Bridge crack monitoring device based on acoustic emission

Abstract

The invention relates to the technical field of bridge monitoring, and particularly discloses a bridge crack monitoring device based on acoustic emission, comprising: a fixed shell; the number of the fixing shells is two, a plurality of monitoring mechanisms are installed at the top ends of the two fixing shells, a plurality of adjusting mechanisms are installed on the outer walls of the two fixing shells, and connecting mechanisms are installed at the two connecting positions of the two fixing shells; the monitoring mechanism comprises a mounting seat, an acoustic emission sensor, an acquisition card, a fixing mechanism, a positioning groove and a fixing groove; elastic wave signals released during bridge crack propagation can be captured through the acoustic emission sensor, dynamic and real-time monitoring of the bridge is achieved, the acoustic emission technology is not prone to interference of environmental factors such as illumination, rain and fog and shielding, the crack recognition accuracy can be improved at night or under the low-visibility condition, meanwhile, the bridge is subjected to camera shooting monitoring in combination with the camera, and the monitoring accuracy is improved. Therefore, cracks on the surface of the structure can be monitored, and cracks in the concrete or at the interface of the reinforcing steel bar and the concrete can be monitored.

Description

Technical Field

[0001] The present invention belongs to the technical field of bridge monitoring, and particularly relates to a bridge crack monitoring device based on acoustic emission. Background Art

[0002] As an artificial structure spanning natural barriers such as rivers, lakes, seas, canyons, and gullies, a bridge provides a safe passage guarantee for vehicles and pedestrians through mechanical systems such as beam bodies, arch ribs, stay cables, or suspension cables. During the long-term service of such structures, due to the degradation of material properties, environmental erosion, and the coupling effect of loads, concealed damage is likely to be induced. As the service life extends or the load-bearing capacity exceeds the design limit, cracks may occur in the bridge. Such damage will significantly weaken the structural bearing capacity and threaten the safety of bridge use. Therefore, it is very necessary to monitor bridge cracks.

[0003] In the Chinese patent with the publication number CN212904569U, a crack monitoring device for monitoring the health status of bridges is mentioned. Since the image acquisition device of this crack monitoring device is installed on the bottom rod, during monitoring, the bottom rod can be extended into the bottom of the bridge to be monitored, and the image acquisition device on the bottom rod is used for video monitoring. The mutually symmetrical moving mechanisms can be directly sleeved on the flange plates of the bridge to be monitored, making the installation operation of this crack monitoring device simpler and more convenient. At the same time, by using the moving mechanisms and the vertical rod to move longitudinally along the bridge flange plate, the image acquisition device on the bottom rod is driven to move under the bridge, greatly improving the monitoring efficiency without affecting normal traffic, reducing manpower and material resources, and having a more novel design. The rollers in the moving mechanisms are connected with precision rolled threaded steel, which is applicable to bridge flange plates with different thicknesses and has stronger applicability. However, this crack monitoring device uses the image acquisition device to conduct video monitoring on the bridge, which is easily interfered by environmental factors such as light, rain, fog, and occlusion, resulting in a decline in imaging quality and a reduction in crack recognition accuracy at night or under low visibility conditions, and it can only monitor surface cracks of the structure and is powerless against cracks inside the concrete or at the interface between the steel bars and the concrete. Summary of the Invention

[0004] The purpose of the present invention is to provide a bridge crack monitoring device based on acoustic emission, which locates cracks by capturing internal acoustic emission signals of the structure to solve the problems of poor imaging and low recognition rate easily caused by environmental interference in image monitoring.

[0005] To achieve the above purpose, the present invention provides the following technical solutions:

[0006] A bridge crack monitoring device based on acoustic emission, comprising:

[0007] A fixed shell;

[0008] There are two fixed shells, and a plurality of monitoring mechanisms are installed at the tops of the two fixed shells. A plurality of adjusting mechanisms are installed on the outer walls of the two fixed shells, and connecting mechanisms are installed at the two joints of the two fixed shells;

[0009] The monitoring mechanism includes a mounting seat, an acoustic emission sensor, a data acquisition card, a fixing mechanism, a positioning groove and a fixing groove. The acoustic emission sensor is installed at the top of the mounting seat, the data acquisition card is installed at one end of the mounting seat, the fixing mechanism is installed on the outer surface of the mounting seat, and the bottom end of the fixing mechanism is installed at the top of the fixed shell. The positioning groove is opened in the middle of the bottom end of the mounting seat. There are two fixing grooves, and the two fixing grooves are respectively opened in the middle of the outer walls on both sides of the mounting seat.

