Multi-probe constant pressure coupling positioning auxiliary device and method for coal sample testing

Abstract

The present application relates to coal rock material mechanics test and acoustic emission monitoring technical field, especially to the multi-probe constant pressure coupling positioning auxiliary device and method for coal sample test, including: base, used for structure assembly and support; coal sample positioning seat, used for coal sample centering positioning; support frame, the outer side of support frame is provided with acoustic emission probe clamping unit, one side of acoustic emission probe clamping unit is provided with acoustic emission probe; probe shell, acoustic emission probe outside one side of acoustic emission probe clamping unit is provided with probe shell, the top of probe shell is provided with constant pressure pressing mechanism for providing preset pressing force for acoustic emission probe, the present application controls the contact pressure of acoustic emission probe and coal sample surface through constant pressure pressing mechanism, reduces the installation error caused by manual hand sticking mode, improves acoustic emission signal acquisition repeatability, controls the coupling layer thickness through coupling layer thickness limiting ring and coupling agent storage groove, reduces the amplitude attenuation and signal dispersion caused by uneven coupling agent coating.

Description

Technical Field

[0001] This invention relates to the field of mechanical testing and acoustic emission monitoring technology for coal and rock materials, and particularly to a multi-probe constant pressure coupling positioning auxiliary device and method for coal sample testing. Background Technology

[0002] Coal samples undergo stages such as primary fracture compaction, microcrack initiation, crack propagation, and through-crack failure during compression, tension, or cyclic loading. Acoustic emission testing (AE) can receive transient elastic wave signals released from crack propagation within the coal sample via a probe, thereby reflecting the damage evolution, pre-fracture precursors, and energy release characteristics of the coal sample. Conventional acoustic emission testing of coal samples typically includes equipment such as an acoustic emission probe, acoustic emission connection cable, preamplifier, and acoustic emission signal analyzer.

[0003] In actual experiments, acoustic emission probes are typically attached to the coal sample surface by hand, binding with tape, tightening with rubber bands, or fixing with simple clamps. While these methods are simple to operate, they present the following problems during the loading and destructive process of the coal sample:

[0004] 1. The contact pressure between the probe and the coal sample surface depends on human experience, and the clamping force is unstable, which can easily lead to increased dispersion in the amplitude, energy and counting parameters of acoustic emission signals at different locations of the same coal sample or between different coal samples.

[0005] 2. When the surface of the coal sample is rough, flaking, or locally damaged, the contact state between the probe and the coal sample changes, which can easily cause signal abrupt changes, reception attenuation, or probe detachment.

[0006] 3. It is difficult to maintain a consistent coupling agent coating thickness. If the coupling layer is too thick, it will cause attenuation of high-frequency acoustic emission signals. If the coupling layer is too thin or there is a lack of adhesive in some areas, it will lead to insufficient contact.

[0007] 4. When multiple probes are arranged, the height, circumferential angle and radial clamping amount of the probes are difficult to reproduce accurately, affecting the spatial positioning consistency between different tests.

[0008] 5. The probe connection cable is easily pulled during loading, testing, or personnel operation, which can change the probe's clamping state and generate mechanical noise or false signals.

[0009] 6. The lack of a unified synchronous trigger or time marker between the acoustic emission acquisition system and the loading test machine leads to an inaccurate correspondence between the load-displacement curve and acoustic emission events.

[0010] Therefore, it is necessary to provide a multi-probe constant pressure coupling positioning auxiliary device and method for coal sample testing, so that the acoustic emission probe can maintain a preset clamping force, stable coupling state and reproducible spatial position throughout the entire process of coal sample loading and fracturing, and achieve synchronous acquisition with the loading test system. Summary of the Invention

[0011] Based on this, it is necessary to provide a multi-probe constant-pressure coupling positioning auxiliary device and method for coal sample testing to address the above-mentioned technical problems, in order to solve the technical problems in existing coal sample acoustic emission testing, such as probe installation relying on manual labor, unstable coupling state, poor repeatability of spatial arrangement, easy pulling of connecting wires, and difficulty in synchronizing loading data and acoustic emission data.

