Welding monitoring method based on magnetic attraction in optical fiber sensing system

Abstract

The invention belongs to the technical field of industrial welding, and discloses a welding monitoring method based on magnetic attraction in an optical fiber sensing system, which comprises the following steps: fixing a magnetic attraction type optical fiber near a welding area of a weldment, and monitoring the vibration of the magnetic attraction type optical fiber on the weldment by using a phase-sensitive optical time domain reflectometer; wherein the weldment has ferromagnetism or a ferromagnetic material is added on the surface of the weldment, and the surface of the magnetic type optical fiber is coated with a soft magnetic material so as to adapt to the weldments in different shapes. The fixture has the advantages that magnetic attraction type optical fiber fixation is not limited by the shape and size of a weldment, the fixture can adapt to the weldment in a complex shape as long as a magnetic force effect can be generated, and the fixture design and replacement cost is reduced; the stress is uniform, so that the optical fiber can accurately sense vibration, vibration characteristics can be analyzed, the welding process is optimized, and the welding quality is improved; the magnetic type fixation greatly simplifies the installation and replacement of the optical fiber, and when a weldment is frequently replaced, an operator can quickly complete the re-fixation, thereby improving the working efficiency.

Description

Technical Field

[0001] The present invention relates to the technical field of industrial welding, and in particular to a welding monitoring method based on magnetic attraction in an optical fiber sensing system. Background Art

[0002] In the early 21st century, advances in materials science and micro-nanofabrication technologies led to the development of new fiber-optic sensors, such as long-period fiber gratings (LPFGs) and photonic crystal fiber (PCF) sensors, expanding their application range. Simultaneously, distributed fiber-optic sensing technologies (such as those based on Brillouin and Rayleigh scattering) advanced, enabling long-distance continuous monitoring and finding applications in oil and gas pipelines, power cables, and other fields. Continuous advances in optical communications have also provided advanced light sources, optical fibers, and other fundamental components, along with sophisticated signal transmission and processing techniques, for optical sensing. Furthermore, signal modulation, demodulation, and multiplexing techniques used in optical communications have been widely applied in the field of optical sensing, improving the performance and functionality of optical sensing systems. Advances in microelectronics have enabled the miniaturization, integration, and high-performance of components such as photodetectors and signal processing circuits in optical sensing systems. The ability to integrate complex signal processing functions onto a single chip enables rapid acquisition, processing, and analysis of optical sensing signals, improving the intelligence and response speed of optical sensing systems. Modern industry pursues a high degree of automation, requiring precise sensing of various parameters in the production process, such as the position and motion of objects, and the speed of production lines. Optical sensing technology can quickly and accurately acquire this information, providing data support for automated control systems, thereby enabling precise control and optimization of the production process. During the pipeline welding process, fiber optic temperature sensors are placed near the welding area to monitor the temperature field distribution and changes during welding in real time. This allows operators to promptly understand whether the welding temperature meets the process requirements and avoid welding defects caused by excessively high or low temperatures, such as coarse grains caused by overheating and brittle welds caused by overcooling, thereby ensuring welding quality. In addition, fiber optic sensing technology is combined with optical imaging or spectral analysis methods to detect the surface and internal quality of welds. Fiber optic sensing technology plays an important role in the field of pipeline welding, from welding process control to quality inspection and subsequent operation monitoring. It helps to improve the quality and safety of pipeline welding and ensure the reliable operation of pipeline systems.

