Miniature acoustic emission loading chamber and test method thereof

Abstract

The invention discloses a miniature acoustic emission loading chamber and a test method thereof, belongs to the technical field of material detection, and solves the problem that a traditional uniaxial compression instrument is not suitable for researching an internal damage mechanism when a rock is damaged. The micro acoustic emission loading chamber comprises a test box, a driving mechanism and a clamping assembly are installed in the test box, and the driving mechanism is in transmission connection with the clamping assembly; a sample is clamped on the clamping assembly; and an acoustic emission probe and a photomultiplier are also arranged in the test box. According to the invention, the driving mechanism drives the clamping assembly to move, a sample on the clamping assembly is extruded and crushed by the movement, the acoustic emission probe collects acoustic signals generated in the sample fracture process during crushing, the photomultiplier collects optical signals emitted by the sample, data of acoustic emission and a press-optical effect are obtained, and the fractured sample is observed after an experiment is finished. Not only can the sample damage rule be macroscopically obtained, but also the material damage evolution can be detected and analyzed by analyzing the internal defect damage of the sample.

Description

Technical Field

[0001] The present invention relates to the technical field of material detection, and in particular to a miniature acoustic emission loading chamber and a test method thereof. Background Art

[0002] Some small-particle materials have certain joints and cracks inside, and these defects inside the particles have a huge impact on their strength. The cracks and other internal defects of this part of the material are more likely to cause damage under the action of external forces, and in this process, they transmit energy through elastic waves, light, etc. However, the small size of this part of the material makes it inconvenient to detect with traditional equipment. Traditional uniaxial compression instruments have improved many functions to meet experimental needs, such as power design, which can control the pressure and compression speed. The control accuracy of different instruments varies. As a basic experimental instrument, its design for mechanical index testing is relatively complete and its development in the commercial field is relatively mature.

[0003] However, traditional uniaxial compression instruments still have some shortcomings for studying the internal mechanism of rock failure. First, they can only judge the macroscopic damage of the sample by measuring mechanical data such as stress and strain, or by visually observing the sample. The internal damage of the sample cannot be seen with the naked eye, nor can it be accurately judged using stress and strain data. Therefore, there are certain limitations when studying the internal structural damage of rocks. Secondly, during the test, when the sample is damaged, debris will fall. The open placement platform in the traditional uniaxial compression instrument is not convenient to clean, which is not conducive to quickly carrying out the next experiment; the data cable of the acoustic emission probe usually has no fixed position, but is placed randomly on the table and needs to be wiped frequently, which is not conducive to the long-term maintenance and use of the line; the sample is exposed to the indoor environment for testing, and there is no guarantee that the photomultiplier tube collects all the light emitted by the broken sample. Summary of the Invention

[0004] In view of the deficiencies in the prior art, the present invention provides a miniature acoustic emission loading chamber and a test method thereof, which solves the problem that traditional uniaxial compression instruments are not suitable for studying the internal failure mechanism of rock failure.

[0005] In order to achieve the above object, the technical solution adopted by the present invention is: A miniature acoustic emission loading chamber comprises a test box, wherein a driving mechanism and a clamping assembly are installed in the test box, and the driving mechanism and the clamping assembly are transmission-connected; a sample is clamped on the clamping assembly; and an acoustic emission probe and a photomultiplier tube are also arranged in the test box.

[0006] In this scheme, the driving mechanism drives the clamping assembly to move, and the movement squeezes and crushes the sample on the clamping assembly. During the crushing, the acoustic emission probe collects the acoustic signal generated during the sample rupture process, and the photomultiplier tube collects the light signal emitted by the sample to obtain data on the acoustic emission and pressure light effects in the test. By observing the broken sample after the experiment, not only can the sample failure law be obtained from a macroscopic perspective, but also the internal defect damage of the sample can be analyzed to detect and analyze the evolution of material damage.

