Workpiece remote flaw detection system and method based on laser ultrasound

Abstract

The invention discloses a workpiece remote flaw detection system and method based on laser ultrasound, and the system comprises a laser generation module which is used for remotely transmitting a pulse laser signal to a to-be-detected workpiece, and the to-be-detected workpiece generates an ultrasonic signal carrying defect information under the excitation of the pulse laser signal; the laser detection module is used for receiving a laser echo signal carrying an ultrasonic signal; the signal processing module is used for demodulating the ultrasonic signal from the laser echo signal and analyzing the laser echo signal and the ultrasonic signal by using a preset quantitative analysis model; and determining an outer surface defect of the to-be-detected workpiece based on the laser echo signal, and determining an internal structure defect of the to-be-detected workpiece based on the ultrasonic signal. Remote flaw detection is achieved through the laser ultrasonic technology, the outer surface defect and the internal structure defect of the to-be-detected workpiece can be detected at the same time, and the sensitivity, accuracy and reliability of defect detection are improved.

Description

Technical Field

[0001] The present invention relates to the technical field of workpiece flaw detection, and particularly to a remote workpiece flaw detection system and method based on laser ultrasound. Background Art

[0002] Nondestructive flaw detection can help detect defects, cracks or fatigue damage hidden inside materials, ensuring the safety and reliability of workpieces. This is particularly important for some key components, such as aeroengine parts, bridge structures, etc., and can avoid accidents and losses caused by hidden defects. Compared with traditional destructive detection methods (such as sampling detection), nondestructive flaw detection does not require destructive testing of workpieces, thus saving material and labor costs. At the same time, it can also provide more information to help optimize the daily maintenance plan of components and extend the equipment life.

[0003] Ultrasonic detection technology is a commonly used nondestructive detection method at present. Ultrasonic waves can penetrate most solid materials. When encountering defects or interfaces inside the materials, reflection, refraction or scattering will occur. By analyzing and processing the received signals, the characteristics such as the location, shape and size of defects inside the workpiece can be determined. To improve the detection sensitivity, it is usually necessary to coat ultrasonic coupling agents on the surface of the detection object and the ultrasonic probe. The coupling agent can make the detection device fit more closely with the material, ensuring that ultrasonic waves can effectively be transmitted from the probe to the object to be measured and reflected back from the object. However, if the surface of the workpiece or the probe is not cleaned properly before use, the coupling agent may mix with the dirt and grease on the surface, forming an uneven medium layer, which may affect the transmission efficiency of ultrasonic waves and thus the accuracy of the detection results. In addition, during the process of applying the coupling agent, if the operation is improper, air bubbles may be introduced into the coupling agent, and these air bubbles will become scattering sources or reflection sources of ultrasonic waves, thus interfering with the ultrasonic signals and affecting the measurement accuracy of defect detection.

[0004] Therefore, it is necessary to provide a remote workpiece flaw detection system and method based on laser ultrasound, which can improve the sensitivity of defect detection, perform flaw detection on workpieces with smaller sizes, and improve the accuracy and reliability of detection. Summary of the Invention

[0005] In view of this, the present invention provides a remote workpiece flaw detection system and method based on laser ultrasound to solve the technical problems that the existing contact flaw detection methods are prone to introduce damage or contamination when detecting defects in small-sized and sensitive workpieces, and there are deficiencies in detection accuracy and resolution.

[0006] To achieve the above technical objectives, the present invention adopts the following technical solutions:

[0007] In a first aspect, the present invention provides a remote flaw detection system for workpieces based on laser ultrasound, including a laser generation module, a laser detection module, and a signal processing module connected in sequence:

[0008] The laser generation module is used to remotely transmit a pulsed laser signal to the workpiece to be detected. Under the excitation of the pulsed laser signal, the workpiece to be detected generates an ultrasonic signal carrying defect information.

[0009] The laser detection module is used to receive the laser echo signal carrying the ultrasonic signal.

