of stress uniformity and constant strain rate loading. Currently, there is no shaper noise adding device that uses the components of each frequency band of a complex waveform through a shaper for later wavelet transform and other processing and analysis of the waveform to analyze damage. Summary of the Invention

[0005] In view of the above existing problems, the present invention proposes an SHPB shaper noise adding device and a damage analysis method. By designing a shaper noise adding device, the components of each frequency band of the incident wave are enriched, and later, through the wavelet analysis method, the amplitude changes of the waves in different frequency bands of the incident wave and the transmitted wave are compared, so as to analyze the damage conditions such as cracks and pores inside the specimen.

[0006] To achieve the above object, a noise-adding device for an SHPB shaper designed by the present invention is characterized in that it includes a device body disposed between the incident bar of a true triaxial Hopkinson bar device and a high-pressure gas gun; the device body is a steel cylindrical closed cavity structure, and several steel balls with different particle sizes are arranged in the inner cavity of the device body; one end of the device body is abutted against the high-pressure gas gun, and the other end is abutted against the incident bar of the true triaxial Hopkinson bar device through a rubber gasket.

[0007] Further, the particle size range of the steel balls in the device body is 5-30 mm, and different particle gradations D are obtained by controlling the proportion of different particle sizes of the steel balls.

[0008] Furthermore, the length L of the device body 钢 and the total length L of the test device 总 The ratio of is the decoupling coefficient By changing the decoupling coefficient, the incident wave is subjected to different degrees of noise addition treatment, so that the incident wave obtains more high-frequency and low-frequency bands.

[0009] Furthermore, the contact surfaces of the rubber gasket with the device body and the incident bar of the true triaxial Hopkinson bar device are smeared with vaseline to ensure fitting.

[0010] Furthermore, there are five kinds of particle sizes of the steel balls, which are 5 mm, 10 mm, 15 mm, 20 mm, and 30 mm respectively.

[0011] Furthermore, the volume of the steel balls is 1 / 10-1 / 9 of the inner cavity volume of the device body.

[0012] The present invention also proposes a damage analysis method for a noise-adding device of an SHPB shaper, and the method is realized based on the above-mentioned noise-adding device of the SHPB shaper, and includes the following steps;

[0013] 1) Install the device body between the incident bar of the true triaxial Hopkinson bar device and the high-pressure gas gun;

[0014] 2) Place the specimen, start the Hopkinson bar impact system, conduct an impact test, use the high-pressure gas in the high-pressure gas gun to drive the impact bar to impact the device body and the incident bar, the force and shock wave act on the specimen and are transmitted to the transmission bar, the transmission bar collides with the absorption bar, and the absorption bar is used to absorb the remaining energy, and the strain signals measured by the strain gauges on the incident bar and the transmission bar are recorded by the data acquisition system;

[0015] 3) The force and shock wave acting on the incident bar act on the specimen, and the specimen deforms and breaks under the action of the force and shock wave;

[0016] 4) After the impact ends, the incident wave and the transmitted wave are obtained through the strain gauges on the incident bar and the transmitted bar. Then, the wavelet transform processing is performed on these two waves using the wavelet toolbox in Matlab to analyze the amplitude differences in the corresponding frequency bands of the incident wave and the transmitted wave, and further analyze the internal crack conditions of the specimen.

[0017] Preferably, different particle gradations D are obtained by controlling the proportion of different particle sizes of the steel balls in the device body. Through the coefficient of uniformity and the coefficient of curvature to represent the gradation situation. The coefficient of uniformity Cu reflects the distribution of different particle groups. The larger Cu is, the wider the distribution range of the steel ball particle sizes. When the cumulative percentage of the mass of the steel balls smaller than a certain particle size is less than or equal to 10%, the corresponding particle size is called the effective particle size d 10 ; when the cumulative percentage of the mass of the steel balls smaller than a certain particle size is less than or equal to 30%, the particle size is represented by d 30 ; when the cumulative percentage of the mass of the steel balls smaller than a certain particle size is less than or equal to 60%, this particle size is called the limiting particle size and is represented by d 60 ; when Cu < 5, the gradation is poor, that is, the distribution range of the steel ball particle sizes is narrow; when Cu > 10, the gradation is good, that is, the distribution range of the steel ball particle sizes is wide and the steel balls are evenly distributed; it is not enough to determine the steel ball gradation situation only with one index Cu, and the overall shape of the cumulative curve needs to be considered at the same time, so the value of the coefficient of curvature Cc needs to be referred to; when both conditions of Cu ≥ 5 and Cc = 1 - 3 are satisfied, the gradation is good.

