CN113984894A - Laser ultrasonic nondestructive testing device and method based on double wave mixing - Google Patents
Laser ultrasonic nondestructive testing device and method based on double wave mixing Download PDFInfo
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- 238000009659 non-destructive testing Methods 0.000 title claims abstract description 11
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N29/00—Investigating or analysing materials by the use of ultrasonic, sonic or infrasonic waves; Visualisation of the interior of objects by transmitting ultrasonic or sonic waves through the object
- G01N29/04—Analysing solids
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N21/00—Investigating or analysing materials by the use of optical means, i.e. using sub-millimetre waves, infrared, visible or ultraviolet light
- G01N21/17—Systems in which incident light is modified in accordance with the properties of the material investigated
- G01N21/1702—Systems in which incident light is modified in accordance with the properties of the material investigated with opto-acoustic detection, e.g. for gases or analysing solids
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N29/00—Investigating or analysing materials by the use of ultrasonic, sonic or infrasonic waves; Visualisation of the interior of objects by transmitting ultrasonic or sonic waves through the object
- G01N29/22—Details, e.g. general constructional or apparatus details
Abstract
The invention discloses a laser ultrasonic nondestructive testing device based on double wave mixing and a method thereof, wherein the method comprises the following steps: the device comprises an optical fiber pulse laser, an array generation module, a first scanning galvanometer, a detection module, a synchronous generation module and a processing module. The pulse laser is changed into a plurality of pulse lasers through the array generating module, each pulse laser irradiates a tested piece and simultaneously excites ultrasonic signals at different positions of the tested piece, the ultrasonic signals are modulated by cracks on the surface of the tested piece, the detecting module detects the ultrasonic signals and converts the ultrasonic signals into electric signals, and the processing module analyzes and processes the electric signals and evaluates the tested piece. The invention also discloses a laser ultrasonic nondestructive testing method. The invention has the advantages of wide detection range, high detection efficiency and the like, and can resist low-frequency noise interference.
Description
Technical Field
The invention belongs to the field of laser detection, and particularly relates to a laser ultrasonic nondestructive detection device based on double wave frequency mixing and a method thereof.
Background
The traditional ultrasonic nondestructive detection technology basically utilizes a piezoelectric transducer to transmit and receive ultrasonic signals, and the method has the advantages of higher sensitivity, simple steps and lower price of devices, so the method is widely used. However, the bandwidth of this method is limited, the transducer must be attached to the sample for detection, and is relatively easily interfered by the external environment, and under some severe industrial environments (such as high temperature, high pressure, high corrosion, etc.), this technique has great limitations, and can not realize non-contact online detection.
Compared with the traditional ultrasonic transducer technology, laser ultrasonic is a non-contact detection method, the basic idea is that pulse laser is irradiated on a workpiece to be detected, ultrasonic signals generated by the workpiece to be detected are detected through a vibration meter or a transducer, the method can detect the workpiece to be detected without contacting the surface of the workpiece, and the detected signals have high resolution in time and space.
Common laser ultrasonic excitation is single-point light source excitation, the detection efficiency is low, the amplitude of an excited ultrasonic signal is small, and the signal is easily annihilated in noise. Common laser ultrasonic detection methods include an optical deflection detection technology, an optical heterodyne interference technology, a double-wave mixing interference detection technology and the like, but the methods have some defects. The optical deflection detection technology is generally resistant to interference and the detection method is limited by the response time and sensitivity of the optical intensity receiving device. The optical heterodyne interference technology has wide response frequency and is sensitive to surface displacement, but can not eliminate the interference of various vibrations on the detection in an industrial field, and is generally only suitable for ultrasonic vibration detection of a smooth surface under the condition of a laboratory. The double-wave mixing interferometer has strong light-gathering capacity and can measure a rough surface, but the existing double-wave mixing interferometer has no scanning function and can only complete the detection of each measuring point of a test piece by moving the tested workpiece.