[0010] The signal processing module is used to demodulate the ultrasonic signal from the laser echo signal, analyze the laser echo signal and the ultrasonic signal using a preset quantitative analysis model, determine the outer surface defects of the workpiece to be detected based on the laser echo signal, and determine the internal structure defects of the workpiece to be detected based on the ultrasonic signal; the quantitative analysis model establishes the correlation between the material parameters of the workpiece to be detected, the pulsed laser parameters, and the laser echo waveform based on Fourier transform.

[0011] In another aspect, the present invention also provides a remote flaw detection method for workpieces based on laser ultrasound, which is applied to the remote flaw detection system for workpieces based on laser ultrasound described in the above technical solution, and includes:

[0012] Remotely send a pulsed laser signal to the workpiece to be detected through the laser generation module. Under the excitation of the pulsed laser signal, the workpiece to be detected generates an ultrasonic signal carrying defect information.

[0013] Receive the laser echo signal carrying the ultrasonic signal through the laser detection module.

[0014] Demodulate the ultrasonic signal from the laser echo signal through the signal processing module, analyze the laser echo signal and the ultrasonic signal using a preset quantitative analysis model, determine the outer surface defects of the workpiece to be detected based on the laser echo signal, and determine the internal structure defects of the workpiece to be detected based on the ultrasonic signal; the quantitative analysis model establishes the correlation between the material parameters of the workpiece to be detected, the pulsed laser parameters, and the laser echo waveform based on Fourier transform.

[0015] Further, the remotely sending a pulsed laser signal to the workpiece to be detected through the laser generation module includes:

[0016] Set the emission parameters of the pulsed laser signal according to the material parameters and shape characteristics of the workpiece to be detected, and the emission parameters include the frequency, incident angle, and waveform of the pulsed laser signal.

[0017] Further, the demodulating the ultrasonic signal from the laser echo signal through the signal processing module includes:

[0018] Based on the thermo-mechanical coupling equation, the longitudinal wave and transverse wave corresponding to the ultrasonic signal are obtained according to the pulsed laser emission parameters, the material parameters of the workpiece, and the current ambient temperature.

[0019] Further, determining the external surface defects of the workpiece to be measured based on the laser echo signal and the internal structure defects of the workpiece to be measured based on the ultrasonic signal includes:

[0020] Determine the attenuation coefficient and the reference delay according to the distance between the laser generation module and the workpiece, the material parameters of the workpiece, and the current ambient temperature;

[0021] Based on the attenuation coefficient and the reference delay, determine the scattering mode of the laser echo signal, and judge whether there is wear on the surface of the workpiece to be measured according to the scattering mode, and locate the wear position;

[0022] Perform Fourier transform on the longitudinal wave and the transverse wave, and determine the internal structure defects of the workpiece to be measured according to the amplitude attenuation and phase change of the preset frequency.

[0023] Further, performing Fourier transform on the longitudinal wave and the transverse wave, and determining the internal structure defects of the workpiece to be measured according to the amplitude attenuation and phase change of the preset frequency includes:

[0024] Determine the first amplitude and the first phase information corresponding to the first frequency component in the longitudinal wave. When the error between the first amplitude and the first phase information and the preset first standard value exceeds the first threshold range, it is determined that the workpiece to be measured is corroded;

[0025] When the workpiece to be measured is corroded, judge the second amplitude and the second phase information corresponding to the second frequency component in the transverse wave, and determine the corrosion depth of the workpiece according to the second amplitude and the second phase information.

[0026] Further, the external surface defects include deformation and fracture; the internal structure defects include pores, slag inclusions, and corrosion.

[0027] Further, the pulsed laser signal is a pulsed laser with a wavelength band of 905 nm.

[0028] Further, the method further includes: establishing a simulation model corresponding to the workpiece according to the laser echo signal and the ultrasonic signal.

[0029] In a third aspect, the present invention further provides a computer-readable storage medium for storing computer-readable programs or instructions. When the programs or instructions are executed by a processor, the steps in the method for remote flaw detection of a workpiece based on laser ultrasound in any of the above implementation manners can be implemented.

