Lead breaking device and method for active guided wave field scanning

Abstract

The invention relates to a lead breaking device and method for active guided wave field scanning, and the device is characterized in that a propelling pencil for conveying a graphite lead core is fixed in a device housing, a device front cover is detachably connected with the device housing, and a breaking assembly is installed in the device housing; the graphite lead core penetrates through the breaking assembly and a through hole in the device front cover to be connected with a tested structure, the upper electrode plate is welded and fixed to the outer side of the device front cover, the battery assembly is fixed to the rear end of the device shell, the lower side of the battery assembly is connected with a metal device shell of the propelling pencil through a metal connecting piece, and the upper side of the battery assembly is connected with the lower electrode plate. The upper electrode plate, the device front cover, the graphite pencil lead, the propelling pencil, the metal connecting plate, the battery assembly, the lower electrode plate and the oscilloscope form an electric trigger loop for capturing the pencil lead fracture moment. Compared with the prior art, through cooperative work of mechanical linkage and synchronous electric triggering, accurate synchronous control of signal acquisition and triggering time is realized in combination with the oscilloscope.

Description

Technical Field

[0001] This invention relates to the field of acoustic emission detection technology, and in particular to a lead-breaking device and method for active guided wave field scanning. Background Technology

[0002] Active guided wave field scanning uses active excitation of ultrasonic guided waves and array sensors or scanning devices to spatially sample and image the propagation wave field of guided waves in a structure, thereby enabling the location, assessment and visual monitoring of defects (such as cracks and corrosion).

[0003] Accurate acquisition of dispersion characteristics is a core prerequisite for structural health monitoring using ultrasonic guided wave technology. In experiments, laser Doppler vibrometers are typically used for wavefield scanning; however, this device is limited by the surface morphology of the structure and cannot be used in actual engineering sites. The lead-breaking experiment is a commonly used method in acoustic emission, offering advantages such as stability, reliability, high repeatability, wide signal spectrum, and ease of implementation. The diameter of the pencil lead is much smaller than that of various transducers, and using a moving PLB (PencilLead Breakage) as the excitation source satisfies the spatial resolution and wavenumber range requirements of wavenumber analysis while being more cost-effective. However, the mechanical waves generated by the PLB only propagate within the tested structure and the lead, and cannot be directly converted into the electrical trigger signal required by the acquisition system. This results in a significant error between the actual lead-breaking time and the acquisition trigger time, thus affecting calculation accuracy.

[0004] Chinese patent CN111272431B discloses an automatic lead-breaking device for acoustic emission during engine testing. One end of a telescopic probe is mounted on a displacement control mechanism, and the other end has a telescopic head. One end of a lead core fixing plate is fixed to the telescopic head, and the other end has a lead core. An acoustic emission probe is mounted on the lead core fixing plate. This device can be remotely controlled by an operator to perform lead-breaking experiments on the test target, simulating typical acoustic emission signals generated by manual lead breaking. This patent solves the problem of high-risk environments such as high temperature radiation, high-speed airflow, low oxygen, and high oil and gas concentrations during engine testing, making manual operation impossible in such environments. It achieves automatic lead-breaking operation, but it cannot precisely control the lead breaking, nor can it align the actual lead-breaking moment with the acquisition trigger moment, resulting in low lead-breaking accuracy.

[0005] Current research focuses only on how to stably break pencil leads, without addressing the core issue of synchronizing the trigger moment. Therefore, there is an urgent need for a device that can accurately convert the lead breakage moment into a valid trigger signal and synchronize the lead breakage and acquisition moments. Summary of the Invention

[0006] The purpose of this invention is to overcome the defects of the prior art by providing a lead-breaking device and method for active guided wave field scanning. It utilizes the conductivity of the graphite lead core itself to construct a closed loop, and the signal changes synchronously at the moment of lead breaking, thereby achieving precise synchronization between lead breaking and acquisition.