[0012] To solve the above-mentioned technical problems, the present invention adopts the following technical solution:

[0013] A multi-probe constant-pressure coupling positioning auxiliary device and method for coal sample testing, including:

[0014] The base is used for structural assembly and support.

[0015] A coal sample positioning seat is installed in the middle of the top of the base to center and position the coal sample.

[0016] A support frame is set on the outside of the coal sample at the top of the coal sample positioning seat. An acoustic emission probe clamping unit is set on the outside of the support frame. An acoustic emission probe is set on one side of the acoustic emission probe clamping unit for detecting the coal sample.

[0017] The probe housing is located on the outside of the acoustic emission probe on one side of the acoustic emission probe clamping unit. The top of the probe housing is provided with a constant pressure clamping mechanism for providing a preset clamping force to the acoustic emission probe. The probe contact end at the bottom of the acoustic emission probe faces the axial direction of the coal sample.

[0018] A compression loading head is positioned on top of the coal sample, and the top of the compression loading head is connected to a loading test machine for applying axial pressure to the coal sample.

[0019] As a preferred embodiment of the multi-probe constant pressure coupling positioning auxiliary device and method for coal sample testing provided by the present invention, the support frame includes:

[0020] Multiple vertical guide rails are bolted to the top of the base, and the outer side of the vertical guide rails is connected to the acoustic emission probe clamping unit;

[0021] A circumferential adjustment ring, fixed to the top of multiple vertical guide rails, is used to adjust the circumferential position of the acoustic emission probe clamping unit around the coal sample axis.

[0022] The acoustic emission probe clamping unit includes:

[0023] A sliding seat is slidably connected to the outside of the vertical guide rail, and a locking screw is provided on the inner side of one end of the sliding seat;

[0024] A cable fixing clip is provided on the top of the sliding seat.

[0025] As a preferred embodiment of the multi-probe constant pressure coupling positioning auxiliary device and method for coal sample testing provided by the present invention, a cable outlet is fixed at one end of the top of the probe housing, and the acoustic emission connecting wire inside the cable outlet extends out and enters the cable fixing clamp.

[0026] As a preferred embodiment of the multi-probe constant pressure coupling positioning auxiliary device and method for coal sample testing provided by the present invention, a coupling layer thickness limiting ring is provided on the periphery of the probe contact end, and a coupling agent storage groove is provided on the inner side of the coupling layer thickness limiting ring to accommodate a small amount of coupling agent.

[0027] As a preferred embodiment of the multi-probe constant pressure coupling positioning auxiliary device and method for coal sample testing provided by the present invention, the constant pressure clamping mechanism includes:

[0028] A threaded adjusting rod is threadedly connected to the inside of the top of the probe housing, and a locking knob is threadedly connected to the outside of the top of the threaded adjusting rod;

[0029] A compression spring, located inside the probe housing at the bottom of the threaded adjusting rod, is used to contact the top of the acoustic emission probe.

[0030] As a preferred embodiment of the multi-probe constant pressure coupling positioning auxiliary device and method for coal sample testing provided by the present invention, a signal cable is fixed to the inner side of the threaded adjustment rod, the bottom of the signal cable is connected to the acoustic emission probe, and the top of the signal cable is fixed by a cable clamp and then connected to the preamplifier and the acoustic emission signal analyzer.

[0031] As a preferred embodiment of the multi-probe constant pressure coupling positioning auxiliary device and method for coal sample testing provided by the present invention, it further includes a synchronous triggering module, which is used to receive the loading test machine signal and output a synchronous triggering signal to the acoustic emission signal analyzer, and output a test status signal to the computer.

