Acoustic emission wave guiding monitoring method for damage of single truss girder of highway bridge girder erection machine

Abstract

The invention provides an acoustic emission guided wave monitoring method for damage of a single truss girder of a highway bridge girder erection machine, which comprises the following steps of: acquiring damage signals of an upper chord, a bolt splice plate and a lower chord by adopting a serial structure of three layers of transverse waveguide rods and longitudinal hook waveguide rods, amplifying the signals through a black hole waveguide rod, and determining the damage of the single truss girder of the highway bridge girder erection machine; key parts of the single truss girder can be covered by only two sensors, so that the number and the cost of the sensors are greatly reduced; a spring type black hole waveguide rod is designed, the functions of signal amplification and deformation buffering are achieved, and damage caused by stress concentration of a waveguide rod buckle is effectively avoided; the problems that a traditional monitoring method is poor in timeliness and hidden damage is difficult to find are solved, through the innovative waveguide rod arrangement scheme, the real-time performance and economical efficiency of acoustic emission monitoring are remarkably improved, in addition, transportation and installation are also facilitated through the splicing design of the short waveguide rods, and by combining an annular hoop fixing mode, the acoustic emission monitoring effect is improved. And tight attachment of the waveguide rod and the truss girder is ensured, and efficient and reliable technical guarantee is provided for safe operation of the bridge girder erection machine.

Description

Technical Field

[0001] The present invention relates to the technical field of health monitoring of highway bridge erection machines, and in particular to a method for overall health monitoring of a single truss of a highway bridge erection machine by performing damage acoustic emission based on a waveguide rod. Background Art

[0002] Due to the complex operating environment and stress conditions of bridge-erecting machines during operation, accidents such as overturning, derailment, and breakage are common, often resulting in significant casualties and economic losses. Accident analysis reveals that design flaws, improper operational management, untimely inspection of critical components, and inadequate monitoring are all contributing factors, with inadequate inspection of key components being the primary factor. Existing monitoring methods primarily rely on multi-sensor fusion technology, which combines sensors such as strain, acceleration, and deflection with finite element models and algorithms such as wavelet transforms to achieve multi-dimensional data fusion and analysis. This approach overcomes the limitations of a single data source and significantly improves accuracy, but it cannot directly identify structural damage and is not always timely. Machine vision and image processing technologies utilize high-definition cameras to capture surface images of the structure and combine them with AI algorithms to identify surface damage such as cracks and rust. This method, which requires no contact with the structure and is suitable for complex operating conditions, requires massive amounts of data and significant computing power, and insufficient model training can affect damage identification accuracy. Furthermore, damage in some hidden areas may be difficult to detect. Acoustic emission refers to the physical phenomenon of instantaneous elastic waves emitted by the rapid release of energy at defects in materials or structures. As a concomitant phenomenon in the process of material or structural destruction, its signal contains a wealth of information about the material and its damage. The acoustic emission signal can be used to determine the location of the acoustic emission source, analyze the nature of the acoustic emission source, and determine the stress history and degree of damage to the material. Therefore, acoustic emission monitoring is a very good non-destructive monitoring method and can be used to monitor the health of bridge-building machines. However, since common forms of damage to bridge-building machine structures include steel fatigue cracking, weld cracking, and loose bolts, the energy of such acoustic emission signals is low. Parameters such as the energy and amplitude of the acoustic emission signal will attenuate during propagation, and bridge-building machines are not only complex in structure but also have large spans. Therefore, comprehensive monitoring of the bridge-building machine truss beams requires a large number of sensors, which is not economically efficient.

[0003] A waveguide rod is a metal rod-shaped structure that uses waveguide technology. It can guide the acoustic signal from the object to be measured to the waveguide rod. By controlling the cross-sectional shape and diameter of the waveguide rod, the attenuation of the acoustic signal during propagation is reduced, allowing the acoustic signal to propagate over a longer distance and reducing the number of required sensors.

[0004] Because the truss beam of the bridge-building machine is made of steel plates and bolts in the longitudinal direction, changes in boundary conditions will cause some sound signals to be reflected, hindering the mutual transmission of sound signals between the upper and lower trusses. A single transversely arranged waveguide rod cannot fully monitor the truss beam structure of the entire bridge-building machine.