[0030] The present invention provides a remote flaw detection system and method for workpieces based on laser ultrasound. The system emits pulsed laser through a laser generation module. The laser energy excites electron migration, causing lattice vibration and increasing the surface temperature of the workpiece. The use of pulsed laser causes the laser irradiation point to rapidly thermally expand, thereby generating thermoelastic waves. These thermoelastic waves can propagate inside the object and produce echoes when encountering different interfaces, thus causing ultrasonic signals to be generated on the surface of the workpiece. The laser detection module receives the laser echo modulated with ultrasonic signals, and finally the signal processing module restores the ultrasonic information from the echo signals. By analyzing the laser echo signals, the external surface defects of the workpiece to be measured can be determined; while by analyzing the ultrasonic signals, the internal structure defects of the workpiece to be measured can be determined.

[0031] The advantages of the present invention are as follows:

[0032] 1. Non-contact detection is achieved, without the need to directly contact the surface of the workpiece to be measured, avoiding errors in detection caused by possible damage or contamination, and is suitable for remote flaw detection of workpieces with complex structures;

[0033] 2. The system has good real-time performance. Laser ultrasound technology can achieve rapid data acquisition and processing, thereby realizing real-time monitoring and instant feedback, which helps to improve production efficiency and product quality;

[0034] 3. The detection accuracy and resolution are high. By using a preset quantitative analysis model to analyze the laser echo signals and ultrasonic signals, small-sized defects can be detected, improving the accuracy and reliability of detection;

[0035] 4. The system comprehensively utilizes laser echo signals and ultrasonic signals, and can comprehensively analyze the external surface and internal structure defects of the workpiece to be measured, which helps to timely discover and solve problems, and improve production efficiency and product quality. Description of the Drawings

[0036] Figure 1 It is a schematic structural diagram of an embodiment of the remote flaw detection system for workpieces based on laser ultrasound provided by the present invention;

[0037] Figure 2 It is a schematic flow diagram of an embodiment of the remote flaw detection method for workpieces based on laser ultrasound provided by the present invention. Detailed Embodiments

[0038] The following specifically describes the preferred embodiments of the present invention in conjunction with the drawings. The drawings form a part of this application and are used together with the embodiments of the present invention to explain the principle of the present invention, and are not used to limit the scope of the present invention.

[0039] The present invention provides a remote flaw detection method for workpieces based on laser ultrasound, an electronic device, and a computer-readable storage medium, which will be described separately below.

[0040] Combined with Figure 1 As shown, a specific embodiment of the present invention discloses a remote flaw detection system 100 for workpieces based on laser ultrasound, including a laser generation module 101, a laser detection module 102, and a signal processing module 103 connected in sequence:

[0041] The laser generation module 101 is used to remotely transmit a pulsed laser signal to the workpiece to be detected. Under the excitation of the pulsed laser signal, the workpiece to be detected generates an ultrasonic signal carrying defect information;

[0042] The laser detection module 102 is used to receive the laser echo signal carrying the ultrasonic signal;

[0043] The signal processing module 103 is used to demodulate the ultrasonic signal from the laser echo signal, analyze the laser echo signal and the ultrasonic signal using a preset quantitative analysis model, determine the external surface defects of the workpiece to be measured based on the laser echo signal, and determine the internal structure defects of the workpiece to be measured based on the ultrasonic signal; the quantitative analysis model establishes the correlation relationship between the material parameters of the workpiece to be measured, the pulsed laser parameters, and the laser echo waveform based on the Fourier transform.

[0044] Compared with the prior art, in the system of this embodiment, a pulsed laser is emitted by a laser generation module. The laser energy is used to excite electron migration, causing lattice vibration and increasing the surface temperature of the workpiece. Using a pulsed laser will cause the laser irradiation point to rapidly thermally expand, thereby generating a thermoelastic wave. This thermoelastic wave can be transmitted inside the object and produce an echo when encountering different interfaces, thus causing an ultrasonic signal to be generated on the surface of the workpiece. The laser detection module receives the laser echo modulated with the ultrasonic signal, and finally the signal processing module restores the ultrasonic information from the echo signal. By analyzing the laser echo signal, the external surface defects of the workpiece to be measured can be determined; while by analyzing the ultrasonic signal, the internal structure defects of the workpiece to be measured can be determined. This system realizes non-contact detection, does not need to directly contact the surface of the workpiece to be measured, and avoids the errors caused by possible damage or contamination to the detection; secondly, this system has good real-time performance. The laser ultrasonic technology can realize rapid data acquisition and processing, so as to realize real-time monitoring and instant feedback, which helps to improve production efficiency and product quality; thirdly, the detection accuracy and resolution are high. Using a preset quantitative analysis model to analyze the laser echo signal and the ultrasonic signal can detect small-sized defects, improving the accuracy and reliability of the detection; finally, this system comprehensively uses the laser echo signal and the ultrasonic signal, and can comprehensively analyze the external surface and internal structure defects of the workpiece to be measured, which helps to discover and solve problems in time, and improve production efficiency and product quality.

