Thickness measurement and bolt stress integrated detection system and method based on electromagnetic ultrasound

Abstract

The invention provides a thickness measurement and bolt stress integrated detection system and method based on electromagnetic ultrasonic, and the system comprises an excitation signal drive circuit which is configured to send an ultrasonic excitation signal to an electromagnetic ultrasonic probe; the electromagnetic ultrasonic probe comprises a transverse wave probe and a longitudinal wave probe; wherein the transverse wave probe is configured to excite an object to be measured to generate transverse ultrasonic waves based on ultrasonic excitation signals and receive echo signals of the transverse ultrasonic waves, and the longitudinal wave probe is configured to excite the object to be measured to generate longitudinal ultrasonic waves based on the ultrasonic excitation signals and receive echo signals of the longitudinal ultrasonic waves; and the echo processing module is configured to determine the thickness of the to-be-detected object based on the echo signal of the transverse ultrasonic wave through central peak detection, and determine the bolt axial stress of the to-be-detected object based on the echo signal of the transverse ultrasonic wave and the echo signal of the longitudinal ultrasonic wave.

Description

Technical Field

[0001] This disclosure relates to the field of nondestructive testing technology, and more specifically, to an integrated testing system and method for thickness measurement and bolt stress based on electromagnetic ultrasound. Background Technology

[0002] Electromagnetic ultrasonic testing is a non-destructive testing method based on the principle of electromagnetic induction, which excites and receives ultrasonic waves through electromagnetic coupling. Compared with traditional piezoelectric ultrasonic technology, electromagnetic ultrasonic technology has significant advantages such as no need for coupling agents, non-contact testing, and adaptability to high-temperature and harsh environments. Electromagnetic ultrasonic testing is mainly achieved through an electromagnetic ultrasonic transducer. Its working principle is as follows: when an alternating current is passed through a high-frequency coil, moving charges are generated on the surface of the object being tested, thereby inducing eddy currents. These moving charges are subjected to Lorentz force under the action of a static magnetic field, thus exciting ultrasonic waves; for ferromagnetic materials, a magnetostrictive effect also exists. The ultrasonic wave reception process of electromagnetic ultrasonic technology is the reverse process described above. Based on the relative positional relationship between the static magnetic field direction and the eddy current plane generated by the high-frequency coil, the electromagnetic ultrasonic transducer can excite different types of ultrasonic waves: when the static magnetic field is perpendicular to the eddy current plane, it mainly excites transverse wave ultrasonic waves; when the static magnetic field is parallel to the eddy current plane, it mainly excites longitudinal wave ultrasonic waves. This characteristic allows for the flexible excitation of transverse or longitudinal wave ultrasonic waves by designing ultrasonic probes with different structures to meet different testing needs.

[0003] Ultrasonic thickness measurement is an important application in industrial inspection, widely used in pipeline wall thickness monitoring, metal sheet quality control, and other fields. Traditional piezoelectric ultrasonic thickness measurement requires the use of a coupling agent, and its measurement accuracy is easily affected by the coupling state. Electromagnetic ultrasonic thickness measurement, on the other hand, has unique advantages because it does not require a coupling agent. Existing ultrasonic thickness measurement methods typically use the peak detection method to determine the echo transit time, i.e., detecting the position of the maximum peak value of the echo signal to determine the echo arrival time. However, due to factors such as transducer bandwidth and material properties, ultrasonic echo signals are usually composed of multiple different echo groups, each containing multiple peak values. The traditional peak method has the following problems: when detecting the first echo group signal, the first peak value detected may be the maximum peak value, and when detecting the second echo group signal, the second peak value detected may be the maximum peak value. Because the reference points for the two detections are inconsistent, systematic errors occur in the transit time calculation, affecting the thickness measurement accuracy.

[0004] High-strength bolts are widely used in wind power, bridges, railways, aerospace, and other fields. Axial stress in bolts is a key parameter affecting the reliability of bolt connections. Excessive axial stress can lead to bolt fatigue failure or stress corrosion cracking; insufficient axial stress can cause vibration relaxation or seal leakage. Traditional torque wrench methods suffer from measurement errors of up to ±40% due to the dispersion of friction coefficients. Ultrasonic testing methods based on the acoustoelastic effect can achieve high-precision measurement of bolt stress. According to acoustoelastic theory, the propagation speed of ultrasonic waves in a material changes with the stress state. There are two main methods for ultrasonic bolt stress measurement: single-wave and dual-wave methods. The single-wave method requires pre-measuring the ultrasonic wave transit time of the bolt in a stress-free state, making it unsuitable for installed bolts already in service. The dual-wave method, by simultaneously measuring the transit times of transverse and longitudinal ultrasonic waves and performing a ratio calculation, can eliminate the influence of bolt length and is suitable for stress measurement of in-service bolts. When using traditional piezoelectric ultrasound to implement the dual-wave method, transverse wave coupling is difficult, and errors caused by coupling dispersion can reach 15%~25%. Electromagnetic ultrasonic technology, because it does not require a coupling agent, can effectively solve the problem of difficult transverse wave coupling.

[0005] Based on the above analysis, the existing electromagnetic ultrasonic testing technology has the following main problems:

[0006] (1) Single function: Existing electromagnetic ultrasonic testing equipment is usually designed for a single application scenario. Thickness measuring equipment and bolt stress testing equipment are independent of each other, resulting in low equipment utilization. Users need to purchase multiple sets of equipment to meet different testing needs.

[0007] (2) Waste of hardware resources: Although thickness measurement and bolt stress detection have different application scenarios, the core signal excitation circuit and signal acquisition circuit are highly similar. Designing separate independent systems will result in the duplication and waste of hardware resources.

