Frequency domain laser ultrasonic defect detection method and system for bonding structure material

Abstract

The invention discloses a frequency domain laser ultrasonic defect detection method and system for a bonding structure material, and relates to the technical field of defect detection, and the method comprises the following steps: generating a modulation signal according to a simple harmonic waveform and a resonant frequency corresponding to a to-be-detected bonding structure material, and sending modulation laser to a preset excitation point on the surface of the to-be-detected bonding structure material according to the modulation signal; emitting incident detection laser to an excitation point to detect an ultrasonic signal excited by the modulation laser, and determining a reflection detection laser electric signal; determining the amplitude or phase of the excitation point relative to the ultrasonic signal based on the reflection detection laser electric signal; and carrying out moving defect detection on the to-be-detected bonding structure material, and determining a defect detection result by adopting the amplitudes or phases of the plurality of excitation points. Based on the scheme, the photo-thermal-acoustic effect detection mode based on the modulated laser is beneficial to improving the reliability of laser ultrasonic defect detection of the bonding structure material.

Description

Technical Field

[0001] The present invention relates to the technical field of defect detection, and in particular to a frequency domain laser ultrasonic defect detection method and system for bonding structural materials. Background Art

[0002] Bonded structural materials refer to composite materials with a bonding structure. Their excellent structural properties have enabled them to be widely used in many fields such as civil industrial production, aerospace, and military industry. At the same time, this material has a higher challenge to quality inspection during the production process due to its diverse composition, significant anisotropy, and complex manufacturing process. The main problem faced is how to overcome the interference of the complex micro-surface structure of the bonded structural material on the detection system, so as to obtain high-resolution internal deep defect information.

[0003] The traditional detection method uses air-coupled probes for transmission and reception. Due to severe attenuation in the air, slow scanning speed, low resolution and low signal-to-noise ratio, only large internal defects can be identified when detecting bonding structural materials with complex surface structures. Laser ultrasonic detection technology has received extensive attention in the field of material defect detection due to its advantages of fast, real-time, non-contact detection and high spatial resolution. Existing laser ultrasonic detection mainly relies on the principle that high-energy pulsed lasers can produce thermoelastic mechanisms and ablation mechanisms for detection. However, the surface displacement generated by the lossless thermoelastic mechanism is less than 10e-7m, and the signal-to-noise ratio is still poor. The plasma directional force generated under ablation conditions improves the problem of low signal-to-noise ratio, but the material surface is easily damaged, which leads to low reliability of laser ultrasonic defect detection of bonding structural materials. Summary of the invention

[0004] The present invention provides a frequency domain laser ultrasonic defect detection method and system for bonding structural materials, which solves the technical problem that the existing laser ultrasonic defect detection technology has limitations such as poor signal-to-noise ratio or easy damage to the material surface when performing defect detection on bonding structural materials, resulting in low reliability of laser ultrasonic defect detection on bonding structural materials.

[0005] The first aspect of the present invention provides a frequency domain laser ultrasonic defect detection method for bonding structural materials, comprising:

[0006] Generate a modulation signal according to the simple harmonic waveform and the resonance frequency corresponding to the bonded structural material to be tested, and emit a modulated laser to a preset excitation point on the surface of the bonded structural material to be tested according to the modulation signal;

[0007] Sending an incident detection laser to the excitation point to detect the ultrasonic signal excited by the modulated laser, and determining a reflected detection laser electrical signal;

[0008] determining the amplitude or phase of the excitation point with respect to the ultrasonic signal based on the reflected detection laser electrical signal;

[0009] The moving defect detection is performed on the bonded structural material to be detected, and the defect detection result is determined by using the amplitudes or phases of the multiple excitation points.

[0010] Optionally, determining the amplitude or phase of the excitation point with respect to the ultrasonic signal based on the reflected detection laser electrical signal comprises:

[0011] Using the synchronization signal corresponding to the modulation signal and the reflected detection laser electrical signal to perform phase-locked analysis, and outputting the amplitude or phase of the excitation point with respect to the ultrasonic signal;

[0012] Alternatively, the reflected detection laser electrical signal is subjected to Fourier transform to output the amplitude or phase of the excitation point with respect to the ultrasonic signal.

[0013] Optionally, the adopting the amplitudes or phases of the plurality of excitation points to determine the defect detection result includes:

[0014] Using the amplitudes or phases of the plurality of excitation points to perform ultrasonic C-scan imaging to generate a C-scan diagram;

[0015] Defect analysis is performed based on the C-scan image to determine defect detection results.