[0032] The testing method for a multi-probe constant-pressure coupling positioning auxiliary device used for coal sample testing is as follows:

[0033] S1: Prepare coal samples and measure their diameter, height, mass, moisture content, and surface smoothness;

[0034] S2: Install the coal sample on top of the coal sample positioning seat and make the coal sample axis coincide with the center line of the compression loading head;

[0035] S3: Install the support frame and adjust the positions of the circumferential adjusting ring, vertical guide rail and acoustic emission probe clamping unit;

[0036] S4: Coupling agent is applied to the contact end of the acoustic emission probe, and the thickness of the coupling layer is controlled by a coupling layer thickness limiting ring;

[0037] S5: Rotate the threaded adjustment rod to compress the spring to generate the preset clamping amount, and lock it by the locking knob;

[0038] S6: Secure the acoustic emission connection cable to the cable clamp and check the signal, threshold value and noise level of each channel;

[0039] S7: Set the loading regime, acoustic emission acquisition parameters, preamplification factor, and synchronization trigger conditions;

[0040] S8: Start the synchronous trigger module and begin loading, real-time acquisition of acoustic emission signals and loading test data;

[0041] S9: After the test, export the acoustic emission events, amplitude, energy, count, duration, RA value, AF value, and load-displacement data;

[0042] S10: Corresponding analysis of the coal sample fracture stage and acoustic emission parameters is performed to obtain the characteristics of coal sample damage evolution and fracture precursors.

[0043] It is clear without a doubt that the technical problems to be solved by the present invention can be solved by the above-described technical solutions of the present invention.

[0044] Meanwhile, through the above technical solutions, the present invention has at least the following beneficial effects:

[0045] 1. The multi-probe constant pressure coupling positioning auxiliary device and method for coal sample testing provided by the present invention controls the contact pressure between the acoustic emission probe and the coal sample surface through a constant pressure clamping mechanism, reducing installation errors caused by manual application and improving the repeatability of acoustic emission signal acquisition; controls the coupling layer thickness through a coupling layer thickness limiting ring and a coupling agent storage tank, reducing amplitude attenuation and signal dispersion caused by uneven coupling agent coating; and achieves three-dimensional spatial positioning of the multi-probe through a vertical guide rail, a circumferential adjustment ring, and a threaded adjustment rod, facilitating the reproduction of experimental setups between different tests.

[0046] 2. This invention achieves rapid positioning, constant pressure clamping, thickness-limited coupling, anti-pulling fixation, and synchronous acquisition of the acoustic emission probe on the coal sample surface through the combined design of a support frame, vertical guide rail, circumferential adjustment ring, acoustic emission probe clamping unit, constant pressure clamping mechanism, cable fixing clamp, coupling layer thickness limiting ring, coupling agent storage tank, and synchronous triggering module.

[0047] 3. This invention establishes a unified time reference for loading data and acoustic emission data through a synchronous triggering module, thereby improving the accuracy of coal sample damage stage identification and pre-fracture analysis.

[0048] 4. The device of this invention is compatible with existing acoustic emission probes, connecting lines, amplifiers and signal analyzers without requiring changes to the instrument itself, making it easy to promote and apply based on existing equipment in universities or laboratories. Attached Figure Description

[0049] To more clearly illustrate the technical solutions of the embodiments of the present invention, the accompanying drawings used in the description of the embodiments will be briefly introduced below. Obviously, the accompanying drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0050] Figure 1 This is a schematic diagram of the overall structure of the present invention;

[0051] Figure 2 This is a schematic diagram of the threaded adjusting rod of the present invention;

[0052] Figure 3 This is a schematic diagram of the acoustic emission probe of the present invention;

[0053] Figure 4 For the present invention Figure 3 Front view;

[0054] Figure 5 For the present invention Figure 3 Top view;

[0055] Figure 6 This is a connection block diagram of the acoustic emission testing system of the present invention;

[0056] Figure 7 This is a flowchart of the acoustic emission testing method for coal samples according to the present invention.