[0003] When using fiber optic sensors in industrial welding, the surface of the measured point must first be pre-treated. Rust removal with sandpaper and a wire brush, smoothing with a grinding tool, and cleaning with organic solvents such as alcohol and acetone are essential to remove rust, scale, oil, and dust. This lays a good foundation for subsequent installation. During the pre-positioning phase, the fiber optic sensor's welding post is coaxially aligned with the extended sleeve of the welding post of the pre-positioning device and installed within it. A spot welder is then used. Parameters such as welding current, time, and electrode pressure are pre-set based on the characteristics of the sensor and the material being measured to ensure welding quality while protecting the sensor. This fiber optic installation technique for welding has several drawbacks. First, it suffers from limited flexibility in adjusting the installation position: once the weld point is determined, the sensor's installation orientation is essentially fixed. If deviations are detected during installation, or if the sensor's position needs to be adjusted to accommodate different welding conditions, the welding model must be re-created, significantly reducing installation flexibility and efficiency. Complex structures are also limited. For workpieces with irregular shapes, confined interiors, or multiple layers, installation may be space-constrained and impossible to achieve in the desired orientation and position. Furthermore, in this scenario, it's difficult to fine-tune the sensor's installation position to adapt to the actual stress distribution. Secondly, it suffers from insufficient adaptability to varying welding conditions: Adjustment to changing conditions is difficult. During industrial welding, welding processes, materials, and parameters may need to be adjusted to meet varying production requirements. For example, switching from one welding material to another, or changing parameters like welding current and speed, can cause changes in the stress distribution during welding. However, existing installation technologies struggle to quickly adapt to these changes in operating conditions once the sensor is installed. Readjusting the sensor's installation position and orientation requires repeating a complex series of operations, including surface pretreatment, pre-positioning, and welding. This not only wastes time and money but also impacts production schedules. Furthermore, multi-task welding suffers from limited flexibility. In scenarios requiring multiple welding tasks, such as when the same equipment is required to perform different types of welding operations, existing installation technologies cannot quickly move fiber optic sensors from one welding location to another or flexibly switch between different welding tasks. This is because the sensor's installation is tailored to specific welding structures and working conditions, making it difficult to quickly reconfigure once installed. Furthermore, the installation process lacks flexibility due to limitations in pre-positioning devices. While these devices can improve installation accuracy, they also limit installation flexibility. Pre-positioning devices are typically designed for specific weld structures and sensors, with relatively fixed sizes and shapes.If sensors of different specifications need to be installed or installed on different welding structures, the corresponding pre-positioning device needs to be replaced, which increases the complexity and cost of installation. The welding operation is irreversible. Once the fiber optic sensor is spot-welded to the measured point using a spot welder, its position is difficult to adjust. If the sensor position is found to be inaccurate or needs to be relocated after welding, the sensor needs to be removed from the measured point, which may cause damage to the surface of the measured point and require re-surface pretreatment and welding operations, reducing the flexibility of the installation process.

[0004] Fiber optic magnetic fixtures use magnetic attraction to quickly secure and release optical fibers, eliminating the need for complex mechanical operations and significantly improving the efficiency of fiber installation and commissioning. For example, when frequently replacing or adjusting optical fiber positions, operators can easily attach and remove the fiber, saving time and effort. Through a well-designed magnetic structure and high-precision processing, precise optical fiber positioning is achieved. Magnetic fixtures accurately secure optical fibers in a preset position, ensuring they maintain a stable position and posture during use, thereby improving the performance stability and reliability of fiber optic communication systems and related optical equipment. However, in optical sensing applications, a tight fit between the optical fiber and the sensor device is crucial for accurate sensing of physical quantities. Due to the unique nature of magnetic fixtures, they may not achieve a completely tight fit between the optical fiber and the sensor device, resulting in slight gaps. This can cause unstable loss or scattering of the optical signal during transmission and conversion, affecting the sensor's ability to accurately measure changes in physical quantities and reducing measurement accuracy. Furthermore, the optical signal is more susceptible to interference from external environmental factors such as vibration and temperature fluctuations. These interferences can cause slight changes in the relative position between the optical fiber and the device, resulting in fluctuations in the transmission path and intensity of the optical signal, affecting the stability of the optical fiber backscattered signal. Summary of the Invention

[0005] The purpose of the present invention is to provide a welding monitoring method based on magnetic attraction in a fiber optic sensing system in response to the above-mentioned deficiencies in the prior art. This method fixes the magnetic optical fiber near the welding area of ​​the weldment and uses a phase-sensitive optical time-domain reflectometer to monitor the vibration of the optical fiber on the weldment to adjust the welding method and thereby improve the welding quality.

[0006] The purpose of the present invention is achieved by the following technical solutions:

[0007] A welding monitoring method based on magnetic attraction in an optical fiber sensing system, the method comprising:

[0008] Fixing a magnetic optical fiber near a welding area of ​​a weldment, and monitoring the vibration of the magnetic optical fiber on the weldment using a phase-sensitive optical time-domain reflectometer;

[0009] The weldment is ferromagnetic or has ferromagnetic material attached to its surface, and the surface of the magnetic optical fiber is coated with soft magnetic material to adapt to weldments of different shapes.