[0010] Preferably, lifting rings are installed at the tops of the two fixed shells, two cameras are installed at the tops of the two fixed shells, and a bevel gear ring is jointly installed between the lower parts of the outer surfaces of the two fixed shells.

[0011] Preferably, the fixing mechanism includes a fixing box, a positive and reverse screw rod, an adjusting block, a fixing frame, a positioning block and a limiting groove. The fixing box is installed at the top of the fixed shell. The positive and reverse screw rod is installed between the inner walls on both sides of the fixing box through bearings. There are two adjusting blocks, two fixing frames and two limiting grooves. The two adjusting blocks are respectively installed at both ends of the positive and reverse screw rod. The two fixing frames are both installed on the outer surface of the positive and reverse screw rod. The positioning block is installed in the middle of the top of the fixing box. The two limiting grooves are both opened on the top inner wall of the fixing box.

[0012] Preferably, the fixing frame is arranged in an L-shaped structure. The acoustic emission sensor and the camera are both electrically connected to the data acquisition card. A preamplifier is encapsulated inside the acoustic emission sensor. The bevel gear ring is installed on the lower part of the outer surfaces of the two fixed shells through a split bearing, and the bevel gear ring is composed of two half rings.

[0013] Preferably, a driver is installed on the upper side of the inner wall of one of the fixed shells. The output end of the driver is installed with a driving gear, and the driving gear is installed on the outer wall of one of the fixed shells through a bearing. A driven gear is installed on the outer surface of one of the adjusting mechanisms.

[0014] Preferably, the adjusting mechanism includes an adjusting iron frame, a moving frame, an adjusting screw rod, a threaded cylinder and an adjusting bevel gear. The adjusting iron frame is inserted and installed on the outer wall of the fixed shell. The moving frame is inserted and installed at one end of the adjusting iron frame. The adjusting screw rod is installed between the inner walls on both sides of the adjusting iron frame through bearings. The threaded cylinder is threadedly installed on the outer surface of the adjusting screw rod, and the threaded cylinder is installed on the outer wall of the fixed shell through a bearing. The adjusting bevel gear is installed on the outer surface of the threaded cylinder.

[0015] Preferably, the mobile frame includes a telescopic frame, an electromagnetic block, a distance measuring sensor, a spring and a mobile wheel. The telescopic frame is inserted and installed at one end of the adjusting iron frame. There are two electromagnetic blocks and two springs. Both electromagnetic blocks are embedded at one end of the telescopic frame. The distance measuring sensor is installed in the middle of the inner wall of the telescopic frame. The two springs are respectively installed on both sides of the inner wall of the telescopic frame. The mobile wheel is installed at the other end of the telescopic frame.

[0016] Preferably, the telescopic frame is set as a convex frame. The adjusting bevel gear meshes with the bevel gear ring. The driven gear is installed on the outer surface of the threaded cylinder in the corresponding adjusting mechanism, and the driven gear meshes with the driving gear.

[0017] Preferably, the connecting mechanism includes a connecting frame, positioning holes, connecting holes, connecting bolts and connecting nuts. There are two connecting frames and two positioning holes. Both positioning holes are opened at one end of the connecting frame on one side. The connecting hole is opened at the other end of the connecting frame on the other side. The connecting bolt is inserted and installed between the connecting hole and the two positioning holes. The connecting nut is installed on the outer surface of the connecting bolt.

[0018] Preferably, the connecting frame is set as a V-shaped structure, and the connection mode between the connecting frame and the fixed shell is welding connection. A notch is opened on the outer surface of the connecting bolt.

[0019] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0020] (1) The present invention is provided with a plurality of monitoring mechanisms at the top of the fixed shell. The acoustic emission sensor can capture the elastic wave signals released during the crack propagation of the bridge, realizing the dynamic and real-time monitoring of the bridge. The acoustic emission technology is not easily interfered by environmental factors such as light, rain, fog, and occlusion, and can improve the crack recognition accuracy at night or under low visibility conditions. At the same time, the bridge is monitored by combining a camera, so that both the surface cracks of the structure and the cracks inside the concrete or at the interface between the steel bars and the concrete can be monitored.