[0005] In addition, the traditional waveguide rod has a large rigidity. When the bridge-building machine undergoes a large deformation due to operation, it is easy to cause the waveguide rod to deform or the connecting fasteners to break. The existing waveguide rod arrangement cannot fit the working state of the bridge-building machine well.

[0006] In order to realize the use of acoustic emission technology to monitor the damage and cracking of key parts of steel truss beams and main beams during the operation of bridge-building machines, according to the mechanical mechanism of cracking and crack development of metal materials and steel structures, the use of acoustic emission monitoring technology is gradually realized. The key parts of steel truss beams are connected in series using waveguide rods to identify and locate damage to key parts of bridge-building machines. In view of the above, a method for monitoring the damage of single truss beams of highway bridge-building machines using acoustic emission-induced waves is proposed, so that two acoustic signal sensors can simultaneously monitor the three-layer waveguide rod structure of a single truss beam. Summary of the Invention

[0007] In view of the above situation, the present invention overcomes the shortcomings of the existing technology and provides a method for monitoring the damage of a single truss beam of a highway bridge-building machine by using acoustic emission-induced waves. The method utilizes acoustic emission monitoring technology through two acoustic signal sensors and a multi-layer waveguide rod structure to fully monitor the damage acoustic signals of the risky parts of the steel truss main beam of the LG700 highway bridge-building machine, thereby realizing real-time monitoring of the working stress area of ​​the entire bridge-building machine, thereby improving the real-time and economic efficiency of the monitoring.

[0008] A method for monitoring damage of a single truss beam of a highway bridge erection machine by using acoustic emission induced waves is characterized by comprising the following steps:

[0009] S1: A simplified mechanical analysis of the truss beam of a highway bridge erection machine was performed under three different operating conditions. The highest risk points of the truss beam structure were identified under the three working conditions. The optimal waveguide rod layout was proposed for each working condition, and a multi-layer transverse waveguide rod structure was obtained through superposition.

[0010] S2: Each layer of the multi-layer transverse waveguide rod structure is assembled by splicing short waveguide rods, waveguide rod clips, and spring-type black hole waveguide rods;

[0011] S3: The adjacent layers in the multi-layer transverse waveguide rod structure are connected by specially made small curved hook waveguide rods;

[0012] S4: Arrange ordinary black hole waveguide rod connectors at both ends of the bottom layer of the multi-layer transverse waveguide rod structure;

[0013] S5: Acoustic signal sensors are arranged vertically on the end sections of the common black hole waveguide rods at both ends of the bottom layer to receive acoustic signals when the truss beam is damaged to achieve the purpose of monitoring.

[0014] Compared with the prior art, the present invention has the following beneficial effects:

[0015] (1) The present invention provides a solution for monitoring acoustic emissions from highway bridge erection machines, which uses waveguide rod technology to reduce the attenuation of acoustic signals, allowing damage signals from bridge erection machines to propagate over a longer distance.

[0016] (2) The present invention uses multiple waveguide rods to connect all vulnerable points in series, reducing the number of sensors required for acoustic emission, effectively increasing the monitoring range and reducing monitoring costs;

[0017] (3) The spring-type black hole waveguide rod connector designed by the present invention solves the problem of excessive tension on the waveguide rod causing deformation of the waveguide rod or breaking of the connecting connector due to its own deformation during normal operation of the bridge erection machine in the area where the waveguide rod is severely tensile. This allows the waveguide rod system to always maintain normal operation while amplifying the passing signal in one direction, effectively increasing the monitoring range.

[0018] (4) The present invention provides a hook waveguide rod that can firmly connect waveguide rods of different layers, connects the vulnerable points of waveguide rods of different layers in series in parallel, reduces the number of sensors required for acoustic emission, effectively increases the monitoring range and reduces the monitoring cost. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 This is a schematic diagram of the arrangement of three-layer waveguide rods in the truss beam of the bridge erection machine of the present invention;

[0020] Figure 2 For the present invention Figure 1 A in the middle is an enlarged schematic diagram;

[0021] Figure 3 Schematic diagram of force analysis of three working conditions of highway bridge erecting machine according to the present invention;

[0022] Figure 4 Schematic diagram of the maximum point of force analysis and the optimal arrangement of transverse waveguide rods for the bridge erection machine of the present invention;

[0023] Figure 5 This is a schematic perspective structural diagram of the waveguide rod buckle of the short waveguide rod connecting component of the present invention;

