CN107991393B - Dual-frequency electromagnetic ultrasonic detection system - Google Patents
Dual-frequency electromagnetic ultrasonic detection system Download PDFInfo
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- CN107991393B CN107991393B CN201711132882.7A CN201711132882A CN107991393B CN 107991393 B CN107991393 B CN 107991393B CN 201711132882 A CN201711132882 A CN 201711132882A CN 107991393 B CN107991393 B CN 107991393B
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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
- G01N29/11—Analysing solids by measuring attenuation of acoustic waves
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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
- G01N29/24—Probes
- G01N29/2412—Probes using the magnetostrictive properties of the material to be examined, e.g. electromagnetic acoustic transducers [EMAT]
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
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- G01N2291/01—Indexing codes associated with the measuring variable
- G01N2291/015—Attenuation, scattering
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- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
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Abstract
The invention discloses a double-frequency electromagnetic ultrasonic detection system which comprises a digital signal generator, a power amplifier, a duplexer, a magnet, a coil, a metal sample, a preamplifier, a high-pass filter, a low-pass filter and a signal processor. The digital signal generator alternately generates two digital signals with different frequencies, the two digital signals are input into the power amplifier for power amplification, and the two digital signals pass through the duplexer and drive the coil. The coil is used for exciting ultrasonic waves and receiving ultrasonic echo signals, and the ultrasonic echo signals are input into the preamplifier through the duplexer. The signal is amplified by the preamplifier and then divided into two paths, and the two paths are respectively input into a low-pass filter and a high-pass filter. And inputting the filtered signals into a signal processor, determining the size of the lift-off distance through the amplitude of the low-frequency signal, and determining the size of the defect according to the lift-off distance and the amplitude of the high-frequency defect echo signal, so that the defect size can still be quantitatively represented when the lift-off distance changes.
Description
Technical Field
The invention relates to an electromagnetic ultrasonic nondestructive testing technology, in particular to a dual-frequency electromagnetic ultrasonic testing system and a testing method thereof.
Background
An electromagnetic ultrasonic transducer (emat) is a transducer that excites and receives ultrasonic waves by means of electromagnetic coupling, has the characteristics of high precision, no need of a coupling agent, non-contact, suitability for high-temperature detection and the like, and is mostly applied to defect detection, dimension measurement, stress detection and the like of metal rods, plates, pipes and the like. The action mechanism of electromagnetic ultrasound is divided into two types: the lorentz force mechanism and the magnetostrictive mechanism. The lorentz force mechanism is: high-frequency pulse current is introduced into the exciting coil, an eddy current J is coupled out in the metal sample due to electromagnetic induction, and an external static magnetic field BsAnd a dynamic magnetic field B generated by the exciting coildProduces lorentz force: f ═ Bs×J+BdAnd J, causing the local stress vibration of the metal surface to generate ultrasonic waves. The magnetostrictive mechanism occurs only in ferromagnetic materials, such as: iron, nickel, etc. determined by the magnetostriction of ferromagnetic material, the alternating current in the exciting coil causes the magnetic field around the coil to alternate, thereby causing the ferromagnetic material to alternate and generate ultrasonic wave, and the receiving process is excitingThe process is the reverse process.
The distance between the electromagnetic ultrasonic transducer and the test piece is called a lift-off distance, and the larger the lift-off distance is, the lower the intensity of the ultrasonic wave coupled out by the transducer in the test piece is, the lower the transduction efficiency is, and vice versa, the larger the lift-off distance is. When the electromagnetic ultrasonic detection technology is used for online detection, the relative position between an object to be detected and the transducer changes, the surface appearance of the object to be detected is not necessarily smooth, and the lift-off distance becomes an unknown variable and is input into a detection system. When defect detection is carried out, the size of the defect size is generally judged by the amplitude of the defect echo, but if the lift-off distance varies, the amplitude of the echo is different even if the same defect is detected, which brings difficulty to quantitative characterization of the defect size. In practical applications, a mechanical support is often used to fix the distance from the probe to the sample, but this method is not reliable when the surface topography of the sample is not flat. The invention solves the problem that the defect size cannot be effectively represented under the condition of changing the lift-off distance.
Disclosure of Invention
During online detection, the lift-off distance of an electromagnetic ultrasonic detection system inevitably changes, and the change can cause inaccurate quantitative characterization of the size of the defect. The method comprises the steps of exciting two ultrasonic waves with different frequencies, calculating the lift-off distance according to the amplitude of the low-frequency bottom surface ultrasonic wave, and calculating the size of the defect according to the lift-off distance and the amplitude of the high-frequency defect echo. The invention aims to quantitatively characterize the size of the defect when the lift-off distance changes.
