CN112098520A - Detection system and method for detecting internal defect shape of material based on laser ultrasonic - Google Patents

Abstract

The invention discloses a detection system and method based on laser ultrasonic detection of the shape of internal defects of materials, comprising an excitation module, a detection module, a data acquisition and processing module, and a precise two-dimensional mobile platform, on which a material to be tested is placed ; Excitation module includes pulsed laser generator, heat sink, control handle, excitation light path and laser emission probe; Detection module includes fiber splitter, dual-wave hybrid interferometer, CW laser generator and optical fiber; Data acquisition and processing module includes NI PXI‑ 5114 data acquisition card, ultrasonic testing probe and PC. By performing laser ultrasonic thermoelastic mode C-scan detection on both sides of the tested material, extracting the longitudinal wave time in the ultrasonic signal, calculating the distance from the outer surface of the internal defect to the tested plane, and reconstructing the internal defect in three dimensions, the shape and shape of the internal defect are obtained. position. It can effectively detect the internal defects of the plate, carry out three-dimensional reconstruction of the internal defects, and master the shape and orientation of the internal defects.

Description

A detection system and method based on laser ultrasonic detection of the shape of internal defects in materials

technical field

The invention relates to a laser ultrasonic nondestructive testing technology, in particular to a detection system and method based on the laser ultrasonic detection of the shape of internal defects of materials.

Background technique

Defect is one of the important quality indicators in the material production process, and there is currently a lack of good methods for detecting internal defects in metal sheets. Laser ultrasonic technology is a new type of non-destructive testing technology. It is a non-contact detection method. It can detect defects without damaging the material by using the thermoelastic effect.

However, most of the current laser ultrasonic testing cannot characterize the shape of the internal defects of the material.

SUMMARY OF THE INVENTION

The purpose of the present invention is to provide a detection system and method for detecting the shape of internal defects in materials based on laser ultrasound.

The purpose of this invention is to realize through the following technical solutions:

The detection system based on laser ultrasonic detection of the shape of internal defects in materials of the present invention includes an excitation module, a detection module, a data acquisition and processing module, and a precise two-dimensional mobile platform 1, on which the tested material 2 is placed;

The excitation module includes a pulsed laser generator 9, a radiator 10, a control handle 11, an excitation optical path and a laser emission probe 4;

The detection module includes a fiber splitter 5, a dual-wave hybrid interferometer 6, a continuous laser generator 12 and an optical fiber;

The data acquisition and processing module includes an NI PXI-5114 data acquisition card 7 , an ultrasonic detection probe 3 and a PC 8 .

The above-mentioned detection method for three-dimensional reconstruction based on a detection system for laser ultrasonic detection of internal defect shapes of materials includes the following specific steps:

Step 1: Turn on the experimental power supply, turn on the switches of the CW laser generator 12 and the fiber splitter 5, turn on and set the excitation laser parameters, find a red spot in the area to be detected, adjust the precision two-dimensional mobile platform 1, adjust the excitation beam and detection beam, Make the excitation beam perpendicular to the surface of the measured area and the excitation beam and the detection beam spot coincide;

Step 2: Fine-tune the distance between the laser emission probe 4 and the measured material 2 to change the size of the excitation spot, observe the DC output change, and adjust it to the maximum value;

Step 3: Turn on the dual-wave hybrid interferometer 6, adjust the spectroscopic rate adjustment knob of the fiber splitter 5, adjust the output signal to be a sine signal, and end when the sine signal is adjusted to the maximum;

Step 4: open the radiator 10, set the laser parameters through the control handle 11, excite the continuous pulse laser, open the signal acquisition software on the PC 8, and set the acquisition parameters;

Step 5: The signal acquisition software controls the precise two-dimensional mobile platform 1 to drive the tested material 2 to perform c-scanning according to the specified path, and the step length is 1mm;

Step 6: When the c-scan of the tested material 2 is completed, the tested material rotates by 1800, and the precision 2D mobile platform 1 performs the c-scan according to the original path. The original path starting point is the current path ending point, and the original path ending point is The starting point of this path;

Step 7: Process the detected ultrasonic signal.

It can be seen from the technical solutions provided by the present invention that the detection system and method based on laser ultrasonic detection of the shape of internal defects in materials provided by the embodiments of the present invention perform laser ultrasonic thermoelastic mode C-scan detection on both sides of the tested material to extract The longitudinal wave time in the ultrasonic signal is used to calculate the distance from the outer surface of the internal defect to the measured plane, and three-dimensional reconstruction of the internal defect is performed to obtain the shape and orientation of the internal defect. It can effectively detect the internal defects of the plate, and carry out three-dimensional reconstruction of the internal defects to grasp the shape and orientation of the internal defects.