[0008] (3) Insufficient accuracy of transit time detection: When the traditional peak method detects multiple echoes, the uncertainty of the amplitude of each peak in the echo signal may lead to inconsistent detection reference points and generate systematic errors. Summary of the Invention

[0009] In view of this, this disclosure provides an integrated detection system and method for thickness measurement and bolt stress based on electromagnetic ultrasound.

[0010] One aspect of this disclosure provides an integrated thickness measurement and bolt stress detection system based on electromagnetic ultrasound, comprising: an excitation signal driving circuit electrically connected to an electromagnetic ultrasound probe and configured to send an ultrasonic excitation signal to the electromagnetic ultrasound probe; an electromagnetic ultrasound probe electrically connected to the excitation signal driving circuit and an echo processing module, including a shear wave probe and a longitudinal wave probe; wherein the shear wave probe is configured to excite the object under test to generate shear wave ultrasonic waves based on the ultrasonic excitation signal and receive the echo signal of the shear wave ultrasonic waves, and the longitudinal wave probe is configured to excite the object under test to generate longitudinal wave ultrasonic waves based on the ultrasonic excitation signal and receive the echo signal of the longitudinal wave ultrasonic waves; and an echo processing module electrically connected to the electromagnetic ultrasound probe, configured to determine the thickness of the object under test based on the echo signal of the shear wave ultrasonic waves by detecting the center peak value, and to determine the axial stress of the bolts of the object under test based on the echo signals of the shear wave ultrasonic waves and the longitudinal wave ultrasonic waves.

[0011] According to embodiments of this disclosure, the echo signals of transverse wave ultrasound and longitudinal wave ultrasound include multiple echo group signals. The echo processing module is configured to: determine the maximum peak value of the echo group signals; determine multiple first peak values ​​of the echo group signals based on the maximum peak value; determine the first peak value that satisfies a first preset condition among the multiple first peak values ​​as the center peak value; determine the first transit time and the second transit time of the echo signal of the transverse wave ultrasound and the third transit time of the echo signal of the longitudinal wave ultrasound based on the multiple center peak values ​​of the multiple echo group signals; determine the thickness of the object under test based on the first transit time and the propagation speed of the transverse wave ultrasound in the object under test; and determine the bolt axial stress of the object under test based on the second transit time, the third transit time, a preset calibration slope, and a preset calibration intercept.

[0012] According to an embodiment of this disclosure, the echo processing module is configured to: determine a first time window based on a preset time length and a first time node corresponding to the maximum peak value; determine multiple first peak values ​​of the echo group signal falling within the first time window; arrange the multiple first peak values ​​in chronological order, and determine the first peak value located in the middle of the time sequence as the center peak value.

[0013] According to embodiments of this disclosure, the echo signals of the transverse wave ultrasound and the longitudinal wave ultrasound include multiple echo group signals. The echo processing module is configured to: perform autocorrelation processing on the multiple echo group signals of the transverse wave ultrasound echo signal to obtain the second transit time of the transverse wave ultrasound echo signal; perform autocorrelation processing on the multiple echo group signals of the longitudinal wave ultrasound echo signal to obtain the third transit time of the longitudinal wave ultrasound echo signal; and determine the bolt axial stress of the object under test based on the second transit time, the third transit time, a preset calibration slope, and a preset calibration intercept.

[0014] According to an embodiment of this disclosure, a transverse wave probe includes: a first permanent magnet and a first magnetic conductive sheet. The first permanent magnet is a cylindrical structure and is disposed at the top of the transverse wave probe. The first magnetic conductive sheet is disposed below the first permanent magnet. The first permanent magnet and the first magnetic conductive sheet are configured to generate a first magnetic field whose magnetic field direction is perpendicular to the surface of the object under test. A first helical coil is disposed below the first magnetic conductive sheet and is configured to generate an alternating magnetic field based on an alternating current to generate moving charges inside the object under test. The object under test is subjected to the Lorentz force of the first magnetic field based on the moving charges to excite transverse wave ultrasonic waves whose particle vibration direction is perpendicular to the propagation direction. The first helical coil receives the echo signal of the transverse wave ultrasonic waves based on electromagnetic induction.

[0015] According to an embodiment of this disclosure, the longitudinal wave probe includes: a second permanent magnet and a second magnetic conductive sheet. The second permanent magnet is horseshoe-shaped, and the second magnetic conductive sheet is respectively disposed on the two magnetic end faces of the second permanent magnet. The second permanent magnet and the second magnetic conductive sheet are configured to generate a second magnetic field whose magnetic field direction is parallel to the surface of the object under test. A second helical coil is disposed below the second magnetic conductive sheet and is configured to generate an alternating magnetic field based on alternating current to generate moving charges inside the object under test. The object under test is subjected to the Lorentz force of the second magnetic field based on the moving charges to excite longitudinal wave ultrasonic waves whose particle vibration direction is parallel to the propagation direction. The second helical coil receives the echo signal of the longitudinal wave ultrasonic waves based on electromagnetic induction.

[0016] According to embodiments of this disclosure, the electromagnetic ultrasonic thickness measurement and bolt stress integrated detection system further includes: a control module electrically connected to the excitation signal driving circuit and the echo processing module, configured to generate an ultrasonic excitation signal based on preset parameters, and store the thickness and bolt axial stress determined by the echo processing module.

[0017] According to embodiments of this disclosure, the electromagnetic ultrasonic thickness measurement and bolt stress integrated detection system further includes: a display module electrically connected to the control module, configured to visualize the thickness and bolt axial stress through the control module.

[0018] According to embodiments of this disclosure, the thickness of the first magnetic sheet is adjusted based on the magnetic field strength of the first magnetic field, and the thickness of the second magnetic sheet is adjusted based on the magnetic field strength of the second magnetic field.