[0007] The objective of this invention can be achieved through the following technical solutions: A lead-breaking device for active guided wave field scanning, the device comprising: an upper electrode plate, a front cover, a lower electrode plate, a housing, a mechanical pencil, a breaking assembly, a battery assembly, and a metal connecting piece; the mechanical pencil, which delivers a graphite lead, is fixed to a preset mounting position on the housing; the front cover is detachably connected to the housing; the breaking assembly is installed inside the housing; the graphite lead passes through the breaking assembly and through holes on the front cover and is connected to the structure under test; the upper electrode plate is welded and fixed to the outside of the front cover; the battery assembly is fixed to the rear end of the housing; the lower side of the battery assembly is connected to the metal housing of the mechanical pencil via the metal connecting piece; and the upper side of the battery assembly is connected to the lower electrode plate. The upper electrode is connected to the positive terminal of the oscilloscope channel, and the lower electrode is connected to the negative terminal of the oscilloscope channel. The upper electrode, the front cover of the device, the graphite lead core, the mechanical pencil, the metal connecting piece, the battery assembly, the lower electrode, and the oscilloscope constitute an electrical trigger circuit for capturing the moment when the lead core breaks.

[0008] Furthermore, the front cover of the device is connected to the outer shell of the device by a snap-fit ​​connection.

[0009] Furthermore, the front end of the device housing is provided with an inclined surface that fixes the lead breaking angle.

[0010] Furthermore, except for the upper electrode plate, the front cover of the device, the front end of the mechanical pencil, the metal connecting plate, and the lower electrode plate, all other parts of the lead-breaking device are made of insulating material.

[0011] Furthermore, the breaking assembly includes a trigger button, a first reset spring, a lead core breaking mechanism, a transmission push rod, and a second reset spring; The lead core breaking mechanism has a through hole at its center, is fixed to a rotating shaft inside the device housing, and can rotate around the rotating shaft. The graphite lead core passes through this through hole and then through the through hole at the front end of the device's front cover. The first return spring is assembled between the device housing and the lead core breaking mechanism, providing a return thrust to the lead core breaking mechanism. The transmission push rod is installed on the side opposite to the assembly position of the first return spring. The transmission push rod consists of a cylindrical push rod and a cube with a ramp. The second return spring is installed at the front end of the cylindrical push rod of the transmission push rod, providing a return thrust to the transmission push rod. The trigger button is embedded in the device housing, and the ramp of the trigger button is in contact with the ramp of the cube of the transmission push rod. When the trigger button is pressed, the ramp of the cube of the transmission push rod receives a lateral thrust, moves laterally, and provides the lead core breaking mechanism with a thrust opposite to that of the first return spring, pushing the lead core breaking mechanism to rotate around the rotating shaft.

[0012] Furthermore, the cylindrical push rod is embedded in a horizontal groove inside the device housing and moves horizontally along the horizontal groove of the device housing.

[0013] Furthermore, the trigger button is embedded in the device housing by a limiting buckle, and can only be pressed in the vertical direction.

[0014] Furthermore, the battery assembly includes a lower battery compartment shell, an upper battery compartment shell, and a button cell; The lower and upper battery compartments are detachably connected to form the battery compartment. The battery compartment is fixed to the rear end of the device housing. The button battery is placed inside the battery compartment. The negative terminal of the button battery is led out from the upper battery compartment through the lower electrode plate and is connected to the negative terminal of the oscilloscope channel when in use. The metal connecting piece passes through the lower battery compartment and connects to the positive terminal of the button battery, so that the metal shell of the mechanical pencil is connected to the positive terminal of the button battery.

[0015] A lead-breaking method based on the lead-breaking device for active guided wave field scanning as described above, the method comprising: Combined with the aforementioned lead-breaking device for active guided wave field scanning; The graphite lead is fed to a preset length using a mechanical pencil, passing through the central through-hole of the broken component and extending to the front through-hole of the device's front cover for fitting and positioning. The angle of the broken lead is fixed by the beveled front surface of the device's outer shell, and the end of the graphite lead is connected to the structure being tested. The upper electrode is connected to the positive terminal of the oscilloscope channel, and the lower electrode is connected to the negative terminal of the oscilloscope channel. Relying on the conductivity of the graphite lead core, a closed electrical circuit is formed through the metal connecting piece, the metal shell of the mechanical pencil, the button battery, the front cover of the device, and the trigger channel of the oscilloscope. By controlling the breaking component to apply a stable torque to the graphite lead core, the lead core breaks at a preset angle. The mechanical wave generated by the broken lead enters the structure under test, and the breaking action and the breaking time are collected by an oscilloscope. The graphite lead is fed back to the preset length using a mechanical pencil, and the above operation is repeated to complete continuous lead breakage excitation until the batch testing requirements of active guided wave field scanning are met.