[0057] In the diagram: 1. Base; 2. Coal sample; 3. Coal sample positioning seat; 4. Support frame; 5. Vertical guide rail; 6. Circumferential adjustment ring; 7. Acoustic emission probe clamping unit; 8. Constant pressure clamping mechanism; 9. Cable fixing clamp; 10. Signal cable; 11. Coupling layer thickness limiting ring; 12. Acoustic emission probe; 13. Compression loading head; 14. Mounting block; 15. Sliding seat; 16. Locking knob; 17. Threaded adjustment rod; 18. Compression spring; 19. Probe housing; 20. Coupling agent storage tank; 21. Probe contact end; 22. Cable outlet. Detailed Implementation

[0058] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention.

[0059] To enable those skilled in the art to better understand the present invention, the technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings.

[0060] It should be noted that, unless otherwise specified, the embodiments and features and technical solutions in the present invention can be combined with each other.

[0061] It should be noted that similar labels and letters in the following figures indicate similar items. Therefore, once an item is defined in one figure, it does not need to be further defined and explained in subsequent figures.

[0062] Example 1

[0063] Reference Figures 1-6 A multi-probe constant-pressure coupling positioning auxiliary device for coal sample testing includes:

[0064] Base 1, used for structural assembly and support;

[0065] The coal sample positioning seat 3 is installed in the middle of the top of the base 1 and is used to center the coal sample 2.

[0066] Preferably, the coal sample 2 can be cylindrical or square. The coal sample positioning seat 3 is an annular groove seat, a V-shaped positioning seat, a replaceable limiting sleeve, or a three-jaw positioning structure. For cylindrical coal samples 2, the coal sample positioning seat 3 is preferably provided with an annular limiting groove that matches the diameter of the coal sample 2; for square coal samples 2, the coal sample positioning seat 3 can be provided with an adjustable stop block or a right-angle limiting block. The coal sample positioning seat 3 can be detachably installed on the base 1 to accommodate coal samples 2 with different diameters or different cross-sectional dimensions.

[0067] A support frame 4 is set on the outside of the coal sample 2 at the top of the coal sample positioning seat 3. An acoustic emission probe clamping unit 7 is set on the outside of the support frame 4 to realize the height adjustment of the acoustic emission probe clamping unit 7. An acoustic emission probe 12 is set on one side of the acoustic emission probe clamping unit 7 for detecting the coal sample 2.

[0068] In this embodiment, there are four acoustic emission probes 12, which are arranged at 90° intervals along the circumference of the coal sample 2. Multiple acoustic emission probes 12 can be arranged at the same height to form a circumferential monitoring array, or multiple acoustic emission probes 12 can be arranged at different heights to form a spatial monitoring array.

[0069] Supporting framework 4 includes:

[0070] Multiple vertical guide rails 5 are bolted to the top of the base 1. The outer side of the vertical guide rails 5 is connected to the acoustic emission probe clamping unit 7, thereby enabling the acoustic emission probe clamping unit 7 to slide and adjust its height on the outer side of the vertical guide rails 5.

[0071] The circumferential adjustment ring 6 is fixed on the top of multiple vertical guide rails 5 and is used to adjust the circumferential position of the acoustic emission probe clamping unit 7 around the axis of the coal sample 2.

[0072] In this embodiment, an arc-shaped groove, positioning hole, or scale mark can be provided on the circumferential adjustment ring 6 along the circumferential direction, so that the acoustic emission probe clamping unit 7 is connected to the arc-shaped groove through the sliding seat 15 and fixed in a predetermined circumferential position, thereby realizing the adjustment of the height direction, circumferential direction, and radial direction of the acoustic emission probe clamping unit 7, and thus allowing multiple acoustic emission probes 12 to be arranged at a predetermined angle, such as 90°, 120°, or 180° symmetrically.

[0073] The acoustic emission probe clamping unit 7 includes:

[0074] The sliding seat 15 is slidably connected to the outside of the vertical guide rail 5. A locking screw is provided on the inner side of one end of the sliding seat 15, which is used to position the height of the sliding seat 15 outside the vertical guide rail 5 by pressing the locking screw against the vertical guide rail 5.