Disclosure of Invention
In order to solve the above problems, the present invention provides a laser ultrasonic nondestructive testing apparatus based on dual wave frequency mixing, comprising: the optical fiber pulse laser is used for generating pulse laser; the array generation module is used for expanding the pulse laser into a plurality of beams of pulse laser to be output; the first scanning galvanometer is used for projecting a plurality of pulse lasers of the array generating module onto a tested piece; the detection module is used for collecting the ultrasonic signals modulated by the tested piece and converting the ultrasonic signals into electric signals to be output; the processing module is used for acquiring and analyzing the electric signals output by the detection module; the synchronous signal generating module is used for sending a synchronous instruction to the optical fiber pulse laser and the processing module so as to synchronize the working time of the optical fiber pulse laser and the working time of the processing module; the optical fiber pulse laser is connected with the array generation module, the synchronous signal generation module is connected with the optical fiber pulse laser, and the synchronous signal generation module is also connected with the processing module; the array generation module comprises an optical fiber coupler, and the optical fiber coupler can expand one path of pulse laser input by the optical fiber pulse laser into at least 2 paths of pulse laser; the optical fiber coupler comprises at least 2 paths of optical fibers, and the distances passed by the pulse laser on each path of optical fiber are different, so that each path of pulse laser has a certain time interval when being emitted; the optical fiber coupler can adjust the emitting time interval of each path of pulse laser by adjusting the length of each path of optical fiber.
Furthermore, the array generation module also comprises at least 2 collimators, each collimator is connected to one path of optical fiber, and the array generation module can adjust the distance between each path of pulse laser by changing the distance between each collimator, so as to change the propagation direction of the ultrasonic signal in the tested piece.
Further, the array generating module can change the propagation direction of the ultrasonic signals in the tested piece by changing the length of each optical fiber.
Further, the detection module comprises a laser, a dimming component, a first detection unit, a second detection unit and a receiving unit; the laser is used for generating continuous laser; the dimming component is used for adjusting continuous laser; the first detection unit or the second detection unit is used for dividing the continuous laser into test light and reference light, and only one detection unit of the first detection unit and the second detection unit works at the same time; the test light is projected onto the tested piece, the signal light reflected from the tested piece is collected, the signal light contains tested information, and the first detection unit or the second detection unit transmits the signal light and the reference light to the receiving unit; the receiving unit is used for demodulating the detected information in the signal light and converting the optical signal into an electric signal to be output.
Furthermore, the first detection unit is provided with a first focus, the second detection unit is provided with a second focus, and the tested piece is arranged on a straight line formed by the first focus and the second focus.
Further, the first detection unit includes: the first polarization beam splitter prism is used for dividing the continuous laser entering the first detection unit into reference light and test light; the second scanning galvanometer is used for projecting the test light onto the tested piece; the second polarization beam splitter prism is used for changing the direction of the reflected signal light; the first quarter-wave plate is used for changing the polarization states of the signal light and the test light; the first lens and the second lens are used for forming a first Galileo optical system, expanding the test light and contracting the signal light; and a third lens for collecting the signal light.
Further, the dimming component comprises a reflector wheel, the reflector wheel comprises at least 2 mounting holes, at least one of the mounting holes is used for mounting the reflector, and at least one of the mounting holes is in an empty state; the reflector wheel and the continuous laser emitted by the laser form an included angle of 45 degrees.
Further, the optical fiber coupler comprises 4 optical fibers, and the length difference between any optical fiber and the adjacent optical fiber is equal.
Furthermore, the dimming component comprises a second half-wave plate and a third half-wave plate, the second half-wave plate is used for adjusting the polarization state of the reference light of the second detection unit to enable the reference light to transmit the first detection unit to enter the receiving unit, and the third half-wave plate is used for adjusting the polarization state of the signal light of the second detection unit to enable the signal light of the second detection unit to transmit the first detection unit to enter the receiving unit.
Based on the above purpose, the invention also provides a laser ultrasonic nondestructive testing method based on double wave mixing, which comprises the following steps:
s1, converting the single-point pulse laser into array pulse laser by using an array generating module;
s2, projecting the array pulse laser onto the tested piece according to the scanning path by using the first scanning galvanometer to generate ultrasonic signals on the tested piece;
s3, adjusting a scanning galvanometer in the detection module according to the detection range;
s4, sequentially opening the detection units in the detection module, projecting the test light to the tested piece by the detection units, collecting the signal light reflected from the loop on the tested piece, and converting the detection result into an electric signal to be output to the processing module;
s5, repeating the steps S2 and S4 until the detection of all the areas of the tested piece is completed;
and S6, analyzing and processing all detection results by the processing module to obtain the defect parameters of the tested piece.
Compared with the prior art, the invention has the following benefits: the laser ultrasonic nondestructive testing device based on double wave mixing can automatically eliminate low-frequency noise interference caused by environment and the like, and can also detect different positions of a tested piece, thereby enlarging the detection range and improving the resolution of the device. In addition, the working state of the detection units is selected by adopting the reflector rotating wheel, the continuous laser power entering each detection unit is not lost, the use efficiency of the single longitudinal mode laser is improved, a plurality of ultrasonic signals with adjustable directions can be excited, the plurality of ultrasonic signals can be mutually superposed to obtain the ultrasonic signals with obviously increased amplitude, and the signal to noise ratio of the device is improved; the damage is prevented, the direction is adjustable, a non-contact measurement detection mode is adopted, and the test piece can be detected in severe environment (such as high temperature and high pressure).