[0016] A second aspect of the present invention provides a frequency domain laser ultrasonic defect detection system for bonding structural materials, comprising: a function generator, a modulated laser, a mobile platform, a detection laser, an amplitude-to-phase converter, a computer and a mobile drive module;

[0017] The function generator is connected to the modulated laser, the amplitude-to-phase converter is connected to the detection laser and the computer respectively, and the mobile driving module is connected to the mobile platform, the amplitude-to-phase converter and the computer respectively;

[0018] The mobile platform is used to place the bonding structure material to be tested, and moves in response to the mobile pulse signal;

[0019] The function generator is used to generate a modulation signal according to a simple harmonic waveform and a resonance frequency corresponding to the bonding structure material to be tested;

[0020] The modulated laser is used to emit modulated laser to a preset excitation point on the surface of the bonding structure material to be tested according to the modulation signal;

[0021] The detection laser is used to emit incident detection laser to the excitation point to detect the ultrasonic signal excited by the modulated laser, and receive the corresponding reflected detection laser to convert it into a reflected detection laser electrical signal;

[0022] The amplitude-to-phase converter is used to respond to an external trigger signal and determine the amplitude or phase of the excitation point with respect to the ultrasonic signal based on the reflected detection laser electrical signal;

[0023] The mobile driving module is used to respond to the mobile instruction and generate a mobile pulse signal and an external trigger signal;

[0024] The computer is used to generate movement instructions, store the amplitude or phase of the excitation point and determine the defect detection result according to the amplitude or phase of multiple excitation points.

[0025] Optionally, an optical path component is also included;

[0026] The optical path component is arranged in the light output path of the modulating laser and the detecting laser;

[0027] The optical path component is used to focus the modulated laser on the excitation point, focus the incident detection laser on the excitation point, and reflect the corresponding reflected detection laser to the detection laser.

[0028] Optionally, the optical path component includes a reflector, a beam splitter and a convex lens;

[0029] The reflector is located in the light output path of the modulated laser;

[0030] The beam splitter is located in the reflection light path of the reflector and in the light output light path of the detection laser;

[0031] The convex lens is located on the beam splitting path of the beam splitter.

[0032] Optionally, the amplitude-to-phase converter is a phase-locked amplifier, the amplitude-to-phase converter is connected to the function generator, and the amplitude-to-phase converter is specifically used to use the synchronization signal corresponding to the modulation signal generated by the function generator and the reflected detection laser electrical signal to perform phase-locked analysis, and output the amplitude or phase of the excitation point with respect to the ultrasonic signal;

[0033] Alternatively, the amplitude-to-phase converter is specifically used to perform Fourier transform on the reflected detection laser electrical signal, and output the amplitude or phase of the excitation point with respect to the ultrasonic signal.

[0034] A third aspect of the present invention provides a computer device, comprising a memory and a processor, wherein the memory stores a computer program, and when the computer program is executed by the processor, the processor executes the steps of the frequency domain laser ultrasonic defect detection method for bonding structural materials as described in any one of the above items.

[0035] A fourth aspect of the present invention provides a computer-readable storage medium having a computer program stored thereon, which, when executed, implements the frequency domain laser ultrasonic defect detection method for bonding structural materials as described in any one of the above items.

[0036] A fifth aspect of the present invention provides a computer program product, comprising a computer program / instruction, which, when executed by a processor, implements the frequency domain laser ultrasonic defect detection method for bonding structural materials as described in any one of the above items.

[0037] It can be seen from the above technical solutions that the present invention has the following advantages:

[0038] The above scheme of the present invention provides a frequency domain laser ultrasonic defect detection method for bonding structural materials, including: generating a modulation signal according to a simple harmonic waveform and the resonance frequency corresponding to the bonding structural material to be tested, sending a modulated laser to a preset excitation point on the surface of the bonding structural material to be tested according to the modulation signal; sending an incident detection laser to the excitation point to detect the ultrasonic signal excited by the modulated laser, and determining the reflected detection laser electrical signal; determining the amplitude or phase of the ultrasonic signal at the excitation point based on the reflected detection laser electrical signal; performing mobile defect detection on the bonding structural material to be tested, and using the amplitude or phase of multiple excitation points to determine the defect detection result. Based on the above scheme, the modulated laser is applied to the surface of the bonding structural material to be tested to cause resonance and generate a modulated ultrasonic wave, and the corresponding single-frequency ultrasonic information such as the amplitude or phase is extracted after the incident detection laser is used to detect the modulated ultrasonic wave, and the defect state of the bonding structural material to be tested is obtained by analyzing the frequency domain information. This photothermoacoustic effect detection method based on modulated laser helps to improve the reliability of laser ultrasonic defect detection of bonding structural materials. BRIEF DESCRIPTION OF THE DRAWINGS

[0039] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative labor.