[0075] The top of the sliding seat 15 is provided with a cable fixing clip 9. The cable fixing clip 9 can be a rubber clamp, an elastic buckle or a clamping clip with a buffer pad to reduce the mechanical noise introduced by the cable shaking. In this way, the acoustic emission connecting wire inside the cable outlet 22 can be fixed to the top of the sliding seat 15. The top of the sliding seat 15 is provided with a mounting block 14 for assembling the position of the cable fixing clip 9.

[0076] In other embodiments, the cable clamp 9 can be fixed to the support frame 4 or the vertical guide rail 5.

[0077] In this embodiment, a flexible bending allowance is reserved between the cable fixing clamp 9 and the acoustic emission probe 12, so that the pulling force of the external cable is preferentially borne by the support frame 4 or the sliding seat 15, rather than directly acting on the acoustic emission probe 12.

[0078] The probe housing 19 is located on the outside of the acoustic emission probe 12 on one side of the acoustic emission probe clamping unit 7. The top of the probe housing 19 is provided with a constant pressure clamping mechanism 8 for providing a preset clamping force to the acoustic emission probe 12. This allows each acoustic emission probe clamping unit 7 to be evenly positioned to position a corresponding acoustic emission probe 12. The probe contact end 21 at the bottom of the acoustic emission probe 12 faces the axial direction of the coal sample 2, allowing the acoustic emission probe 12 to contact the coal sample 2 through the probe contact end 21.

[0079] Preferably, a cable outlet 22 is fixed at one end of the top of the probe housing 19, and the acoustic emission connecting wire inside the cable outlet 22 extends out and enters the cable fixing clamp 9.

[0080] In this embodiment, a coupling layer thickness limiting ring 11 is provided around the probe contact end 21. The coupling layer thickness limiting ring 11 can be a thin metal ring, a wear-resistant plastic ring, an elastic rubber ring, or a composite material ring. The end face height of the coupling layer thickness limiting ring 11 is slightly higher than or equal to the reference surface of the probe contact end 21, so that after the acoustic emission probe 12 is attached to the coal sample 2, a coupling agent layer of predetermined thickness is formed between the probe contact end 21 and the surface of the coal sample 2. A coupling agent storage groove 20 is provided on the inner side of the coupling layer thickness limiting ring 11 to hold a small amount of coupling agent. The coupling agent inside the coupling agent storage groove 20 fills the gap between the probe contact end 21 and the coal sample 2, realizing stable acoustic coupling. At the same time, even if the surface of the coal sample 2 undergoes slight deformation or local rough contact during loading, the coupling agent in the storage groove can still compensate for the small gaps at the interface, thereby maintaining a stable coupling state. The thickness of the coupling layer can be set to a value in the range of 0.1 mm to 1.0 mm, preferably 0.2 mm to 0.5 mm, depending on the frequency response characteristics of the acoustic emission probe 12 and the surface condition of the coal sample 2.

[0081] In other embodiments, the coupling agent storage tank 20 may also be located on the outside of the coupling layer thickness limiting ring 11.

[0082] The constant pressure clamping mechanism 8 includes:

[0083] The threaded adjusting rod 17 is threadedly connected to the inside of the top of the probe housing 19, so that the threaded adjusting rod 17 can be axially adjusted by rotation inside the probe housing 19. The outer side of the top of the threaded adjusting rod 17 is threadedly connected to a locking knob 16, so that the rotation of the threaded adjusting rod 17 can be locked by locking the knob 16 when the outer side of the threaded adjusting rod 17 contacts the top of the probe housing 19.

[0084] Preferably, a signal cable 10 is fixed to the inner side of the threaded adjustment rod 17. The bottom of the signal cable 10 is connected to the acoustic emission probe 12, and the top of the signal cable 10 is fixed by the cable fixing clip 9 and then connected to the preamplifier and the acoustic emission signal analyzer.