[0045] An embodiment of the present invention further provides a remote flaw detection method for a workpiece based on laser ultrasound, which is applied to the above-mentioned remote flaw detection system for a workpiece based on laser ultrasound, as Figure 2 described, the method includes:

[0046] Step S201: Remotely send a pulsed laser signal to the workpiece to be detected through the laser generation module. Under the excitation of the pulsed laser signal, the workpiece to be detected generates an ultrasonic signal carrying defect information;

[0047] Step S202: Receive the laser echo signal carrying the ultrasonic signal through the laser detection module;

[0048] Step S203: Demodulate the ultrasonic signal from the laser echo signal through the signal processing module, use a preset quantitative analysis model to analyze the laser echo signal and the ultrasonic signal, determine the external surface defects of the workpiece to be measured based on the laser echo signal, and determine the internal structure defects of the workpiece to be measured based on the ultrasonic signal; the quantitative analysis model establishes the correlation relationship between the material parameters of the workpiece to be measured, the pulsed laser parameters, and the laser echo waveform based on the Fourier transform.

[0049] As a preferred embodiment, remotely sending a pulsed laser signal to the workpiece to be detected through the laser generation module includes:

[0050] Set the emission parameters of the pulsed laser signal according to the material parameters and shape characteristics of the workpiece to be measured, where the emission parameters include the frequency, incident angle, and waveform of the pulsed laser signal.

[0051] Exciting electron migration causes lattice vibration, increasing the surface temperature of the object. Using a pulsed laser will cause the laser irradiation point to rapidly thermally expand, thereby generating a thermoelastic wave. This thermoelastic wave can propagate inside the object and produce an echo when encountering different interfaces. Specifically, the emission parameters of the pulsed laser signal need to consider the material parameters and shape characteristics of the workpiece to be measured to ensure that the laser signal can interact with the workpiece most effectively and generate a clear echo signal.

[0052] Among them, the selection of the frequency of the pulsed laser signal depends on the density and thickness of the workpiece to be measured. For workpieces with higher density or larger thickness, a higher frequency laser signal is required to obtain better penetration ability and signal resolution.

[0053] The incident angle is set according to the characteristics of the workpiece surface and specific detection targets. A smaller incident angle can increase the penetration depth of the signal.

[0054] The waveform of the pulsed laser signal usually selects the form of a narrow pulse, which can provide higher time resolution and is suitable for detecting small-sized defects. For larger workpieces, a wide pulse can also be used to increase the energy density and penetrate a greater thickness.

[0055] In some embodiments, the power of the pulsed laser can be adjusted by gear settings or knobs to achieve adaptive remote flaw detection in the range of 5 - 100m.

[0056] As a preferred embodiment, the pulsed laser signal is a pulsed laser with a wavelength band of 905nm.

[0057] The wavelength of the 905nm band is in the near-infrared spectrum range, with good reflection performance on the metal surface, which can effectively detect surface defects of metal workpieces. At the same time, it can effectively excite ultrasonic waves for semiconductor materials and metal materials, realizing effective interaction with the workpiece and generating a clear echo signal.

[0058] As a preferred embodiment, the demodulation of the ultrasonic signal from the laser echo signal by the signal processing module includes:

[0059] Based on the thermo-mechanical coupling equation, obtain the longitudinal wave and transverse wave corresponding to the ultrasonic signal according to the pulsed laser emission parameters, the material parameters of the workpiece, and the current ambient temperature.