[0024] Figure 6 Schematic diagram of two adjacent layers of transverse waveguide rod structures of the present invention being connected via two mutually perpendicular small curved hook waveguide rods;

[0025] Figure 7 This is a schematic diagram of the structure of the spring-type black hole waveguide rod of the present invention;

[0026] Figure 8 For the present invention Figure 2 Schematic diagram of the structural connection where the spring-type black hole waveguide rod needs to be arranged at A in the middle;

[0027] Figure 9 For the present invention Figure 2 Schematic diagram of the arrangement and structural connection of the small hook waveguide rod at B in the middle;

[0028] Figure 10 A schematic diagram of a method for calculating the cross-sectional height of one end of a black hole in the present invention;

[0029] Figure 11 It is a perspective structural diagram of an annular hoop according to a specific embodiment of the present invention. DETAILED DESCRIPTION

[0030] In order to make the purpose, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are part of the embodiments of the present invention, not all the embodiments; based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of the present invention.

[0031] In Example 1, a simplified mechanical analysis of the truss beam of a highway bridge-building machine is performed under three different working conditions. The risk points of the truss beam structure under the three working conditions are analyzed, and the corresponding optimal waveguide rod arrangement position is proposed for each working condition. After superposition, a multi-layer transverse waveguide rod structure is obtained; the three different working conditions of the bridge-building machine are cantilever through-hole, beam erection and reverse lifting. The multi-layer transverse waveguide rod structure is divided into: an upper layer, which is mainly used to collect damage signals on the upper chord of the bridge-building machine, including steel fatigue and weld cracking, and transmit the acoustic signals when damaged; a middle layer, which transmits the acoustic signals when the bolts at the junction of the upper and lower trusses of the bridge-building machine are loose or rusted; and a lower layer, which collects the acoustic signals when the lower chord is damaged.

[0032] Specifically, such as Figure 3 As shown in the figure, all straight lines are curves, and straight lines are used instead of curves in order to find the maximum points of bending moment and shear force. First, a stress analysis is conducted on the three working conditions of the bridge crane. The bending moment diagram is obtained by performing finite element stress analysis in the modeling software to determine the maximum points of bending moment and shear force under the three working conditions, that is, the most unfavorable points under the working state. In addition, due to its unique splicing structure, the welding surface of the bolt splicing plate and the steel truss beam is a defect of the structure itself when the steel truss beam is working. Combining the most unfavorable point of the stress condition and the defects of the structure itself, such as Figure 4As shown in the figure, after the maximum risk point is obtained from the bridge crane force analysis diagram, the optimal waveguide rod arrangement scheme for monitoring this risk is the theoretically optimal waveguide rod arrangement scheme under three working conditions. The three arrangement schemes are superimposed to obtain the arrangement scheme of the two-layer transverse waveguide rod structure. However, only the most unfavorable point of force is considered. The transverse waveguide rods are only arranged above and below the truss beam near the I-beam, ignoring the bolt splicing plate at the joint of the upper and lower truss rods. The splicing plate will be subjected to a large extrusion force in the working state, causing the bolts to loosen. Therefore, the transverse waveguide rod is arranged again in the middle of the two layers. The optimal waveguide rod schemes in the two cases are superimposed to obtain the following: Figure 1 The three-layer transverse waveguide rod structure layout is shown.

[0033] Example 2: Based on Example 1, each layer of the multi-layer transverse waveguide rod structure is assembled by splicing short waveguide rods 1, waveguide rod clips 2, and spring-type black hole waveguide rods 3. Each layer of the transverse waveguide rod structure is connected end-to-end as needed by short waveguide rods 1 or spring-type black hole waveguide rods 3 via waveguide rod clips 2. During the connection process, a coupling agent is applied to the ends of the two adjacent waveguide rods. After splicing, the short waveguide rods 1 are fixed to the truss beam using an annular hoop to ensure a snug contact. The short waveguide rods 1 are standard waveguide rods of varying lengths. Standard waveguide rods are generally solid, thin, round stainless steel rods used for lossless transmission of acoustic emission signals.