[0040] Figure 1 A flowchart of the steps of a frequency domain laser ultrasonic defect detection method for bonding structural materials provided by an embodiment of the present invention;

[0041] Figure 2 A schematic structural diagram of a frequency domain laser ultrasonic defect detection system for bonding structural materials provided by an embodiment of the present invention;

[0042] In the figure: 1. function generator; 2. modulated laser; 3. reflector; 4. spectroscope; 5. convex lens; 6. bonding structure material to be tested; 7. mobile platform; 8. detection laser; 9. amplitude-to-phase converter; 10. computer; 11. mobile drive module. DETAILED DESCRIPTION

[0043] The embodiments of the present invention provide a frequency domain laser ultrasonic defect detection method and system for bonding structural materials, which are used to solve the technical problem that the existing laser ultrasonic defect detection technology has limitations such as poor signal-to-noise ratio or easy damage to the material surface when performing defect detection on bonding structural materials, resulting in low reliability of laser ultrasonic defect detection on bonding structural materials.

[0044] In order to make the purpose, features and advantages of the present invention more obvious and easy to understand, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the embodiments described below are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0045] See also Figure 1 , Figure 1 A flowchart of the steps of a frequency domain laser ultrasonic defect detection method for bonding structural materials provided in an embodiment of the present invention.

[0046] The present invention provides a frequency domain laser ultrasonic defect detection method for bonding structural materials, comprising:

[0047] Step 101 : generating a modulation signal according to a simple harmonic waveform and a resonance frequency corresponding to the bonded structural material to be tested, and emitting a modulated laser to a preset excitation point on the surface of the bonded structural material to be tested according to the modulation signal.

[0048] A simple harmonic waveform refers to a periodic waveform that can be described by a sine function or a cosine function. The wavelength of this waveform is fixed and has a single frequency, including sine waveforms and cosine waveforms.

[0049] Resonant frequency refers to the frequency that can produce a resonant response with the bonded structural material to be tested.

[0050] The modulation signal refers to the electrical signal used to control the output corresponding laser characteristics.

[0051] Modulated laser refers to the laser generated by modulation signal.

[0052] The excitation point refers to the location where the external excitation is applied.

[0053] It should be noted that, in this embodiment, a modulation signal is generated by using a simple harmonic waveform as a modulation waveform and a resonance frequency corresponding to the bonding structure material to be tested as a modulation frequency, and the corresponding modulated laser is controlled to be emitted according to the modulation signal, and acts on a preset excitation point on the surface of the bonding structure material to be tested to generate a modulated ultrasonic wave, so that the modulated ultrasonic wave can propagate and act on the inside of the bonding structure material to be tested, causing a resonance response; in a specific implementation, the resonance frequency can be a frequency that is the same as or close to the natural frequency of the bonding structure material to be tested.

[0054] Step 102: Send an incident detection laser to the excitation point to detect the ultrasonic signal excited by the modulated laser, and determine the reflected detection laser electrical signal.

[0055] The incident detection laser refers to the laser beam that is irradiated into the detection target surface for the purpose of detection; the reflected detection laser refers to the light signal reflected back after the incident detection laser is irradiated onto the detection target surface, and the reflected detection laser electrical signal refers to the electrical signal corresponding to the reflected detection laser.

[0056] It should be noted that this embodiment uses the incident detection laser to irradiate the position of the excitation point excited by the modulated laser, so that the ultrasonic signal generated by the modulated ultrasonic wave, that is, the vibration information of the bonding structure material to be tested caused by the modulated ultrasonic wave, can be detected and reflected in the reflected detection laser. In order to facilitate subsequent analysis, the reflected detection laser is photoelectrically converted into a reflected detection laser electrical signal.

[0057] Step 103: Determine the amplitude or phase of the excitation point with respect to the ultrasonic signal based on the reflected detection laser electrical signal.

[0058] Step 103 includes the following sub-steps:

[0059] The synchronous signal corresponding to the modulation signal and the reflected detection laser electrical signal are used to perform phase-locked analysis, and the amplitude or phase of the ultrasonic signal at the excitation point is output;

[0060] Alternatively, the reflected detection laser electrical signal is subjected to Fourier transform to output the amplitude or phase of the excitation point with respect to the ultrasonic signal.

[0061] A synchronization signal refers to a signal that is synchronized with the modulation signal, that is, the two have the same frequency and fixed phase.