Description of drawings

FIG. 1 is a schematic diagram of a detection system for detecting shapes of internal defects in materials based on laser ultrasound provided by an embodiment of the present invention.

FIG. 2 is a schematic diagram of optical fiber connection in an embodiment of the present invention.

FIG. 3 is a schematic diagram of the excitation route of the internal defects of the laser ultrasonic testing test material according to the embodiment of the present invention.

FIG. 4 is a schematic diagram of three-dimensional reconstruction of an ultrasonic longitudinal wave internal defect according to an embodiment of the present invention.

In the picture:

1. Precision two-dimensional mobile platform, 2. Materials to be tested, 3. Ultrasonic detection probe, 4. Laser emission probe, 5. Optical fiber splitter, 6. Dual-wave hybrid interferometer, 7. NI PXI-5114 data acquisition card, 8. PC, 9. Pulse laser generator, 10, Radiator, 11, Control handle, 12, Continuous laser generator, 13, Signal fiber, 14, Probe fiber, 15, Probe light, 16, Reference light, 17 , Splitting ratio adjustment knob, 18. Continuous laser entry.

Detailed ways

The embodiments of the present invention will be described in further detail below. Contents that are not described in detail in the embodiments of the present invention belong to the prior art known to those skilled in the art.

The preferred specific embodiment of the detection system based on the laser ultrasonic detection material internal defect shape of the present invention is:

It includes an excitation module, a detection module, a data acquisition and processing module, and a precise two-dimensional mobile platform 1, on which the tested material 2 is placed;

The excitation module includes a pulsed laser generator 9, a radiator 10, a control handle 11, an excitation optical path and a laser emission probe 4;

The detection module includes a fiber splitter 5, a dual-wave hybrid interferometer 6, a continuous laser generator 12 and an optical fiber;

The data acquisition and processing module includes an NI PXI-5114 data acquisition card 7 , an ultrasonic detection probe 3 and a PC 8 .

The laser emission probe 4 is connected with the pulsed laser generator 9 through the excitation optical path;

The pulsed laser generator 9 is connected with the radiator 10;

The control handle 11 is connected with the radiator 10;

The radiator 10 is connected with the NI PXI-5114 data acquisition card 7;

The ultrasonic detection probe 3 is respectively connected with the fiber optic splitter 5 and the dual-wave hybrid interferometer 6 through the optical fiber;

The continuous laser generator 12 is connected with the fiber splitter 5;

The optical fiber splitter 5 is connected with the dual-wave hybrid interferometer 6;

The wave mixing interferometer 6 is connected with the NI PXI-5114 data acquisition card 7;

The NI PXI-5114 data acquisition card 7 is connected with the PC 8;

The precise two-dimensional mobile platform 1 is connected with a PC 8 .

The laser emitting probe 4 and the ultrasonic detection probe 3 are located on the same side of the material to be tested, and the light spots are basically coincident.

The continuous laser generator 12 is a solid Nd:YAG pulsed laser with a wavelength of 1064 nm and a pulse width of 6 ns. The maximum energy of a single excitation pulse can reach 50 mJ. The aperture of the excitation probe is 25 mm and the focal length is 50 mJ. -100mm, the spot diameter is 100-200μm, the control handle 11 can adjust the capability, power, pulse repetition frequency and excitation mode of the pulsed laser;

The detection bandwidth of the dual-wave hybrid interferometer 6 is 120M;

The real-time sampling rate of the NI PXI-5114 data acquisition card 7 is 250 MS/s;

The measured surface of the measured material 2 has a coating, and the main function of the coating is to suppress the generation of surface waves and transverse waves, and to amplify longitudinal waves.

The effective movement range of the precise two-dimensional moving platform 1 in the X-axis and the Y-axis is 0-400 mm, and the minimum step size is 6.3 microns.