[0034] Specifically, such as Figures 1 to 10 As shown, a multi-layered transverse waveguide rod structure is arranged outside the truss beams of the bridge erection machine. The bridge erection machine joint is a 30cm-high steel plate, so the first layer is placed 40cm above the bottom chord, and the second layer is placed 10cm below the middle joint of the bridge erection machine. The top layer is the same as the bottom layer and is therefore placed 40cm below the top chord. The length of each layer depends on the stresses during the three different working conditions of the bridge erection machine: cantilever through-hole, beam erection, and reverse lifting. Therefore, if the waveguide rods are all placed in the middle of the bridge erection machine, the length will decrease layer by layer, with the bottom layer being 164m long, the middle layer being 116m, and the top layer being 68m long. For the horizontal waveguide rods on the same floor, since the full-length waveguide rods are difficult to transport, and the bridge-building machine is made of 12m and 16m trusses, the standard waveguide rods are prefabricated into short waveguide rods 1 with a length of 6m and a length of 4m. The 12m truss beam is made of two 6m short waveguide rods 1, and the 16m truss beam is made of two 6m short waveguide rods 1 and one 4m short waveguide rod 1. Figure 5 As shown, the short waveguide rods 1 are connected by special waveguide rod buckles 2. During the connection process, coupling agent should be applied to the ends of the two waveguide rods to ensure high-quality and high-quantity propagation of the sound signal on the waveguide rods. Figure 11 The annular collar shown allows it to fit over the truss beam.

[0035] In Example 3, based on Example 2, spring-type black hole waveguide rods 3 are placed only in the middle of each layer of the truss beam of the transverse waveguide rod structure, where deformation is greatest. One end of the black hole points in the direction of the shortest acoustic signal propagation path. This prevents the bridge crane from undergoing significant deformation during reverse lifting, which can cause stress concentration at the joints of the transverse waveguide rod structure and lead to bending and deformation damage to the transverse waveguide rod structure. The spring-type black hole waveguide rod 3 is formed by bending a standard waveguide rod, with a spring-shaped center and a straight waveguide rod at each end. Because the acoustic signal propagates from the middle of each layer of the waveguide rod structure to both ends, the end of the straight waveguide rod pointing to the sensor is designed in the form of a black hole to amplify the signal.

[0036] Specifically, such as Figure 3 、 4 As shown in Figures 7 and 8, when the bridge erection machine is in the reverse lifting state, the steel truss beam will sink and deform up to 300mm due to the heavy weight of the steel box beam and bridge deck. Figure 3 、 4 As shown, the waveguide rod buckle 2 will produce stress concentration, causing the horizontal waveguide rod structure of the layer to deform or the buckle to loosen, so the following is designed Figure 7 、 8 The spring-type black hole waveguide rod 3 shown can not only amplify the acoustic signal but also deform when the steel truss beam of the bridge erection machine is deformed to reduce the stress of the connecting components.

[0037] More specifically, Figure 7 、 Figure 8 As shown, the spring portion is bent from a standard waveguide rod with a diameter of 6 mm, with a total of 8 turns. Its maximum radius is 25 mm, the minimum radius is 3 mm, and the axial pitch is 10 mm. Since the length of the waveguide rod buckle 2 is 6 cm, a 4 cm long standard waveguide rod is provided at each end of the spring portion. The arrangement of the sensor determines that the main propagation path of the signal is from the middle position of the overall waveguide rod structure to both ends. Therefore, the 3 cm end of the 4 cm standard waveguide rod pointing to the acoustic signal sensor is designed as a black hole to amplify the signal.

[0038] Example 4: Based on Example 3, adjacent layers in a multi-layer transverse waveguide rod structure are connected via specially made small hook waveguide rods 4. The two adjacent layers of the transverse waveguide rod structure are connected as follows: First, a small hook waveguide rod 4 is horizontally installed and connected at each end of the upper transverse waveguide rod structure via waveguide rod clips 2, with the hook ends of the small hook waveguide rods 4 facing away from each other; then, the hook ends of the small hook waveguide rods 4 in the upper layer are vertically hooked and connected to the hook ends of the other small hook waveguide rods 4. Finally, the unhooked ends of the vertical small hook waveguide rods 4 are tightly wrapped with fine ties 5 to the transverse waveguide rod structure of the lower layer, forming a close contact connection. This allows the damage acoustic signals captured by all layers of the multi-layer transverse waveguide rod structure to be transmitted to the lowest layer. The specially made small hook waveguide rod 4 is made by bending one end of a standard waveguide rod into a hook.