[0021] (2) The present invention is provided with a plurality of adjusting mechanisms on the outer surface of the fixed shell. Through the meshing transmission between the bevel gear ring and a plurality of bevel gears, the corresponding threaded cylinder can be driven to rotate, and then the adjusting iron frame can stably drive the mobile wheel to move towards the pier, realizing the high-precision centering and stable displacement of the monitoring device and the pier. At the same time, through the telescopic movement of the telescopic frame, the mobile wheel can always fit the outer wall of the pier, and the distance measuring sensor is used to monitor the change in the movement distance of the telescopic frame, and the dynamic deformation of the pier can be monitored according to this data.

[0022] (3) Two connecting mechanisms are provided on the outer surface of the fixed housing of the present invention. By passing the connecting bolts through the connecting holes and inserting them into the two positioning holes, and then sleeving and tightening the connecting nuts on the connecting bolts, the two connecting frames can be firmly installed, and then the assembly of the entire monitoring device can be completed. The monitoring device can be sleeved and installed on the outer surface of the bridge pier to achieve comprehensive monitoring of the bridge pier. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 is a perspective view of the present invention;

[0024] Figure 2 is a perspective view of the monitoring mechanism of the present invention;

[0025] Figure 3 is a perspective view of the mounting base of the present invention;

[0026] Figure 4 is a cross-sectional view of the fixing mechanism of the present invention;

[0027] Figure 5 For the present invention Figure 1 is an enlarged view of A in;

[0028] Figure 6 is a perspective view of the adjusting mechanism of the present invention;

[0029] Figure 7 is a perspective view of the moving frame of the present invention;

[0030] Figure 8 is an exploded view of the connecting mechanism of the present invention;

[0031] In the figure: 1, fixed housing; 2, monitoring mechanism; 3, adjusting mechanism; 4, connecting mechanism; 5, lifting ring; 6, camera; 7, bevel gear ring; 8, driver; 9, driving gear; 10, driven gear;

[0032] 21, mounting base; 22, acoustic emission sensor; 23, acquisition card; 24, fixing mechanism; 25, positioning groove; 26, fixing groove;

[0033] 241, fixing box; 242, positive and negative screw rod; 243, adjusting block; 244, fixing frame; 245, positioning block; 246, limiting groove;

[0034] 31, adjusting iron frame; 32, moving frame; 33, adjusting screw rod; 34, threaded barrel; 35, adjusting bevel gear;

[0035] 321, telescopic frame; 322, electromagnetic block; 323, distance measuring sensor; 324, spring; 325, moving wheel;

[0036] 41, connecting frame; 42, positioning hole; 43, connecting hole; 44, connecting bolt; 45, connecting nut. Specific embodiments

[0037] Next, the technical solutions in the embodiments of the present invention will be clearly and completely described in conjunction with the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts shall fall within the protection scope of the present invention.

[0038] Embodiment 1:

[0039] Please refer to Figures 1 to 8 As shown, a bridge crack monitoring device based on acoustic emission includes:

[0040] Fixed housing 1;

[0041] There are two fixed housings 1. A plurality of monitoring mechanisms 2 are installed at the tops of the two fixed housings 1. A plurality of adjusting mechanisms 3 are installed on the outer walls of the two fixed housings 1. Connecting mechanisms 4 are installed at the two joints of the two fixed housings 1;

[0042] The monitoring mechanism 2 includes a mounting seat 21, an acoustic emission sensor 22, a data acquisition card 23, a fixing mechanism 24, a positioning groove 25 and a fixing groove 26. The acoustic emission sensor 22 is installed at the top of the mounting seat 21. The data acquisition card 23 is installed at one end of the mounting seat 21. The fixing mechanism 24 is installed on the outer surface of the mounting seat 21, and the bottom end of the fixing mechanism 24 is installed at the top of the fixed housing 1. The positioning groove 25 is opened in the middle of the bottom end of the mounting seat 21. There are two fixing grooves 26, and the two fixing grooves 26 are respectively opened in the middle of the outer walls on both sides of the mounting seat 21.