[0060] As a specific embodiment, the thermo-mechanical coupling equation for laser excitation is:

[0061] [zT]+ρQ=ρcT1+T0βU[kε-βT]+f=ρU

[0062] Where z is the heat conduction tensor, ρ is the material density, Q is the heat source, c is the heat capacity, β is the thermal coupling tensor, T is the absolute temperature, U is the displacement tensor, k is the elastic modulus tensor, and f is the external force tensor per unit volume.

[0063] Based on the above thermo-mechanical coupling equation, the transverse wave velocity and longitudinal wave velocity are obtained according to the shear modulus and Young's modulus of the material:

[0064]

[0065]

[0066] Where c p and c s represent the longitudinal wave velocity and transverse wave velocity respectively, E is the Young's modulus of the material, and G is the shear modulus of the material.

[0067] Furthermore, the longitudinal wave waveform and transverse wave waveform, as well as characteristics such as field displacement and Lamb wave, can be obtained. By analyzing the phase and amplitude of the transverse wave, longitudinal wave, field displacement, Lamb wave, etc., the vibration information can be effectively restored to interpret the defect situation inside the workpiece.

[0068] As a preferred embodiment, the method for determining the external surface defects of the workpiece to be measured based on the laser echo signal and the internal structure defects of the workpiece to be measured based on the ultrasonic signal includes:

[0069] Determining the attenuation coefficient and reference delay according to the distance between the laser generation module and the workpiece, the material parameters of the workpiece, and the current ambient temperature;

[0070] Based on the attenuation coefficient and reference delay, determining the scattering mode of the laser echo signal, and judging whether there is wear on the surface of the workpiece to be measured according to the scattering mode, and positioning the wear position;

[0071] Performing Fourier transform on the longitudinal wave and transverse wave, and determining the internal structure defects of the workpiece to be measured according to the amplitude attenuation and phase change at a preset frequency.

[0072] Specifically, when the laser irradiates a smooth surface, most of the light will be reflected from the surface in a reflective manner to form specular reflection, and only a very small part of the light will be scattered, and the scattering angle is very small. Therefore, when the laser irradiates a rough surface, the light will be scattered at a wider angle to form diffuse reflection. In this scattering mode, the intensity distribution of the echo signal will be more extensive and the waveform may be irregular. Therefore, by analyzing the characteristic waveform or abnormal intensity value generated in the echo signal, it is possible to analyze and judge whether there is wear on the outer surface of the workpiece.

[0073] As a preferred embodiment, performing Fourier transform on the longitudinal wave and the transverse wave, and determining internal structure defects of the workpiece to be measured according to amplitude attenuation and phase change of a preset frequency, includes:

[0074] Determining a first amplitude and first phase information corresponding to a first frequency component in the longitudinal wave, and when an error between the first amplitude and the first phase information and a preset first standard value exceeds a first threshold range, determining that corrosion occurs in the workpiece to be measured;

[0075] When corrosion occurs in the workpiece to be measured, judging second amplitude and second phase information corresponding to a second frequency component in the transverse wave, and determining the corrosion depth of the workpiece according to the second amplitude and the second phase information.

[0076] By performing Fourier transform on the ultrasonic signal, the frequency components of the signal can be clearly displayed, the characteristics of different frequency components are analyzed, and by comparing the amplitude and phase information of different frequency components with preset standard values, defects that may exist in the material, such as corrosion, through damage, semi-through damage, pores and other defects, can be determined. The defect reflection wave is greatly affected by the defect depth and obvious reflection wave peaks will appear.

[0077] It is found in practical applications that through the above analysis method, cracks with a precision of 0.2 mm can be effectively identified and located, meeting the requirements of industrial production.

[0078] It should be noted that for formed parts, a fast scanning method can be used to store spectral signals and establish samples, and defects can be quickly identified through comparison.

[0079] As a preferred embodiment, the outer surface defects include deformation and fracture; the internal structure defects include pores, slag inclusions and corrosion.