[0062] It should be noted that, as this embodiment uses frequency domain laser ultrasound based on the light / heat / acoustic multi-physics field coupling theory to obtain the resonance response of the bonded structure material to be tested under the action of modulated ultrasound, thereby obtaining the structural characteristics of the bonded structure material to be tested, so as to realize the explanation of defect detection, taking amplitude as an example:

[0063] Assuming that the heat absorption on the material surface is uniform, and the thermal expansion caused by modulated laser irradiation only generates stress waves in the longitudinal direction; the material is regarded as having infinite lateral dimensions, so the influence of lateral boundary reflection is ignored, and the light absorption layer is extremely thin, then based on the heat conduction equation, it can be obtained:

[0064] ;

[0065] In the formula, is the material density, is the specific heat capacity of the material, is the partial differential, is the temperature, is the material in the Cartesian coordinate system The position of the coordinate axes, For time, is the thermal conductivity of the material, is the heat source term in the time domain;

[0066] In the frequency domain, the time derivative can be expressed as Therefore, the frequency domain heat conduction equation is:

[0067] ;

[0068] in, ;

[0069] In the formula, is the power of the modulated laser in the frequency domain heat source term, is an imaginary unit, is the current modulation angular frequency, is the modulation frequency, is the thermal expansion coefficient of the material, is the Diktola function (indicating that the heat source acts on the material surface, i.e. Location);

[0070] Taking the cosine waveform as the modulation waveform as an example, the heat source term caused by the cosine modulated laser can be expressed as , and transform it into the frequency domain to obtain:

[0071] ;

[0072] In the formula, is the power of the modulated laser in the time domain heat source term, is the reference modulation angular frequency, is the peak power of the modulated laser; according to the Dikla function, for hour is 1, so Substituting into the frequency domain heat conduction equation, we have:

[0073] ;

[0074] For the surface heat source caused by modulated laser, the temperature can be obtained by solving the frequency domain heat conduction equation according to the general solution form of heat conduction and the boundary conditions of the heat source term; the general solution form of heat conduction includes:

[0075] ;

[0076] in, is the first heat conduction correlation coefficient, the second heat conduction correlation coefficient ;

[0077] Since the modulated laser energy is mainly absorbed by the material surface, the modulated laser energy is equivalent to the heat flux load on the solid surface, and it is assumed that the lower surface of the material is in adiabatic condition. The boundary condition of the heat source term is expressed as:

[0078] ;

[0079] In the formula, is the material thickness; under the boundary conditions of the heat source term, substituting into the frequency domain heat conduction equation, we get:

[0080] ;

[0081] So the temperature is:

[0082] ;

[0083] Stress can be derived based on temperature. According to the thermoelastic effect, temperature changes will cause changes in stress. The temperature-stress equation can be expressed as:

[0084] ;

[0085] In the formula, is stress, is the first Lamé constant, is the second Lamé constant; substituting the temperature into the temperature-stress equation, we can obtain:

[0086] ;

[0087] The frequency domain analytical formula for the displacement is:

[0088] ;

[0089] Therefore, according to the relationship between stress and displacement, the displacement satisfies the wave equation:

[0090] ;

[0091] in, ;

[0092] In the formula, is the displacement, is the longitudinal wave number, is the material longitudinal wave velocity;

[0093] According to the wave general solution form and wave boundary conditions, the wave equation can be solved to determine the displacement; the wave general solution is the sum of the homogeneous solution and the special solution, so the wave general solution form includes:

[0094] ;

[0095] in, , ;

[0096] In the formula, is a homogeneous solution, is the constant coefficient of the first homogeneous solution, is the constant coefficient of the second homogeneous solution, For a special solution, is the constant coefficient of the particular solution;

[0097] Solving the non-homogeneous wave equation, we can obtain:

[0098] ;

[0099] Assumptions about the wave boundary conditions:

[0100] 1) In (the upper surface of the material) is a free surface, then:

[0101] ;

[0102] 2) In At the defect position (lower surface of the sample), the sound wave is basically fully reflected, so there is no surface stress, then:

[0103] ;

[0104] Solve the homogeneous wave equation based on the wave boundary condition and determine and , thus, the analytical expression of displacement is:

[0105] ;

[0106] From the above displacement analytical expression, it can be seen that if the structure of the bonded structure material to be tested is evenly distributed, it will have the most ideal resonant response characteristics at its natural frequency. When the internal structure of the bonded structure material to be tested has uneven characteristics, such as holes, debonding and material damage, the natural frequency of the material will change, which will cause the displacement amplitude of the modulated ultrasonic wave to change. Therefore, the structure of the bonded structure material to be tested can be characterized according to the change in displacement amplitude to determine whether there are defects or further estimate the size of the defects according to the degree of change in amplitude.