[0010] The phase-sensitive optical time-domain reflectometer includes a laser, a beam splitter, an acousto-optic modulator, a first erbium-doped fiber amplifier, a first bandpass filter, an optical circulator, a second erbium-doped fiber amplifier, a second bandpass filter, a coupler, a balanced photodetector, and a digital signal processing module. The laser is used to output narrowband laser light. The output end of the laser is connected to the input end of the beam splitter. The beam splitter is used to split the narrowband laser light into local oscillator light and signal light. The signal light output end of the beam splitter is connected to the light input end of the acousto-optic modulator. The acousto-optic modulator is used to convert the signal light into pulse light. The output end of the acousto-optic modulator is connected to the input end of the first erbium-doped fiber amplifier. The first erbium-doped fiber amplifier is used to amplify the power of the pulse light. The output end of the first erbium-doped fiber amplifier is connected to the input end of the first bandpass filter. The first bandpass filter is used to filter out noise generated after the pulse light is amplified. The output end of the first bandpass filter is connected to the input end of the optical circulator. The optical circulator is used for optical path transmission. The bidirectional end of the optical circulator is connected to the magnetic optical fiber. One end of the optical circulator is connected, the magnetic optical fiber is used to transmit the pulse light generated by amplification and denoising and generate backward Rayleigh scattered light, the output end of the optical circulator is connected to the input end of the second erbium-doped fiber amplifier, the second erbium-doped fiber amplifier is used to amplify the backward Rayleigh scattered light, the output end of the second erbium-doped fiber amplifier is connected to the input end of the second band-pass filter, the second band-pass filter is used to filter out the noise generated after the backward Rayleigh scattered light is amplified, the local oscillator light output end of the beam splitter and the output end of the second band-pass filter are respectively connected to the first input end and the second input end of the coupler, the coupler is used to mix the local oscillator light and the backward Rayleigh scattered light generated by amplification and denoising and generate a beat frequency optical signal, the output end of the coupler is connected to the input end of the balanced photodetector, the balanced photodetector is used to convert the beat frequency optical signal into a beat frequency electrical signal, the output end of the balanced photodetector is connected to the input end of the digital signal processing module, and the digital signal processing module is used to perform vibration monitoring and vibration signal restoration on the beat frequency electrical signal.

[0011] The electrical input end of the AOM is connected to the electrical output end of a signal generator, and the signal generator is used to drive the AOM.

[0012] Before monitoring the vibration of the magnetic optical fiber on the weldment, the magnetic optical fiber is connected to a piezoelectric ceramic transducer, and the piezoelectric ceramic transducer serves as a vibration simulation source.

[0013] The soft magnetic material is one or more of a ferrite material, a ferrite-resin composite material, and a cobalt-based alloy material.

[0014] The magnetic optical fibers are arranged along the circumference of the weldment.

[0015] The advantages of the present invention are:

[0016] 1. High universality: Magnetic optical fiber fixation is not limited by the shape and size of welded parts. As long as magnetic force can be generated, it can adapt to welded parts with complex shapes, reducing the cost of fixture design and replacement;

[0017] 2. Improved measurement accuracy: Uniform stress enables the optical fiber to accurately sense vibration, which is beneficial for analyzing vibration characteristics, optimizing welding processes, and improving welding quality;

[0018] 3. Convenient operation: Magnetic fixation greatly simplifies the installation and replacement of optical fibers. When frequently changing welding parts, operators can quickly complete re-fixation, improving work efficiency. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 This is a schematic diagram of fixing the magnetic optical fiber on the first welding piece of the present invention;

[0020] Figure 2 This is a schematic diagram of fixing the magnetic optical fiber on the third welding piece of the present invention;

[0021] Figure 3 This is a schematic diagram of fixing the magnetic optical fiber on the fourth welding piece of the present invention;

[0022] Figure 4 The figure is a block diagram of the working principle of the welding monitoring method based on magnetic attraction in the optical fiber sensing system of the present invention.