[0016] Furthermore, when the graphite lead core breaks, the closed electrical circuit breaks instantly, generating a sudden change in electrical signal, which is synchronously transmitted to the oscilloscope, thus realizing the synchronous acquisition of the lead-breaking action and the moment of lead breaking.

[0017] Compared with the prior art, the beneficial effects of the present invention include: 1. This invention utilizes the conductivity of graphite lead cores themselves, and combines them with components such as metal connecting pieces, mechanical pencil metal casings, and button batteries to construct a closed electrical trigger circuit. The circuit breaks at the moment the lead core breaks, generating a sudden change in electrical signal. This signal is synchronously transmitted to the oscilloscope, which solves the problem of asynchronous signal acquisition between the lead breakage excitation and the traditional lead breakage excitation, ensuring the consistency of the acquisition starting point.

[0018] 2. This invention has high synchronization accuracy. Relying on the controllable lead-breaking structure of mechanical linkage and the design of electrical trigger synchronization, the repeated acquisition error of the same point is less than 2μs. The precise time synchronization provides a reliable original data foundation for subsequent guided wave signal analysis and wavenumber-frequency calculation, avoiding data analysis deviations caused by synchronization errors.

[0019] 3. This invention adopts a sloping linkage design of trigger button-transmission push rod-lead core breaking mechanism, which, together with the sloping surface at the front end of the device housing, achieves precise limiting of the lead breaking angle, so that the torque and angle when the lead core breaks remain stable, solving the randomness problem of manual lead breaking, and making the mechanical wave signal generated by each lead breaking excitation highly consistent, thus improving the repeatability of wave field scanning.

[0020] 4. All components of the device of the present invention are made of readily available conventional materials and are assembled using simple processes such as bonding, snap-fit ​​connection and welding. There are no complex precision components, and the scanning cost can be controlled within 5 yuan. Compared with traditional professional excitation equipment, it significantly reduces the detection cost of active guided wave field scanning and is suitable for batch use.

[0021] 5. The present invention has an integrated portable structure, which can be used for both precise laboratory testing and on-site engineering scanning. With the help of the angle limiting design of the outer shell, it can adapt to the waveguide excitation requirements of various planar structures and irregularly shaped structures with curvature, breaking through the limitation that some excitation devices can only be used on regular planes. Attached Figure Description

[0022] Figure 1This is a schematic diagram of the overall structure of the present invention; Figure 2 This is a schematic diagram of the internal structure of the present invention; Figure 3 This is a schematic diagram of the trigger circuit formed when the present invention is used; Figure 4 This refers to the guided wave signal collected on the aluminum plate using the lead-breaking device in this embodiment of the invention. Figure 5 This is the actual wavenumber frequency diagram obtained by using a lead-breaking device to perform active guided wave field scanning on an aluminum plate in an embodiment of the present invention; Figure 6 This is the actual wavenumber frequency diagram obtained by using a lead-breaking device to perform active guided wave field scanning on a carbon fiber plate in an embodiment of the present invention. In the diagram: 1-Upper electrode plate, 2-Front cover of device, 3-Trigger button, 4-Lower electrode plate, 5-Lower battery compartment shell, 6-Upper battery compartment shell, 7-Outer shell of device, 8-Mechanical pencil, 9-First return spring, 10-Lead core breaking mechanism, 11-Transmission push rod, 12-Second return spring, 13-Metal connecting piece, 14-Button battery, 15-Graphite lead core. Detailed Implementation

[0023] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort should fall within the scope of protection of the present invention.

[0024] Example 1 A lead-breaking device for active guided wave field scanning, the device as a whole is as follows Figure 1 and Figure 2 As shown, it includes: upper electrode plate 1, front cover of device 2, trigger button 3, lower electrode plate 4, lower battery compartment shell 5, upper battery compartment shell 6, outer casing of device 7, mechanical pencil 8, first return spring 9, lead core breaking mechanism 10, transmission push rod 11, second return spring 12, metal connecting piece 13, button battery 14, and graphite lead core 15.

[0025] The trigger button 3, the first reset spring 9, the lead core breaking mechanism 10, the transmission push rod 11, and the second reset spring 12 constitute the breaking assembly, which is used to controllably break the graphite lead core 15.

[0026] The lower battery compartment shell 5, the upper battery compartment shell 6, and the button battery 14 constitute the battery assembly for power supply.