Drawings
The accompanying drawings, which are included to provide a further understanding of the invention and are incorporated in and constitute a part of this application, illustrate embodiment(s) of the invention and together with the description serve to explain the invention without limiting the invention. In the drawings:
FIG. 1 is a schematic structural diagram of a laser ultrasonic nondestructive testing device based on double wave mixing;
FIG. 2 is a schematic diagram of an array generation module;
FIG. 3 is a schematic structural diagram of a detection module;
FIG. 4 is a schematic view of the construction of the mirror wheel;
FIG. 5 is a schematic diagram of the operation of the first detecting unit;
FIG. 6 is a schematic diagram of the operation of the second detecting unit;
FIG. 7 is a flow chart of the steps of a laser non-destructive inspection method.
Detailed Description
The present invention will be described in detail with reference to the specific embodiments shown in the drawings, which are not intended to limit the present invention, and structural, methodological, or functional changes made by those skilled in the art according to the specific embodiments are included in the scope of the present invention.
As shown in fig. 1, the present application discloses a laser ultrasonic nondestructive testing apparatus 100, which includes a fiber-optic pulse laser 13 for generating a pulse laser. The array generating module 14 is configured to expand the pulsed laser into a plurality of beams of pulsed laser for output. The first galvanometer scanner 15 is used for projecting the plurality of pulsed laser beams of the array generating module 14 onto the test piece 16. The detection module 17 is used for collecting the ultrasonic signals modulated by the tested piece 16 and converting the ultrasonic signals into electric signals to be output. The processing module 11 is used for collecting and analyzing the electrical signals output by the detection module 17. The synchronization signal generation module 12 is configured to send a synchronization instruction to the fiber pulse laser 13 and the processing module 11, so that the working times of the fiber pulse laser 13 and the processing module 11 are synchronized. The fiber pulse laser 13 is connected to the array generating module 14, and the synchronizing signal generating module 12 is connected to the fiber pulse laser 13 and the processing module 11, respectively. The array generating module 14 includes an optical fiber coupler 141, and the optical fiber coupler 141 can expand one path of pulse laser input by the optical fiber pulse laser 13 into at least two paths of pulse laser; the optical fiber coupler 141 includes at least 2 optical fibers, and the time that the pulse laser passes through on each optical fiber is different, so that each pulse laser has a certain time interval when emitting; the fiber coupler 141 can adjust the time interval of emitting each pulse laser by adjusting the length of each optical fiber.
The array generation module 14 further comprises at least 2 collimators, each collimator is connected to one optical fiber, and the array generation module 14 can change the distance between each collimator, so as to adjust the distance between each pulse laser, so that the distance between the positions where each pulse laser is projected to the tested piece 16 is changed, and further the propagation direction of the ultrasonic signal excited by the pulse laser irradiated on the tested piece 16 is influenced, so that the propagation direction of the ultrasonic signal is controllable, the tested piece 16 can be detected in an all-dimensional manner, and the detection range is wider. As an implementation manner, the optical fiber coupler 141 is configured to equally divide optical signals to four output ends, the optical fiber coupler 141 is connected to 4 optical fibers, which are the first optical fiber 142, the second optical fiber 143, the third optical fiber 144, and the fourth optical fiber 145 respectively, and the pulse laser output by the optical fiber pulse laser 13 is equally divided into four optical signals with equal optical intensity through the first optical fiber 142, the second optical fiber 143, the third optical fiber 144, and the fourth optical fiber 145. Corresponding to the 4 optical fibers, the array generating module 14 in this embodiment is provided with 4 collimators, i.e. a first collimator 146 and a second collimatorA collimator 147, a third collimator 148 and a fourth collimator 149, the first optical fiber 142 being connected to the first collimator 146, the second optical fiber 143 being connected to the second collimator 147, the third optical fiber 144 being connected to the third collimator 148, the fourth optical fiber 145 being connected to the fourth collimator 149. The pulse laser is split by each optical fiber, transmitted to the corresponding collimator, and emitted from the collimator to the first scanning galvanometer 15. It is to be noted that, according to the formula
Another implementation is possible for changing the propagation direction of the ultrasonic signal excited by the pulsed laser on the test piece 16, in which θ0Deflection angle in the normal direction of the ultrasonic wave, d0Δ t is a time interval at which each laser beam is emitted in order to irradiate the distance between each laser beam on the test piece 16.