[0019] Another aspect of this disclosure provides a detection method applied to the aforementioned electromagnetic ultrasonic-based thickness measurement and bolt stress integrated detection system, comprising: exciting the object under test to generate transverse wave ultrasonic waves and receiving the echo signal of the transverse wave ultrasonic waves; exciting the object under test to generate longitudinal wave ultrasonic waves and receiving the echo signal of the longitudinal wave ultrasonic waves; determining the thickness of the object under test based on the echo signal of the transverse wave ultrasonic waves by detecting the center peak value, and determining the bolt axial stress of the object under test based on the echo signals of the transverse wave ultrasonic waves and the longitudinal wave ultrasonic waves.

[0020] According to embodiments of this disclosure, a shear wave probe is used to excite the object under test to generate shear wave ultrasonic waves, and the echo signal of the shear wave ultrasonic waves is received. A longitudinal wave probe is used to excite the object under test to generate longitudinal wave ultrasonic waves, and the echo signal of the longitudinal wave ultrasonic waves is received. Thus, the thickness of the object under test can be determined based on the echo signal of the shear wave ultrasonic waves by detecting the center peak value, and the axial stress of the bolts on the object under test can be determined based on the echo signals of the shear wave ultrasonic waves and the echo signals of the longitudinal wave ultrasonic waves. This solves the problems of low utilization rate of detection equipment and waste of redundant hardware resources, and improves the detection accuracy of thickness and bolt stress. Attached Figure Description

[0021] The above and other objects, features and advantages of this disclosure will become clearer from the following description of embodiments with reference to the accompanying drawings, in which:

[0022] Figure 1 A schematic diagram of an integrated thickness measurement and bolt stress detection system based on electromagnetic ultrasound according to an embodiment of the present disclosure is shown.

[0023] Figure 2 A schematic diagram of an integrated thickness measurement and bolt stress detection system based on electromagnetic ultrasound according to another embodiment of the present disclosure is shown.

[0024] Figure 3 A comparative schematic diagram of the conventional peak method and the center-peak method according to embodiments of the present disclosure is shown;

[0025] Figure 4 A flowchart of an integrated method for thickness measurement and bolt stress detection based on electromagnetic ultrasound according to an embodiment of the present disclosure is shown.

[0026] Figure 5 A schematic diagram of a thickness measurement and bolt stress integrated detection system based on electromagnetic ultrasound according to an embodiment of the present disclosure is shown.

[0027] Figure 6 A schematic diagram of bolt axial stress detection is shown in an integrated electromagnetic ultrasonic thickness measurement and bolt stress detection system according to an embodiment of the present disclosure. Detailed Implementation

[0028] The embodiments of the present disclosure will now be described with reference to the accompanying drawings. However, it should be understood that these descriptions are exemplary only and are not intended to limit the scope of the disclosure. In the following detailed description, numerous specific details are set forth to provide a thorough understanding of the embodiments of the present disclosure for ease of explanation. However, it will be apparent that one or more embodiments may be practiced without these specific details. Furthermore, descriptions of well-known structures and techniques are omitted in the following description to avoid unnecessarily obscuring the concepts of the present disclosure.

[0029] The terminology used herein is for the purpose of describing particular embodiments only and is not intended to limit this disclosure. The terms “comprising,” “including,” etc., as used herein indicate the presence of the stated features, steps, operations, and / or components, but do not exclude the presence or addition of one or more other features, steps, operations, or components.

[0030] All terms used herein (including technical and scientific terms) have the meanings commonly understood by those skilled in the art, unless otherwise defined. It should be noted that the terms used herein are to be interpreted in a manner consistent with the context of this specification, and not in an idealized or overly rigid way.

[0031] When using expressions such as "at least one of A, B and C", they should generally be interpreted in accordance with the meaning that is commonly understood by those skilled in the art (e.g., "a system having at least one of A, B and C" should include, but is not limited to, a system having A alone, a system having B alone, a system having C alone, a system having A and B, a system having A and C, a system having B and C, and / or a system having A, B and C, etc.).

[0032] Figure 1 A schematic diagram of an integrated electromagnetic ultrasonic thickness measurement and bolt stress detection system according to an embodiment of the present disclosure is shown.

[0033] like Figure 1 As shown, the integrated thickness measurement and bolt stress detection system based on electromagnetic ultrasound includes an excitation signal driving circuit 101, an electromagnetic ultrasonic probe 102, and an echo processing module 103. The excitation signal driving circuit 101 is electrically connected to the electromagnetic ultrasonic probe 102 and configured to send an ultrasonic excitation signal to the electromagnetic ultrasonic probe 102. The electromagnetic ultrasonic probe 102 is electrically connected to the excitation signal driving circuit 101 and the echo processing module 103, and includes a shear wave probe 1021 and a longitudinal wave probe 1022. The shear wave probe 1021 is configured to excite the object under test to generate shear wave ultrasonic waves based on the ultrasonic excitation signal and receive the echo signal of the shear wave ultrasonic waves. The longitudinal wave probe 1022 is configured to excite the object under test to generate longitudinal wave ultrasonic waves based on the ultrasonic excitation signal and receive the echo signal of the longitudinal wave ultrasonic waves. That is, the shear wave probe 1021 and the longitudinal wave probe 1022 adopt a single-transmitter, single-receiver, self-transmitting and self-receiving working mode. The echo processing module 103 is electrically connected to the electromagnetic ultrasonic probe 102 and is configured to determine the thickness of the object under test based on the echo signal of the transverse wave ultrasonic wave by detecting the center peak value, and to determine the axial stress of the bolts of the object under test based on the echo signals of the transverse wave ultrasonic wave and the echo signals of the longitudinal wave ultrasonic wave.