[0039] Specifically, such as Figures 6-10 As shown, according to the arrangement method of the waveguide rods in Examples 1 and 2, the acoustic signal sensor should be arranged at the end of each layer of the transverse waveguide rod structure. A three-layer transverse waveguide rod structure requires six sensors, which is too costly. Therefore, a special Figure 6 The waveguide rods with small hooks shown connect two adjacent layers of transverse waveguide rod structures through the small hook waveguide rods 4.

[0040] More specifically, Figure 9 To reduce the number of sensors and leverage the linear positioning advantages of waveguide rods, the transverse waveguide rod structures between different layers are also connected in parallel. This allows only two sensors, installed at each end of the lowest waveguide rod layer, to monitor key locations throughout the truss girder and facilitate the subsequent localization of received acoustic signals. Adjacent layers of waveguide rods are connected using a waveguide rod 4 with a specially designed hook. The hook has an 8mm diameter and a length of 50mm. This hook ensures that a 6mm diameter waveguide rod can be attached without falling due to deformation and vibration of the structure.

[0041] Example 5, based on Example 4, features conventional black hole waveguide rod connectors at both ends of the bottommost layer of the multi-layer transverse waveguide rod structure. Specifically, conventional black hole waveguide rods are installed at both ends of the bottommost transverse waveguide rod layer. These rods, constructed by shaping one end of a standard waveguide rod into a black hole, amplify acoustic signals, effectively increasing the monitoring range. Acoustic signal sensors are positioned perpendicular to the cross-sections of the ends of the conventional black hole waveguide rods at both ends of the bottommost layer to receive acoustic signals when truss beams are damaged, enabling monitoring.

[0042] Specifically, ordinary black hole waveguide rods are installed at both ends of the bottom layer (Note: ordinary black hole waveguide rods are standard waveguide rods with one end processed as follows Figure 10The structure shown is shaped and is used to amplify acoustic signals during acoustic signal monitoring (this technology is relatively mature and currently available). Acoustic signal sensors (Note: Acoustic signal sensors, also known as sound pressure sensors, are sensors that convert sound pressure signals into electrical signals for capturing acoustic signals. Due to existing technology, they are not shown in the figure) are installed at both ends of the ordinary black hole waveguide rod to capture the acoustic signals when the truss beam of the bridge erection machine is damaged.

[0043] Example 6: Based on Example 5, the cross-sectional height of the black hole end of the spring-type black hole waveguide rod 3 and the ordinary black hole waveguide rod is expressed as follows:

[0044] h(x)=εx 2 +h0

[0045] Where x is the distance from the cross section to the end, and its value range is (0≤x≤3); h0 is the cutoff height of the structure, and the smaller the value, the better the convergence effect of the acoustic signal; the parameter ε is a constant.

[0046] Specifically, h0 is the cutoff height of the structure. The smaller the value, the better the convergence effect of the sound signal. However, considering the docking in the project, it is set to 2 mm.

Claims

1. A method for monitoring damage of a single truss beam of a highway bridge erection machine using acoustic emission waves, characterized in that: The following steps are involved: S1: A simplified mechanical analysis of the truss beam of a highway bridge erection machine was performed under three different operating conditions. The highest risk points of the truss beam structure were identified under the three working conditions. The optimal waveguide rod layout was proposed for each working condition, and a multi-layer transverse waveguide rod structure was obtained through superposition. S2: Each layer of the multi-layer transverse waveguide rod structure is assembled by splicing a short waveguide rod (1), a waveguide rod buckle (2), and a spring-type black hole waveguide rod (3); S3: The adjacent two layers in the multi-layer transverse waveguide rod structure are connected by a specially made small curved hook waveguide rod (4); S4: Arrange ordinary black hole waveguide rod connectors at both ends of the bottom layer of the multi-layer transverse waveguide rod structure; S5: Acoustic signal sensors are arranged vertically on the end sections of the common black hole waveguide rods at both ends of the bottom layer to receive acoustic signals when the truss beam is damaged to achieve the purpose of monitoring.

2. The method for monitoring damage of a single truss beam of a highway bridge erection machine by using acoustic emission waves according to claim 1, characterized in that: The mechanical analysis in step S1 includes analyzing the stress conditions of the truss beam in three different working states of the bridge erection machine, including cantilever passing, beam erection and reverse lifting, and finding the maximum shear force position point and the maximum bending moment position point under different working conditions.