[0027] The outer casing 7 serves as the overall mounting carrier, and its front end is as follows: Figure 2The inclined plane shown allows for precise control of the lead breakage angle.

[0028] The mechanical pencil 8 is fixed to the preset mounting position of the device housing 7 by adhesive bonding for stable feeding of the graphite lead 15. The mechanical pencil 8 is a common existing mechanical pencil with a metal tip and an insulating material at the rear for operational safety. Alternatively, a mechanical pencil made entirely of metal can be used for ease of production. This invention does not limit the specific structure of the mechanical pencil 8.

[0029] The metal front cover 2 is detachably connected to the outer casing 7 of the device, specifically using a snap-fit ​​connection, which makes it easy to replace the front cover at any time and facilitates maintenance.

[0030] The upper electrode plate 1 is welded and fixed to the outside of the front cover 2 of the device, and is used to connect to the positive terminal of the oscilloscope channel during use.

[0031] The break-off assembly is installed inside the device housing 7, and the graphite lead core 15 passes through the break-off assembly and the through hole on the front cover 2 of the device to connect with the structure under test.

[0032] Specifically, the lead core breaking mechanism 10 has a through hole in the center, is fixed on a rotating shaft inside the device housing 7, and can rotate around the rotating shaft. The graphite lead core 15 passes through the through hole and then through the through hole at the front end of the device front cover 2.

[0033] The first reset spring 9 is assembled between the device housing 7 and the lead core breaking mechanism 10, and provides a reset thrust to the lead core breaking mechanism 10 when the lead core breaking mechanism 10 is twisted.

[0034] Under normal conditions, the lead core breaking mechanism 10 Figure 2 The image shows the vertical position.

[0035] The transmission push rod 11 is installed on the side opposite to the assembly position of the first return spring 9. The transmission push rod 11 consists of a cylindrical push rod at the front end and two cubes with ramps at the rear end. The second return spring 12 is installed at the front end of the cylindrical push rod of the transmission push rod 11 to provide a return thrust to the transmission push rod 11.

[0036] The cylindrical push rod is specifically embedded in the horizontal groove inside the device housing 7 and moves horizontally along the horizontal groove of the device housing 7.

[0037] The trigger button 3 is embedded in the device housing 7 by a limit buckle and can only move up and down in the vertical direction. The two inclined surfaces at the lower end of the trigger button 3 are respectively in contact with the two cubic inclined surfaces of the transmission push rod 11.

[0038] When the trigger button 3 is pressed, the trigger button 3 moves downward in the vertical direction, squeezing the transmission push rod 11. The cubic inclined surface of the transmission push rod 11 is subjected to lateral thrust under the squeezing and moves laterally, giving the lead core breaking mechanism 10 a thrust opposite to that of the first reset spring 9, pushing the lead core breaking mechanism 10 to rotate around the axis, and the lead core breaking mechanism 10 then breaks the graphite lead core 15 that passes through the through hole.

[0039] The upper electrode plate 1 is welded and fixed to the outside of the front cover 2 of the device, and is used to connect to the positive terminal of the oscilloscope channel during use.

[0040] The battery assembly is fixed to the rear end of the device housing 7. The lower side of the battery assembly is connected to the metal housing of the mechanical pencil 8 via a metal connecting piece 13, and the upper side of the battery assembly is connected to the lower electrode piece 4.

[0041] Specifically, the lower battery compartment 5 and the upper battery compartment 6 are detachably connected to form the battery compartment. The battery compartment is fixed to the rear end of the device housing 7. The button battery 14 is placed in the battery compartment. The negative terminal of the button battery 14 is led out from the upper battery compartment 6 through the lower electrode plate 4 and connected to the negative terminal of the oscilloscope channel when in use. The metal connecting piece 13 passes through the lower battery compartment 5 and connects to the positive terminal of the button battery 14, so that the metal shell of the mechanical pencil 8 is connected to the positive terminal of the button battery 14.

[0042] The upper electrode 1 is connected to the positive terminal of the oscilloscope channel, and the lower electrode 4 is connected to the negative terminal of the oscilloscope channel. The upper electrode 1, the front cover 2, the graphite lead core 15, the mechanical pencil 8, the metal connecting piece 13, the battery assembly, the lower electrode 4, and the oscilloscope constitute an electrical trigger circuit for capturing the moment the lead core breaks. A schematic diagram of the electrical trigger circuit is shown below. Figure 3 As shown.