[0018] Preferably, different degrees of noise addition processing are performed on the incident wave by changing the decoupling coefficient S, so that the incident wave obtains more high-frequency and low-frequency bands.

[0019] The decoupling coefficient L 钢 is the length of the device body and L 总 is the total length of the test device.

[0020] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0021] 1. The present invention can analyze the internal damage conditions of the specimen through noise addition to the incident wave and wavelet transform processing of the incident wave and the transmitted wave.

[0022] 2. The present invention solves the problem that in the traditional Hopkinson bar dynamic and static loading, after the specimen is damaged, the specimen needs to be disassembled and other equipment is used to detect the damage of the specimen, which will cause different degrees of disturbance to the specimen during this process, resulting in experimental errors.

[0023] 3. The present invention provides a method for testing and analyzing the dynamic impact damage evolution, as well as the attenuation laws of amplitude and frequency spectrum, etc., of solid materials such as rocks and concrete under the in-situ pressure-maintaining state. It makes up for the defects of the existing technical methods for dynamic testing of solid materials such as rocks and concrete based on Hopkinson bars in terms of dynamic damage testing of materials under the in-situ pressure-maintaining state. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 FIG. is a schematic diagram of the overall structure of a noise-adding device for a SHPB shaper according to the present invention.

[0025] Figure 2 FIG. is a sectional view of the device body.

[0026] Figure 3 FIG. is a schematic diagram of a steel ball.

[0027] Figure 4 FIG. is a comparison diagram of the incident wave and the transmitted wave before and after.

[0028] Figure 5 FIG. is a flowchart of the damage analysis method.

[0029] Figure 6 FIG. is a schematic diagram of wavelet analysis of the incident wave.

[0030] Figure 7 FIG. is a schematic diagram of wavelet analysis of the transmitted wave.

[0031] Figure 8 FIG. is a schematic diagram of the comparison of the amplitudes of each frequency band of wavelet analysis of the incident wave and the transmitted wave.

[0032] In the figure, the device body 1, the incident bar 2, the high-pressure gas gun 3, the rubber gasket 4, and the steel ball 5. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0033] The following further describes the present invention in detail with reference to the accompanying drawings and specific embodiments.

[0034] As Figure 1 shown, a noise-adding device for a SHPB shaper proposed by the present invention includes a device body 1 disposed between the incident bar 2 and the high-pressure gas gun 3 of a true triaxial Hopkinson pressure bar device. As Figure 2 shown, the device body 1 is a steel cylinder structure with a closed cavity. A number of steel balls 5 with different particle sizes are arranged in the inner cavity of the device body 1; one end of the device body 1 abuts against the high-pressure gas gun 3, and the other end abuts against the incident bar 2 of the true triaxial Hopkinson pressure bar device through the rubber gasket 4. The bottom area of the device body 1 is the same as that of the rubber gasket 4 and the incident bar 2.

[0035] As Figure 3 shown, in this embodiment, the steel balls are divided into five different sizes.

[0036] In actual operation, the rubber gasket 4 is attached to the front end of the incident bar 2, and the other end of the rubber gasket 4 is aligned with the device body 1. The above contact surfaces are smeared with vaseline to ensure fitting. The comparison of the incident wave and the transmitted wave before and after adding this device is as follows Figure 4 shown

[0037] Based on the above SHPB shaper noise addition device, the damage analysis method proposed by the present invention includes the following steps;

[0038] 1) Install the device body 1 between the incident bar 2 and the high-pressure gas gun 3 of the true triaxial Hopkinson bar device;

[0039] 2) Place the specimen, start the Hopkinson bar impact system, conduct an impact test, use the high-pressure gas in the high-pressure gas gun 3 to drive the impact bar to impact the device body 1 and the incident bar 2, the force and shock wave act on the specimen and are transmitted to the transmission bar, and the transmission bar collides with the absorption bar, and the absorption bar is used to absorb the remaining energy. The strain signals measured by the strain gauges on the incident bar 2 and the transmission bar are recorded by the data acquisition system;

[0040] 3) The force and shock wave acting on the incident bar 2 act on the specimen, and the specimen deforms and breaks under the action of the force and shock wave;

[0041] 4) After the impact ends, the incident wave and the transmitted wave are obtained through the strain gauges on the incident bar 2 and the transmission bar, and then the wavelet transform processing is performed on these two waves using the wavelet toolbox in Matlab, and the amplitude differences of the corresponding frequency bands of the incident wave and the transmitted wave are analyzed, and then the internal crack conditions of the specimen are analyzed.