[0034] The electromagnetic ultrasonic probe 102 is the core component of electromagnetic ultrasonic testing. It is a sensor that can generate and receive ultrasonic waves within the material being tested without contact or a coupling agent. The electromagnetic ultrasonic probe 102 functions to both emit and receive ultrasonic waves. Its advantage lies in its non-contact operation, eliminating the need for a coupling agent. Traditional piezoelectric ultrasonic probes require a coupling agent (oil, water, gel) to expel air and transmit sound waves. However, when testing high-temperature objects, the coupling agent may evaporate or affect the measurement; it cannot be used when testing high-speed moving objects. The electromagnetic ultrasonic probe 102, however, requires no coupling agent and can operate using only air. Therefore, when testing objects with coatings, grease, or slight oxidation, complex surface cleaning is unnecessary, and coupling agent contamination of the product is avoided. By designing different coil and magnetic field configurations, the electromagnetic ultrasonic probe 102 can flexibly excite various forms of ultrasonic waves, including but not limited to transverse waves, longitudinal waves, and Lamb waves.

[0035] The excitation signal drive circuit 101 is a dedicated circuit that provides high-energy, high-frequency, and high-voltage pulse signals to the electromagnetic ultrasonic probe 102. The excitation signal drive circuit 101 can consist of a pulse generation module, a power amplification module, an impedance matching module, and a high-voltage power supply module, used to transform weak control signals into strong drive signals that enable the probe to generate ultrasound. The pulse generation module generates a high-frequency, narrow-pulse-width, fast-edge basic pulse waveform to control the transmission frequency, pulse quantity, and repetition period, providing command signals to the subsequent power amplification module. The power amplification module amplifies the weak signal from the pulse generation module into high-voltage, high-current, and high-power drive pulses to provide sufficient energy for the electromagnetic ultrasonic probe 102 to generate ultrasound. The power amplification module also ensures steep edges on the pulse waveform to improve ultrasound conversion efficiency. The impedance matching module adjusts the circuit impedance of the excitation signal drive circuit 101 to match the impedance of the electromagnetic ultrasonic probe 102, reducing pulse signal energy reflection and improving ultrasound generation efficiency. The high-voltage power supply module provides a stable high-voltage DC power supply. The echo processing module 103 processes the weak ultrasonic echo signals received by the electromagnetic ultrasonic probe 102, analyzing the relevant parameter information of the object under test from the weak ultrasonic echo signals. The echo processing module 103 can perform signal amplification, filtering and noise reduction, and signal shaping on the echo signals of transverse and longitudinal ultrasonic waves to obtain cleaner and more stable echo signals. Simultaneously, the echo processing module 103 can perform data calculation and analysis on the echo signals based on specific algorithms to obtain the thickness of the object under test and the axial stress of the bolts within the object.

[0036] In the embodiments of this disclosure, the shear wave probe and the longitudinal wave probe can be independently installed in the electromagnetic ultrasonic thickness measurement and bolt stress integrated detection system, each corresponding to an independent signal access channel. The shear wave probe and the longitudinal wave probe can also share the same signal interface of the detection system, and the access and operation switching of different probes under the same interface can be realized through interface switching or signal recognition.

[0037] Through the embodiments of this disclosure, a shear wave probe is used to excite the object under test to generate shear wave ultrasonic waves, and the echo signal of the shear wave ultrasonic waves is received. A longitudinal wave probe is used to excite the object under test to generate longitudinal wave ultrasonic waves, and the echo signal of the longitudinal wave ultrasonic waves is received. Thus, the thickness of the object under test can be determined based on the echo signal of the shear wave ultrasonic waves by detecting the center peak value, and the axial stress of the bolts on the object under test can be determined based on the echo signals of the shear wave ultrasonic waves and the echo signals of the longitudinal wave ultrasonic waves. This solves the problems of low utilization rate of detection equipment and waste of redundant hardware resources, and improves the detection accuracy of thickness and bolt stress.

[0038] According to embodiments of this disclosure, the electromagnetic ultrasonic thickness measurement and bolt stress integrated detection system further includes: a control module electrically connected to the excitation signal driving circuit and the echo processing module, configured to generate an ultrasonic excitation signal based on preset parameters, and store the thickness and bolt axial stress determined by the echo processing module.

[0039] In the embodiments of this disclosure, the control module can be used to configure parameters, generate excitation signals, control timing, and store and manage test results during the electromagnetic ultrasonic testing process. Preset parameters include, but are not limited to, excitation frequency, excitation amplitude, pulse width, and transmission timing. The control module can generate and output ultrasonic excitation signals according to the preset parameters. These ultrasonic excitation signals can be output independently or alternately depending on the material properties, structural form, and target of the object being tested, to achieve adaptive testing for different types of defects, thicknesses, and stress states. During the testing process, the control module can precisely regulate the ultrasonic excitation signals according to the preset parameters, enabling the excitation signal driving circuit to drive the electromagnetic ultrasonic transducer to generate corresponding ultrasonic vibrations in a predetermined manner, thereby exciting ultrasonic waves with specific propagation modes within the workpiece being tested. Simultaneously, the control module also interacts with the echo processing module, receiving test results determined by the echo processing module, including but not limited to the thickness information of the object being tested, bolt axial stress values, and relevant ultrasonic echo characteristic parameters. These test results are stored in real time for subsequent querying, display, or further analysis and processing. The control module can be implemented using a microprocessor, programmable logic device, or dedicated control chip. It features flexible parameter configuration, high control precision, and fast response speed, ensuring the stability of the electromagnetic ultrasonic testing process and the reliability of the test data.