In order to achieve the above purpose, the invention adopts the following technical scheme:
a dual-frequency electromagnetic ultrasonic detection system comprises a digital signal generator (1), a power amplifier (2), a duplexer (3), a magnet (4), a coil (5), a metal sample (6), a preamplifier (7), a high-pass filter (8), a low-pass filter (9) and a signal processor (10), wherein the magnet (4) and the coil (5) form an electromagnetic ultrasonic transducer, the digital signal generator (1) alternately generates two digital signals with different frequencies, the digital signals are input into the power amplifier (2) for power amplification, the digital signals pass through the duplexer (3) and the drive coil (5), the coil (5) is used for exciting ultrasonic waves and receiving ultrasonic echo signals, the ultrasonic echo signals are input into the preamplifier (7) through the duplexer (3), are amplified by the preamplifier (7) and then are divided into two paths and input into the low-pass filter (9) and the high-pass filter (8) respectively, and inputting the filtered signals into a signal processor (10), and judging the defect information through ultrasonic echo signals with two different frequencies.
Another preferred embodiment of the present invention is: the digital signal generator (1) generates digital pulse signals with two different frequencies at intervals, wherein one frequency is higher, the other frequency is lower, the ultrasonic wave wavelength corresponding to the frequency of the high-frequency digital signal is equivalent to the defect size, and the frequency of the low-frequency digital signal is smaller than 1/3 of the frequency of the high-frequency signal.
Another preferred embodiment of the present invention is: the cut-off frequencies of the high-pass filter (8) and the low-pass filter (9) are respectively larger than the frequency of the low-frequency signal generated by the digital signal generator (1) and smaller than the frequency of the high-frequency signal generated by the digital signal generator.
The coil (5) is a racetrack coil or a spiral coil.
The duplexer (3) is used for separating the excitation signal and the echo signal and preventing mutual interference.
After the parameters of the probe, the excitation signal source and the properties of the metal sample are fixed, the intensity of the excited ultrasonic wave is only related to the lifting distance, and the amplitude of the high-frequency ultrasonic wave excited by the probe is set as As(g) Amplitude of low frequency ultrasonic wave is Al(g) G is the lift-off distance, s is the high-frequency short wave, and l is the low-frequency long wave. When ultrasonic waves propagate in a sample, the attenuation rates of the ultrasonic waves with different frequencies are also different, the attenuation amount is related to the distance, and the attenuation coefficients are respectively as follows: alpha is alphas(h)、αl(h) And h is the propagation distance. When the detection sound wave meets discontinuous interfaces such as defects, reflection sound waves can be generated, the detection sound waves continuously propagate, the intensities of the reflection sound waves and the detection sound waves are represented by attenuation coefficients, and the attenuation coefficients of the reflection sound waves are respectively as follows: r iss(d)、rl(d) And the attenuation coefficient of the detected sound wave intensity is as follows: beta is as(d)、βl(d) Wherein d is the defect size. The attenuation coefficient of the interface reflected wave when the ultrasonic wave meets the boundary is as follows: bs、bl(ii) a When the ultrasonic wave is transmitted to the receiving probe and received by the receiving probe, the energy is converted from the mechanical energy of the sound wave to the electric energy, and the conversion efficiency is only related to the lifting distance g when the basic parameter is fixed. As the lift-off distance g increases, the conversion efficiency decreases, where the receive conversion is characterized using a decay function related to the lift-off distance g: f. ofs(g)、fl(g) Then, the amplitude of the received low-frequency bottom echo signal is:
Rl＝blαl(h)βl(d)fl(g)Al(g) (1)，
the amplitude of the high-frequency defect echo signal is as follows:
here, the defect size is comparable to the high-frequency ultrasonic wavelength and much smaller than the low-frequency ultrasonic wavelength, then βl(d)≈1，rs(d)＞0。
The invention provides a defect size measuring method which can be realized through a calibration stage and a detection stage.
A calibration stage:
calibration using defect-free samples, where betal(d) 1, g and RlHas unique mapping relation, and can calibrate the corresponding bottom surface low-frequency reflection echo amplitude value R under different lifting distances gl：
g＝f1(Rl) (3)，
Recalibration using defective samples, where rs(d)≠0，
The defect size d and the lift-off distance g have a mapping relation, so that the defect high-frequency reflection echo amplitude values under different lift-off distances g and different defect sizes d can be calibrated
A detection stage:
high frequency echo amplitude of a defect, if any
And low frequency reflection echo R of the bottom surfacelA known amount, the lift-off distance g can be obtained by the formula (3); then according to the lift-off distance g and the amplitude of the high-frequency defect echo
The defect size d is obtained by equation (4).