As another implementation manner, the array generating module 14 can change the time of each pulse laser reaching the tested object 16 by changing the length of each optical fiber, so that the arrival of each pulse laser has a certain delay, and further change the propagation direction of the ultrasonic signal in the tested object 16, where the delay time can be obtained according to the preset length of the optical fiber. As an implementation mode, the length of the first optical fiber 142 is 0.5m, the length of the second optical fiber 143 is 40.5m, the length of the third optical fiber 144 is 80.5m, and the length of the fourth optical fiber 145 is 120.5m, so that four ultrasonic signals can be excited on the tested piece 16 and superimposed and interfered at the defect position on the tested piece 16, the amplitude of the ultrasonic signals is enlarged, and the signal-to-noise ratio is improved.
As an implementation manner, the first galvanometer scanner 15 includes a mirror, and the mirror is driven by an X-Y axis motor to deflect to implement plane scanning, so as to irradiate each path of pulse laser emitted from the array generating module 14 onto the tested piece 16 in a scanning manner, so that the irradiation range of all pulse lasers can cover the surface of the tested piece 16. When the pulse laser is irradiated onto the surface of the test piece 16 and the pulse laser has an energy insufficient to melt the test piece 16, a part of the energy of the pulse laser is absorbed by the test piece 16 and another part is reflected from the surface of the test piece 16 due to the thermo-elastic effect. When the test piece 16 absorbs the energy of the laser light to rapidly raise the temperature thereof, so that the test piece 16 expands, in this case, a part of the surface of the test piece 16 deforms, and the deformation amount periodically changes along with the continuous irradiation of the pulse laser light, that is, the part of the surface of the test piece 16 periodically deforms, thereby causing an ultrasonic signal to be excited in the test piece 16. Because the amplitude of the ultrasonic signal that the single-point pulse laser can excite is small, the output power of the fiber pulse laser 13 needs to be increased to be able to excite the ultrasonic signal with the large amplitude, however, due to the thermal ignition effect, the increase of the output power of the fiber pulse laser 13 can cause the tested piece 16 to absorb excessive energy in a short time, so that the tested piece 16 generates the condition of melting loss. In the application, the output of the pulse laser is equally divided into a plurality of parts through the first scanning galvanometer 15, so that the power of the laser pulse output by each path can reach the maximum value of the thermoelastic effect, ultrasonic signals adjustable in all directions can be excited, meanwhile, coherent superposition can be performed among a plurality of ultrasonic signals, and the amplitude of the ultrasonic signals generated on the tested piece 16 is further enhanced.
The processing module 11 comprises an upper computer 111 and a data acquisition card 112, the upper computer 111 is connected with a synchronous signal generator, and the upper computer 111 controls the synchronous signal generator to simultaneously send synchronous signals to the data acquisition card 112 and the fiber pulse laser 13, so that the excitation of ultrasonic signals and the detection of ultrasonic signals on the tested piece 16 are synchronously carried out. The data acquisition card 112 is connected to the upper computer 111, the data acquisition card 112 transmits the acquired detection data to the upper computer 111, the upper computer 111 processes the acquired detection data, for example, noise reduction, smoothing, deburring and the like are performed on the ultrasonic signal, a time domain signal of the ultrasonic signal is converted into a frequency domain signal, and then the characteristic information of the tested piece 16 can be obtained by performing relevant processing on the frequency domain signal. As an implementation mode, the data acquisition card 112 selects single-ended dual-channel signal input, the sampling rate of each channel is 250MS/s, the resolution is 12 bits, the on-board speed is 2GB, and the bandwidth is 100MHz, and the data acquisition card 112 supports continuous sampling and finite point sampling.