[0043] It can be seen from Figures 1 to 4 that lifting rings 5 are installed at the tops of the two fixed housings 1. Two cameras 6 are installed at the tops of the two fixed housings 1. A bevel gear ring 7 is jointly installed between the lower parts of the outer surfaces of the two fixed housings 1;

[0044] The fixing mechanism 24 includes a fixing box 241, a positive and negative screw 242, an adjusting block 243, a fixing frame 244, a positioning block 245 and a limiting groove 246. The fixing box 241 is installed at the top of the fixed housing 1. The positive and negative screw 242 is installed between the inner walls on both sides of the fixing box 241 through bearings. There are two adjusting blocks 243, two fixing frames 244 and two limiting grooves 246. The two adjusting blocks 243 are respectively installed at both ends of the positive and negative screw 242. The two fixing frames 244 are both installed on the outer surface of the positive and negative screw 242. The positioning block 245 is installed in the middle of the top of the fixing box 241. The two limiting grooves 246 are both opened on the top inner wall of the fixing box 241.

[0045] As described above, during use, the acoustic emission sensor 22 can capture the elastic wave signals released during the crack propagation of the bridge, realizing dynamic and real-time monitoring of the bridge. The acoustic emission technology is not affected by environmental factors such as light, rain, fog, and occlusion, and can improve the crack recognition accuracy at night or under low visibility conditions. At the same time, multiple cameras 6 are combined to monitor the bridge. The image data captured by the cameras 6 and the acoustic emission signals monitored by the acoustic emission sensor 22 are transmitted to the acquisition card 23. The acquisition card 23 realizes the synchronous transmission and fusion analysis of the acoustic emission signals and the image data, which can significantly improve the reliability, accuracy, and intelligent level of the bridge structural health monitoring, strengthen the monitoring effect of the bridge, enabling the monitoring device to monitor not only the cracks on the surface of the pier structure but also the cracks inside the pier concrete or at the interface between the steel bars and the concrete. The multiple annular array monitoring mechanisms 2 can achieve comprehensive coverage monitoring of the pier, effectively improving the accuracy of the monitoring data. When it is necessary to replace the damaged acoustic emission sensor 22, the rotation adjustment block 243 drives the positive and negative screw rod 242 to rotate, and then drives the two fixing frames 244 to move outward, so that they can be taken out from the fixing groove 26, releasing the positioning and fixing of the mounting seat 21, facilitating the disassembly of the acoustic emission sensor 22 for replacement or maintenance.

[0046] Specifically, referring to Figures 1 to 4 As shown, the fixing frame 244 is set as an L-shaped structure. Both the acoustic emission sensor 22 and the camera 6 are electrically connected to the acquisition card 23. A preamplifier is encapsulated inside the acoustic emission sensor 22. The bevel gear ring 7 is installed on the lower outer surface of the two fixing shells 1 through a split bearing, and the bevel gear ring 7 is composed of two half rings.

[0047] As described above, it is beneficial for the fixing frame 244 to be inserted into the fixing groove 26 to achieve firm installation of the mounting seat 21, enabling the synchronous transmission of the acoustic emission signal and the image signal to the acquisition card 23 to realize multi-source data fusion. The preamplifier amplifies the weak voltage signal output by the acoustic emission sensor 22 to the range that can be recognized by the acquisition card 23. The split design is beneficial for the half-splitting of the entire monitoring device.

[0048] Embodiment 2:

[0049] Referring to Figures 5 to 7 As shown, a driver 8 is installed on the upper side of the inner wall of one of the fixing shells 1. The output end of the driver 8 is installed with a driving gear 9, and the driving gear 9 is installed on the outer wall of one of the fixing shells 1 through a bearing. A driven gear 10 is installed on the outer surface of one of the adjusting mechanisms 3;

[0050] The adjusting mechanism 3 includes an adjusting iron frame 31, a moving frame 32, an adjusting screw 33, a threaded cylinder 34 and an adjusting bevel gear 35. The adjusting iron frame 31 is inserted and installed on the outer wall of the fixed shell 1. The moving frame 32 is inserted and installed at one end of the adjusting iron frame 31. The adjusting screw 33 is installed between the inner walls on both sides of the adjusting iron frame 31 through bearings. The threaded cylinder 34 is threadedly installed on the outer surface of the adjusting screw 33, and the threaded cylinder 34 is installed on the outer wall of the fixed shell 1 through bearings. The adjusting bevel gear 35 is installed on the outer surface of the threaded cylinder 34;