[0023] like Figures 1 to 4 As shown, the marks in the figure represent:

[0024] Magnetic optical fiber 10, weld 20, first weld 2001, second weld 2002, first weld 2003, third weld 2004, curved surface build-up weld 2005, fourth weld 2006, fifth weld 2007, second weld 2008, phase-sensitive optical time-domain reflectometer 30, laser 3001, beam splitter 3002, acousto-optic modulator 3003, signal generator 3004, first erbium-doped fiber amplifier 3005, first bandpass filter 3006, optical circulator 3007, second erbium-doped fiber amplifier 3008, second bandpass filter 3009, coupler 3010, balanced photodetector 3011, digital signal processing module 3012, piezoelectric ceramic transducer 3013. DETAILED DESCRIPTION

[0025] The features of the present invention and other related features are further described in detail below through embodiments in conjunction with the accompanying drawings to facilitate understanding by those skilled in the art:

[0026] Example: Figures 1 to 4 As shown, this embodiment relates to a welding monitoring method based on magnetic attraction in an optical fiber sensing system, which mainly includes the following steps:

[0027] The magnetic optical fiber 10 is fixed near the welding area of ​​the weldment 20, and the phase-sensitive optical time-domain reflectometer 30 is used to monitor the vibration of the magnetic optical fiber 10 on the weldment 20. By collecting the vibration information of the magnetic optical fiber 10 on the weldment 20, the welding method is adjusted to improve the welding quality.

[0028] In this embodiment, the weldment 20 is ferromagnetic or has a ferromagnetic material attached to its surface. The weldment 20 is typically made of steel and possesses ferromagnetism. The surface of the magnetic optical fiber 10 is coated with a soft magnetic material. The appropriate soft magnetic material is selected to ensure that the magnetic strength meets the required attraction while not significantly interfering with the optical performance of the magnetic optical fiber 10. Furthermore, the thickness of the soft magnetic material is precisely controlled to ensure that the magnetic function is achieved while not affecting the flexibility and signal transmission performance of the magnetic optical fiber 10. Specifically, the soft magnetic material is one or more of a ferrite, a ferrite-resin composite, and a cobalt-based alloy. The ferrite material is selected to be one or both of manganese-zinc ferrite and nickel-zinc ferrite. The cobalt-based alloy is selected to be one or more of a cobalt-iron-boron alloy, a cobalt-zirconium-niobium alloy, or an iron-cobalt-ruthenium alloy. The magnetic optical fiber 10 is magnetically attracted to and adheres to the surface of the weldment 20, adapting to weldments 20 of varying shapes. The position at which the magnetic optical fiber 10 is fixed to the weldment 20 is determined by the shape of the weldment 20. Furthermore, the magnetic optical fiber 10 does not need to be very close to the welding area and can be kept away from high-temperature areas, effectively preventing damage to the magnetic optical fiber 10 caused by the high temperatures during welding. The magnetic optical fiber 10 is arranged along the circumference of the weldment 20. The magnetic optical fiber 10 can be wrapped around the surface of the weldment 20 once, or the magnetic optical fiber 10 can be wrapped around the surface of the weldment 20 in a spiral shape. This method ensures a more uniform magnetic field intensity around the weldment 20, and the magnetic optical fiber 10 does not experience significant strain due to the magnetic force, thereby accurately sensing vibrations generated by welding. This effectively prevents the sensing accuracy from being affected by poor fit between the magnetic optical fiber 10 and the weldment 20 being sensed.

[0029] In this embodiment, the weldment 20 is a pipe, such as Figure 1 As shown, the first weldment 2001 and the second weldment 2002 are both tube structures. The first weldment 2001 is composed of a round tube and a reducer. The first weldment 2001 and the second weldment 2002 are coaxially arranged. A first weld seam 2003 is formed between the end of the second weldment 2002 and the end of the first weldment 2001. The magnetic optical fiber 10 is wound around the round tube of the first weldment 2001; Figure 2 As shown, the third weldment 2004 is a semicircular tube structure, and a curved surface welding 2005 is formed on the inner ring wall of the third weldment 2004, and the magnetic optical fiber 10 is wound on the third weldment 2004; Figure 3 As shown, the fourth weld 2006 and the fifth weld 2007 are both tubular structures, the outer diameter of the fourth weld 2006 gradually changes, and the outer wall of the fourth weld 2006 is a concave-convex structure, the fourth weld 2006 and the fifth weld 2007 are coaxially arranged, the fifth weld 2007 is installed in the fourth weld 2006, and a second weld 2008 is formed between the fourth weld 2006 and the fifth weld 2007, and the magnetic optical fiber 10 is wound on the concave-convex structure of the fourth weld 2006. Since the magnetic optical fiber 10 and the weldment 20 are magnetically connected, on the one hand, the magnetic optical fiber 10 can be easily wound around the weldment 20 before welding. When installing the magnetic optical fiber 10 before welding, there is no need to spend too much time. You only need to wind the magnetic optical fiber 10 around the weldment 20. Due to the effect of the magnetic field, the magnetic optical fiber 10 can be close to the weldment 20; on the other hand, after completing the welding of one weldment 20, it is also more convenient to weld the next weldment 20. Since the thickness of the soft magnetic material on the surface of the magnetic optical fiber 10 is very thin, the staff can easily remove the magnetic optical fiber 10 to assist in the welding of the next weldment 20 without the aid of other equipment, that is, ensuring the welding quality without adversely affecting the welding efficiency.