The detection module 17 includes a laser 171, a dimming component 172, a first detection unit 173, a second detection unit 174, and a receiving unit 175, the laser 171 being used to generate continuous laser light; the dimming component 172 is used to adjust the continuous laser light; the first detecting unit 173 or the second detecting unit 174 is configured to divide the continuous laser light into the test light and the reference light, and only one of the first detecting unit 173 and the second detecting unit 174 operates at the same time; the test light is projected onto the test piece 16 and the signal light reflected from the test piece 16, the signal light containing the information to be tested, the first detection unit 173 or the second detection unit 174 transmits the signal light and the reference light to the receiving unit 175; the receiving unit 175 is used to demodulate the detected information in the signal light and convert the optical signal into an electrical signal for output. Wherein the distance of the test light from the sixth lens 1746 to the test piece 16 is equal to the distance of the test light from the third lens 1736 to the test piece 16; the dimming component 172 comprises an attenuation plate 1721, a polarizer 1722, a beam expander 1723, a first half-wave plate 1724, a second half-wave plate 1725, a third half-wave plate 1726 and a mirror wheel 1727, the laser power output by the laser 171 is greater than 150mw, the power stability is less than 1%, the transverse mode is TEM00, the line width is less than 0.00001nm, the polarization ratio is greater than 100:1, and the coherence length is greater than 50 m. The attenuation sheet 1721 is used for adjusting the power of the continuous laser beam output by the single longitudinal mode laser 171, and in the present embodiment, the attenuation sheet 1721 is a gradient neutral density attenuation sheet with a relative density range of 0 to 3. The polarizer 1722 is used to emit the continuous laser beam as linearly polarized light, and in this embodiment, the polarizer 1722 is a linear thin film polarizer having a light transmission aperture of 10 mm. The beam expander 1723 is used for expanding the input continuous laser beam, and in this embodiment, the beam expander 1723 is a beam expander whose beam expansion ratio is continuously adjustable from 5 times to 10 times. The half-wave plate is used for changing the polarization state of the continuous laser. The continuous laser emitted by the laser 171 sequentially passes through the attenuation plate 1721, the polarizer 1722, the beam expander 1723 and the first half-wave plate 1724 and then enters the first detection unit 173 or the second detection unit 174 through the reflector wheel 1727, the continuous laser is divided into reference light and test light in the detection unit and respectively enters different light paths, the test light is irradiated onto the tested piece 16, and the signal light reflected back after being modulated by the tested piece 16 is collected by the first detection unit 173 or the second detection unit 174. The reflector wheel comprises at least 2 mounting holes, wherein at least one mounting hole is used for mounting the reflector and is in a vacant state; mirror wheel 1727 makes a 45 angle with the continuous laser light emitted by laser 171.
The first detection unit 173 includes: the first polarization beam splitter prism 1731 is configured to split the continuous laser light entering the first detection unit 173 into the reference light and the test light; the second scanning galvanometer 1737 is used for projecting the test light onto the tested piece 16; a second polarization splitting prism 1732 for changing the direction of the reflected signal light; a first quarter-wave plate 1733 for changing the polarization states of the signal light and the test light; the first lens 1734 and the second lens 1735 are used to form a first galileo optical system, which expands the test light and contracts the signal light. The third lens 1736 is used to collect the signal light.
The second detection unit 174 includes: a third polarization beam splitter prism 1741, a fourth polarization beam splitter prism 1742, a second quarter wave plate 1743, a fourth lens 1744, a fifth lens 1745, a sixth lens 1746 and a third scanning galvanometer 1747. The third polarization beam splitter prism 1741 is used to split the continuous laser light entering the second detection unit 174 into the reference light and the test light. The fourth polarization splitting prism 1742 is used to change the direction of the reflected signal light. The second quarter waveplate 1743 is used to change the polarization states of the signal light and the test light. The fourth lens 1744 and the fifth lens 1745 are used to form a second galileo optical system, which expands the test light and contracts the reflected signal light. The sixth lens 1746 is used to collect the signal light, the third scanning galvanometer 1747 is used to project the test light onto the tested object 16, and the optical path of the test light projected from the sixth lens 1746 to the tested object 16 through the third scanning galvanometer 1747 is the same as the optical path of the test light projected from the third lens 1736 to the tested object 16 through the second scanning galvanometer 1737.
In one embodiment, the first detection unit 173 has a first focal point, the second detection unit 174 has a second focal point, and the test piece 16 is disposed on a straight line formed by the first focal point and the second focal point, so that each detection unit can collect the most signal light from the test piece 16, thereby increasing the collection efficiency.
The receiving unit 175 includes a reference light splitting prism 1751, a signal light splitting prism 1752, a first optical crystal 1753, a second optical crystal 1754, a first photodiode 1755, and a second photodiode 1756. The reference light splitting prism 1751 is for splitting the input reference light into light having an intensity ratio of 1: 1. The signal light splitting prism 1752 is used to split the input signal light into a light intensity ratio of 1: 1. The first optical crystal 1753 and the second optical crystal 1754 are used for demodulating an ultrasonic signal included in a signal light phase to the light intensity of the signal light, in this embodiment, the first optical crystal 1753 and the second optical crystal 1754 are the same in structure and material, the first optical crystal 1753 and the first optical crystal 1753 both use bismuth silicate crystals, the crystals are cut in the [001], [110] and [110] directions, an antireflection film with a wavelength of 532nm is plated on a surface perpendicular to the [110] direction, and an electrode is plated on a surface perpendicular to the [001] direction. When the detection module 17 is in operation, a voltage of 3.5kV is applied to the first optical crystal 1753, and a voltage of-3.5 kV is applied to the second optical crystal 1754.