[0040] In the embodiments of this disclosure, the control module can be implemented based on host computer software, and the control module and the echo processing module can share a software processing system. For example, the control module receives the thickness and bolt axial stress information determined by the echo processing module via a UART (Universal Asynchronous Receiver / Transmitter). The host computer software can be configured to provide a parameter configuration interface, through which the user inputs or selects preset parameters related to the ultrasonic excitation signal. The host computer software generates an ultrasonic excitation signal based on the preset parameters, wherein the ultrasonic excitation signal can be digital waveform data, such as sine wave data, square wave data, pulse data, etc. The host computer software transmits the generated ultrasonic excitation signal data to the excitation signal driving circuit via UART. In some embodiments, the host computer software can also dynamically adjust the preset parameters based on the detection results determined by the echo processing module in real time, thereby updating the waveform characteristics of the ultrasonic excitation signal in real time and realizing adaptive excitation control.

[0041] According to embodiments of this disclosure, the electromagnetic ultrasonic thickness measurement and bolt stress integrated detection system further includes: a display module electrically connected to the control module, configured to visualize the thickness and bolt axial stress through the control module.

[0042] In embodiments of this disclosure, the display module can be implemented based on a 4042BS LED (Light Emitting Diode) digital tube.

[0043] Figure 2 A schematic diagram of an integrated thickness measurement and bolt stress detection system based on electromagnetic ultrasound according to another embodiment of the present disclosure is shown.

[0044] like Figure 2 As shown, the integrated thickness measurement and bolt stress detection system based on electromagnetic ultrasound includes an excitation signal driving circuit 101, an electromagnetic ultrasonic probe 102, an echo processing module 103, a control module 104, and a display module 105. The control module 104 is electrically connected to the excitation signal driving circuit 101 and is used to generate an ultrasonic excitation signal and transmit it to the excitation signal driving circuit 101. Simultaneously, the control module 104 is electrically connected to the echo processing module 103 and is used to receive and store the detection results determined by the echo processing module 103. The display module 105 is electrically connected to the control module 104 and is used to visualize the thickness and bolt axial stress through the control module 104. The connection relationship and function of the excitation signal driving circuit 101, the electromagnetic ultrasonic probe 102, and the echo processing module 103 have been described above and will not be repeated here.

[0045] According to an embodiment of this disclosure, a transverse wave probe includes: a first permanent magnet and a first magnetic conductive sheet. The first permanent magnet is a cylindrical structure and is disposed at the top of the transverse wave probe. The first magnetic conductive sheet is disposed below the first permanent magnet. The first permanent magnet and the first magnetic conductive sheet are configured to generate a first magnetic field whose magnetic field direction is perpendicular to the surface of the object under test. A first helical coil is disposed below the first magnetic conductive sheet and is configured to generate an alternating magnetic field based on an alternating current to generate moving charges inside the object under test. The object under test is subjected to the Lorentz force of the first magnetic field based on the moving charges to excite transverse wave ultrasonic waves whose particle vibration direction is perpendicular to the propagation direction. The first helical coil receives the echo signal of the transverse wave ultrasonic waves based on electromagnetic induction.

[0046] In the embodiments of this disclosure, the first magnetic field is a constant static magnetic field, the first permanent magnet is used to generate the magnetic field, and the first magnetic conductive sheet plays a role in focusing and guiding the magnetic field, constraining and guiding the magnetic field lines to the surface of the object under test below the transverse wave probe, ensuring that the magnetic field lines penetrate the surface perpendicularly into the interior of the object under test. When a high-frequency alternating current is applied to the coil, according to the law of electromagnetic induction, alternating eddy currents of the same frequency will be induced in the skin layer of the surface of the object under test, that is, moving charges will be generated. The moving charges will be subjected to Lorentz force in the first magnetic field. Since the magnetic field direction of the first magnetic field is perpendicular to the surface of the object under test, the direction of the generated Lorentz force is parallel to the surface of the object under test. This periodic force drags the particles of the object under test to perform horizontal shear vibration, thereby exciting transverse wave ultrasound. The first helical coil receives the echo signal of the transverse ultrasonic wave based on electromagnetic induction, which is achieved by reversing the above transmission process. When the reflected transverse ultrasonic wave reaches the surface of the object under test, the transverse ultrasonic wave will drive the particles on the surface of the object under test to vibrate horizontally in a tangential direction. These vibrating particles move in the first magnetic field, cutting magnetic field lines. According to the principle of motional electromotive force, an induced current will be generated inside the object under test. The induced current will generate an alternating magnetic field. The alternating magnetic field passes through the first helical coil above. According to Faraday's law of electromagnetic induction, a voltage signal is induced at both ends of the coil, which is then captured by the detection circuit.

[0047] In embodiments of this disclosure, the first permanent magnet of the transverse wave probe may also be square.

[0048] According to an embodiment of this disclosure, the longitudinal wave probe includes: a second permanent magnet and a second magnetic conductive sheet. The second permanent magnet is horseshoe-shaped, and the second magnetic conductive sheet is respectively disposed on the two magnetic end faces of the second permanent magnet. The second permanent magnet and the second magnetic conductive sheet are configured to generate a second magnetic field whose magnetic field direction is parallel to the surface of the object under test. A second helical coil is disposed below the second magnetic conductive sheet and is configured to generate an alternating magnetic field based on alternating current to generate moving charges inside the object under test. The object under test is subjected to the Lorentz force of the second magnetic field based on the moving charges to excite longitudinal wave ultrasonic waves whose particle vibration direction is parallel to the propagation direction. The second helical coil receives the echo signal of the longitudinal wave ultrasonic waves based on electromagnetic induction.