[0007] Furthermore, the driving mechanism includes two bidirectional threaded screws arranged in parallel, and threads with opposite spiral directions are provided at both ends of the bidirectional threaded screws; the two bidirectional threaded screws are installed in the test box through a shaft seat; one end of the two bidirectional threaded screws is connected through a pulley transmission assembly, and one of the bidirectional threaded screws is connected to the motor through a reduction gear assembly.

[0008] In this solution, the motor is started, and the power of the motor is decelerated by the reduction gear assembly and then transmitted to the pulley transmission assembly. The pulley transmission assembly drives two bidirectional threaded screws to rotate synchronously, driving the clamping assembly to move during the rotation.

[0009] Furthermore, the clamping assembly includes a left moving block and a right moving block, which are respectively threadedly connected to two sections of threads in opposite directions at both ends of the bidirectional threaded screw; the tops of the left moving block and the right moving block are both provided with mounting grooves, and an L-shaped clamping plate is detachably connected to the mounting groove of the left moving block, and a flat plate is detachably connected to the mounting groove of the right moving block, and a rectangular through hole is provided on the flat plate, and one end of the L-shaped clamping plate connected to the vertical plate is passed through the rectangular through hole, and a sample placement area is formed between the vertical plate and the inner wall of the rectangular through hole, and the sample is placed in the sample placement area.

[0010] In this scheme, two bidirectional threaded screws rotate synchronously to drive the left and right moving blocks to move in opposite directions, and the L-shaped clamping plate and the flat plate follow the two synchronous movements. During the movement, the vertical plate of the L-shaped clamping plate and the rectangular through-hole of the flat plate squeeze the sample where the sample is placed. The sample is squeezed and deformed until it breaks. Polarization will occur inside the sample, and opposite positive and negative charges will appear on the two opposite surfaces of the sample, which means that a piezoelectric effect is generated.

[0011] Furthermore, several threaded holes are opened in the mounting grooves of the left moving block and the right moving block along the length direction of the groove body, and bolt holes are opened on the L-shaped clamping plate and the flat plate. The bolts passing through the L-shaped clamping plate are threadedly connected to the mounting groove of the left moving block; the bolts passing through the flat plate are threadedly connected to the mounting groove of the right moving block.

[0012] In this solution, the positions of the L-shaped clamping plate and the flat panel on the left moving block and the right moving block are adjustable, respectively. This is suitable for testing specimens of various sizes and models, and the position adjustment is more flexible and convenient.

[0013] Furthermore, 2-5 acoustic emission probes are provided in the test box, two of which are respectively provided on the L-shaped clamping plate and the flat plate on both sides of the sample.

[0014] In this solution, this installation structure not only allows the acoustic emission probe to follow the movement of the L-shaped clamping plate and the flat panel during the extrusion process, but also can collect the acoustic signal of the specimen during the crushing process at close range.

[0015] Furthermore, a mounting column is provided inside the test box, a mounting plate is mounted on the mounting column by bolts, the photomultiplier tube is mounted on the mounting plate at a position directly above the sample, and the photocathode of the photomultiplier tube corresponds to the location where the sample is placed.

[0016] In this scheme, the photomultiplier tube is placed directly above the sample, which can more accurately collect the light signal during the specimen crushing process, which is conducive to the analysis and study of internal defects and damage of the specimen.

[0017] Furthermore, the side wall of the test box is provided with an acoustic emission probe connection port, a photomultiplier tube power supply port and a test machine line outlet port; the acoustic emission probe wire is connected to the external acoustic emission collection equipment through the acoustic emission probe connection port; the photomultiplier tube connection line is connected to the external power supply through the photomultiplier tube power supply port; the motor power line is connected to the external power supply through the test machine line outlet.

[0018] In this solution, a wiring port is set up for each wiring harness, which ensures the neatness of the internal wiring of the loading chamber and avoids the inconvenience of maintenance caused by the clutter of internal wiring; it also has a certain protective effect on the long-term use of the wiring.

[0019] Furthermore, the test box is a box structure formed by connecting six plates; a handle is provided on the top of the box structure.

[0020] In this solution, the six plates are preferably opaque steel plates to prevent external light from entering the test chamber and affecting the light signal collection of the photomultiplier tube.