[0042] The principle of the damage analysis method is that after passing through the shaping and noise addition device, the complex stress wave will be absorbed by cracks of different sizes in the rock sample that are similar in wavelength to their crack sizes when passing through the rock sample, resulting in a certain difference between the waveform of the transmitted wave and the incident wave. By performing wavelet analysis on the incident wave and the transmitted wave, wave bands of different frequencies can be obtained. By comparing the amplitudes of the incident and transmitted wave bands, it can be clearly seen which frequency band of the wave energy is absorbed and the amplitude decreases, so that the crack composition in the rock sample can be analyzed.

[0043] By controlling the proportion of different particle sizes of steel balls in the steel cylinder, different particle gradations D are obtained, through the coefficient of uniformity and the coefficient of curvature It is used to represent the grading situation. The coefficient of uniformity Cu reflects the distribution of different-sized particle groups. The larger the Cu, the larger the distribution range of the steel ball particle sizes, and the better the grading. When the content of small-sized steel balls in the cylinder is relatively large, the high-frequency components in the shaped waveform account for a relatively large proportion. When the content of large-sized steel balls in the cylinder is relatively large, the low-frequency components in the shaped waveform account for a relatively large proportion. When the cumulative percentage of the mass of steel balls smaller than a certain particle size is less than or equal to 10%, the corresponding particle size is called the effective particle size d 10 ; when the cumulative percentage of the mass of steel balls smaller than a certain particle size is less than or equal to 30%, the particle size is represented by d 30 ; when the cumulative percentage of the mass of steel balls smaller than a certain particle size is less than or equal to 60%, this particle size is called the limiting particle size and is represented by d 60 ; when Cu < 5, the grading is poor, that is, the distribution range of the steel ball particle sizes is relatively narrow; when Cu > 10, the grading is good, that is, the distribution range of the steel ball particle sizes is wide and the steel balls are evenly distributed; it is not enough to determine the steel ball grading situation only with a single index Cu. The overall shape of the cumulative curve needs to be considered simultaneously, so the curvature coefficient Cc value needs to be referred to; when both conditions of Cu ≥ 5 and Cc = 1 - 3 are met, the grading is good.

[0044] Define the ratio of the steel cylinder length to the total length of the device as the decoupling coefficient By changing the grading and the decoupling coefficient, different degrees of noise addition processing are performed on the incident wave, so that the incident wave obtains more high-frequency and low-frequency bands. The larger the decoupling coefficient S, the longer the steel cylinder length, and the more components in different frequency bands in the shaped waveform, and the more complex the waveform; on the contrary, the smaller the decoupling coefficient S, the shorter the steel cylinder length, and the fewer components in different frequency bands in the shaped waveform, and the relatively simpler the waveform.

[0045] After the impact ends, the incident wave and the transmitted wave are obtained through the strain gauges on the incident bar and the transmitted bar, and then the wavelet transform processing is performed on these two waves using the wavelet toolbox in matlab to analyze the amplitude differences of the corresponding frequency bands of the incident wave and the transmitted wave, and then analyze the situation of the internal cracks of the specimen. Figure 5 It is the flow chart of the damage analysis method.

[0046] Figures 6 to 8 It is the spectrogram after the wavelet analysis of the incident wave and the transmitted wave after being noise-added by the shaper. Through the Figure 8 detail comparison diagram, it can be clearly seen that the amplitudes of each frequency band of the transmitted wave are significantly reduced compared to the amplitudes of the corresponding frequency bands of the incident wave. The situation of the cracks in the rock specimen can be analyzed through the reduced values of the amplitudes.

[0047] Although the preferred embodiments of the present invention have been described above in conjunction with the accompanying drawings, the present invention is not limited to the above specific implementation manners. The above specific implementation manners are merely illustrative and not restrictive. Under the inspiration of the present invention, those of ordinary skill in the art can also make many specific transformations in various forms without departing from the spirit of the present invention and the scope protected by the claims. All of these fall within the protection scope of the present invention.