The above-mentioned detection method for three-dimensional reconstruction based on a detection system for laser ultrasonic detection of internal defect shapes of materials is characterized in that it includes the following specific steps:

Step 1: Turn on the experimental power supply, turn on the switches of the CW laser generator 12 and the fiber splitter 5, turn on and set the excitation laser parameters, find a red spot in the area to be detected, adjust the precision two-dimensional mobile platform 1, adjust the excitation beam and detection beam, Make the excitation beam perpendicular to the surface of the measured area and the excitation beam and the detection beam spot coincide;

Step 2: Fine-tune the distance between the laser emission probe 4 and the measured material 2 to change the size of the excitation spot, observe the DC output change, and adjust it to the maximum value;

Step 3: Turn on the dual-wave hybrid interferometer 6, adjust the spectroscopic rate adjustment knob of the fiber splitter 5, adjust the output signal to be a sine signal, and end when the sine signal is adjusted to the maximum;

Step 4: open the radiator 10, set the laser parameters through the control handle 11, excite the continuous pulse laser, open the signal acquisition software on the PC 8, and set the acquisition parameters;

Step 5: The signal acquisition software controls the precise two-dimensional mobile platform 1 to drive the tested material 2 to perform c-scanning according to the specified path, and the step length is 1mm;

Step 6: When the c-scan of the tested material 2 is completed, the tested material rotates by 1800, and the precision 2D mobile platform 1 performs the c-scan according to the original path. The original path starting point is the current path ending point, and the original path ending point is The starting point of this path;

Step 7: Process the detected ultrasonic signal.

Three-dimensional reconstruction is performed on the internal defects of the tested material 2, and a three-dimensional rectangular coordinate system is established. The origin of the coordinate system is the starting point of laser excitation, and each excitation point on the excitation path is set to (X, Y, L), where X, Y is the plane coordinate of the excitation point, L is the distance from the edge of the defect inside the excitation point to the excitation plane, L=CL*t/2, where CL is the longitudinal wave velocity, and t is the time from the laser excitation to the reception of the longitudinal wave;

Turn the tested material 2 over 1800 degrees, and do c-scan according to the first excitation path. The starting point of the first excitation path is the second excitation path termination point, and the first excitation path termination point is the second excitation path start point. . At this time, each excitation point on the excitation path is still set to (X, Y, L), where X, Y are the plane coordinates of the excitation point, L is the distance from the edge of the defect inside the excitation point to the excitation plane, L=d -CL*t/2, where d is the thickness of the measured material, CL is the longitudinal wave velocity, and t is the time from the laser excitation to the reception of the longitudinal wave;

Connecting the points located on the inside into a face is the shape of the defect inside the material.

The detection system and method based on the laser ultrasonic detection of the shape of the internal defect of the material of the present invention can effectively detect the internal defect of the plate, carry out three-dimensional reconstruction of the internal defect, and grasp the shape and orientation of the internal defect.

Specific examples:

As shown in Figures 1 to 4, a detection system based on laser ultrasonic detection of internal defect shapes of materials mainly includes an excitation module, a detection module, a data acquisition and processing module, a precision two-dimensional mobile platform 1 and a material to be tested 2. The excitation module includes a pulsed laser generator 9, a radiator 10, a control handle 11, an excitation light path and a laser emission probe 4, and the continuous laser generator 12 is a solid Nd:YAG type pulsed laser with a wavelength of 1064 nm, The pulse width is 6ns, and the maximum energy of a single excitation pulse can reach 50mJ. The aperture of the excitation probe is 25mm, the focal length is 50-100mm, and the spot diameter is 100-200μm. The control handle 11 can adjust the ability of the pulsed laser , power, pulse repetition rate and excitation mode. The detection module includes an optical fiber splitter 5, a dual-wave hybrid interferometer 6, a continuous laser generator 12 and an optical fiber. The detection bandwidth of the dual-wave hybrid interferometer 6 is 120MHz. The data acquisition and processing module includes an NI PXI-5114 data acquisition card 7, an ultrasonic detection probe 3 and a PC 8, and the NI PXI-5114 data acquisition card 7 has a real-time sampling rate of 250 MS/s. The tested surface of the tested material 2 has a special coating, which is mainly used to suppress the generation of surface waves and transverse waves and to amplify longitudinal waves. The effective movement range of the 1X-axis and the Y-axis of the precise two-dimensional moving platform is 0-400mm, and the minimum step size is 6.3 microns.

The specific connection mode of the present invention is as follows:

The laser emission probe 4 is connected with the pulsed laser generator 9 through the excitation optical path.

The pulsed laser generator 9 is connected to the heat sink 10 .

The control handle 11 is connected to the radiator 10 .

The radiator 10 is connected to the NI PXI-5114 data acquisition card 7 .

The ultrasonic detection probe 3 is connected to the fiber optic splitter 5 and the dual-wave hybrid interferometer 6 through optical fibers, respectively.

The continuous laser generator 12 is connected to the fiber splitter 5 .