[0051] The moving frame 32 includes a telescopic frame 321, an electromagnet 322, a distance measuring sensor 323, a spring 324 and a moving wheel 325. The telescopic frame 321 is inserted and installed at one end of the adjusting iron frame 31. There are two electromagnets 322 and two springs 324. The two electromagnets 322 are both embedded at one end of the telescopic frame 321. The distance measuring sensor 323 is installed in the middle of the inner wall of the telescopic frame 321. The two springs 324 are respectively installed on both sides of the inner wall of the telescopic frame 321. The moving wheel 325 is installed at the other end of the telescopic frame 321.

[0052] As can be seen from the above, when the monitoring device is sleeved and installed on the outer surface of the bridge pier, the driver 8 is started through the controller, so that the driving gear 9 drives the driven gear 10 to rotate, and then drives the corresponding threaded cylinder 34 and the adjusting bevel gear 35 thereon to rotate together. At this time, with the meshing transmission of the bevel gear ring 7 and the multiple adjusting bevel gears 35, multiple adjusting mechanisms 3 can be synchronously driven to operate. The rotation of the threaded cylinder 34 will drive the adjusting screw 33 to rotate, thereby driving the adjusting iron frame 31 to move on the fixed shell 1, so that the telescopic frame 321 drives the moving wheel 325 to move towards the bridge pier until it contacts the outer wall of the bridge pier, realizing the high-precision centering and stable displacement of the monitoring device and the bridge pier. During the movement of the monitoring device along the bridge pier, the controller controls the electromagnet 322 to be powered off, and the elasticity of the spring 324 enables the telescopic frame 321 to telescopically move, ensuring that the moving wheel 325 always fits the outer wall of the bridge pier, adapting to the shape changes of different parts of the bridge pier, ensuring good contact between the device and the bridge pier during the monitoring process, improving the accuracy of the monitoring data. At the same time, the distance measuring sensor 323 is used to monitor the change in the distance between the telescopic frame 321 and the adjusting iron frame 31 in real time. Based on this data, the dynamic deformation monitoring of the bridge pier can be realized, and the dynamic deformation of the bridge pier under various factors can be accurately captured, and the structural changes of the bridge pier can be discovered in time, providing key data support for the safety assessment and maintenance of the bridge.

[0053] Preferably, as shown in Figures 5 to 7 shown, the telescopic frame 321 is set as a convex frame. The adjusting bevel gear 35 meshes with the bevel gear ring 7. The driven gear 10 is installed on the outer surface of the threaded cylinder 34 in the corresponding adjusting mechanism 3, and the driven gear 10 meshes with the driving gear 9.

[0054] As can be seen from the above, the convex telescopic frame 321 can be stably limited on the adjusting iron frame 31. The adjusting bevel gear 35 converts the rotary motion of the driver 8 into the circumferential rotation of the bevel gear ring 7, facilitating the driven gear 10 to drive one of the adjusting bevel gears 35 to rotate, and facilitating the bevel gear ring 7 to drive the other adjusting bevel gears 35 to rotate together.

[0055] Embodiment Three:

[0056] Reference Figure 8 As shown, the connecting mechanism 4 includes a connecting frame 41, positioning holes 42, connecting holes 43, connecting bolts 44 and connecting nuts 45. There are two connecting frames 41 and two positioning holes 42. Both of the two positioning holes 42 are opened at one end of the connecting frame 41 on one side. The connecting hole 43 is opened at the other end of the connecting frame 41 on the other side. The connecting bolt 44 is inserted and installed between the connecting hole 43 and the two positioning holes 42, and the connecting nut 45 is installed on the outer surface of the connecting bolt 44.

[0057] As can be seen from the above, first, the two fixed shells 1 are sleeved on the outer surface of the bridge pier and closed. Then, the connecting bolt 44 is passed through the connecting hole 43 on one connecting frame 41, and then, by using the notch on the connecting bolt 44, it is passed through the two positioning holes 42 on the other connecting frame 41. After that, the connecting nut 45 is sleeved on the connecting bolt 44 and tightened. When the connecting nut 45 is tightened, local plastic deformation will occur at the notch of the connecting bolt 44, forming mechanical locking with the inner wall of the positioning hole 42, effectively inhibiting loosening, thereby enhancing the connection strength between the two connecting frames 41 and completing the firm assembly of the entire monitoring device. Finally, the monitoring device is sleeved and installed on the outer surface of the pier, enabling comprehensive monitoring of the pier.