[0021] In a second aspect, the present invention provides a micro-acoustic emission test method based on the micro-acoustic emission loading chamber provided in the first aspect, comprising the following steps: S1: Place the specimen at the sample placement location; S2: Start the motor to drive the bidirectional threaded screw to rotate; during the rotation of the bidirectional threaded screw, the left and right moving blocks are driven by the action of the threads to move in opposite directions at the same time, thereby driving the L-shaped clamping plate and the flat plate to move in opposite directions, so that the gap between the vertical plate of the L-shaped clamping plate and the inner wall of the rectangular through hole of the flat plate is reduced, and the sample is squeezed and crushed; S3: During the extrusion process, the acoustic emission probe collects the acoustic signal emitted by the sample rupture; the photomultiplier tube collects the light signal emitted by the sample rupture.

[0022] The beneficial effects of the present invention are: When the micro-acoustic emission loading chamber provided by the present invention is used for testing, the entire sample crushing process is completed within the test chamber, which can avoid the problem of debris flying out and being difficult to clean during the sample crushing process; while measuring stress and strain, the acoustic emission probe and photomultiplier tube are used to collect data on acoustic emission and piezoresistance effect, and then by observing the broken sample after the experiment, not only can the sample failure law be obtained from a macroscopic perspective, but also the internal defect damage of the sample can be analyzed and then linked to the overall failure of the sample. By using this micro-acoustic emission loading chamber, the piezoresistance effect can be utilized to capture signals and process information using mathematical methods to detect and analyze the evolution of material damage, which is of great significance for in-depth research on the fracture and instability mechanism of small-particle materials, and then for predicting geological disasters and guiding engineering construction. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 This is a schematic structural diagram of a micro acoustic emission loading chamber of the present invention; Figure 2 This is a schematic diagram of the horizontal cross-section structure of a micro-acoustic emission loading chamber of the present invention; Figure 3 The figure is a schematic diagram of the vertical cross-section structure of a micro acoustic emission loading chamber of the present invention.

[0024] Reference numerals: 1. Test chamber; 11. Mounting column; 12. Mounting plate; 13. Handle; 101. Power supply port for photomultiplier tube; 102. Connection port for acoustic emission probe; 103. Cable outlet for testing machine; 2. Clamping assembly; 21. Left moving block; 22. Right moving block; 23. L-shaped clamping plate; 231. Vertical plate; 24. Flat plate; 25. Sample placement area; 3. Drive mechanism; 31. Bidirectional threaded screw; 32. Shaft seat; 33. Pulley drive assembly; 34. Reduction gear assembly; 35. Motor; 4. Acoustic emission probe; 5. Photomultiplier tube; DETAILED DESCRIPTION The present invention will be further described below with reference to the accompanying drawings and specific embodiments. Specific embodiments of the present invention are described below to facilitate understanding of the present invention by those skilled in the art. However, it should be understood that the present invention is not limited to the scope of the specific embodiments. For those skilled in the art, as long as various changes are within the spirit and scope of the present invention as defined and determined by the appended claims, these changes are obvious, and all inventions and creations utilizing the concepts of the present invention are protected.

[0025] like Figure 1 and Figure 2 As shown, this embodiment provides a micro-AE loading chamber, which can use the piezoresistance effect to capture signals and process information using mathematical methods to detect and analyze material damage evolution; specifically, it includes: Test chamber 1, driving mechanism 3, clamping assembly 2, acoustic emission probe 4 and photomultiplier tube 5; The test chamber 1 is equipped with a drive mechanism 3 and a clamping assembly 2, which are connected by a transmission mechanism. The clamping assembly 2 holds a specimen. An acoustic emission probe 4 and a photomultiplier tube 5 are also located within the test chamber 1. The drive mechanism 3 drives the clamping assembly 2, which crushes the specimen on the clamping assembly 2. During this crushing process, the acoustic emission probe 4 collects the acoustic signal generated by the specimen's fracture process, and the photomultiplier tube 5 collects the optical signal emitted by the specimen. This data is used to obtain acoustic emission and piezoelectric effect data during the test. By observing the fractured specimen after the experiment, not only can the macroscopic failure pattern of the specimen be determined, but also the internal defects of the specimen can be analyzed to detect and analyze the evolution of material damage.