[0043] In another embodiment, the lead-breaking device is made of insulating material except for the upper electrode plate 1, the front cover 2, the front end of the mechanical pencil 8, the metal connecting piece 13, and the lower electrode plate 4, which can ensure safe operation.

[0044] The working principle of this device is as follows: Through the coordinated operation of mechanical linkage and synchronous electric triggering, and in conjunction with an oscilloscope, precise synchronous control of signal acquisition and triggering timing is achieved. Before use, the graphite lead 15 is fed to a preset length by the mechanical pencil 8, so that it passes through the central through hole of the lead core breaking mechanism 10 and extends to the front through hole of the device front cover 2 for fitting and positioning. The lead breaking angle is fixed by the inclined surface at the front of the device housing 7. At the same time, the upper electrode plate 1 and the lower electrode plate 4 are connected to the positive and negative terminals of the oscilloscope trigger channel, respectively. Relying on the conductivity of the graphite lead 15, a closed electrical circuit is formed through the metal connecting piece 13, the metal housing of the mechanical pencil 8, the button battery 14, the metal device front cover 2, and the trigger channel of the oscilloscope.

[0045] When in use, pressing the trigger button 3 causes the button to engage with the inclined surface of the transmission push rod 11, driving it to move laterally. This, in turn, causes the lead core breaking mechanism 10 to rotate around its axis, applying a stable torque to the graphite lead core 15. This causes the lead core to break at a preset angle, and the mechanical wave generated by the broken lead is guided into the structure under test. Simultaneously, the circuit breaks at the moment the lead core breaks, generating a sudden change in electrical signal, which is synchronously transmitted to the oscilloscope, achieving precise synchronization between the lead breaking action and the acquisition time. Releasing the trigger button 3 causes the second reset spring 12 to return the transmission push rod 11 to its original position, and the first reset spring 9 simultaneously pushes the lead core breaking mechanism 10 to reset. By using the automatic pencil 8 to feed the graphite lead core 15 back to the preset length, the operation can be repeated to complete continuous lead breaking excitation, meeting the batch testing requirements of active guided wave field scanning.

[0046] This device utilizes the conductivity of the graphite lead core 15, and relies on the metal connecting piece 13, the metal shell of the mechanical pencil 8, the button battery 14, and the front cover 2 of the device to form an electrical trigger circuit, which can capture the moment when the lead core breaks.

[0047] The trigger button 3, the transmission push rod 11, and the lead core breaking mechanism 10 form a linkage mechanism, making the breakage of the lead core more controllable.

[0048] Example 2 This embodiment, based on Embodiment 1 above, discloses a lead-breaking method based on a lead-breaking device for active guided wave field scanning, the method comprising: Step S1: Combine the lead-breaking device for active guided wave field scanning; In step S2, the graphite lead core 15 is fed to a preset length by the mechanical pencil 8, so that it passes through the central through hole of the lead core breaking mechanism 10 and extends to the front through hole of the device front cover 2 for fitting and positioning. The lead breaking angle is fixed by the front inclined surface of the device housing 7, and the end of the graphite lead core 15 is connected to the structure being tested.

[0049] In step S3, the upper electrode 1 is connected to the positive terminal of the oscilloscope channel, and the lower electrode 4 is connected to the negative terminal of the oscilloscope channel. Relying on the conductivity of the graphite lead core 15, a closed electrical circuit is formed through the metal connecting piece 13, the metal shell of the mechanical pencil 8, the button battery 14, the front cover 2 of the device, and the trigger channel of the oscilloscope.

[0050] Step S4: By controlling the breaking component to apply a stable torque to the graphite lead core 15, the lead core breaks at a preset angle. The mechanical wave generated by the broken lead enters the structure under test, and the breaking action and the breaking time are collected by an oscilloscope.

[0051] Step S5: The graphite lead core 15 is fed to the preset length again by the automatic pencil 8. The above operation is repeated to complete the continuous lead breakage excitation until the batch detection requirements of the active guided wave field scanning are met.

[0052] When the graphite lead core 15 breaks, the closed electrical circuit breaks instantly, generating a sudden change in electrical signal, which is synchronously transmitted to the oscilloscope, realizing the synchronous acquisition of the lead breaking action and the moment of lead breaking.