[0030] In this embodiment, Figure 4As shown, the phase-sensitive optical time-domain reflectometer 30 includes a laser 3001, a beam splitter 3002, an acousto-optic modulator 3003, a signal generator 3004, a first erbium-doped fiber amplifier 3005, a first bandpass filter 3006, an optical circulator 3007, a second erbium-doped fiber amplifier 3008, a second bandpass filter 3009, a coupler 3010, a balanced photodetector 3011 and a digital signal processing module 3012. The laser 3001 is used to output narrow-band laser light. The output end of the laser 3001 is connected to the input end of the beam splitter 3002. The beam splitter 3002 is used to split the narrow-band laser light into local oscillator light and signal light. The signal light output end of the beam splitter 3002 is connected to the light input end of the acousto-optic modulator 3003. The modulator 3003 is used to convert signal light into pulsed light. The electrical output of the signal generator 3004 is connected to the electrical input of the AOM 3003. The signal generator 3004 is used to drive the AOM 3003. The output of the AOM 3003 is connected to the input of a first erbium-doped fiber amplifier 3005. The first erbium-doped fiber amplifier 3005 is used to amplify the power of the pulsed light to compensate for the insertion loss of the AOM 3003. The output of the first erbium-doped fiber amplifier 3005 is connected to the input of a first bandpass filter 3006. The first bandpass filter 3006 is used to filter out noise generated after the pulsed light is amplified. The output of the first bandpass filter 3006 is connected to the input of an optical circulator 3007. The optical circulator 3007 is used for optical path transmission. The optical circulator 3007 has three ports: an input end, a bidirectional end, and an output end. The bidirectional end of the optical circulator 3007 is connected to one end (proximal end) of the magnetic optical fiber 10, and the other end (distal end) of the magnetic optical fiber 10 is subjected to anti-reflection treatment. The magnetic optical fiber 10 is used to transmit the pulsed light generated by amplification and denoising and generate backscattered Rayleigh light (Rayleigh scattered light is very sensitive to vibration). That is, the pulsed light generated by amplification and denoising is input from the proximal end of the magnetic optical fiber 10, and backscattered Rayleigh light is generated in the magnetic optical fiber 10, and the backscattered Rayleigh light is also output from the proximal end of the magnetic optical fiber 10. The output end of the optical circulator 3007 is connected to the input end of the second erbium-doped fiber amplifier 3008. The second erbium-doped fiber amplifier 3008 is used to amplify the backscattered Rayleigh light. The output end of the second erbium-doped fiber amplifier 3008 is connected to the input end of the second bandpass filter 3009. The second bandpass filter 3009 is used to filter out noise generated after the backscattered Rayleigh light is amplified. The local oscillator light output end of the beam splitter 3002 and the output end of the second bandpass filter 3009 are respectively connected to the first input end and the second input end of the coupler 3010. The coupler 3010 is used to mix the local oscillator light and the backscattered Rayleigh light generated after amplification and denoising to generate a beat frequency optical signal. The output end of the coupler 3010 is connected to the input end of the balanced photodetector 3011. The balanced photodetector 3011 is used to convert the beat frequency optical signal into a beat frequency electrical signal.The output of the balanced photodetector 3011 is connected to the input of the digital signal processing module 3012. The digital signal processing module 3012 is used to monitor the vibration of the beat frequency electrical signal and restore the vibration signal. Based on the phase changes of the beat frequency optical signal, it can accurately sense the external disturbance of the magnetic optical fiber 10. In other words, external vibration will change the length, refractive index and other physical properties of the magnetic optical fiber 10, thereby changing the phase of the backscattered Rayleigh light. In addition, before monitoring the vibration of the magnetic optical fiber 10 on the weldment 20, the magnetic optical fiber 10 can be connected to the piezoelectric ceramic transducer 3013. The piezoelectric ceramic transducer 3013 serves as a vibration simulation source for simulated monitoring to ensure the accuracy of the actual monitoring data.