[0107] Similar to the principle of defect detection based on amplitude, the change in phase can also be used to locate the position of the defect or further determine the type of defect. Therefore, the amplitude or phase of the ultrasonic signal corresponding to the modulated ultrasonic wave detected by the reflected detection laser can be used to complete defect analysis. In specific implementation, the amplitude or phase of the signal can be determined based on phase-locked analysis or Fourier transform. The specific principle can be referred to the existing technology and will not be repeated here.

[0108] Step 104: Perform moving defect detection on the bonded structural material to be tested, and use the amplitudes or phases of multiple excitation points to determine the defect detection result.

[0109] Step 104 includes the following sub-steps:

[0110] The amplitude or phase of multiple excitation points is used to perform ultrasonic C-scan imaging to generate a C-scan diagram;

[0111] Perform defect analysis based on the C-scan image to determine the defect detection results.

[0112] It should be noted that a plurality of excitation points may be set on the surface of the bonding structure material to be tested, and by performing moving defect detection on each excitation point according to steps 101 to 103, the internal structural characteristics of the bonding structure material to be tested may be determined based on the global defect information, thereby analyzing and determining the defect detection result; in one implementation, the internal structural distribution of the bonding structure material to be tested may be characterized by generating a C-scan image by ultrasonic C-scan imaging based on the amplitude of each excitation point or the phase of each excitation point, so as to facilitate analysis and determination of the defect detection situation.

[0113] In an embodiment of the present invention, a modulated laser is applied to the surface of the bonding structure material to be tested to cause resonance and generate a modulated ultrasonic wave. The ultrasonic signal of the modulated ultrasonic wave is detected by an incident detection laser, and then the corresponding single-frequency ultrasonic information such as the amplitude or phase is extracted. The defect state of the bonding structure material to be tested is obtained by analyzing the frequency domain information. This photothermoacoustic effect detection method based on modulated laser has the advantages of non-contact, non-destructive, low cost and high signal-to-noise ratio. It is of great significance for the non-destructive characterization of bonding structure materials and helps to improve the reliability of laser ultrasonic defect detection of bonding structure materials.

[0114] See also Figure 2 , Figure 2 A schematic structural diagram of a frequency domain laser ultrasonic defect detection system for bonding structural materials provided in an embodiment of the present invention.

[0115] The present invention provides a frequency domain laser ultrasonic defect detection system for bonding structural materials, comprising: a function generator 1, a modulated laser 2, a mobile platform 7, a detection laser 8, an amplitude-to-phase converter 9, a computer 10 and a mobile drive module 11;

[0116] The function generator 1 is connected to the modulated laser 2, the amplitude-phase converter 9 is connected to the detection laser 8 and the computer 10 respectively, and the mobile driving module 11 is connected to the mobile platform 7, the amplitude-phase converter 9 and the computer 10 respectively;

[0117] The mobile platform 7 is used to place the bonding structure material 6 to be tested, and moves in response to the mobile pulse signal;

[0118] The function generator 1 is used to generate a modulation signal according to the simple harmonic waveform and the resonance frequency corresponding to the bonded structural material 6 to be tested;

[0119] The modulated laser 2 is used to emit modulated laser to a preset excitation point on the surface of the bonding structure material 6 to be tested according to the modulation signal;

[0120] The detection laser 8 is used to send an incident detection laser to the excitation point to detect the ultrasonic signal excited by the modulated laser, and receive the corresponding reflected detection laser to convert it into a reflected detection laser electrical signal;

[0121] The amplitude-to-phase converter 9 is used to respond to the external trigger signal and determine the amplitude or phase of the excitation point with respect to the ultrasonic signal based on the reflected detection laser electrical signal;

[0122] The mobile driving module 11 is used to respond to the mobile instruction and generate a mobile pulse signal and an external trigger signal;

[0123] The computer 10 is used to generate movement instructions, store the amplitude or phase of the excitation point, and determine the defect detection result according to the amplitude or phase of multiple excitation points.