[0053] The following is an example of actual aluminum plate testing: Preliminary debugging of the lead-breaking device: The graphite lead core 15 is fed to the preset length through the mechanical pencil 8, passes through the lead core breaking mechanism 10 and fits into the front through hole of the device front cover 2, and the lead-breaking angle is fixed by the inclined surface at the front of the device housing 7; the upper electrode plate 1 and the lower electrode plate 4 of the device are connected to the positive and negative terminals of the oscilloscope trigger channel respectively, and a closed electrical trigger circuit is formed by relying on the conductivity of the graphite lead core 15. At the same time, a piezoelectric sensor is arranged at the measured position of the aluminum plate and connected to the oscilloscope.

[0054] Perform lead breakage operation: Press the device to trigger button 3, and through mechanical linkage, the graphite lead core breaks at a preset angle. The mechanical wave generated by the lead breakage is transmitted to the aluminum plate to form a guided wave.

[0055] Synchronous signal acquisition: While the oscilloscope captures the voltage drop signal (black line) generated by the lead core breakage in the device's electrical trigger circuit, it uses this voltage drop signal as a trigger signal to acquire the broken lead guided wave signal (red line) on the aluminum plate through a piezoelectric sensor.

[0056] The two types of signals were visualized in the time domain to obtain... Figure 4 The guided wave signal diagram.

[0057] like Figure 4 As shown, the black line represents the voltage drop signal of the trigger circuit constructed by this device at the trigger moment, and the red line represents the lead breakage signal acquired by the piezoelectric sensor and oscilloscope when the voltage drop signal is used as the trigger signal. The guided wave signal generated by the lead breakage is completely captured, and the zero point of time is stable and controllable. In the figure, "Voltage drop signal" means the voltage drop signal, "Guided wave signal" means the guided wave signal after being transmitted to the structure under test, and "PLB signal" is an abbreviation for "Pencil LeadBreakage signal," which is the lead breakage signal.

[0058] Figure 5 To obtain the actual wavenumber frequency map by active guided wave field scanning on an aluminum plate using this device, the specific acquisition process is as follows: Active guided wave field scanning is carried out on an aluminum plate using a lead-breaking device. Controllable lead breaking is performed on the surface of the aluminum plate as an active guided wave excitation source, which excites multi-mode ultrasonic guided waves within the plate. Guided waves are generated through multiple controllable lead-breaking excitations, and multiple sets of original guided wave signals from the aluminum plate are collected simultaneously during the scanning process. Signal preprocessing: The acquired raw signal is preprocessed by denoising, filtering, and removing DC components to eliminate environmental noise and system interference; Two-dimensional Fourier transform: A two-dimensional Fourier transform is performed on the preprocessed aluminum plate guided wave signal to convert the time-domain (t) and spatial-domain (x) guided wave signal into a frequency-domain (f) and wavenumber (k) domain signal, obtaining the frequency-wavenumber (kf) energy distribution matrix; the energy distribution matrix is ​​then converted into a kf energy spectrum (e.g., amplitude squared), and color gradients (e.g., ...) are used to represent the spectrum. Figure 5 The red and blue heatmap in the figure represents the energy intensity at different kf points. The colors form a preliminary wavenumber-frequency distribution map. In the kf energy spectrum, different guided wave modes correspond to different energy concentration regions, namely the bright bands / red bands in the figure. Experimental curve extraction: By peak detection or threshold filtering, the kf data points corresponding to each energy peak are extracted to obtain the experimental wavenumber-frequency curves for each mode. Based on the material parameters of the aluminum plate (density, elastic modulus, thickness) and waveguide theory, the theoretical wavenumber-frequency curves for modes A0, S0, and A1 are calculated. Figure 5 The red dashed line in the middle; Curve verification and labeling: The theoretical curve is superimposed on the experimental kf spectrum. By comparing the overlap between the theoretical curve and the experimental energy peaks, the corresponding energy peaks are labeled as A0, S0, and A1 modes, forming a pattern as follows: Figure 5 The final wavenumber-frequency distribution plot is shown.