[0058] Preferably, as shown in Figure 8 the connecting frame 41 is arranged in a V-shaped structure, and the connection mode between the connecting frame 41 and the fixed shell 1 is welding connection. A notch is opened on the outer surface of the connecting bolt 44.

[0059] As can be seen from the above, the V-shaped structure improves the torsional stiffness of the connecting frame 41 through the triangular support principle. The welding connection can strengthen the connection strength between the connecting frame 41 and the fixed shell 1. The notch on the connecting bolt 44 facilitates its insertion into the two positioning holes 42 and can also achieve a firm connection between the two connecting frames 41.

[0060] Application Example:

[0061] This design is suitable for monitoring the structural health of bridges in complex environments, covering a variety of types, including cross-sea bridges, mountain canyon bridges, and urban viaducts. In cold regions, bridge temperatures can drop as low as -40°C in winter and as high as 40°C in summer. Such a huge temperature difference causes concrete to expand and contract, which can easily cause cracks. On coastal or cross-sea bridges, long-term exposure to high salt spray environments significantly increases the risk of steel corrosion. In tropical rainforest climate zones, bridges receive annual rainfall exceeding 2,000 mm. Water penetration can exacerbate concrete carbonation, which is also prone to cracking.

[0062] This design is based on acoustic emission technology. By setting up multiple monitoring mechanisms 2 and using acoustic emission sensors 22 to capture the elastic wave signals released when bridge cracks expand, dynamic and real-time monitoring of bridge structures can be achieved. The acoustic emission signals are not interfered with by environmental factors such as light, rain, fog, and obstructions, and can improve the accuracy of crack identification, so that it can not only monitor cracks on the surface of the structure, but also effectively monitor cracks inside the concrete or at the interface between steel bars and concrete. In addition, by setting up multiple adjustment mechanisms 3, high-precision alignment of the monitoring device and the bridge pier can be achieved, and the monitoring device can be ensured to move stably on the pier, which is suitable for monitoring piers of different sizes. At the same time, by setting up a connecting mechanism 4, the device can be disassembled in half, making it easy to install the monitoring device on the outer surface of the pier.

[0063] While embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that various changes, modifications, substitutions, and variations may be made to these embodiments without departing from the principles and spirit of the invention, and that the scope of the invention is defined by the appended claims and their equivalents.

Claims

1. A bridge crack monitoring device based on acoustic emission, characterized in that Including: Fixed housing (1); There are two of the fixed housings (1). A plurality of monitoring mechanisms (2) are installed at the top ends of the two fixed housings (1). A plurality of adjusting mechanisms (3) are installed on the outer walls of the two fixed housings (1). Connecting mechanisms (4) are installed at the two connection parts of the two fixed housings (1); The monitoring mechanism (2) includes a mounting base (21), an acoustic emission sensor (22), a data acquisition card (23), a fixing mechanism (24), a positioning groove (25) and a fixing groove (26). The acoustic emission sensor (22) is installed at the top end of the mounting base (21). The data acquisition card (23) is installed at one end of the mounting base (21). The fixing mechanism (24) is installed on the outer surface of the mounting base (21), and the bottom end of the fixing mechanism (24) is installed at the top end of the fixed housing (1). The positioning groove (25) is opened in the middle of the bottom end of the mounting base (21). There are two fixing grooves (26), and the two fixing grooves (26) are respectively opened in the middle of the outer walls on both sides of the mounting base (21).

2. The acoustic emission-based bridge crack monitoring device according to claim 1, wherein: Lifting rings (5) are installed at the top ends of the two fixed housings (1). Two cameras (6) are installed at the top ends of the two fixed housings (1). A bevel gear ring (7) is jointly installed between the lower parts of the outer surfaces of the two fixed housings (1).