[0124] It should be noted that, in the process of defect detection, after the bonded structural material 6 to be tested is placed on the mobile platform 7, the computer 10 generates a movement instruction to drive the mobile platform 7 to move to the preset excitation point on the surface of the bonded structural material 6 to be tested, which can correspond to the laser position emitted by the modulated laser 2 and the detection laser 8, and sends it to the mobile drive module 11. The mobile drive module 11 can be specifically an FPGA module. The mobile drive module 11 responds to the received movement instruction, generates a movement pulse signal to drive the mobile platform 7 to move to the mobile platform 7, and generates an external trigger signal to be sent to the amplitude-to-phase converter 9 to trigger the sampling and acquisition of the amplitude or phase of the laser ultrasonic detection of the current excitation point. At the same time, a modulation signal is generated by the function generator 1 according to the simple harmonic waveform and the resonance frequency corresponding to the bonded structural material 6 to be tested and sent to the modulated laser 2, thereby adjusting the modulation. The control laser 2 outputs a modulated laser with a preset modulated laser power to the current excitation point for excitation to generate a modulated ultrasonic wave, so that the modulated ultrasonic wave can propagate and act on the inside of the bonded structural material 6 to be tested. After that, the detection laser 8 sends an incident detection laser to the excitation point to detect the ultrasonic signal of the modulated ultrasonic wave, and the corresponding reflected detection laser is photoelectrically converted into a reflected detection laser electrical signal and then input into the amplitude-to-phase converter 9. The amplitude-to-phase converter 9 outputs the amplitude or phase of the ultrasonic signal based on the reflected detection laser electrical signal according to the preset operation logic to the computer 10 for storage; then, the computer 10 continues to send a movement instruction about the next excitation point to the mobile drive module 11. After moving and detecting multiple excitation points according to the above steps, the computer 10 finally determines the defect detection result according to the amplitude or phase of each excitation point.

[0125] In a specific embodiment, the amplitude-to-phase converter 9 is a phase-locked amplifier, and the amplitude-to-phase converter 9 is connected to the function generator 1. The amplitude-to-phase converter 9 is specifically used to perform phase-locked analysis using the synchronization signal corresponding to the modulation signal generated by the function generator 1 and the reflected detection laser electrical signal, and output the amplitude or phase of the excitation point with respect to the ultrasonic signal;

[0126] Alternatively, the amplitude-to-phase converter 9 is specifically used to perform Fourier transform on the reflected detection laser electrical signal, and output the amplitude or phase of the excitation point with respect to the ultrasonic signal.

[0127] It should be noted that, in specific implementation, the amplitude-to-phase converter 9 can determine the amplitude or phase of the ultrasonic signal corresponding to the modulated ultrasonic wave of the current excitation point based on phase-locked analysis or Fourier transform; if phase-locked analysis is adopted, the amplitude-to-phase converter 9 can be specifically a phase-locked amplifier, and the amplitude-to-phase converter 9 is connected to the function generator 1. At this time, the modulation signal generated by the function generator 1 will also send the corresponding synchronization signal to the amplitude-to-phase converter 9. The amplitude-to-phase converter 9 can use orthogonal demodulation to perform phase-locked analysis according to the received synchronization signal and the reflected detection laser electrical signal to output the amplitude or phase of the ultrasonic signal; if Fourier transform is adopted, the Fourier transform operation logic is deployed in the amplitude-to-phase converter 9 to output the amplitude or phase of the ultrasonic signal based on the reflected detection laser electrical signal.

[0128] In a specific embodiment, the mobile platform 7 is a three-axis mobile platform.

[0129] It should be noted that the three-axis mobile platform includes an X-axis mobile platform, a Y-axis mobile platform and a Z-axis mobile platform. The X-axis mobile platform is used to drive the bonding structure material 6 to be tested to move along the X-axis direction, the Y-axis mobile platform is used to drive the bonding structure material 6 to be tested to move along the Y-axis direction, and the Z-axis mobile platform is used to drive the bonding structure material 6 to be tested to move along the Z-axis direction.

[0130] In a more specific embodiment, it also includes an optical path component;

[0131] The optical path component is arranged in the light output path of the modulation laser 2 and the detection laser 8;

[0132] The optical path component is used to focus the modulated laser on the excitation point, focus the incident detection laser on the excitation point and reflect the corresponding reflected detection laser to the detection laser 8.

[0133] In a specific embodiment, the optical path component includes a reflector 3, a beam splitter 4 and a convex lens 5;

[0134] The reflector 3 is located in the light path of the modulated laser 2;

[0135] The beam splitter 4 is located in the reflection light path of the reflector 3 and in the light output path of the detection laser 8;

[0136] The convex lens 5 is located in the beam splitting path of the beam splitter 4 .

[0137] It should be noted that, in order to limit the lasers emitted by the modulated laser 2 and the detection laser 8 to accurately focus on the excitation point of the bonded structural material 6 to be tested, it is considered to set an optical path component and set it on the light output path of the modulated laser 2 and the detection laser 8;

[0138] In one implementation, the optical path component includes a reflector 3, a beam splitter 4 and a convex lens 5, the beam splitter 4 is located on the reflecting optical path of the reflector 3, and the convex lens 5 is located on the beam splitting optical path of the beam splitter 4. At the same time, the reflector 3 is located on the light output path of the modulated laser 2, so that the modulated laser of the modulated laser 2 is focused on the excitation point along the reflector 3-beam splitter 4-convex lens 5 in sequence, and the beam splitter 4 is located on the light output path of the detection laser 8, so that the incident detection laser emitted by the detection laser 8 is focused on the excitation point along the beam splitter 4-convex lens 5 in sequence, and the corresponding reflected detection laser can also be reflected back to the detection laser 8 along the convex lens 5-beam splitter 4 in sequence; in a specific implementation, the above optical path relationship can be implemented as follows: the reflector 3 is located on the lower side of the modulated laser 2, the beam splitter 4 is located on the right side of the reflector 3 and on the lower side of the detection laser 8, and the convex lens 5 is located on the lower side of the beam splitter 4.