Claims

1. A noise-adding device for an SHPB shaper, characterized in that: It includes a device body (1) disposed between an incident bar (2) of a true triaxial Hopkinson bar device and a high-pressure gas gun (3); the device body (1) is a steel cylindrical closed cavity structure, and several steel balls (5) with different particle sizes are arranged in the inner cavity of the device body (1); one end of the device body (1) abuts against the high-pressure gas gun (3), and the other end abuts against the incident bar (2) of the true triaxial Hopkinson bar device through a rubber gasket (4); The particle size range of the steel balls (5) in the device body (1) is 5 - 30 mm, and different particle gradings D are obtained by controlling the proportion of different particle sizes of the steel balls (5); The volume of the steel balls (5) is 1 / 10 - 1 / 9 of the inner cavity volume of the device body (1).

2. The SHPB shaper noise addition device according to claim 1, wherein: The length L of the device body (1) 钢 and the total length L of the test device 总 The ratio is the decoupling coefficient By changing the decoupling coefficient, the incident wave is subjected to different degrees of noise addition processing, so that the incident wave obtains more high-frequency and low-frequency bands.

3. The SHPB shaper noise addition device according to claim 1, characterized in that: The contact surfaces of the rubber gasket (4) with the device body (1) and the incident bar (2) of the true triaxial Hopkinson bar device are smeared with vaseline to ensure fitting.

4. The SHPB shaper noise adding device according to claim 1, characterized in that: The particle sizes of the steel balls (5) are five kinds, namely 5 mm, 10 mm, 15 mm, 20 mm, and 30 mm respectively.

5. A damage analysis method for a noise-adding device of an SHPB shaper, characterized in that: The method is implemented based on the SHPB shaper noise addition device described in any one of claims 1 - 4, and includes the following steps; 1) Install the device body (1) between the incident bar (2) of the true triaxial Hopkinson bar device and the high-pressure gas gun (3); 2) Place the specimen, start the Hopkinson bar impact system, conduct an impact test, use the high-pressure gas in the high-pressure gas gun (3) to drive the impact bar to impact the device body (1) and the incident bar (2), the force and shock wave act on the specimen and are transmitted to the transmission bar through the specimen, the transmission bar collides with the absorption bar, and the absorption bar is used to absorb the remaining energy, and the strain signals measured by the strain gauges on the incident bar (2) and the transmission bar are recorded by the data acquisition system; 3) The force and shock wave acting on the incident bar (2) act on the specimen, and the specimen deforms and breaks under the action of the force and shock wave; 4) After the impact ends, the incident wave and the transmission wave are obtained through the strain gauges on the incident bar (2) and the transmission bar, and then the wavelet transform processing is performed on these two waves using the wavelet toolbox in Matlab, and the amplitude differences of each corresponding frequency band of the incident wave and the transmission wave are analyzed, and then the internal crack situation of the specimen is analyzed.

6. The damage analysis method of the SHPB shaper noise addition device according to claim 5, characterized in that: By controlling the proportion of steel balls (5) with different particle sizes in the control device body (1), different particle gradations D are obtained. The gradation situation is represented by the coefficient of uniformity and the coefficient of curvature . The coefficient of uniformity Cu reflects the distribution of particle groups with different sizes. The larger Cu is, the larger the distribution range of the steel ball particle sizes. When the cumulative percentage of the mass of steel balls smaller than a certain particle size is less than or equal to 10%, the corresponding particle size is called the effective particle size d 10 ; when the cumulative percentage of the mass of steel balls smaller than a certain particle size is less than or equal to 30%, the particle size is represented by d 30 ; when the cumulative percentage of the mass of steel balls smaller than a certain particle size is less than or equal to 60%, this particle size is called the limiting particle size and is represented by d 60 . When Cu < 5, the gradation is poor, that is, the distribution range of the steel ball particle sizes is narrow. At the same time, considering the overall shape of the cumulative curve, the reference coefficient of curvature Cc value is introduced. When both conditions of Cu ≥ 5 and Cc = 1 - 3 are satisfied, the gradation is good.

7. The damage analysis method of the SHPB shaper noise addition device according to claim 6, characterized in that: By changing the decoupling coefficient S, different degrees of noise addition processing are performed on the incident wave, so that the incident wave obtains more high-frequency and low-frequency bands, The decoupling coefficient L 钢 is the length of the device body (1) and L 总 is the total length of the test device.

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