3. The acoustic emission-based bridge crack monitoring device according to claim 2, wherein: The fixing mechanism (24) includes a fixing box (241), a positive and reverse screw (242), an adjusting block (243), a fixing frame (244), a positioning block (245) and a limiting groove (246). The fixing box (241) is installed at the top end of the fixed housing (1). The positive and reverse screw (242) is installed between the inner walls on both sides of the fixing box (241) through bearings. There are two adjusting blocks (243), two fixing frames (244) and two limiting grooves (246). The two adjusting blocks (243) are respectively installed at both ends of the positive and reverse screw (242). The two fixing frames (244) are both installed on the outer surface of the positive and reverse screw (242). The positioning block (245) is installed in the middle of the top end of the fixing box (241). The two limiting grooves (246) are both opened on the top inner wall of the fixing box (241).

4. The acoustic emission-based bridge crack monitoring device according to claim 3, wherein: The fixing frame (244) is arranged in an L-shaped structure. The acoustic emission sensor (22) and the camera (6) are both electrically connected to the data acquisition card (23). A preamplifier is encapsulated inside the acoustic emission sensor (22). The bevel gear ring (7) is installed on the lower parts of the outer surfaces of the two fixed housings (1) through a split bearing, and the bevel gear ring (7) is composed of two half rings.

5. The acoustic emission-based bridge crack monitoring device according to claim 1, wherein: A driver (8) is installed on the upper side of the inner wall of one side of the fixed housing (1). The output end of the driver (8) is installed with a driving gear (9), and the driving gear (9) is installed on the outer wall of the fixed housing (1) on one side through a bearing. A driven gear (10) is installed on the outer surface of the adjusting mechanism (3) on one side.

6. The acoustic emission-based bridge crack monitoring device according to claim 5, characterized in that: The adjusting mechanism (3) includes an adjusting iron frame (31), a moving frame (32), an adjusting screw (33), a threaded cylinder (34), and an adjusting bevel gear (35). The adjusting iron frame (31) is inserted and installed on the outer wall of the fixed shell (1). The moving frame (32) is inserted and installed at one end of the adjusting iron frame (31). The adjusting screw (33) is installed between the inner walls on both sides of the adjusting iron frame (31) through bearings. The threaded cylinder (34) is threadedly installed on the outer surface of the adjusting screw (33), and the threaded cylinder (34) is installed on the outer wall of the fixed shell (1) through bearings. The adjusting bevel gear (35) is installed on the outer surface of the threaded cylinder (34).

7. The acoustic emission-based bridge crack monitoring device according to claim 6, characterized in that: The moving frame (32) includes a telescopic frame (321), an electromagnetic block (322), a distance measuring sensor (323), a spring (324), and a moving wheel (325). The telescopic frame (321) is inserted and installed at one end of the adjusting iron frame (31). There are two electromagnetic blocks (322) and two springs (324). The two electromagnetic blocks (322) are both embedded and installed at one end of the telescopic frame (321). The distance measuring sensor (323) is installed in the middle of the inner wall of the telescopic frame (321). The two springs (324) are respectively installed on both sides of the inner wall of the telescopic frame (321). The moving wheel (325) is installed at the other end of the telescopic frame (321).

8. The bridge crack monitoring device based on acoustic emission according to claim 7, wherein: The telescopic frame (321) is set as a convex frame. The adjusting bevel gear (35) meshes with the bevel gear ring (7). The driven gear (10) is installed on the outer surface of the threaded cylinder (34) in the corresponding adjusting mechanism (3), and the driven gear (10) meshes with the driving gear (9).

9. The bridge crack monitoring device based on acoustic emission according to claim 1, characterized in that: The connecting mechanism (4) includes a connecting frame (41), a positioning hole (42), a connecting hole (43), a connecting bolt (44), and a connecting nut (45). There are two connecting frames (41) and two positioning holes (42). The two positioning holes (42) are both opened at one end of the connecting frame (41) on one side. The connecting hole (43) is opened at the other end of the connecting frame (41) on the other side. The connecting bolt (44) is inserted and installed between the connecting hole (43) and the two positioning holes (42). The connecting nut (45) is installed on the outer surface of the connecting bolt (44).

10. The acoustic emission-based bridge crack monitoring device according to claim 9, characterized in that: The connecting frame (41) is set as a V-shaped structure, and the connection mode between the connecting frame (41) and the fixed shell (1) is welding connection. A notch is opened on the outer surface of the connecting bolt (44).

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