[0139] In an embodiment of the present invention, a modulated laser is applied to the surface of the bonding structure material to be tested to cause resonance and generate a modulated ultrasonic wave. The ultrasonic signal of the modulated ultrasonic wave is detected by an incident detection laser, and then the corresponding single-frequency ultrasonic information such as the amplitude or phase is extracted. The defect state of the bonding structure material to be tested is obtained by analyzing the frequency domain information. This photothermoacoustic effect detection method based on modulated laser has the advantages of non-contact, non-destructive, low cost and high signal-to-noise ratio. It can not only effectively improve the imaging resolution, but also has the advantages of modularization and miniaturization. It is of great significance for the non-destructive characterization of bonding structure materials and helps to improve the reliability of laser ultrasonic defect detection of bonding structure materials.

[0140] An embodiment of the present invention also provides a computer device, including a memory and a processor, wherein a computer program is stored in the memory; when the computer program is executed by the processor, the processor executes the steps of the frequency domain laser ultrasonic defect detection method for bonding structural materials as described in any of the above embodiments.

[0141] An embodiment of the present invention further provides a computer-readable storage medium having a computer program / instruction stored thereon. When the computer program / instruction is executed by a processor, the steps of the frequency domain laser ultrasonic defect detection method for bonding structural materials as described in any of the above embodiments are implemented.

[0142] An embodiment of the present invention further provides a computer program product, including a computer program / instruction, which, when executed by a processor, implements the steps of the frequency domain laser ultrasonic defect detection method for bonding structural materials as in any of the above embodiments.

[0143] Those skilled in the art can clearly understand that, for the convenience and brevity of description, the specific working processes of the systems and units described above can refer to the corresponding processes in the aforementioned method embodiments, and will not be repeated here.

[0144] In the several embodiments provided in the present application, it should be understood that the disclosed systems and methods can be implemented in other ways. For example, the system embodiments described above are only schematic. For example, the division of the units is only a logical function division. There may be other division methods in actual implementation, such as multiple units or components can be combined or integrated into another system, or some features can be ignored or not executed. Another point is that the mutual coupling or direct coupling or communication connection shown or discussed can be through some interfaces, indirect coupling or communication connection of systems or units, which can be electrical, mechanical or other forms.

[0145] The units described as separate components may or may not be physically separated, and the components shown as units may or may not be physical units, that is, they may be located in one place or distributed on multiple network units. Some or all of the units may be selected according to actual needs to achieve the purpose of the solution of this embodiment.

[0146] In addition, each functional unit in each embodiment of the present invention may be integrated into one processing unit, or each unit may exist physically separately, or two or more units may be integrated into one unit. The above-mentioned integrated unit may be implemented in the form of hardware or in the form of software functional units.

[0147] If the integrated unit is implemented in the form of a software functional unit and sold or used as an independent product, it can be stored in a computer-readable storage medium. Based on this understanding, the technical solution of the present invention, in essence, or the part that contributes to the prior art, or all or part of the technical solution can be embodied in the form of a software product. The computer software product is stored in a storage medium, including several instructions for a computer device (which can be a personal computer, a server, or a network device, etc.) to perform all or part of the steps of the method described in each embodiment of the present invention. The aforementioned storage medium includes: U disk, mobile hard disk, read-only memory (ROM, Read-Only Memory), random access memory (RAM, Random Access Memory), disk or optical disk, etc. Various media that can store program codes.

[0148] As described above, the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit the same. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that the technical solutions described in the aforementioned embodiments may still be modified, or some of the technical features thereof may be replaced by equivalents. However, these modifications or replacements do not deviate the essence of the corresponding technical solutions from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A frequency domain laser ultrasonic defect detection method for bonding structural materials, characterized in that: include: Generate a modulation signal according to the simple harmonic waveform and the resonance frequency corresponding to the bonded structural material to be tested, and emit a modulated laser to a preset excitation point on the surface of the bonded structural material to be tested according to the modulation signal; Sending an incident detection laser to the excitation point to detect the ultrasonic signal excited by the modulated laser, and determining a reflected detection laser electrical signal; determining the amplitude or phase of the excitation point with respect to the ultrasonic signal based on the reflected detection laser electrical signal; The moving defect detection is performed on the bonded structural material to be detected, and the defect detection result is determined by using the amplitudes or phases of the multiple excitation points.