[0026] The drive mechanism 3 includes two parallel, bidirectional threaded screws 31, a pulley transmission assembly 33, a reduction gear assembly 34, and a motor 35. The two ends of the bidirectional threaded screws 31 are provided with threads with opposite helical directions. The two bidirectional threaded screws 31 are mounted within the test chamber 1 via a shaft seat 32. One end of the two bidirectional threaded screws 31 is connected to the pulley transmission assembly 33, and one of the bidirectional threaded screws 31 is connected to the motor 35 via the reduction gear assembly 34. When the motor 35 is started, the power of the motor 35 is reduced by the reduction gear assembly 34 and then transmitted to the pulley transmission assembly 33. The pulley transmission assembly 33 drives the two bidirectional threaded screws 31 to rotate synchronously, and the rotation drives the clamping assembly 2 to move.

[0027] like Figure 3As shown, the clamping assembly 2 includes a left moving block 21 and a right moving block 22, which are respectively threadedly connected to two sections of threads in opposite directions at both ends of the bidirectional threaded screw 31; the tops of the left moving block 21 and the right moving block 22 are both provided with mounting grooves, and an L-shaped clamping plate 23 is detachably connected to the mounting groove of the left moving block 21, and a flat plate 24 is detachably connected to the mounting groove of the right moving block 22, and a rectangular through hole is provided on the flat plate 24, and one end of the L-shaped clamping plate 23 is connected to the vertical plate 231 and is inserted into the rectangular through hole, and a sample placement area 25 is formed between the vertical plate 231 and the inner wall of the rectangular through hole, and the sample is placed in the sample placement area 25. The two bidirectional threaded screws 31 rotate synchronously to drive the left moving block 21 and the right moving block 22 to move in opposite directions, thereby driving the L-shaped clamping plate 23 and the flat plate 24 to move in opposite directions, so that the gap between the vertical plate 231 of the L-shaped clamping plate 23 and the inner wall of the rectangular through hole of the flat plate 24 is reduced, and the sample is squeezed and deformed until the sample breaks. Polarization will occur inside the sample, and opposite positive and negative charges will appear on the two opposite surfaces of the sample, which means that a piezoelectric effect is generated.

[0028] The mounting slots of both the left and right moving blocks 21 and 22 are equipped with several threaded holes along their lengths. Bolt holes are also provided on both the L-shaped clamping plate 23 and the flat plate 24. Bolts passing through the L-shaped clamping plate 23 are threaded into the mounting slots of the left moving block 21, while bolts passing through the flat plate 24 are threaded into the mounting slots of the right moving block 22. This design allows for adjustable positions of the L-shaped clamping plate 23 and flat plate 24 on the left and right moving blocks 21 and 22, respectively, making it suitable for testing specimens of various sizes and models, and providing greater flexibility and convenience in position adjustment.

[0029] There are 2-5 acoustic emission probes 4 installed inside the test box 1, two of which are respectively installed on the L-shaped clamping plate 23 and the flat panel 24 on both sides of the sample; this installation structure not only allows the acoustic emission probe 4 to follow the movement of the L-shaped clamping plate 23 and the flat panel 24 during the squeezing process, but also can collect the acoustic signals of the specimen during the crushing process at close range.

[0030] The test chamber 1 is provided with a mounting post 11, to which a mounting plate 12 is bolted. A circular hole is defined in the mounting plate 12, and a photomultiplier tube 5 is positioned within the circular hole, with the photocathode of the photomultiplier tube 5 aligned with the sample placement area 25. Placing the photomultiplier tube 5 directly above the specimen allows for more accurate acquisition of optical signals during specimen crushing, facilitating analysis and research of internal defects and damage within the specimen.