[0049] The working principle of the longitudinal wave probe is similar to that of the transverse wave probe. The difference is that the direction of the magnetic field of the second magnetic field generated in the longitudinal wave probe is parallel to the surface of the object to be measured, which causes the vibration direction of the particles of the object to be measured to be consistent with the propagation direction of the ultrasonic wave. This will not be elaborated here.

[0050] In the embodiments of this disclosure, the second permanent magnet of the longitudinal wave probe may also adopt a dual permanent magnet opposed structure or a Heilbeck array structure. The thickness of the first and second magnetic conductive sheets may be 3 mm. The materials of the first and second magnetic conductive sheets include, but are not limited to, silicon steel sheets, permalloy, ferrite, or other soft magnetic materials. The first and second helical coils may also adopt other coil structures, such as butterfly coils, racetrack-shaped coils, etc.

[0051] According to embodiments of this disclosure, the thickness of the first magnetic sheet is adjusted based on the magnetic field strength of the first magnetic field, and the thickness of the second magnetic sheet is adjusted based on the magnetic field strength of the second magnetic field.

[0052] The thickness of the magnetic conductive sheet is adjusted according to the magnetic field strength to achieve a balance between avoiding magnetic saturation and optimizing the spatial distribution of the magnetic field. When the magnetic field strength is high, the thickness of the magnetic conductive sheet needs to be increased to improve the magnetic flux carrying capacity, prevent magnetic saturation, and ensure effective magnetic field focusing. When the magnetic field strength is low, the thickness of the magnetic conductive sheet needs to be decreased to reduce magnetic reluctance, enhance the local magnetic field focusing effect, and improve the electromagnetic ultrasonic excitation efficiency. The thickness of the first and second magnetic conductive sheets can be adjusted within the range of 1 mm to 5 mm.

[0053] According to embodiments of this disclosure, the echo signals of transverse wave ultrasound and longitudinal wave ultrasound include multiple echo group signals. The echo processing module is configured to: determine the maximum peak value of the echo group signals; determine multiple first peak values ​​of the echo group signals based on the maximum peak value; determine the first peak value that satisfies a first preset condition among the multiple first peak values ​​as the center peak value; determine the first transit time and the second transit time of the echo signal of the transverse wave ultrasound and the third transit time of the echo signal of the longitudinal wave ultrasound based on the multiple center peak values ​​of the multiple echo group signals; determine the thickness of the object under test based on the first transit time and the propagation speed of the transverse wave ultrasound in the object under test; and determine the bolt axial stress of the object under test based on the second transit time, the third transit time, a preset calibration slope, and a preset calibration intercept.

[0054] An echo group signal is a superposition of multiple echo signals with fixed time intervals, amplitude attenuation patterns, or phase correlations formed after the same transmitted signal is reflected by different paths, interfaces, or multiple targets. It is different from a single isolated echo. Echo group signals usually appear as wave packets containing multiple peaks, and the amplitude relationships of the peaks in different echo group signals may be different.

[0055] Figure 3 A comparative schematic diagram of the conventional peak method and the center-peak method according to embodiments of the present disclosure is shown.

[0056] like Figure 3 As shown, the echo signal of ultrasound consists of two echo groups, each containing three signal peaks. In the first echo group, the second peak is the maximum value of the peaks, and in the second echo group, the first peak is the maximum value of the peaks. If the traditional peak method is used, the transit time is the time difference between the second peak of the first echo group and the first peak of the second echo group. Since the reference points for the two measurements are not consistent, this leads to systematic errors in the transit time calculation, affecting measurement accuracy. Using the center-peak method, the transit time can be determined to be the time difference between the second peak of the first echo group and the second peak of the second echo group, ensuring that the reference points for the two measurements are consistent and guaranteeing measurement accuracy.

[0057] According to an embodiment of this disclosure, the echo processing module is configured to: determine a first time window based on a preset time length and a first time node corresponding to the maximum peak value; determine multiple first peak values ​​of the echo group signal falling within the first time window; arrange the multiple first peak values ​​in chronological order, and determine the first peak value located in the middle of the time sequence as the center peak value.

[0058] For example, if the echo group signal has a maximum peak at the 5-second mark, and the preset time length is 2 seconds, then the first time window is from 3 to 6 seconds. If the echo group signal has a maximum peak at the 6-second mark, and the preset time length is 1 second, then the first time window is from 5.5 to 6.5 seconds. When the first time window is from 3 to 6 seconds, all the first peaks of the echo group signal within this time period are identified and arranged in chronological order. When the number of first peaks is 5, the first peak with a timing of 3 within the first time window is identified as the center peak; when the number of first peaks is 8, the first peak with a timing of 4 within the first time window is identified as the center peak.

[0059] The thickness d can be determined by the following formula:

[0060] (1)

[0061] in, This represents the propagation speed of transverse ultrasonic waves within the object being measured. This is the first crossing time.

[0062] According to embodiments of this disclosure, the echo signals of the transverse wave ultrasound and the longitudinal wave ultrasound include multiple echo group signals. The echo processing module is configured to: perform autocorrelation processing on the multiple echo group signals of the transverse wave ultrasound echo signal to obtain the second transit time of the transverse wave ultrasound echo signal; perform autocorrelation processing on the multiple echo group signals of the longitudinal wave ultrasound echo signal to obtain the third transit time of the longitudinal wave ultrasound echo signal; and determine the bolt axial stress of the object under test based on the second transit time, the third transit time, a preset calibration slope, and a preset calibration intercept.