2. The frequency domain laser ultrasonic defect detection method for bonding structural materials according to claim 1 is characterized in that: The determining the amplitude or phase of the excitation point with respect to the ultrasonic signal based on the reflected detection laser electrical signal comprises: Using the synchronization signal corresponding to the modulation signal and the reflected detection laser electrical signal to perform phase-locked analysis, and outputting the amplitude or phase of the excitation point with respect to the ultrasonic signal; Alternatively, the reflected detection laser electrical signal is subjected to Fourier transform to output the amplitude or phase of the excitation point with respect to the ultrasonic signal.

3. The frequency domain laser ultrasonic defect detection method for bonding structural materials according to claim 1, characterized in that: The method of using the amplitudes or phases of the plurality of excitation points to determine the defect detection result comprises: Using the amplitudes or phases of the plurality of excitation points to perform ultrasonic C-scan imaging to generate a C-scan diagram; Defect analysis is performed based on the C-scan image to determine defect detection results.

4. A frequency domain laser ultrasonic defect detection system for bonding structural materials, characterized in that: include: Function generator, modulated laser, mobile platform, detection laser, amplitude-to-phase converter, computer and mobile drive module; The function generator is connected to the modulated laser, the amplitude-to-phase converter is connected to the detection laser and the computer respectively, and the mobile driving module is connected to the mobile platform, the amplitude-to-phase converter and the computer respectively; The mobile platform is used to place the bonding structure material to be tested, and moves in response to the mobile pulse signal; The function generator is used to generate a modulation signal according to a simple harmonic waveform and a resonance frequency corresponding to the bonding structure material to be tested; The modulated laser is used to emit modulated laser to a preset excitation point on the surface of the bonding structure material to be tested according to the modulation signal; The detection laser is used to emit incident detection laser to the excitation point to detect the ultrasonic signal excited by the modulated laser, and receive the corresponding reflected detection laser to convert it into a reflected detection laser electrical signal; The amplitude-to-phase converter is used to respond to an external trigger signal and determine the amplitude or phase of the excitation point with respect to the ultrasonic signal based on the reflected detection laser electrical signal; The mobile driving module is used to respond to the mobile instruction and generate a mobile pulse signal and an external trigger signal; The computer is used to generate movement instructions, store the amplitude or phase of the excitation point and determine the defect detection result according to the amplitude or phase of multiple excitation points.

5. The frequency domain laser ultrasonic defect detection system for bonding structural materials according to claim 4, characterized in that: Also included are optical path components; The optical path component is arranged in the light output path of the modulating laser and the detecting laser; The optical path component is used to focus the modulated laser on the excitation point, focus the incident detection laser on the excitation point, and reflect the corresponding reflected detection laser to the detection laser.

6. The frequency domain laser ultrasonic defect detection system for bonding structural materials according to claim 5, characterized in that: The optical path components include a reflector, a beam splitter and a convex lens; The reflector is located in the light output path of the modulated laser; The beam splitter is located in the reflection light path of the reflector and in the light output light path of the detection laser; The convex lens is located on the beam splitting path of the beam splitter.

7. The frequency domain laser ultrasonic defect detection system for bonding structural materials according to claim 4, characterized in that: The amplitude-to-phase converter is a phase-locked amplifier, which is connected to the function generator. The amplitude-to-phase converter is specifically used to perform phase-locked analysis using the synchronization signal corresponding to the modulation signal generated by the function generator and the reflected detection laser electrical signal, and output the amplitude or phase of the excitation point with respect to the ultrasonic signal; Alternatively, the amplitude-to-phase converter is specifically used to perform Fourier transform on the reflected detection laser electrical signal, and output the amplitude or phase of the excitation point with respect to the ultrasonic signal.

8. A computer device, characterized in that: It comprises a memory and a processor, wherein a computer program is stored in the memory, and when the computer program is executed by the processor, the processor executes the steps of the frequency domain laser ultrasonic defect detection method for bonding structural materials as described in any one of claims 1 to 3.

9. A computer-readable storage medium having a computer program / instruction stored thereon, characterized in that: When the computer program / instructions are executed by a processor, the steps of the frequency domain laser ultrasonic defect detection method for bonding structural materials as described in any one of claims 1 to 3 are implemented.

10. A computer program product comprising a computer program / instructions, characterized in that When the computer program / instructions are executed by a processor, the steps of the frequency domain laser ultrasonic defect detection method for bonding structural materials as described in any one of claims 1 to 3 are implemented.

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