[0031] It's important to note that traditional welding control technology has primarily focused on temperature control. This is because welding temperature directly impacts weld quality, such as the weld's metallurgical structure and mechanical properties. For example, excessively high temperatures can lead to overheating of the weld metal, resulting in coarsened grains and reduced weld strength and toughness; while excessively low temperatures can cause defects such as incomplete fusion and slag inclusions. Therefore, the primary focus is on accurately measuring temperature changes during welding and adjusting the temperature by controlling welding parameters to ensure weld quality. Vibration, however, has received insufficient attention in traditional welding control. While some vibration is generated during welding, its impact on weld quality is relatively indirect and complex, unlike the direct and obvious impact of temperature. Furthermore, temperature measurement exhibits a certain degree of hysteresis. For example, temperature sensors such as thermocouples require time to reach thermal equilibrium during welding and accurately reflect temperature changes in the weld area. Furthermore, temperature sensors typically only measure the average temperature at a specific point or region, making it difficult to quickly and accurately capture transient temperature fluctuations and localized temperature changes during welding. This hysteresis can lead to delays in adjusting welding parameters, impacting the stability of weld quality. This solution can sense the tiny vibrations generated during the welding process in real time. This vibration information can reflect various welding conditions, such as the stability of the welding arc, fluctuations in the weld pool, and changes in welding speed. Compared to temperature measurement, vibration sensing has almost no lag and can capture the corresponding signals the moment changes occur in the welding process, providing a more accurate and rapid basis for timely adjustment of welding parameters. For example, when the welding speed changes, the changes in vibration frequency and amplitude can be detected immediately, while a temperature sensor may take some time to reflect the temperature difference caused by the change in welding speed.

[0032] In traditional welding techniques, optical fibers are typically secured with clamps. However, clamping can easily cause stress concentration at the clamping point, affecting measurement accuracy. When using mechanical clamps to secure optical fibers, the primary goal is to ensure stable positioning during the welding process. The welding process is often accompanied by complex conditions such as high temperatures, strong light, and a certain degree of mechanical vibration. To ensure accurate welding temperature measurement, the emphasis is on securely securing the optical fiber with mechanical clamps, ensuring that it remains in the intended measurement position despite high-temperature deformation and vibration interference, thereby obtaining stable and reliable temperature data. This overemphasis on stability leads to the design and selection of clamps primarily focusing on their ability to withstand the effects of high temperatures and normal vibration on the optical fiber's position, with less attention paid to the clamp's impact on the optical fiber's vibration sensing performance. Furthermore, traditional optical fiber securing often relies on mechanical clamping, requiring specialized clamps designed specifically for the shape of the component being welded. For example, a circular pipe might require a ring-shaped clamp to secure the optical fiber; square or irregularly shaped components require custom-designed clamps. This not only increases the cost and time of fixture design and manufacturing, but also requires precise adjustment of the fit between the fixture and the device during actual installation to ensure the stable position of the optical fiber. The operation process is complicated and time-consuming. When the shape or size of the device to be welded changes, the original fixture may not be applicable and needs to be redesigned and manufactured. For example, when switching from welding large-diameter pipes to small-diameter pipes, or from welding straight pipes to curved pipes, the original clamping device is difficult to adjust and use directly, and a suitable fixture needs to be remade. This reduces the efficiency of the welding operation and limits the rapid switching and application of welding technology on different types of devices to be welded.

[0033] Most existing magnetic devices are designed for fixing optical fibers in the communications field. The working environment of communication optical fibers is relatively stable, and the main requirement for fixation is to ensure that the optical fibers do not shift during installation and use, thereby ensuring stable transmission of optical signals. For example, in the installation of communication base stations or optical fiber networks, magnetic devices only need to fix the optical fibers in a specific position to prevent them from falling off due to external forces or slight vibrations. In addition, communication optical fibers have relatively low requirements for the precision of the fixed position. However, in welding process control, in order to accurately measure the temperature and vibration of the welding part, the optical fiber needs to be precisely placed in a specific position, and existing magnetic devices may lack flexibility.