When the first detecting unit 173 is selected to operate, the mounting hole with the reflecting mirror is located at the center of the light path, and the continuous laser enters the first detecting unit 173; when the second detecting unit 174 is selected to operate, the mounting hole in the selected vacant state is positioned at the center of the optical path, and the continuous laser enters the second detecting unit 174. The first detection unit 173 and the second detection unit 174 are configured to divide the continuous laser light output from the single longitudinal mode laser 171 into a test light and a reference light, wherein the test light projects onto the test object 16, collect the signal light reflected by the test object 16, and output the collected signal light and the reference light to the detection unit.
As shown in fig. 5, the reflector wheel 1727 selects the detecting units, the continuous laser enters the first detecting unit 173 and is divided into reference light and test light by the first polarization splitting prism 1731 and emitted to two directions, the reference light leaves the detecting unit and is reflected to the reference splitting prism 1751 by the second reflector, the reference splitting prism 1751 divides the reference light into first reference light and second reference light, the first reference light is emitted to the first optical crystal 1753 by the third reflector, and the second reference light is emitted to the second optical crystal 1754 by the fourth reflector. The p-linear polarized test light is transmitted through the second polarization splitting prism 1732, then converted into circularly polarized light by the first quarter wave plate 1733, and enters the first galileo optical system composed of the first lens 1734 and the second lens 1735, and the galileo optical system expands the beam of the test light, collimates the beam, and then projects the beam onto the tested piece 16 at different angles by the third lens 1736 and the second scanning galvanometer 1737. The signal light reflected by the test piece 16 is collected by the second scanning galvanometer 1737 and the third lens 1736 and enters the first galileo optical system, the signal light is condensed by the galileo optical system and enters the first quarter-wave plate 1733, the signal light converted into s-linear polarization by the first quarter-wave plate 1733 is reflected by the second polarization splitting prism 1732 and leaves the first detection unit 173, the signal light leaving the detection unit is split into first signal light and second signal light by the signal splitting prism 1752, the first signal light enters the first optical crystal 1753 after passing through the seventh lens, and the second signal light enters the second optical crystal 1754 after passing through the eighth lens.
As shown in fig. 6, the mirror turning wheel 1727 selects the detecting unit, the continuous laser enters the second detecting unit 174 and is divided into reference light and test light by the third polarization beam splitter 1741 and emits the reference light to two directions, the s-polarized reference light leaves the detecting unit and is converted into p-polarized light by s-polarization through the second half wave plate 1725 and transmits through the first polarization beam splitter 1731 of the first detecting unit 173, the reference light exiting the first polarization beam splitter 1731 is reflected to the reference beam splitter 1751 by the second mirror, the reference beam splitter 1751 divides the reference light into first reference light and second reference light, the first reference light emits into the first optical crystal 1753 through the third mirror, and the second reference light emits into the second optical crystal 1754 through the fourth mirror. The p-linear polarization test light is transmitted through the fourth polarization splitting prism 1742, converted into circularly polarized light by the second quarter wave plate 1743, and enters the second galileo optical system composed of the fourth lens 1744 and the fifth lens 1745, and the galileo optical system expands the beam of the test light, and then is projected onto the tested piece 16 through the sixth lens 1746 and the third scanning galvanometer 1747 at different angles. The signal light reflected by the test piece 16 is collected by the third scanning galvanometer 1747 and the sixth lens 1746 and then enters the second galileo optical system, the signal light is condensed by the galileo optical system and then enters the second quarter wave plate 1743, the signal light converted into s-linear polarization by the second quarter wave plate 1743 is reflected by the fourth polarization beam splitter prism 1742 and leaves the second detection unit 174, the s-linear polarization signal light is converted into p-linear polarization signal light by the third half wave plate 1726, the p-linear polarization signal light is divided into first signal light and second signal light by the signal beam splitter prism 1752 after transmitting the second polarization beam splitter 1732 of the first detection unit 173, the first signal light enters the first optical crystal 1753 after passing through the seventh lens, and the second signal light enters the second optical crystal 1754 after passing through the eighth lens.