[0085] A compression spring 18 is located inside the probe housing 19 at the bottom of the threaded adjustment rod 17 and is used to contact the top of the acoustic emission probe 12 to adjust the preset clamping amount of the acoustic emission probe 12.

[0086] In other embodiments, a clamping force scale is provided on the outside of the threaded adjustment rod 17, or a miniature pressure sensor is provided between the probe housing 19 and the spring. The operator can select an appropriate clamping force range according to the strength, surface roughness, coupling agent type and probe size of the coal sample 2, to avoid insufficient contact due to insufficient clamping force, and to avoid local pressure damage to the surface of the coal sample 2 due to excessive clamping force.

[0087] A compression loading head 13 is set on top of the coal sample 2, and the top of the compression loading head 13 is connected to the loading test machine to apply axial pressure to the coal sample 2.

[0088] It also includes: a synchronous trigger module, used to receive the load testing machine signal and output a synchronous trigger signal to the acoustic emission signal analyzer, and output the test status signal to the computer;

[0089] Preferably, the loading start signal, load threshold signal, displacement threshold signal, or failure criterion trigger signal output by the loading test machine are input to the synchronous trigger module. The synchronous trigger module outputs a synchronous trigger signal to the acoustic emission signal analyzer, enabling the acoustic emission signal analyzer to start acquiring or marking data from a unified trigger moment. The acoustic emission signal received by the acoustic emission probe array 12 is input to the acoustic emission signal analyzer via a preamplifier. The acoustic emission signal analyzer establishes a time correspondence between the acoustic emission data and loading parameters such as load, displacement, and strain according to the synchronous trigger moment, and transmits the analysis results to the computer and data storage and analysis module. This allows for a more accurate analysis of the acoustic emission response characteristics of coal sample 2 during the compaction stage, elastic stage, stable crack propagation stage, unstable crack propagation stage, and post-peak failure stage.

[0090] Synchronous triggering can be achieved through loading start triggering, load threshold triggering, displacement threshold triggering, or external TTL pulse triggering. This method ensures that the acoustic emission event time, load time, and displacement time are within the same time frame, improving the accuracy of identifying the fracture stage of coal sample 2.

[0091] In this embodiment, each structure has its own service life. In actual manufacturing and application, the corresponding structure made of different materials can be replaced according to the needs of use.

[0092] The usage process of the multi-probe constant pressure coupling positioning auxiliary device and method for coal sample testing provided by this invention is as follows:

[0093] In use, place coal sample 2 at the top center of coal sample positioning seat 3, aligning the axis of coal sample 2 with the axis of coal sample positioning seat 3. Install support frame 4 on top of base 1, and adjust the positions of vertical guide rail 5 and circumferential adjustment ring 6 on support frame 4 as needed. Simultaneously adjust the height of acoustic emission probe clamping unit 7 outside vertical guide rail 5. Apply coupling agent to the contact end of acoustic emission probe 12, and control the coupling layer thickness through coupling layer thickness limiting ring 11. Then, adjust acoustic emission probe clamping unit 7 to make contact end of acoustic emission probe 12 contact coal sample 2. At the same time, adjust the preset clamping amount of acoustic emission probe 12 inside probe housing 19 through constant pressure clamping mechanism 8. Fix the connecting wire through cable fixing clip 9 to facilitate signal transmission. Simultaneously check the signal, threshold value and noise level of each channel. Start synchronous triggering module and begin loading, and collect acoustic emission signals and loading test data in real time.

[0094] Example 2

[0095] Based on the above embodiment 1, the acoustic emission probes 12 can be six, eight or other selected numbers. When there are six, a spatial arrangement of three acoustic emission probes 12 in each of two layers can be adopted to improve the ability to identify the direction and height of crack propagation.

[0096] Example 3

[0097] Based on the above embodiment one or embodiment two, the following is disclosed:

[0098] In the auxiliary device, the bottom of the vertical guide rail 5 and the base 1 can be circumferentially rotated and adjusted, and a fastening bolt is set between the vertical guide rail 5 and the base 1 for positioning the vertical guide rail 5 after circumferential adjustment on the base 1, thereby realizing the rotation of the auxiliary device, and the acoustic emission probe can be placed at any position.