[0059] Figure 5 In the diagram, Wavenumber refers to the wave number that describes the propagation characteristics of guided waves, and Frequency refers to the frequency. In the diagram, A0 is the 0th antisymmetric mode of the ultrasonic guided wave, S0 is the 0th symmetric mode, and A1 is the 1st antisymmetric mode. These are all typical modes of ultrasonic guided wave propagation in thin plate-like components and are the core parameters characterizing the vibration form, propagation speed, and dispersion characteristics of guided waves within the component.

[0060] like Figure 5 As shown, the actual wavenumber-frequency distribution diagram of the aluminum plate obtained by the two-dimensional Fourier transform is in high agreement with the red dashed line representing the wavenumber-frequency curve obtained by theoretical calculation, which shows that the accuracy of this device is extremely high.

[0061] Figure 6 To obtain the actual wavenumber frequency map by active guided wave field scanning on a carbon fiber plate using this device, the specific acquisition steps are the same as described above. Figure 4 and Figure 5 The acquisition method is the same: Active guided wave field scanning was carried out on carbon fiber laminate using a lead-breaking device. Guided waves were generated by multiple lead-breaking excitations, and the original guided wave signals of the carbon fiber laminate were collected simultaneously during the scanning process. A two-dimensional Fourier transform is performed on the acquired raw signal of the carbon fiber plate guided wave to complete the conversion from the time / space domain to the frequency and wavenumber domains, and obtain the energy distribution matrix of the frequency domain-wavenumber domain (kf); the energy distribution matrix is ​​converted into a kf energy spectrum, and the energy intensity of different kf points is represented by color gradients to form a preliminary wavenumber-frequency distribution map. The wavenumber-frequency curve (red dashed line) obtained from superposition theory calculations forms Figure 6 .

[0062] Figure 6 In the diagram, Wavenumber refers to the wave number that describes the propagation characteristics of guided waves, and Frequency refers to the frequency. In the diagram, A0 is the 0th antisymmetric mode of the ultrasonic guided wave, and S0 is the 0th symmetric mode. These are typical modes of ultrasonic guided wave propagation in thin plate-like components and are core parameters that characterize the vibration form, propagation speed, and dispersion characteristics of guided waves within the component.

[0063] like Figure 6 As shown, the actual wavenumber-frequency diagram of the carbon fiber laminate obtained by two-dimensional Fourier transform is in high agreement with the red dashed line representing the wavenumber-frequency curve obtained by theoretical calculation, which shows that the device has extremely high accuracy.

[0064] The above description is merely a specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any person skilled in the art can easily conceive of various equivalent modifications or substitutions within the technical scope disclosed in the present invention, and these modifications or substitutions should all be covered within the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be determined by the scope of the claims.

Claims

1. A lead break device for active guided wave field scanning, comprising: The device comprises an upper electrode sheet (1), a device front cover (2), a lower electrode sheet (4), a device shell (7), a mechanical pencil (8), a breaking assembly, a battery assembly and a metal connecting sheet (13), the mechanical pencil (8) conveying a graphite lead core (15) is fixed at a preset installation position of the device shell (7), the device front cover (2) is detachably connected with the device shell (7), the breaking assembly is installed inside the device shell (7), the graphite lead core (15) is connected with a structure to be measured by passing through the breaking assembly and a through hole on the device front cover (2), the upper electrode sheet (1) is welded and fixed outside the device front cover (2), the battery assembly is fixed at the rear end of the device shell (7), the lower side of the battery assembly is connected with the metal shell of the mechanical pencil (8) through the metal connecting sheet (13), and the upper side of the battery assembly is connected with the lower electrode sheet (4). The upper electrode sheet (1) is connected with a positive electrode of an oscilloscope channel, the lower electrode sheet (4) is connected with a negative electrode of the oscilloscope channel, and the upper electrode sheet (1), the device front cover (2), the graphite lead core (15), the mechanical pencil (8), the metal connecting sheet (13), the battery assembly, the lower electrode sheet (4) and the oscilloscope constitute an electric trigger loop for capturing the moment of lead core breaking.

2. A lead break device for active guided wave field scanning according to claim 1, wherein, The device front cover (2) and the device shell (7) are connected in a buckle type.

3. A lead break device for active guided wave field scanning according to claim 1, wherein, The device shell (7) is provided with an inclined surface for fixing the breaking angle at the front end.

4. A lead break device for active guided wave field scanning according to claim 1, wherein, The lead breaking device is made of insulating materials except the upper electrode sheet (1), the device front cover (2), the front end part of the mechanical pencil (8), the metal connecting sheet (13) and the lower electrode sheet (4).

