Stress monitoring system based on ultrasonic method

Abstract

The invention relates to the field of stress monitoring, and discloses a stress monitoring system based on an ultrasonic method, which comprises a bolt, an ultrasonic sensor mounted at the end part of the bolt and used for transmitting and receiving ultrasonic longitudinal wave signals, a data acquisition module connected with the ultrasonic sensor and used for acquiring ultrasonic echo signals and acquiring ultrasonic propagation time, and a data processing module connected with the data acquisition module and used for processing the ultrasonic echo signals. The data acquisition module is used for acquiring ultrasonic signals, the signal processing module is connected with the data acquisition module and used for carrying out noise reduction and time delay estimation processing on the ultrasonic signals, the stress calculation module is connected with the signal processing module, and the temperature compensation module is connected with the stress calculation module; through cooperative work of all the modules, a complete stress online monitoring system is constructed, high-precision measurement and real-time monitoring of axial stress are achieved, and the technical problems that a traditional method is insufficient in measurement precision, large in environmental interference and incapable of achieving real-time early warning are effectively solved by combining an early warning module and a monitoring mode based on symmetrical point distribution.

Description

Technical Field

[0001] This invention relates to the field of stress monitoring, and in particular to a stress monitoring system based on ultrasonic methods. Background Technology

[0002] Bolted connections are widely used due to their advantages such as direct force transmission, convenient disassembly, and good economy. However, during long-term operation, the combined effects of temperature periodic changes and vibration impacts can easily cause bolts to experience stress relaxation, fatigue, or even breakage, directly threatening the safe and stable operation of the equipment.

[0003] Currently, the main methods for measuring the axial stress of bolts include the torque wrench method, the shim-based force sensor method, and the ultrasonic method. The torque wrench method is an indirect measurement method that calculates axial stress from torque. However, because the torque coefficient is not a constant and is affected by thread friction, its measurement error can be as high as 40%. It is a destructive testing method that can damage the connecting parts and is unsuitable for critical applications requiring precise measurement. The shim-based force sensor method requires specially designed sensors, which are costly and impractical. Furthermore, the surface roughness of the bolt can affect the measurement results.

[0004] The ultrasonic method is based on the theory of acoustoelasticity, which states that the speed of ultrasound changes linearly with the stress state. The stress is calculated by measuring the propagation time of ultrasound in the bolt. This method has the advantages of high accuracy (up to ±2%) and non-destructive testing.

[0005] However, existing ultrasonic bolt stress monitoring technologies still have the following problems: measurement accuracy is unstable under complex working conditions (such as vibration, electromagnetic interference, and temperature fluctuations); there is a lack of effective temperature compensation methods, and changes in ambient temperature will significantly affect the wave velocity; and the real-time performance is insufficient, making it difficult to achieve online early warning and life assessment of bolt health status. Summary of the Invention

[0006] Therefore, the technical problem to be solved by the present invention is that existing bolt stress monitoring methods have problems such as low measurement accuracy, susceptibility to environmental temperature and noise interference, poor real-time performance, and lack of effective early warning capabilities.

[0007] The above-mentioned technical problems are solved by the following technical solution: This invention proposes a stress monitoring system based on ultrasonic method, which includes, bolt; An ultrasonic sensor, mounted on the end of the bolt, is used to transmit and receive ultrasonic longitudinal wave signals; The data acquisition module, connected to the ultrasonic sensor, is used to acquire ultrasonic echo signals and obtain ultrasonic propagation time; The signal processing module, connected to the data acquisition module, is used to perform noise reduction and time delay estimation processing on the ultrasonic signal; The stress calculation module is connected to the signal processing module and calculates the axial stress value of the bolt based on the mapping relationship between stress and acoustic time. A temperature compensation module, connected to the stress calculation module, is used to correct the effect of ambient temperature on ultrasonic speed.

[0008] In a preferred embodiment of the ultrasonic-based stress monitoring system of the present invention: the ultrasonic sensor includes a piezoelectric wafer and a magnetic pickup; The piezoelectric wafer is bonded to the end face of the bolt using epoxy resin adhesive; The magnetic pickup is connected to the piezoelectric wafer and is used to transmit electrical signals to the data acquisition module.

[0009] In a preferred embodiment of the ultrasonic-based stress monitoring system of the present invention: the data acquisition module includes a data acquisition board that supports high-voltage pulse excitation and high-speed acquisition functions.