Because all calibration data are discrete data, the echo amplitude measured during actual measurement may not be on the data point, and fitting processing needs to be performed on the data during searching.
Drawings
FIG. 1 is a block diagram of a dual-frequency electromagnetic ultrasonic testing system according to the present invention.
FIG. 2 is a signal diagram of a pulse signal generated by the pulse signal generator according to the present invention.
FIG. 3 is a block diagram of an exemplary probe of the present invention.
Detailed Description
Exemplary embodiments of the present invention will be described below with reference to the accompanying drawings.
The invention consists of a digital signal generator (1), a power amplifier (2), a duplexer (3), a magnet (4), a coil (5), a metal sample (6), a preamplifier (7), a high-pass filter (8), a low-pass filter (9) and a signal processor (10), wherein the magnet (4) and the coil (5) form an electromagnetic ultrasonic transducer. The digital signal generator (1) alternately generates two digital signals with different frequencies, inputs the digital signals into the power amplifier (2) for power amplification, passes through the duplexer (3) and drives the coil (5). The coil (5) is used for exciting ultrasonic waves and receiving ultrasonic echo signals, and the ultrasonic echo signals are input into the preamplifier (7) through the duplexer (3). After being amplified by a preamplifier (7), the signals are respectively input into a low-pass filter (9) and a high-pass filter (8) in two paths. And inputting the filtered signals into a signal processor (10), and judging the defect information through ultrasonic echo signals with two different frequencies.
The coil (5) is spiral in shape, the magnet is a cylindrical magnet, the magnetization direction is along the axial direction of the cylinder, and the structure is shown in figure 3.
The digital signal generator 1 transmits the digital pulse signal with the high frequency signal frequency of 2MHz and the low frequency signal frequency of 200kHz, and the two signals are transmitted at intervals as shown in fig. 2.
The low-pass filter (9) has a cut-off frequency of 250kHz and is designed to filter out high-frequency components and to retain low-frequency components.
The high-pass filter (8) has a cut-off frequency of 1.5MHz and is intended to filter out low-frequency components and to retain high-frequency components.
In the signal processing, a defect echo method is adopted, and two stages of calibration and detection are required. The calibration method comprises the following steps: and calibrating the system for the first time by using a calibration sample without defects, and calibrating the amplitudes of the low-frequency bottom echo signals corresponding to different lift-off distances. And then, calibrating the system again by using a calibration sample containing the defects, and calibrating the high-frequency defect echo signal amplitude corresponding to different defect sizes at different lift-off distances (same as the first calibration).
In the detection stage, the lift-off distance is calculated through the amplitude of the received low-frequency signal and the first calibration information. And then searching for second calibration information according to the lift-off distance, and calculating the defect size corresponding to the amplitude of the current high-frequency defect echo signal. Since all calibration data are discrete values, continuous values need to be calculated by the fitting method.
While the foregoing is directed to embodiments of the present invention, it will be understood by those skilled in the art that various changes in form and details may be made therein without departing from the spirit and scope of the invention as defined by the appended claims.
Claims (3)
1. The method for detecting the defects by using the dual-frequency electromagnetic ultrasonic detection system is characterized by comprising the following steps of: the dual-frequency electromagnetic ultrasonic detection system comprises a digital signal generator (1), a power amplifier (2), a duplexer (3), a magnet (4), a coil (5), a metal sample (6), a preamplifier (7), a high-pass filter (8), a low-pass filter (9) and a signal processor (10), wherein the magnet (4) and the coil (5) form an electromagnetic ultrasonic transducer, the electromagnetic ultrasonic transducer is arranged above the metal sample (6), the digital signal generator (1) alternately generates two digital signals with different frequencies, one of the digital signals is higher in frequency and the other digital signal is lower in frequency, the two digital signals are input into the power amplifier (2) for power amplification, the two digital signals pass through the duplexer (3) and drive the coil (5), the coil (5) is used for exciting ultrasonic waves and receiving ultrasonic echo signals, and the ultrasonic echo signals are input into the preamplifier (7) through the duplexer (3), the signals are respectively input into a low-pass filter (9) and a high-pass filter (8) in two paths after being amplified by a preamplifier (7), the signals after being filtered are input into a signal processor (10), and defect information judgment is carried out through ultrasonic echo signals with two different frequencies, wherein the defect information judgment comprises the following specific steps:
in the calibration stage, firstly, a calibration sample without defects is used for calibrating the system, and the lift-off distance g from the electromagnetic ultrasonic transducer to the sample and the amplitude R of the low-frequency bottom echo signal are calibratedlThe corresponding relation of (1): g ═ f1(Rl) (ii) a Then, the system is calibrated again by using a calibration sample containing the defects, and the defect size d, the lift-off distance g and the amplitude of the high-frequency defect echo signal are calibrated
The corresponding relation of (1):
in the detection stage, according to the received low-frequency signal amplitude RlBy g ═ f1(Rl) Obtaining a lift-off distance g, and then obtaining a high frequency according to the lift-off distance gAmplitude of defect echo signal
By passing
The defect size d is obtained.