After any detection unit finishes working, a first signal light entering the crystal interferes with a first reference light entering the crystal, a second signal light entering the crystal interferes with a second reference light entering the crystal, light and dark stripes generated by interference modulate the refractive index of the crystal to form a refractive index grating, the incident reference light and the incident signal light are diffracted through the refractive index grating, only first-order diffracted light exists because the diffraction of the refractive index grating meets the Bragg condition, a first photodiode 1755 receives an optical signal that the first-order diffracted light of the first reference light interferes with the transmitted light of the first signal light, and a second photodiode 1756 receives an optical signal that the first-order diffracted light of the second reference light interferes with the transmitted light of the second signal light.
Referring to fig. 7, the present invention also provides a detection method using the above laser ultrasonic nondestructive detection apparatus 100 based on duplex wave mixing, including the following steps: s1, converting the single-point pulse laser output by the pulse laser 171 into an array pulse laser by the array generating module 14; s2, projecting the array pulse laser to the tested piece 16 according to the scanning path by using the two-dimensional scanning galvanometer 15 to generate an ultrasonic signal; s3, adjusting the scanning galvanometer of the detection unit according to the detection range; s4, the detection units are sequentially turned on, the detection units project test light to the tested piece 16, signal light of corresponding areas is collected, and meanwhile, detection results are converted into electric signals to be output to the upper computer 111 module; and S5, repeating the steps S2 and S4 until the detection of all the areas of the tested piece 16 is completed. S6, the processing module 11 analyzes and processes all the detection results to obtain the defect parameters of the tested piece 16. It can be understood that, in step S1, the fiber output of the fiber pulse laser 13 is collimated into four paths of laser light after passing through the array generating module 14, the four pulse laser lights are sequentially projected to different positions of the object to be tested according to a certain delay time and excite an ultrasonic signal, the delay time is controlled by selecting the optical fibers with different lengths, the distance between the four pulse laser lights is controlled by setting the distance between the collimators, the delay time of the four pulse laser lights and the distance between the pulse laser lights are modulated to control the ultrasonic wave excited by the pulse laser lights, the four excited ultrasonic signal lights are linearly superposed due to interference, thereby the amplitude of the ultrasonic signal is enlarged, the signal-to-noise ratio is improved, and the four paths of pulse laser lights scan the whole tested object 16 along the scanning path. It can be understood that, in step S3, the crack of the test object 16 modulates the ultrasonic signal, the ultrasonic signal containing crack information modulates the phase of the signal light of the scanning type dual wave mixing interferometer detection module 17, the reference light of the scanning type dual wave mixing interferometer detection module 17 interferes with the signal light in the crystal to form an interference fringe, due to the photorefractive effect, the interference fringe modulates the refractive index of the crystal to form a dynamic refractive index grating, the reference light passes through the grating and is diffracted into the reference light with a wavefront "distortion", the "distorted" reference light interferes with the signal light, the ultrasonic signal modulated in the phase is demodulated in the form of light intensity, and the photodiode converts the optical signal into an electrical signal.
In the claims, the word "comprising" does not exclude other elements or steps; the word "a" or "an" does not exclude a plurality. Use of ordinal terms such as "first," "second," etc., in the claims to modify a claim element does not by itself connote any priority, order, or temporal order of execution of one claim element over another, but are used merely for distinguishing one claim element from another. Although certain features may be described in different dependent claims, this does not imply that these features cannot be used in combination. Various aspects of the present invention may be used alone, in combination, or in a variety of arrangements not specifically discussed in the embodiments described in the foregoing and is therefore not limited in its application to the details and arrangement of components set forth in the foregoing description or illustrated in the drawings. For example, aspects described in one embodiment may be combined in any manner with aspects described in other embodiments. The steps, functions or features recited in a plurality of modules or units may be performed or satisfied by one module or one unit. The steps of the methods disclosed herein are not limited to being performed in any particular order, as some or all of the steps may be performed in other orders. Any reference signs in the claims shall not be construed as limiting the scope of the claims.
Although the preferred embodiments of the present invention have been disclosed for illustrative purposes, those skilled in the art will appreciate that various modifications, additions and substitutions are possible, without departing from the scope and spirit of the invention as disclosed in the accompanying claims.