[0063] The autocorrelation method calculates the autocorrelation function among multiple echo groups to find the time shift with the highest correlation; this time shift is the transit time. Therefore, by performing autocorrelation processing on multiple echo groups of a shear wave ultrasonic wave, the second transit time of the shear wave ultrasonic wave echo signal can be obtained. Autocorrelation processing is performed on multiple echo group signals of the longitudinal wave ultrasonic wave echo signal to obtain the third transit time of the longitudinal wave ultrasonic wave echo signal. Compared to direct peak detection, the autocorrelation method utilizes the overall waveform information of the echo signal, resulting in higher noise immunity and time resolution accuracy. Bolt axial stress It can be obtained based on the two-wave method formula, which is as follows:

[0064] (2)

[0065] in, To calibrate the slope, To calibrate the intercept, the calibration slope and calibration intercept can be obtained through calibration tests on bolts of the same type.

[0066] Figure 4 A flowchart of an integrated method for thickness measurement and bolt stress detection based on electromagnetic ultrasound according to an embodiment of the present disclosure is shown.

[0067] like Figure 4 As shown, the electromagnetic ultrasonic thickness measurement and bolt stress integrated detection method can be applied to the above-mentioned electromagnetic ultrasonic thickness measurement and bolt stress integrated detection system, including operations S410~S430.

[0068] In operation S410, the object under test is excited to generate transverse wave ultrasonic waves, and the echo signal of the transverse wave ultrasonic waves is received.

[0069] In operation S420, the object under test is excited to generate longitudinal wave ultrasonic waves, and the echo signal of the longitudinal wave ultrasonic waves is received.

[0070] In operation S430, the thickness of the object under test is determined by center peak detection based on the echo signal of the transverse wave ultrasonic wave, and the axial stress of the bolts of the object under test is determined based on the echo signals of the transverse wave ultrasonic wave and the echo signals of the longitudinal wave ultrasonic wave.

[0071] The specific method for determining the thickness of the object under test and the axial stress of the bolts of the object under test by center peak detection is as described above and will not be repeated here.

[0072] Figure 5 A schematic diagram of a thickness measurement system based on electromagnetic ultrasound and integrated bolt stress detection according to an embodiment of the present disclosure is shown.

[0073] like Figure 5 As shown, the excitation signal generation unit of the main control circuit generates a pulse width modulation wave and outputs it to the excitation signal driving circuit. The excitation signal driving circuit generates a pulse signal and outputs it to the shear wave probe. The shear wave probe excites shear wave ultrasound in the object under test and receives the echo signal of the shear wave ultrasound. The echo preprocessing circuit is used to preprocess the original echo signal corresponding to the echo signal of the shear wave ultrasound based on the gain adjustment voltage signal to obtain the signal to be sampled. The gain adjustment voltage signal is generated by the gain control unit of the main control circuit. The signal acquisition unit receives the signal to be sampled and outputs the sampling result to the data settlement unit. The data settlement unit generates the calculation result and outputs it to the digital tube.

[0074] Figure 6 A schematic diagram of bolt axial stress detection is shown in an integrated electromagnetic ultrasonic thickness measurement and bolt stress detection system according to an embodiment of the present disclosure.

[0075] like Figure 6 As shown, the excitation signal generation unit of the main control circuit generates a pulse width modulation wave and outputs it to the excitation signal driving circuit. The excitation signal driving circuit generates a pulse signal and outputs it to the shear wave probe and longitudinal wave probe in the electromagnetic ultrasonic probe. The shear wave probe and longitudinal wave probe respectively excite shear wave ultrasonic waves and longitudinal wave ultrasonic waves, which act on the bolt. At the same time, the shear wave probe and longitudinal wave probe respectively receive the echo signals of the shear wave ultrasonic waves and the longitudinal wave ultrasonic waves. The echo preprocessing circuit is used to preprocess the original echo signals corresponding to the echo signals of the shear wave ultrasonic waves and the longitudinal wave ultrasonic waves based on the gain adjustment voltage signal to obtain the signal to be sampled. The gain adjustment voltage signal is generated by the gain control unit of the main control circuit. The signal acquisition unit receives the signal to be sampled and outputs the sampling result to the host computer. The host computer analyzes the sampling result based on calibration detection to obtain the axial stress result of the bolt.

[0076] Those skilled in the art will understand that the features described in the various embodiments of this disclosure can be combined and / or combined in various ways, even if such combinations or combinations are not explicitly described in this disclosure. In particular, the features described in the various embodiments of this disclosure can be combined and / or combined in various ways without departing from the spirit and teachings of this disclosure. All such combinations and / or combinations fall within the scope of this disclosure.

[0077] The embodiments of this disclosure have been described above. However, these embodiments are for illustrative purposes only and are not intended to limit the scope of this disclosure. Although various embodiments have been described above, this does not mean that the measures in the various embodiments cannot be used advantageously in combination. Various substitutions and modifications can be made by those skilled in the art without departing from the scope of this disclosure, and all such substitutions and modifications should fall within the scope of this disclosure.

Claims

1. A thickness measurement and bolt stress integrated detection system based on electromagnetic ultrasound, characterized in that, include: An excitation signal driving circuit is electrically connected to an electromagnetic ultrasonic probe and configured to send an ultrasonic excitation signal to the electromagnetic ultrasonic probe. An electromagnetic ultrasonic probe, electrically connected to the excitation signal driving circuit and the echo processing module, includes a transverse wave probe and a longitudinal wave probe; The transverse wave probe is configured to excite the object under test to generate transverse wave ultrasonic waves based on the ultrasonic excitation signal and receive the echo signal of the transverse wave ultrasonic waves. The longitudinal wave probe is configured to excite the object under test to generate longitudinal wave ultrasonic waves based on the ultrasonic excitation signal and receive the echo signal of the longitudinal wave ultrasonic waves. The echo processing module is electrically connected to the electromagnetic ultrasonic probe and is configured to determine the thickness of the object under test based on the echo signal of the transverse wave ultrasonic wave by detecting the center peak value, and to determine the bolt axial stress of the object under test based on the echo signals of the transverse wave ultrasonic wave and the longitudinal wave ultrasonic wave.