[0010] In a preferred embodiment of the stress monitoring system based on ultrasonic method described in this invention: the signal processing module includes a wavelet noise reduction unit and a frequency domain zero-padding cross-correlation time delay estimation unit; The wavelet noise reduction unit is used to suppress the interference of environmental noise on the ultrasonic signal; The frequency domain zero-padded cross-correlation time delay estimation unit is used to calculate the ultrasonic propagation time difference.

[0011] In a preferred embodiment of the stress monitoring system based on ultrasonic method described in this invention: the temperature compensation module establishes a temperature correction model based on acoustoelastic theory; The temperature correction model fits the relationship between ambient temperature and ultrasonic velocity using experimental data, thereby achieving automatic compensation for changes in wave velocity during the measurement process.

[0012] In a preferred embodiment of the stress monitoring system based on ultrasonic method described in this invention: it further includes an early warning module connected to the stress calculation module; The early warning module includes a threshold comparison unit and a life prediction unit, which are used to realize early warning of bolt loosening and assessment of remaining life.

[0013] In a preferred embodiment of the ultrasonic-based stress monitoring system of the present invention: the axial stress measurement results output by the stress calculation module and the early warning information generated by the early warning module are uploaded to the cloud server via a wired network or a wireless network; The cloud server integrates a data visualization interface for real-time display of stress data, temperature data, and early warning status.

[0014] In a preferred embodiment of the ultrasonic stress monitoring system of the present invention: for each group of monitored bolts, the monitoring points of the ultrasonic sensor are arranged in a centrally symmetrical manner, and the number of monitoring points is not less than one-quarter of the total number of bolts.

[0015] The beneficial effects of this invention are as follows: By working together with an ultrasonic sensor, a data acquisition module, a signal processing module, a stress calculation module, and a temperature compensation module, this invention constructs a complete online stress monitoring system, realizing high-precision measurement and real-time monitoring of axial stress. Combined with an early warning module and a monitoring method based on symmetrical point layout, it effectively solves the technical problems of insufficient measurement accuracy, large environmental interference, and inability to provide real-time early warning in traditional methods. Attached Figure Description

[0016] To more clearly illustrate the technical solutions of the embodiments of the present invention, the accompanying drawings of the embodiments of the present invention will be briefly described below. Obviously, the drawings described below only relate to some embodiments of the present invention and are not intended to limit the present invention.

[0017] Figure 1 A schematic diagram of the system workflow of the present invention is shown. Detailed Implementation

[0018] To enable those skilled in the art to better understand the present invention, the present invention will be further described in detail below with reference to specific embodiments and accompanying drawings.

[0019] The terminology used in this invention refers to those general terms currently widely used in the art in consideration of the functionality of the invention; however, these terms may vary according to the intent of those skilled in the art, precedent, or new techniques. Furthermore, specific terms may be chosen independently, and in such cases, their detailed meanings will be described in the detailed description of the invention. Therefore, the terminology used in this specification should not be construed as simple names, but rather based on the meaning of the terms and the overall description of the invention.

[0020] Reference Figure 1 This embodiment provides a stress monitoring system based on ultrasonic methods, including: Bolt 1; Ultrasonic sensor 2, mounted on the end of bolt 1, is used to transmit and receive ultrasonic longitudinal wave signals; Data acquisition module 3, connected to ultrasonic sensor 2, is used to acquire ultrasonic echo signals and obtain ultrasonic propagation time; Signal processing module 4, connected to data acquisition module 3, is used for noise reduction and time delay estimation of ultrasonic signals; Stress calculation module 5 is connected to signal processing module 4 and calculates the axial stress value of the bolt based on the mapping relationship between stress and acoustic time. Temperature compensation module 6, connected to stress calculation module 5, is used to correct the effect of ambient temperature on ultrasonic speed.

[0021] In use, the ultrasonic sensor 2 first emits an ultrasonic longitudinal wave signal into the bolt 1 and receives the echo, and then transmits the electrical signal characterizing the ultrasonic propagation process to the data acquisition module 3.

[0022] Data acquisition module 3 acquires the raw ultrasound signal and obtains the ultrasound propagation time, and transmits this time data to signal processing module 4.

[0023] The signal processing module 4 performs noise reduction and time delay estimation on the received signal, and sends the processed precise time difference data to the stress calculation module 5.

[0024] Based on the pre-calibrated stress-time mapping relationship, stress calculation module 5 converts the time difference data into the initial calculated value of bolt axial stress and sends the initial value to temperature compensation module 6.

[0025] The temperature compensation module 6 uses a temperature correction model to compensate for the initial stress value based on real-time ambient temperature data, and feeds the corrected accurate stress value back to the stress calculation module 5, which then outputs the final bolt axial stress measurement result.