Claims (10)
1. The utility model provides a laser supersound nondestructive test device based on two ripples frequencies mixing which characterized in that includes:
the optical fiber pulse laser is used for generating pulse laser;
the array generation module is used for expanding the single pulse laser into a plurality of pulse lasers to output;
the first scanning galvanometer is used for projecting the multi-beam pulse laser of the array generating module onto a tested piece;
the detection module is used for collecting the ultrasonic signals modulated by the tested piece and converting the ultrasonic signals into electric signals to be output;
the processing module is used for acquiring and analyzing the electric signal output by the detection module;
the synchronous signal generation module is used for sending a synchronous instruction to the optical fiber pulse laser and the processing module so as to synchronize the working time of the optical fiber pulse laser and the working time of the processing module;
the optical fiber pulse laser is connected with the array generation module, the synchronous signal generation module is connected with the optical fiber pulse laser, and the synchronous signal generation module is also connected with the processing module; the array generation module comprises a fiber coupler, and the fiber coupler can expand one path of the pulse laser input by the fiber pulse laser into at least 2 paths of the pulse laser; the optical fiber coupler comprises at least 2 optical fibers, and the distances passed by the pulse laser on each optical fiber are different, so that each path of pulse laser has a certain time interval when being emitted; the optical fiber coupler can adjust the time interval of the emitting of each path of pulse laser by adjusting the length of each path of optical fiber.
2. The apparatus of claim 1, wherein said array generating module further comprises at least 2 collimators, each of said collimators is connected to one of said optical fibers, and said array generating module is capable of adjusting the distance between each of said pulsed lasers by changing the distance between each of said collimators, thereby changing the propagation direction of said ultrasonic signal in said test object.
3. The apparatus of claim 1, wherein said array generating module is capable of changing the propagation direction of said ultrasonic signal in said test object by changing the length of each of said optical fibers.
4. The apparatus of claim 1, wherein the detection module comprises a laser, a light-adjusting component, a first detection unit, a second detection unit, and a receiving unit; the laser is used for generating continuous laser; the dimming component is used for adjusting the continuous laser; the first detection unit or the second detection unit is used for dividing the continuous laser into test light and reference light, and only one detection unit of the first detection unit and the second detection unit works at the same time; the test light is projected onto the tested piece, and signal light reflected from the tested piece is collected, the signal light contains tested information, and the first detection unit or the second detection unit transmits the signal light and the reference light to the receiving unit; the receiving unit is used for demodulating the detected information in the signal light and converting the optical signal into an electric signal to be output.
5. The laser ultrasonic nondestructive testing apparatus based on double wave mixing of claim 4, wherein the first detecting unit has a first focus, the second detecting unit has a second focus, and the test object is disposed on a straight line formed by the first focus and the second focus.
6. The laser ultrasonic nondestructive inspection apparatus based on duplex wave mixing of claim 4, wherein the first inspection unit includes:
the first polarization beam splitter prism is used for dividing the continuous laser entering the first detection unit into reference light and test light;
the second scanning galvanometer is used for projecting the test light onto the tested piece;
the second polarization beam splitter prism is used for changing the direction of the reflected signal light;
the first quarter-wave plate is used for changing the polarization states of the signal light and the test light;
the first lens and the second lens are used for forming a first Galileo optical system, expanding the test light and contracting the signal light;
a third lens for collecting the signal light.
7. The apparatus of claim 1, wherein the light-adjusting module comprises a mirror wheel, the mirror wheel comprises at least 2 mounting holes, at least one of the mounting holes is used for mounting a mirror, and at least one of the mounting holes is in an empty state; the reflector rotating wheel and the continuous laser emitted by the laser form an included angle of 45 degrees.
8. The apparatus of claim 1, wherein the optical fiber coupler comprises 4 optical fibers, and the length difference between any optical fiber and its adjacent optical fiber is equal.
9. The apparatus of claim 1, wherein the light-adjusting module comprises a second half-wave plate and a third half-wave plate, the second half-wave plate is used for adjusting the polarization state of the reference light of the second detecting unit to transmit the reference light of the first detecting unit to the receiving unit, and the third half-wave plate is used for adjusting the polarization state of the signal light of the second detecting unit to transmit the signal light of the first detecting unit to the receiving unit.
10. A laser ultrasonic nondestructive testing method based on double wave frequency mixing is characterized by comprising the following steps:
s1, converting the single-point pulse laser into array pulse laser by using an array generating module;
s2, projecting the array pulse laser onto a tested piece according to a scanning path by using a first scanning galvanometer so as to generate an ultrasonic signal on the tested piece;
s3, adjusting a scanning galvanometer in the detection module according to the detection range;
s4, opening the detecting units in the detecting module in sequence to make the detecting units project the testing light to the tested piece, collecting the signal light reflected from the loop on the tested piece, and converting the detecting result into an electric signal to be output to the processing module;
s5, repeating the steps S2 and S4 until the detection of all the areas of the tested piece is completed;
and S6, analyzing and processing all detection results by the processing module to obtain the defect parameters of the tested piece.
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