The optical fiber splitter 5 is connected with the dual-wave hybrid interferometer 6 .

The wave mixing interferometer 6 is connected to the NI PXI-5114 data acquisition card 7 .

The NI PXI-5114 data acquisition card 7 is connected with the PC 8 .

The precise two-dimensional mobile platform 1 is connected with a PC 8 .

The laser emitting probe 4 and the ultrasonic detection probe 3 are located on the same side of the material to be tested, and the light spots are basically coincident.

A detection system and method based on laser ultrasonic detection of the shape of internal defects in materials, the detection method mainly includes the following specific steps:

Step 1: Turn on the experimental power supply, turn on the switches of the CW laser generator 12 and the fiber splitter 5, turn on and set the excitation laser parameters, find a red spot in the area to be detected, adjust the precision two-dimensional mobile platform 1, adjust the excitation beam and detection beam, Make the excitation beam perpendicular to the surface of the area to be measured and the excitation beam and detection beam spots coincide.

Step 2: Fine-tune the distance between the laser emitting probe 4 and the material to be tested 2 to change the size of the excitation spot, observe the change in the DC output, and adjust it to the maximum value.

Step 3: Turn on the dual-wave hybrid interferometer 6, adjust the light splitting rate adjustment knob of the fiber splitter 5, adjust the output signal to be a sine signal, and end when the sine signal is adjusted to the maximum.

Step 4: Open the radiator 10, set the laser parameters through the control handle 11, excite the continuous pulse laser, open the signal acquisition software on the PC 8, and set the acquisition parameters.

Step 5: The signal acquisition software controls the precise two-dimensional mobile platform 1 to drive the tested material 2 to perform c-scanning according to the specified path, and the step length is 1mm.

Step 6: When the c-scan of the tested material 2 is completed, the tested material rotates by 1800, and the precision 2D mobile platform 1 performs the c-scan according to the original path. The original path starting point is the current path ending point, and the original path ending point is The starting point of this path.

Step 7: Process the detected ultrasonic signal.

Three-dimensional reconstruction is performed on the internal defects of the tested material 2, and a three-dimensional rectangular coordinate system is established. The origin of the coordinate system is the starting point of laser excitation, and each excitation point on the excitation path is set to (X, Y, L), where X, Y is the plane coordinate of the excitation point, L is the distance from the edge of the defect inside the excitation point to the excitation plane, L=CL*t/2, where CL is the longitudinal wave velocity, and t is the time from the laser excitation to the reception of the longitudinal wave. Turn the tested material 2 over 1800 degrees, and do c-scan according to the first excitation path. The starting point of the first excitation path is the second excitation path termination point, and the first excitation path termination point is the second excitation path start point. . At this time, each excitation point on the excitation path is still set to (X, Y, L), where X, Y are the plane coordinates of the excitation point, L is the distance from the edge of the defect inside the excitation point to the excitation plane, L=d -CL*t/2, where d is the thickness of the material to be measured, CL is the longitudinal wave velocity, and t is the time from the laser excitation to the reception of the longitudinal wave. Connecting the points located on the inside into a face is the shape of the defect inside the material.

The above description is only a preferred embodiment of the present invention, but the protection scope of the present invention is not limited to this. Substitutions should be covered within the protection scope of the present invention. Therefore, the protection scope of the present invention should be based on the protection scope of the claims.

Claims (7)