[0026] As one embodiment provided in this application, such as Figure 1 The ultrasonic sensor 2 includes a piezoelectric crystal 21 and a magnetic pickup 22; The piezoelectric wafer 21 is bonded to the end face of the bolt 1 with epoxy resin adhesive; The magnetic pickup 22 is connected to the piezoelectric chip 21 and is used to transmit electrical signals to the data acquisition module 3.

[0027] Data acquisition module 3 includes a data acquisition board that supports high-voltage pulse excitation and high-speed acquisition functions.

[0028] Specifically, the piezoelectric chip 21 is directly and permanently fixed to the end face of the bolt 1 using epoxy resin adhesive to ensure the stability of the coupling layer. Before installation, the surface of the bolt head 1 needs to be cleaned and wiped with anhydrous ethanol to remove stains or oil.

[0029] In use, the piezoelectric crystal 21, after being attached to the end face of the bolt 1, can excite ultrasonic longitudinal waves propagating along the axial direction of the bolt 1 and receive echo signals.

[0030] The magnetic pickup 22 is connected to the piezoelectric crystal 21 by magnetic force. After the electrical signal converted by the piezoelectric crystal is transmitted to the data acquisition module 3, the data acquisition board of the data acquisition module 3 generates a high-voltage pulse excitation signal to drive the piezoelectric crystal 21 to work. At the same time, it acquires the echo signal at high speed, accurately records the emission and reception time of the ultrasonic wave, obtains the ultrasonic propagation time data, and transmits this data to the subsequent signal processing module 4 for further processing.

[0031] As one embodiment provided in this application, such as Figure 1 The signal processing module 4 includes a wavelet noise reduction unit 41 and a frequency domain zero-padding cross-correlation delay estimation unit 42; Wavelet noise reduction unit 41 is used to suppress the interference of environmental noise on ultrasonic signals; Frequency domain zero-padded cross-correlation time delay estimation unit 42 is used to calculate the ultrasonic propagation time difference.

[0032] Temperature compensation module 6 establishes a temperature correction model based on acoustoelasticity theory; The temperature correction model fits the relationship between ambient temperature and ultrasonic velocity using experimental data, thereby achieving automatic compensation for changes in wave velocity during the measurement process.

[0033] In use, the wavelet noise reduction unit 41 of the signal processing module 4 first performs noise reduction processing on the ultrasonic signal received from the data acquisition module 3 to suppress environmental electromagnetic interference and mechanical vibration noise. Then, the frequency domain zero-padding cross-correlation time delay estimation unit 42 analyzes the purified signal, accurately calculates the ultrasonic propagation time difference, and sends this refined time difference data to the stress calculation module 5.

[0034] After the stress calculation module 5 converts the time difference into an initial stress value, the temperature compensation module 6 establishes a temperature correction model based on the acoustoelastic theory, performs wave velocity compensation on the initial stress value according to the real-time ambient temperature, and feeds back the corrected accurate stress value to the stress calculation module 5 to complete the entire signal processing and calculation process.

[0035] As one embodiment provided in this application, such as Figure 1 It also includes an early warning module 7, which is connected to the stress calculation module 5; The early warning module 7 includes a threshold comparison unit 71 and a life prediction unit 72, which are used to realize bolt loosening early warning and remaining life assessment.

[0036] During use, the stress calculation module 5 transmits the final real stress measurement result to the early warning module 7 in real time. The threshold comparison unit 71 in the early warning module 7 continuously compares the received real-time stress value with the preset safety threshold. When abnormal stress changes or exceeding the threshold range are detected, a loosening early warning signal is immediately generated.

[0037] Meanwhile, the life prediction unit 72 assesses the fatigue state of bolt 1 by analyzing the stress change trend based on the received historical stress data sequence, and generates remaining life prediction information, completing the entire process from stress monitoring to early warning assessment.

[0038] As one embodiment provided in this application, such as Figure 1 The axial stress measurement results output by the stress calculation module 5 and the early warning information generated by the early warning module 7 are uploaded to the cloud server via a wired or wireless network. The cloud server integrates a data visualization interface for real-time display of stress data, temperature data, and early warning status.

[0039] Specifically, the stress calculation module 5 outputs the final axial stress measurement result of bolt 1 after correction by the temperature compensation module 6 in real time. At the same time, the early warning module 7 organizes the bolt 1 loosening early warning signal it generates. These data are uploaded to a remote cloud server via fiber optic cables deployed on site or using 4G / 5G wireless networks.