[0034] The beneficial technical effects of this embodiment are:

[0035] 1. High universality: Magnetic optical fiber fixation is not limited by the shape and size of welded parts. As long as magnetic force can be generated, it can adapt to welded parts with complex shapes, reducing the cost of fixture design and replacement;

[0036] 2. Improved measurement accuracy: Uniform stress enables the optical fiber to accurately sense vibration, which is beneficial for analyzing vibration characteristics, optimizing welding processes, and improving welding quality;

[0037] 3. Convenient operation: Magnetic fixation greatly simplifies the installation and replacement of optical fibers. When frequently changing welding parts, operators can quickly complete re-fixation, improving work efficiency.

[0038] Although the above embodiments have described in detail the concepts and embodiments of the present invention with reference to the accompanying drawings, ordinary technicians in this field can recognize that various improvements and modifications can still be made to the present invention without departing from the scope of the claims, so they are not described in detail here.

Claims

1. A welding monitoring method based on magnetic attraction in an optical fiber sensing system, characterized by: The method comprises: Fixing a magnetic optical fiber near a welding area of ​​a weldment, and monitoring the vibration of the magnetic optical fiber on the weldment using a phase-sensitive optical time-domain reflectometer; The weldment is ferromagnetic or has ferromagnetic material attached to its surface, and the surface of the magnetic optical fiber is coated with soft magnetic material to adapt to weldments of different shapes.

2. The welding monitoring method based on magnetic attraction in an optical fiber sensing system according to claim 1, characterized in that: The phase-sensitive optical time-domain reflectometer includes a laser, a beam splitter, an acousto-optic modulator, a first erbium-doped fiber amplifier, a first bandpass filter, an optical circulator, a second erbium-doped fiber amplifier, a second bandpass filter, a coupler, a balanced photodetector, and a digital signal processing module. The laser is used to output narrowband laser light. The output end of the laser is connected to the input end of the beam splitter. The beam splitter is used to split the narrowband laser light into local oscillator light and signal light. The signal light output end of the beam splitter is connected to the light input end of the acousto-optic modulator. The acousto-optic modulator is used to convert the signal light into pulse light. The output end of the acousto-optic modulator is connected to the input end of the first erbium-doped fiber amplifier. The first erbium-doped fiber amplifier is used to amplify the power of the pulse light. The output end of the first erbium-doped fiber amplifier is connected to the input end of the first bandpass filter. The first bandpass filter is used to filter out noise generated after the pulse light is amplified. The output end of the first bandpass filter is connected to the input end of the optical circulator. The optical circulator is used for optical path transmission. The bidirectional end of the optical circulator is connected to the magnetic optical fiber. One end of the optical circulator is connected, the magnetic optical fiber is used to transmit the pulse light generated by amplification and denoising and generate backward Rayleigh scattered light, the output end of the optical circulator is connected to the input end of the second erbium-doped fiber amplifier, the second erbium-doped fiber amplifier is used to amplify the backward Rayleigh scattered light, the output end of the second erbium-doped fiber amplifier is connected to the input end of the second band-pass filter, the second band-pass filter is used to filter out the noise generated after the backward Rayleigh scattered light is amplified, the local oscillator light output end of the beam splitter and the output end of the second band-pass filter are respectively connected to the first input end and the second input end of the coupler, the coupler is used to mix the local oscillator light and the backward Rayleigh scattered light generated by amplification and denoising and generate a beat frequency optical signal, the output end of the coupler is connected to the input end of the balanced photodetector, the balanced photodetector is used to convert the beat frequency optical signal into a beat frequency electrical signal, the output end of the balanced photodetector is connected to the input end of the digital signal processing module, and the digital signal processing module is used to perform vibration monitoring and vibration signal restoration on the beat frequency electrical signal.

3. The welding monitoring method based on magnetic attraction in an optical fiber sensing system according to claim 2, characterized in that: The electrical input end of the AOM is connected to the electrical output end of a signal generator, and the signal generator is used to drive the AOM.

4. The welding monitoring method based on magnetic attraction in an optical fiber sensing system according to claim 1, wherein: Before monitoring the vibration of the magnetic optical fiber on the weldment, the magnetic optical fiber is connected to a piezoelectric ceramic transducer, and the piezoelectric ceramic transducer serves as a vibration simulation source.

5. The welding monitoring method based on magnetic attraction in an optical fiber sensing system according to claim 1, wherein: The soft magnetic material is one or more of a ferrite material, a ferrite-resin composite material, and a cobalt-based alloy material.

6. The welding monitoring method based on magnetic attraction in an optical fiber sensing system according to claim 1, wherein: The magnetic optical fibers are arranged along the circumference of the weldment.

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