[0031] The side walls of the test chamber 1 are provided with an acoustic emission probe connection port 102, a photomultiplier tube power supply port 101, and a test machine wire outlet 103. The wires of the acoustic emission probe 4 pass through the wire holes on the mounting plate 12 and are led out from the acoustic emission probe connection port 102 to connect to the external acoustic emission acquisition equipment. There are five acoustic emission probe connection ports 102, one for each of the five acoustic emission probes 4. The connecting wire of the photomultiplier tube 5 is connected to the external power supply through the photomultiplier tube power supply port 101. The power cord of the motor 35 is connected to the external power supply through the test machine wire outlet 103. Each wiring harness is provided with a corresponding connection port, which ensures the neatness of the internal wiring of the loading chamber and avoids the inconvenience of maintenance caused by the internal wiring clutter. It also has a certain protective effect on the long-term use of the wiring.

[0032] The test box 1 is a box structure formed by connecting six plates; a handle 13 is provided on the top of the box structure. The six plates are preferably opaque steel plates to prevent external light from entering the test box 1 and affecting the light signal collection of the photomultiplier tube 5.

[0033] Preferably, the test box 1 has a length of 300 cm, a width of 220 cm, and a height of 140 cm.

[0034] The working principle of this embodiment is: During use, the sample is first placed in the sample placement area and connected to an external power source through the test machine's wire outlet 103. The motor 35 is started, which drives the reduction gear assembly 34 to rotate. The reduction gear assembly 34 drives one of the bidirectional threaded screws 31 to rotate. Driven by the pulley drive assembly 33, the two bidirectional threaded screws 31 rotate synchronously, driving the left and right moving blocks 21 and 22 to move in opposite directions simultaneously. This in turn drives the L-shaped clamping plate 23 and the flat plate 24 to move in opposite directions, reducing the gap between the vertical plate 231 of the L-shaped clamping plate 23 and the inner wall of the rectangular through-hole of the flat plate 24, thereby squeezing the sample in the sample placement area 25. As the experiment progresses, the sample is squeezed continuously until it ruptures. The sample is deformed by the compression, causing polarization within the sample and the appearance of oppositely charged positive and negative charges on two opposing surfaces of the sample, thus generating a piezoelectric effect. During this process, the acoustic emission probe 4 collects the acoustic signal generated during the sample rupture, and the photomultiplier tube 5 collects the optical signal emitted by the sample.

[0035] Example 2 This embodiment provides a micro-acoustic emission test method based on the micro-acoustic emission loading chamber provided in Example 1, including the following steps: S1: Place the sample at the sample placement position 25; S2: Start the motor 35 to drive the bidirectional threaded screw 31 to rotate; during the rotation of the bidirectional threaded screw 31, the left moving block 21 and the right moving block 22 are driven by the action of the threads to move in opposite directions at the same time, thereby driving the L-shaped clamping plate 23 and the flat plate 24 to move in opposite directions, so that the gap between the vertical plate 231 of the L-shaped clamping plate 23 and the inner wall of the rectangular through hole of the flat plate 24 is reduced, and the sample is squeezed and crushed; S3: During the extrusion process, the acoustic emission probe 4 collects the acoustic signal emitted by the sample rupture; the photomultiplier tube 5 collects the optical signal emitted by the sample rupture.

[0036] Those skilled in the art will appreciate that the embodiments herein are intended to help readers understand the principles of the present invention, and it should be understood that the scope of protection of the present invention is not limited to such specific descriptions and embodiments. Those skilled in the art can make various other specific variations and combinations based on the technical teachings disclosed in the present invention without departing from the essence of the present invention, and such variations and combinations are still within the scope of protection of the invention.

Claims

1. A miniature acoustic emission loading chamber, characterized in that: The invention comprises a test box (1), wherein a driving mechanism (3) and a clamping assembly (2) are installed in the test box (1), and the driving mechanism (3) and the clamping assembly (2) are in transmission connection; a sample is clamped on the clamping assembly (2); and an acoustic emission probe (4) and a photomultiplier tube (5) are also provided in the test box (1).