2. The method of claim 1, wherein the defect detection is performed by a dual frequency electromagnetic ultrasound inspection system, comprising: the ultrasonic wavelength corresponding to the frequency of the higher frequency digital signal is comparable to the defect size, and the frequency of the lower frequency digital signal is less than 1/3 of the frequency of the higher frequency digital signal.
3. The method of claim 1, wherein the defect detection is performed by a dual frequency electromagnetic ultrasound inspection system, comprising: the cut-off frequency of the high-pass filter (8) is greater than the frequency of the low-frequency signal generated by the digital signal generator (1), and the cut-off frequency of the low-pass filter (9) is less than the frequency of the high-frequency signal generated by the digital signal generator (1).
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| CN110261486B (en) * | 2019-05-22 | 2024-06-11 | 杭州意能电力技术有限公司 | Ultrasonic probe capable of transmitting multi-frequency signals and manufacturing process thereof |
| CN111024827A (en) * | 2019-12-11 | 2020-04-17 | 湖北工业大学 | Electromagnetic ultrasonic SV wave and surface wave detection system |
| CN112129837B (en) * | 2020-10-29 | 2021-04-06 | 南京天雀信息科技有限公司 | Rotating shaft crack detection system |
| CN117760507B (en) * | 2023-12-27 | 2024-07-09 | 广州远动信息技术有限公司 | River acoustic chromatographic flow monitoring system and method based on double-frequency underwater acoustic base station |
Citations (5)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN102023186A (en) * | 2010-12-29 | 2011-04-20 | 钢铁研究总院 | Electromagnetic ultrasonic probe and method for detecting pipeline by using same |
| CN105181791A (en) * | 2015-09-30 | 2015-12-23 | 西安交通大学 | Pulsed eddy current and electromagnetic ultrasonic composite based nondestructive body defect testing method |
| CN106540872A (en) * | 2016-10-20 | 2017-03-29 | 北京科技大学 | A kind of coil autoexcitation electromagnetic acoustic Lamb wave transducer |
| CN107064296A (en) * | 2017-01-18 | 2017-08-18 | 中国特种设备检测研究院 | Type multimode electromagnetic ultrasonic testing system and electromagnetic ultrasonic transducer |
| CN107132282A (en) * | 2017-06-26 | 2017-09-05 | 北京海冬青机电设备有限公司 | The automatic detection device and method of a kind of wheel tread wheel rim electromagnetic coupled ultrasound |
-
2017
- 2017-11-15 CN CN201711132882.7A patent/CN107991393B/en active Active
Patent Citations (5)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN102023186A (en) * | 2010-12-29 | 2011-04-20 | 钢铁研究总院 | Electromagnetic ultrasonic probe and method for detecting pipeline by using same |
| CN105181791A (en) * | 2015-09-30 | 2015-12-23 | 西安交通大学 | Pulsed eddy current and electromagnetic ultrasonic composite based nondestructive body defect testing method |
| CN106540872A (en) * | 2016-10-20 | 2017-03-29 | 北京科技大学 | A kind of coil autoexcitation electromagnetic acoustic Lamb wave transducer |
| CN107064296A (en) * | 2017-01-18 | 2017-08-18 | 中国特种设备检测研究院 | Type multimode electromagnetic ultrasonic testing system and electromagnetic ultrasonic transducer |
| CN107132282A (en) * | 2017-06-26 | 2017-09-05 | 北京海冬青机电设备有限公司 | The automatic detection device and method of a kind of wheel tread wheel rim electromagnetic coupled ultrasound |
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