[0099] Example 4

[0100] refer to Figure 7 Based on the above-described embodiment one, a method for testing the acoustic emission of coal samples is disclosed, the steps of which are as follows:

[0101] S1: Prepare coal sample 2 and measure its diameter, height, mass, moisture content, and surface smoothness;

[0102] S2: Install coal sample 2 on coal sample positioning seat 3, so that the axis of coal sample 2 coincides with the center line of compression loading head 13;

[0103] S3: Install the support frame 4, and adjust the positions of the circumferential adjustment ring 6, the vertical guide rail 5 and the acoustic emission probe clamping unit 7 according to the test plan;

[0104] S4: Coupling agent is applied to the contact end of acoustic emission probe 12, and the thickness of coupling layer is controlled by coupling layer thickness limiting ring 11;

[0105] S5: Rotate the threaded adjusting rod 17 to make the compression spring 18 generate a preset clamping amount, and lock it through the locking knob 16;

[0106] S6: Secure the acoustic emission connection cable to the cable clamp 9 and check the signal, threshold value and noise level of each channel;

[0107] S7: Set the loading regime, acoustic emission acquisition parameters, preamplification factor, and synchronization trigger conditions;

[0108] S8: Start the synchronous trigger module and begin loading, real-time acquisition of acoustic emission signals and loading test data;

[0109] S9: After the test, export the acoustic emission events, amplitude, energy, count, duration, RA value, AF value, and load-displacement data;

[0110] S10: Corresponding analysis of the fracture stage and acoustic emission parameters of coal sample 2 was performed to obtain the damage evolution and fracture precursor characteristics of coal sample 2.

[0111] In this embodiment, the test method steps are applicable not only to conventional uniaxial compression acoustic emission tests, but also to acoustic emission tests of coal sample 2 under triaxial compression, splitting tension, cyclic loading, unloading damage, and seepage coupling loading conditions. For different test types, adaptation can be achieved by changing the coal sample positioning seat 3, adjusting the number of acoustic emission probe clamping units 7, and changing the synchronous triggering conditions.

[0112] The preferred embodiments of the present invention disclosed above are merely illustrative of the invention. These preferred embodiments do not exhaustively describe all details, nor do they limit the invention to the specific implementations described. Clearly, many modifications and variations can be made based on the content of this specification. This specification selects and specifically describes these embodiments to better explain the principles and practical applications of the invention, thereby enabling those skilled in the art to better understand and utilize the invention. The invention is limited only by the claims and their full scope and equivalents.

Claims

1. A multi-probe constant-pressure coupling positioning auxiliary device and method for coal sample testing, characterized in that, include: Base (1) is used for structural assembly and support; The coal sample positioning seat (3) is installed in the middle of the top of the base (1) and is used to center the coal sample (2); A support frame (4) is set on the outside of the coal sample (2) at the top of the coal sample positioning seat (3). An acoustic emission probe clamping unit (7) is set on the outside of the support frame (4). An acoustic emission probe (12) is set on one side of the acoustic emission probe clamping unit (7) for detecting the coal sample (2). The probe housing (19) is located on the outside of the acoustic emission probe (12) on one side of the acoustic emission probe clamping unit (7). The top of the probe housing (19) is provided with a constant pressure clamping mechanism (8) for providing a preset clamping force to the acoustic emission probe (12). The probe contact end (21) at the bottom of the acoustic emission probe (12) faces the axial direction of the coal sample (2). A compression loading head (13) is set on top of the coal sample (2), and the top of the compression loading head (13) is connected to the loading test machine for applying axial pressure to the coal sample (2).