1. a detection system based on laser ultrasonic detection material internal defect shape, is characterized in that, comprises excitation module, detection module, data acquisition and processing module, precision two-dimensional mobile platform (1), described precision two-dimensional mobile platform (1) ) on the material to be tested (2); The excitation module comprises a pulsed laser generator (9), a radiator (10), a control handle (11), an excitation light path and a laser emission probe (4); The detection module comprises an optical fiber splitter (5), a dual-wave hybrid interferometer (6), a continuous laser generator (12) and an optical fiber; The data acquisition and processing module includes an NI PXI-5114 data acquisition card (7), an ultrasonic detection probe (3) and a PC (8). 2. The detection system based on laser ultrasonic detection material internal defect shape according to claim 1, is characterized in that: The laser emission probe (4) is connected with the pulsed laser generator (9) through an excitation optical path; The pulsed laser generator (9) is connected with the radiator (10); The control handle (11) is connected with the radiator (10); The radiator (10) is connected with the NI PXI-5114 data acquisition card (7); The ultrasonic detection probe (3) is respectively connected with the optical fiber splitter (5) and the dual-wave hybrid interferometer (6) through the optical fiber; The continuous laser generator (12) is connected with the fiber splitter (5); The optical fiber splitter (5) is connected with the dual-wave hybrid interferometer (6); Described wave mixing interferometer 6 is connected with NI PXI-5114 data acquisition card (7); The NI PXI-5114 data acquisition card (7) is connected with the PC (8); The precise two-dimensional mobile platform (1) is connected with a PC (8). 3. The detection system based on laser ultrasonic detection of the shape of internal defects in materials according to claim 2, wherein the laser emission probe (4) and the ultrasonic detection probe (3) are located on the same side of the material to be tested, and The spots are basically coincident. 4. The detection system based on the laser ultrasonic detection material internal defect shape according to claim 3, is characterized in that: The continuous laser generator (12) is a solid Nd:YAG type pulsed laser, its wavelength is 1064nm, the pulse width is 6ns, the maximum energy of a single excitation pulse can reach 50mJ, the aperture of the excitation probe is 25mm, and the focal length is 25mm. is 50-100mm, the diameter of the light spot is 100-200μm, and the control handle (11) can adjust the capability, power, pulse repetition frequency and excitation mode of the pulsed laser; The detection bandwidth of the dual-wave hybrid interferometer (6) is 120M; The real-time sampling rate of the NI PXI-5114 data acquisition card (7) is 250 MS/s; The measured surface of the measured material (2) has a coating, and the main function of the coating is to suppress the generation of surface waves and transverse waves, and to amplify longitudinal waves. 5. The detection system based on laser ultrasonic detection of the shape of internal defects in materials according to claim 4, wherein the effective movement range of the precise two-dimensional moving platform (1) in the X-axis and the Y-axis is 0-400mm , with a minimum step size of 6.3 μm. 6. A detection method for three-dimensional reconstruction based on a detection system for laser ultrasonic detection of internal defect shapes in materials according to any one of claims 1 to 5, characterized in that, comprising the following specific steps: Step 1: Turn on the experimental power supply, turn on the switch of the continuous laser generator (12) and the optical fiber splitter 5, turn on and set the excitation laser parameters, find a red spot in the area to be detected, adjust the precision two-dimensional mobile platform (1), and adjust the excitation beam and the detection beam, so that the excitation beam is perpendicular to the surface of the measured area and the excitation beam and the detection beam spot coincide; Step 2: Fine-tune the distance between the laser emission probe (4) and the material to be tested (2) to change the size of the excitation spot, observe the change in the DC output, and adjust it to the maximum value; Step 3: Turn on the dual-wave hybrid interferometer (6), adjust the light splitting rate adjustment knob of the fiber splitter (5), adjust the output signal to be a sine signal, and end when the sine signal is adjusted to the maximum; Step 4: open the radiator (10), set the laser parameters through the control handle (11), excite the continuous pulse laser, open the signal acquisition software on the PC (8), and set the acquisition parameters; Step 5: The signal acquisition software controls the precise two-dimensional mobile platform (1) to drive the material to be tested (2) to perform c-scanning according to the specified path, and the step length is 1mm; Step 6: When the c-scan of the tested material (2) is completed, the tested material rotates 1800, and the precision two-dimensional moving platform (1) performs the c-scan according to the original path. The end point of the path is the start point of the current path; Step 7: Process the detected ultrasonic signal. 7. The detection method based on laser ultrasonic detection of the shape of internal defects in materials according to claim 6, characterized in that, three-dimensional reconstruction is performed on the internal defects of the tested material (2), and a three-dimensional rectangular coordinate system is established, and the origin of the coordinate system is The starting point of laser excitation, each excitation point on the excitation path is set to (X, Y, L), where X, Y are the plane coordinates of the excitation point, L is the distance from the edge of the defect inside the excitation point to the excitation plane, L =CL*t/2, where CL is the longitudinal wave velocity, and t is the time from the laser excitation to the reception of the longitudinal wave; Perform 1800 inversion of the tested material (2), and perform c-scan according to the first excitation path. The starting point of the first excitation path is the end point of the second excitation path, and the end point of the first excitation path is the second excitation path. starting point. At this time, each excitation point on the excitation path is still set to (X, Y, L), where X, Y are the plane coordinates of the excitation point, L is the distance from the edge of the defect inside the excitation point to the excitation plane, L=d -CL*t/2, where d is the thickness of the measured material, CL is the longitudinal wave velocity, and t is the time from the laser excitation to the reception of the longitudinal wave; Connecting the points located on the inside into a face is the shape of the defect inside the material.

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