3. The method for monitoring damage of a single truss beam of a highway bridge erection machine by using acoustic emission induced waves according to claim 1, characterized in that: The multi-layer transverse waveguide rod structure in step S1 includes: Upper layer: mainly used to collect damage signals on the upper chord of the bridge crane, including steel fatigue and weld cracking, and transmit the acoustic signals of damage; Middle layer: transmits the sound signal when the bolts at the junction of the upper and lower trusses of the bridge erection machine are loose or corroded; Lower layer: Collects acoustic signals when the lower chord is damaged.

4. The method for monitoring damage of a single truss beam of a highway bridge erection machine by using acoustic emission waves according to claim 1, characterized in that: The splicing and assembling method of each layer in step S2 includes: Each layer of the transverse waveguide rod structure is connected end to end by a short waveguide rod (1) or a spring-type black hole waveguide rod (3) through a waveguide rod buckle (2) as needed. During the connection process, a coupling agent needs to be applied to the ends of the two adjacent waveguide rods. After the splicing is completed, the short waveguide rod (1) is fixed to the truss beam using an annular hoop to ensure close contact; The spring-type black hole waveguide rod (3) is only arranged at the position with the largest deformation in the middle of the truss beam of each layer of the transverse waveguide rod structure, and one end of the black hole faces the direction with the shortest propagation path of the acoustic signal, so as to cope with the stress concentration at the joint of the transverse waveguide rod structure caused by the large deformation of the bridge crane during reverse lifting, resulting in the transverse waveguide rod structure being bent and deformed and damaged.

5. The method for monitoring damage of a single truss beam of a highway bridge erection machine by using acoustic emission induced waves according to claim 4, characterized in that: The short waveguide rod (1) is a standard waveguide rod of varying lengths, which is generally a solid, thin round rod made of stainless steel and used for lossless transmission of acoustic emission signals; The spring-type black hole waveguide rod (3) is formed by bending a standard waveguide rod, with a spring shape in the middle and a straight waveguide rod at each end. Since the acoustic signal propagation path is from the middle position of the waveguide rod structure of each layer to the two ends, the end of the straight waveguide rod pointing to the sensor is designed in the form of a black hole to amplify the signal.

6. The method for monitoring damage of a single truss beam of a highway bridge erection machine by using acoustic emission waves according to claim 1, characterized in that: The step S3 includes connecting two adjacent layers of transverse waveguide rod structures through the specially made small curved hook waveguide rod (4), and the connection method includes: First, a small curved hook waveguide rod (4) is installed and connected in the horizontal direction at each end of the upper layer's transverse waveguide rod structure through a waveguide rod buckle (2), and the curved hook ends of the small curved hook waveguide rod (4) are spaced apart from each other; Then, the hook ends of the small-sized hook waveguide rods (4) on the upper layer are respectively hooked vertically and contacted with the hook ends of the other small-sized hook waveguide rods (4); Finally, the non-hook end of the vertical small hook waveguide rod (4) is tightly wrapped with a thin wire (5) on the lower transverse waveguide rod structure to achieve a fitting contact connection, so that the damage sound signals captured by all layers of the multi-layer transverse waveguide rod structure can be transmitted to the bottom layer.

7. A method for monitoring damage of a single truss beam of a highway bridge erection machine by acoustic emission induced waves according to claims 5 and 6, characterized in that: The specially made small curved hook waveguide rod (4) is made by bending one end of the standard waveguide rod into a curved hook.

8. The method for monitoring damage of a single truss beam of a highway bridge erection machine by using acoustic emission induced waves according to claims 1 and 5, characterized in that: The step S4 comprises: Ordinary black hole waveguide rods are installed at both ends of the lowest horizontal waveguide rod. The ordinary black hole waveguide rod is made by making one end of a standard waveguide rod into a black hole shape, which amplifies the sound signal and effectively improves the monitoring range.

9. The method for monitoring damage of a single truss beam of a highway bridge erection machine by using acoustic emission induced waves according to claims 5 and 8, characterized in that: The cross-sectional height expression of the black hole end of the spring-type black hole waveguide rod (3) and the common black hole waveguide rod is: h(x)=εx 2 +h0 Where x is the distance from the cross section to the end, and its value range is (0≤x≤3); h0 is the cutoff height of the structure, and the smaller the value, the better the convergence effect of the acoustic signal; the parameter ε is a constant.

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