2. The multi-probe constant-pressure coupling positioning auxiliary device and method for coal sample testing according to claim 1, characterized in that, The supporting framework (4) includes: Multiple vertical guide rails (5) are bolted to the top of the base (1), and the outer side of the vertical guide rails (5) is connected to the acoustic emission probe clamping unit (7); A circumferential adjustment ring (6) is fixed on the top of multiple vertical guide rails (5) to realize the circumferential position adjustment of the acoustic emission probe clamping unit (7) around the coal sample (2) axis; The acoustic emission probe clamping unit (7) includes: The sliding seat (15) is slidably connected to the outside of the vertical guide rail (5), and a locking screw is provided on the inner side of one end of the sliding seat (15). The top of the sliding seat (15) is provided with a cable fixing clip (9).

3. The multi-probe constant-pressure coupling positioning auxiliary device and method for coal sample testing according to claim 2, characterized in that, The top end of the probe housing (19) is fixed with a cable outlet (22), and the acoustic emission connection wire inside the cable outlet (22) extends out and enters the cable fixing clamp (9).

4. The multi-probe constant-pressure coupling positioning auxiliary device and method for coal sample testing according to claim 1, characterized in that, A coupling layer thickness limiting ring (11) is provided on the periphery of the probe contact end (21), and a coupling agent storage groove (20) is provided on the inner side of the coupling layer thickness limiting ring (11) to accommodate a small amount of coupling agent.

5. The multi-probe constant-pressure coupling positioning auxiliary device and method for coal sample testing according to claim 1, characterized in that, The constant pressure clamping mechanism (8) includes: A threaded adjustment rod (17) is threadedly connected to the inside of the top of the probe housing (19), and a locking knob (16) is threadedly connected to the outside of the top of the threaded adjustment rod (17). A compression spring (18) is located inside the probe housing (19) at the bottom of the threaded adjustment rod (17) for contacting the top of the acoustic emission probe (12).

6. The multi-probe constant-pressure coupling positioning auxiliary device and method for coal sample testing according to claim 5, characterized in that, A signal cable (10) is fixed to the inner side of the threaded adjustment rod (17). The bottom of the signal cable (10) is connected to the acoustic emission probe (12). The top of the signal cable (10) is fixed by the cable fixing clip (9) and then connected to the preamplifier and the acoustic emission signal analyzer.

7. The multi-probe constant-pressure coupling positioning auxiliary device and method for coal sample testing according to claim 1, characterized in that, It also includes a synchronization trigger module, which is used to receive the load testing machine signal and output a synchronization trigger signal to the acoustic emission signal analyzer, and output the test status signal to the computer.

8. A test method for a multi-probe constant-pressure coupling positioning auxiliary device for coal sample testing, characterized in that, The steps are as follows: S1: Prepare coal sample (2) and measure the diameter, height, mass, moisture content and surface smoothness of coal sample (2); S2: Install the coal sample (2) on the top of the coal sample positioning seat (3) and make the axis of the coal sample (2) coincide with the center line of the compression loading head (13); S3: Install the support frame (4) and adjust the positions of the circumferential adjustment ring (6), the vertical guide rail (5) and the acoustic emission probe clamping unit (7); S4: Coupling agent is applied to the contact end of the acoustic emission probe (12), and the thickness of the coupling layer is controlled by the coupling layer thickness limiting ring (11); S5: Rotate the threaded adjustment rod (17) to allow the compression spring (18) to generate a preset clamping amount, and lock it by locking the knob (16); S6: Fix the acoustic emission connection cable to the cable clamp (9) and check the signal, threshold value and noise level of each channel; S7: Set the loading regime, acoustic emission acquisition parameters, preamplification factor, and synchronization trigger conditions; S8: Start the synchronous trigger module and begin loading, real-time acquisition of acoustic emission signals and loading test data; S9: After the test, export the acoustic emission events, amplitude, energy, count, duration, RA value, AF value, and load-displacement data; S10: Corresponding analysis of the fracture stage and acoustic emission parameters of coal sample (2) was performed to obtain the damage evolution and fracture precursor characteristics of coal sample (2).

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