[0080] The outer surface shape of the material or product does not conform to the design requirements, which may be caused by mechanical deformation or stress during the processing; cracks or complete fractures on the surface may be caused by insufficient material strength, stress concentration or external forces. The defects on the outer surface can be analyzed and judged according to the reflection intensity, delay time, echo waveform and scattering characteristics of the laser echo signal.

[0081] When impurities in the workpiece raw material cannot be completely removed, the phenomenon of slag inclusion will occur. The density and hardness of the slag inclusion are different from those of the surrounding materials, which will cause the sound wave to change the propagation speed when passing through the slag inclusion area, and thus be reflected in the longitudinal wave and transverse wave signals. Usually, it is manifested as a decrease in the amplitude of the echo signal, a change in shape, a change in the propagation speed near the slag inclusion area, etc.

[0082] As a preferred embodiment, the method further includes: establishing a simulation model corresponding to the workpiece according to the laser echo signal and the ultrasonic signal.

[0083] By establishing a simulation model corresponding to the workpiece, the responses of the laser echo signal and the ultrasonic signal under different defect conditions can be more accurately simulated. By comparing and verifying with the actual detection results, the accuracy and reliability of the detection system can be further improved. Specifically, the simulation model discretizes the workpiece geometric model into finite element meshes, and ABAQUS can also be used to optimize the design and parameter settings of the detection system, thereby improving the detection efficiency and performance.

[0084] An embodiment of the present invention also provides a computer-readable storage medium, in which a computer program is stored. When the computer program is executed by a processor, it implements a workpiece remote flaw detection method based on laser ultrasound as described in any one of the above claims.

[0085] The present invention provides a workpiece remote flaw detection system and method based on laser ultrasound. The system emits pulsed laser through a laser generation module. The laser energy excites electron migration to cause lattice vibration, increasing the temperature of the workpiece surface. Using pulsed laser will cause the laser irradiation point to rapidly thermally expand, thereby generating thermoelastic waves. These thermoelastic waves can be transmitted inside the object and produce echoes when encountering different interfaces, thus generating ultrasonic signals on the workpiece surface. The laser detection module receives the laser echo modulated with the ultrasonic signal, and finally the signal processing module restores the ultrasonic information from the echo signal. By analyzing the laser echo signal, the external surface defects of the workpiece to be measured can be determined; while by analyzing the ultrasonic signal, the internal structure defects of the workpiece to be measured can be determined.

[0086] The advantages of this system are as follows:

[0087] 1. Non-contact detection is realized, without directly contacting the surface of the workpiece to be measured, avoiding errors in detection caused by possible damage or contamination.

[0088] 2. This system has good real-time performance. Laser ultrasound technology can achieve rapid data acquisition and processing, thus realizing real-time monitoring and instant feedback, which helps to improve production efficiency and product quality.

[0089] 3. High detection accuracy and resolution. By using a preset quantitative analysis model to analyze the laser echo signal and the ultrasonic signal, small-sized defects can be detected, improving the accuracy and reliability of detection.

[0090] 4. This system comprehensively utilizes laser echo signals and ultrasonic signals, and can comprehensively analyze the external surface and internal structure defects of the workpiece to be measured, which helps to discover and solve problems in a timely manner, and improve production efficiency and product quality.

[0091] As mentioned above, only the specific preferred embodiments of the present invention are described, but the protection scope of the present invention is not limited thereto. Any changes or substitutions that can be easily thought of by those skilled in the art within the technical scope disclosed by the present invention should be covered within the protection scope of the present invention.

Claims

1. A remote flaw detection system for workpieces based on laser ultrasound, characterized in that, It includes a laser generation module, a laser detection module, and a signal processing module connected in sequence: The laser generation module is used to remotely transmit a pulsed laser signal to the workpiece to be detected. Under the excitation of the pulsed laser signal, the workpiece to be detected generates an ultrasonic signal carrying defect information; The laser detection module is used to receive the laser echo signal carrying the ultrasonic signal; The signal processing module is used to demodulate the ultrasonic signal from the laser echo signal, analyze the laser echo signal and the ultrasonic signal using a preset quantitative analysis model, determine the external surface defects of the workpiece to be detected based on the laser echo signal, and determine the internal structure defects of the workpiece to be detected based on the ultrasonic signal; the quantitative analysis model establishes the correlation relationship between the material parameters of the workpiece to be detected, the pulsed laser parameters, and the laser echo waveform based on Fourier transform.