[0040] The cloud server receives and stores this data. The data visualization interface integrated into the cloud server dynamically displays the real-time stress data of bolt 1, the ambient temperature data collected along with it, and the early warning status in a graphical manner, so that maintenance personnel can monitor the health status of bolt 1, a key part of the hydropower unit, anytime and anywhere.

[0041] As one embodiment provided in this application, such as Figure 1 For each group of monitored bolts 1, the monitoring points of the ultrasonic sensor 2 are arranged in a centrally symmetrical manner, and the number of monitoring points is no less than one-quarter of the total number of bolts 1.

[0042] In use, by limiting the monitoring points of the ultrasonic sensors 2 to be arranged in a centrally symmetrical manner and to a number not less than one-quarter of the total number of bolts 1, it is possible to capture the overall health status and local fault information of the bolts 1 to the maximum extent with the minimum number of ultrasonic sensors 2. Thus, the present invention is not only technically feasible, but also has practical and promotional value in engineering.

[0043] In summary, this invention constructs a complete online stress monitoring system through the collaborative work of ultrasonic sensor 2, data acquisition module 3, signal processing module 4, stress calculation module 5, and temperature compensation module 6. It achieves high-precision measurement and real-time monitoring of axial stress. Combined with early warning module 7 and a monitoring method based on symmetrical point layout, it effectively solves the technical problems of insufficient measurement accuracy, large environmental interference, and inability to provide real-time early warning in traditional methods.

[0044] Finally, it should be noted that the methods and devices described in detail above are merely embodiments, and those skilled in the art can modify these embodiments in different ways as long as they do not depart from the scope of the present invention.

Claims

1. An ultrasonic-based stress monitoring system, characterized by: The utility model relates to a bolt (1); An ultrasonic sensor (2) is installed at the end of the bolt (1) for transmitting and receiving ultrasonic longitudinal wave signals; A data acquisition module (3) is connected to the ultrasonic sensor (2) for collecting ultrasonic echo signals and obtaining ultrasonic propagation time; A signal processing module (4) is connected to the data acquisition module (3) for noise reduction and time delay estimation of ultrasonic signals; A stress calculation module (5) is connected to the signal processing module (4) for calculating bolt axial stress values based on the mapping relationship between stress and acoustic time; A temperature compensation module (6) is connected to the stress calculation module (5) for correcting the influence of ambient temperature on ultrasonic velocity. The ultrasonic sensor (2) includes a piezoelectric wafer (21) and a magnetic pickup (22); 2. The ultrasonic-based stress monitoring system of claim 1, wherein: The piezoelectric wafer (21) is pasted to the end face of the bolt (1) by epoxy resin glue; The magnetic pickup (22) is connected to the piezoelectric wafer (21) for transmitting electrical signals to the data acquisition module (3). The data acquisition module (3) includes a data acquisition board card supporting high-voltage pulse excitation and high-speed acquisition functions.

3. The ultrasonic-based stress monitoring system of claim 2, wherein: The signal processing module (4) includes a wavelet denoising unit (41) and a frequency domain zero-padding cross-correlation time delay estimation unit (42); 4. The ultrasonic-based stress monitoring system of claim 3, wherein: The wavelet denoising unit (41) is used to suppress the interference of environmental noise on ultrasonic signals; The frequency domain zero-padding cross-correlation time delay estimation unit (42) is used to calculate the ultrasonic propagation time difference. The temperature compensation module (6) establishes a temperature correction model based on acoustic elasticity theory; 5. The ultrasonic-based stress monitoring system of claim 4, wherein: The temperature correction model fits the relationship between ambient temperature and ultrasonic velocity through experimental data to realize automatic compensation of velocity changes during measurement. It also includes a warning module (7) connected to the stress calculation module (5); 6. The ultrasonic-based stress monitoring system of any one of claims 2-5, wherein: The warning module (7) includes a threshold comparison unit (71) and a life prediction unit (72) for bolt loosening warning and residual life assessment. The axial stress measurement results output by the stress calculation module (5) and the warning information generated by the warning module (7) are uploaded to the cloud server through wired or wireless networks; 7. The ultrasonic-based stress monitoring system of claim 6, wherein: The cloud server integrates a data visualization interface for real-time display of stress data, temperature data and warning status. For each group of monitored bolts (1), the monitoring points of the ultrasonic sensor (2) are arranged in a central symmetric manner, and the number of monitoring points is not less than one-fourth of the total number of bolts (1).

8. The ultrasonic-based stress monitoring system of claim 7, wherein: ​

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