2. The micro-acoustic emission loading chamber according to claim 1, characterized in that: The driving mechanism (3) comprises two bidirectional threaded screws (31) arranged in parallel, wherein both ends of the bidirectional threaded screws (31) are provided with threads with opposite spiral directions; the two bidirectional threaded screws (31) are installed in the test box (1) through a shaft seat (32); one end of the two bidirectional threaded screws (31) is connected to each other through a pulley transmission assembly (33), and one of the bidirectional threaded screws (31) is connected to the motor (35) through a reduction gear assembly (34).

3. The micro-acoustic emission loading chamber according to claim 2, characterized in that: The clamping assembly (2) includes a left moving block (21) and a right moving block (22), and the left moving block (21) and the right moving block (22) are respectively threadedly connected to two sections of threads at two ends of the bidirectional threaded screw (31) in opposite directions; the tops of the left moving block (21) and the right moving block (22) are both provided with mounting grooves, and an L-shaped clamping plate (23) is detachably connected to the mounting groove of the left moving block (21), and a plane plate (24) is detachably connected to the mounting groove of the right moving block (22), and a rectangular through hole is provided on the plane plate (24), and one end of the L-shaped clamping plate (23) connected to the vertical plate (231) is inserted into the rectangular through hole, and a sample placement area (25) is formed between the vertical plate (231) and the inner wall of the rectangular through hole, and the sample is placed in the sample placement area (25).

4. The micro-acoustic emission loading chamber according to claim 3, characterized in that: The mounting grooves of the left movable block (21) and the right movable block (22) are both provided with a plurality of threaded holes along the length direction of the groove body, and the L-shaped clamping plate (23) and the plane plate (24) are both provided with bolt holes, and the bolts passing through the L-shaped clamping plate (23) are threadedly connected to the mounting groove of the left movable block (21); and the bolts passing through the plane plate (24) are threadedly connected to the mounting groove of the right movable block (22).

5. The micro-acoustic emission loading chamber according to claim 4, characterized in that: 2-5 acoustic emission probes (4) are arranged in the test box (1), wherein two acoustic emission probes (4) are respectively arranged on the L-shaped clamping plate (23) and the plane plate (24) on both sides of the sample.

6. The micro-acoustic emission loading chamber according to claim 3, characterized in that: The test box (1) is provided with a mounting column (11) inside, and a mounting plate (12) is mounted on the mounting column (11) by means of bolts. The photomultiplier tube (5) is mounted on the mounting plate (12) at a position directly above the sample, and the photocathode of the photomultiplier tube (5) corresponds to the sample placement position (25).

7. The micro-acoustic emission loading chamber according to claim 2, characterized in that: The side wall of the test box (1) is provided with an acoustic emission probe connection port (102), a photomultiplier tube power supply port (101) and a test machine line outlet (103); the wire of the acoustic emission probe (4) is connected to an external acoustic emission acquisition device through the acoustic emission probe connection port (102); the connecting line of the photomultiplier tube (5) is connected to an external power supply through the photomultiplier tube power supply port (101); and the power line of the motor (35) is connected to an external power supply through the test machine line outlet (103).

8. The micro-acoustic emission loading chamber according to claim 7, characterized in that: The test box (1) is a box structure formed by connecting six plates; a handle (13) is provided on the top of the box structure.

9. A method for testing a micro-acoustic emission loading chamber according to any one of claims 1 to 8, characterized in that: The following steps are involved: S1: Place the sample on the sample placement area (25); S2: Start the motor (35) to drive the bidirectional threaded screw (31) to rotate; during the rotation of the bidirectional threaded screw (31), the left moving block (21) and the right moving block (22) are driven by the action of the thread to move in the opposite direction at the same time, thereby driving the L-shaped clamping plate (23) and the flat plate (24) to move in the opposite direction, so that the gap between the vertical plate (231) of the L-shaped clamping plate (23) and the inner wall of the rectangular through hole of the flat plate (24) is reduced, and the sample is squeezed and crushed; S3: During the extrusion process, the acoustic emission probe (4) collects the acoustic signal emitted by the sample rupture; the photomultiplier tube (5) collects the optical signal emitted by the sample rupture.

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