2. A remote flaw detection method for workpieces based on laser ultrasound, characterized in that, Applied to the remote flaw detection system for workpieces based on laser ultrasound as described in claim 1, it includes: Remotely send a pulsed laser signal to the workpiece to be detected through the laser generation module. Under the excitation of the pulsed laser signal, the workpiece to be detected generates an ultrasonic signal carrying defect information; Receive the laser echo signal carrying the ultrasonic signal through the laser detection module; Demodulate the ultrasonic signal from the laser echo signal through the signal processing module, analyze the laser echo signal and the ultrasonic signal using a preset quantitative analysis model, determine the external surface defects of the workpiece to be detected based on the laser echo signal, and determine the internal structure defects of the workpiece to be detected based on the ultrasonic signal; the quantitative analysis model establishes the correlation relationship between the material parameters of the workpiece to be detected, the pulsed laser parameters, and the laser echo waveform based on Fourier transform.

3. The method for remote flaw detection of a workpiece based on laser ultrasound according to claim 2, wherein, The remotely sending a pulsed laser signal to the workpiece to be detected through the laser generation module includes: Set the emission parameters of the pulsed laser signal according to the material parameters and shape characteristics of the workpiece to be detected, and the emission parameters include the frequency, incident angle, and waveform of the pulsed laser signal.

4. The method for remote flaw detection of a workpiece based on laser ultrasound according to claim 2, wherein The demodulating the ultrasonic signal from the laser echo signal through the signal processing module includes: Based on the thermo-mechanical coupling equation, obtain the longitudinal wave and transverse wave corresponding to the ultrasonic signal according to the pulsed laser emission parameters, the material parameters of the workpiece, and the current ambient temperature.

5. The method for remote flaw detection of a workpiece based on laser ultrasound according to claim 4, wherein The determining the external surface defects of the workpiece to be detected based on the laser echo signal and determining the internal structure defects of the workpiece to be detected based on the ultrasonic signal include: Determine the attenuation coefficient and the reference delay according to the distance between the laser generation module and the workpiece, the material parameters of the workpiece, and the current ambient temperature; Based on the attenuation coefficient and the reference delay, determine the scattering mode of the laser echo signal, judge whether there is wear on the surface of the workpiece to be detected according to the scattering mode, and locate the wear position; Perform Fourier transform on the longitudinal wave and the transverse wave, and determine the internal structure defects of the workpiece to be detected according to the amplitude attenuation and phase change at a preset frequency.

6. The method for remote flaw detection of a workpiece based on laser ultrasound according to claim 5, characterized in that, The performing Fourier transform on the longitudinal wave and the transverse wave and determining the internal structure defects of the workpiece to be detected according to the amplitude attenuation and phase change at a preset frequency includes: Determine the first amplitude and the first phase information corresponding to the first frequency component in the longitudinal wave. When the error between the first amplitude and the first phase information and the preset first standard value exceeds the first threshold range, it is determined that the workpiece to be tested is corroded; When the workpiece to be tested is corroded, judge the second amplitude and the second phase information corresponding to the second frequency component in the shear wave, and determine the corrosion depth of the workpiece according to the second amplitude and the second phase information.

7. The method for remote flaw detection of a workpiece based on laser ultrasound according to claim 2, characterized in that, The external surface defects include deformation and fracture; the internal structure defects include pores, slag inclusions and corrosion.

8. The method for remote flaw detection of a workpiece based on laser ultrasound according to claim 2, characterized in that, The pulsed laser signal is a pulsed laser with a wavelength band of 905 nm.

9. The method for remote flaw detection of a workpiece based on laser ultrasound according to claim 2, wherein The method further includes: establishing a simulation model corresponding to the workpiece according to the laser echo signal and the ultrasonic signal.

10. A computer-readable storage medium, characterized in that, The computer-readable storage medium stores a computer program, which when executed by a processor, implements a remote flaw detection method for a workpiece based on laser ultrasound as described in any one of claims 2-9.

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