2. The integrated thickness measurement and bolt stress detection system based on electromagnetic ultrasound according to claim 1, characterized in that, The echo signals of the transverse wave ultrasound and the longitudinal wave ultrasound include multiple echo group signals, and the echo processing module is configured as follows: Determine the maximum peak value of the echo group signal; Based on the maximum peak value, a plurality of first peak values ​​of the echo group signal are determined; Among the plurality of first peak values, the first peak value that satisfies the first preset condition is determined as the center peak value; Based on the multiple center peaks of the multiple echo group signals, the first transit time and the second transit time of the echo signal of the transverse wave ultrasound, and the third transit time of the echo signal of the longitudinal wave ultrasound are determined. The thickness of the object under test is determined based on the first transit time and the propagation speed of the transverse wave ultrasonic wave in the object under test. The axial stress of the bolts on the object under test is determined based on the second transit time, the third transit time, the preset calibration slope, and the preset calibration intercept.

3. The integrated thickness measurement and bolt stress detection system based on electromagnetic ultrasound according to claim 2, characterized in that, The echo processing module is configured as follows: The first time window is determined based on the preset time length and the first time node corresponding to the maximum peak value; Determine multiple first peaks of the echo group signal that fall within the first time window; Arrange the multiple first peaks in chronological order and determine the first peak located in the middle of the time sequence as the center peak.

4. The integrated thickness measurement and bolt stress detection system based on electromagnetic ultrasound according to claim 1, characterized in that, The echo signals of the transverse wave ultrasound and the longitudinal wave ultrasound include multiple echo group signals, and the echo processing module is configured as follows: Autocorrelation processing is performed on multiple echo group signals of the echo signal of the shear wave ultrasound to obtain the second transit time of the echo signal of the shear wave ultrasound. Autocorrelation processing is performed on multiple echo group signals of the longitudinal wave ultrasonic wave echo signal to obtain the third transit time of the longitudinal wave ultrasonic wave echo signal. The axial stress of the bolts on the object under test is determined based on the second transit time, the third transit time, the preset calibration slope, and the preset calibration intercept.

5. The integrated thickness measurement and bolt stress detection system based on electromagnetic ultrasound according to claim 1, characterized in that, The shear wave probe includes: The first permanent magnet and the first magnetic conductive sheet are configured to generate a first magnetic field whose magnetic field direction is perpendicular to the surface of the object to be measured. The first permanent magnet is cylindrical and is disposed at the top of the transverse wave probe. The first magnetic conductive sheet is disposed below the first permanent magnet. A first helical coil is disposed below the first magnetic sheet and configured to generate an alternating magnetic field based on alternating current in order to generate moving charges inside the object under test; The object under test is subjected to the Lorentz force of the first magnetic field based on the moving charge, so as to excite transverse ultrasonic waves with the particle vibration direction perpendicular to the propagation direction. The first helical coil receives the echo signal of the transverse ultrasonic waves based on electromagnetic induction.

6. The integrated thickness measurement and bolt stress detection system based on electromagnetic ultrasound according to claim 1, characterized in that, The longitudinal wave probe includes: The second permanent magnet is horseshoe-shaped, and the second magnetic sheet is respectively disposed on the two magnetic end faces of the second permanent magnet. The second permanent magnet and the second magnetic sheet are configured to generate a second magnetic field whose magnetic field direction is parallel to the surface of the object to be tested. The second helical coil is disposed below the second magnetic sheet and is configured to generate an alternating magnetic field based on alternating current in order to generate moving charges inside the object under test; The object under test is subjected to the Lorentz force of the second magnetic field based on the moving charge, which excites longitudinal ultrasonic waves whose particle vibration direction is parallel to the propagation direction. The second helical coil receives the echo signal of the longitudinal ultrasonic waves based on electromagnetic induction.

7. The integrated thickness measurement and bolt stress detection system based on electromagnetic ultrasound according to claim 1, characterized in that, The integrated thickness measurement and bolt stress detection system based on electromagnetic ultrasound also includes: The control module is electrically connected to the excitation signal driving circuit and the echo processing module, and is configured to generate an ultrasonic excitation signal based on preset parameters, and store the thickness and bolt axial stress determined by the echo processing module.

8. The integrated thickness measurement and bolt stress detection system based on electromagnetic ultrasound according to claim 7, characterized in that, The integrated thickness measurement and bolt stress detection system based on electromagnetic ultrasound also includes: The display module is electrically connected to the control module and is configured to visualize the thickness and the axial stress of the bolt through the control module.

9. The integrated thickness measurement and bolt stress detection system based on electromagnetic ultrasound according to claim 5 or claim 6, characterized in that, The thickness of the first magnetic sheet is adjusted based on the magnetic field strength of the first magnetic field, and the thickness of the second magnetic sheet is adjusted based on the magnetic field strength of the second magnetic field.

10. A detection method, applied to the electromagnetic ultrasonic thickness measurement and bolt stress integrated detection system as described in any one of claims 1-9, characterized in that, include: The object under test is excited to generate transverse wave ultrasonic waves, and the echo signal of the transverse wave ultrasonic waves is received. The test object is excited to generate longitudinal wave ultrasonic waves, and the echo signal of the longitudinal wave ultrasonic waves is received. The thickness of the object under test is determined by center peak detection based on the echo signal of the transverse wave ultrasonic wave, and the axial stress of the bolts of the object under test is determined based on the echo signals of the transverse wave ultrasonic wave and the echo signals of the longitudinal wave ultrasonic wave.

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