5. A lead break device for active guided wave field scanning according to claim 1, wherein, The breaking assembly comprises a trigger button (3), a first reset spring (9), a lead core breaking mechanism (10), a transmission push rod (11) and a second reset spring (12). The lead core breaking mechanism (10) is provided with a through hole in the center, is fixed on a rotating shaft in the device shell (7) and can rotate around the rotating shaft, and the graphite lead core (15) passes through the through hole and then passes through a through hole at the front end of the device front cover (2); the first reset spring (9) is assembled between the device shell (7) and the lead core breaking mechanism (10) and gives the lead core breaking mechanism (10) a reset thrust; the transmission push rod (11) is installed on the side opposite to the position where the first reset spring (9) is assembled, the transmission push rod (11) is composed of a cylindrical push rod and a cube with an inclined surface, the second reset spring (12) is installed at the front end of the cylindrical push rod of the transmission push rod (11) and gives the transmission push rod (11) a reset thrust; the trigger button (3) is embedded on the device shell (7), the inclined surface of the trigger button (3) is matched with the inclined surface of the cube of the transmission push rod (11); when the trigger button (3) is pressed, the inclined surface of the cube of the transmission push rod (11) is subjected to a horizontal thrust and moves horizontally, gives the lead core breaking mechanism (10) and the first reset spring (9) an opposite thrust and pushes the lead core breaking mechanism (10) to rotate around the rotating shaft.

6. A lead break device for active guided wave field scanning according to claim 5, wherein, The cylindrical push rod is embedded in a horizontal and straight groove in the device shell (7) and moves horizontally along the horizontal and straight groove of the device shell (7).

7. A lead break device for active guided wave field scanning according to claim 5, wherein, The trigger button (3) is embedded on the device shell (7) by a limiting buckle and can only be pressed in the vertical direction.

8. A lead break device for active guided wave field scanning according to claim 1, wherein, The battery assembly includes a battery compartment lower shell (5), a battery compartment upper shell (6), and a button cell (14). The battery compartment lower shell (5) and the battery compartment upper shell (6) are detachably connected to form a battery compartment, which is fixed to the rear end of the device shell (7), and the button cell (14) is placed in the battery compartment. The negative electrode of the button cell (14) is led out from the battery compartment upper shell (6) through the lower electrode sheet (4), which is connected to the negative electrode of the oscilloscope channel during use. The metal connecting sheet (13) passes through the battery compartment lower shell (5) and is connected to the positive electrode of the button cell (14), so that the metal shell of the automatic pencil (8) is connected to the positive electrode of the button cell (14).

9. A method for breaking a lead based on the lead breaking device for active guided wave field scanning according to any one of claims 1-8, characterized in that, The method comprises: Step S1, combining the lead breaking device for active guided wave field scanning; Step S2, feeding the graphite lead core (15) to the preset length through the automatic pencil (8), so that it passes through the center through hole of the breaking assembly and extends to the front end through hole of the device front cover (2) for positioning, and the lead breaking angle is fixed by the front end inclined surface of the device shell (7), and the end of the graphite lead core (15) is connected to the measured structure; Step S3, connecting the upper electrode sheet (1) to the positive electrode of the oscilloscope channel, and connecting the lower electrode sheet (4) to the negative electrode of the oscilloscope channel, relying on the conductivity of the graphite lead core (15), through the metal connecting sheet (13), the metal shell of the automatic pencil (8), the button cell (14), the device front cover (2), and the trigger channel of the oscilloscope to form a closed electric circuit; Step S4, applying a stable torque to the graphite lead core (15) through the breaking assembly to make the lead core break along the preset angle, and the mechanical wave generated by the lead breaking enters the measured structure and is collected by the oscilloscope to obtain the lead breaking action and the lead breaking time; Step S5, feeding the graphite lead core (15) to the preset length through the automatic pencil (8) again, repeating the above steps S2-S4 to complete continuous lead breaking excitation until the batch detection requirement of active guided wave field scanning is met.

10. The method of claim 9, wherein the lead is broken by, When the graphite lead core (15) breaks, the closed electric circuit is disconnected at the moment of lead breaking, generating an electrical signal mutation, which is transmitted to the oscilloscope at the same time, realizing synchronous collection of lead breaking action and lead breaking time.

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