CN104330476A - Electromagnetic ultrasonic excitation probe design method - Google Patents
Electromagnetic ultrasonic excitation probe design method Download PDFInfo
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- CN104330476A CN104330476A CN201410488374.2A CN201410488374A CN104330476A CN 104330476 A CN104330476 A CN 104330476A CN 201410488374 A CN201410488374 A CN 201410488374A CN 104330476 A CN104330476 A CN 104330476A
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Abstract
The invention discloses an electromagnetic ultrasonic excitation probe design method, according to the sound propagation principle, namely SH type guided wave propagation rule, in a solid plate, optimum excitation frequency is determined, and according to the frequency, an electromagnetic ultrasonic excitation probe is designed; enhancement of SH type 0 order mode guided wave and inhibition of 1 order mode guided wave in the plate can be realized, simplification of the mode of a guided wave excited in a particular frequency can be realized, the signal-to-noise ratio is improved, and defect detection probability and quantization accuracy can be effectively improved.
Description
Technical field
The present invention relates to technical field of nondestructive testing, particularly a kind of method for designing of electromagnetic acoustic incentive probe.
Background technology
Ultrasonic Detection is one of method of industrial conventional Non-Destructive Testing.When ultrasound wave propagate in object run into defect time, a part of sound wave can produce reflection and be received by ultrasonic probe, analyzes reflection wave, just accurately can measure defect, and can show position and the size of inherent vice, mensuration material thickness etc.
Electromagnetic acoustic technology participates in transducing directly due to measured object, does not need extra couplant, thus some special occasions become only can the means of effective excitation ultrasound ripple.For ferrimagnet, there are three kinds of mechanism in electromagnetic acoustic shooting techniques: Lorentz force, magnetizing force and magnetostrictive effect.Wherein, magnetostrictive effect two orders of magnitude larger than Lorentz force, magnetizing force, therefore mainly consider magnetostrictive effect to ferrimagnet.The ultrasound wave of propagation various modes that can be stable in sheet metal.Electromagnetic acoustic incentive probe designed in the past considers exciting of mode wave, but does not consider the coupling between each pattern, causes excited ultrasound mode impure.Existence due to multiple ultrasound mode not only causes each mode of energy to disperse, but also causes data analysis complicated.Because electromagnetic acoustic lift-off technology electromechanical coupling factor is lower for other acoustic emission, the electromagnetic acoustic incentive probe therefore designing a kind of excitation mode single is very necessary.
Summary of the invention
The invention provides a kind of method for designing of electromagnetic acoustic incentive probe, the technical matters that the ultrasound mode excited with the probe solving design is in the past impure.
For solving the problems of the technologies described above, the invention provides a kind of method for designing of electromagnetic acoustic incentive probe, described method comprises: according to the propagation law of SH type supersonic guide-wave in plate, determine the characteristic frequency f ' of described supersonic guide-wave, under this characteristic frequency f ', the SH type supersonic guide-wave excited has 0 rank pattern and 1 rank pattern, and 1 rank pattern to lead phase velocity of wave be 2 times that 0 rank pattern leads phase velocity of wave; Based on the characteristic frequency f ' of described supersonic guide-wave, determine the characteristic parameter of described electromagnetic acoustic drive coil, to build described probe, described probe is made up of permanent magnet magnetic patch and electromagnetic acoustic drive coil, and described electromagnetic acoustic drive coil is placed between the N pole of permanent magnet magnetic patch and S pole; Wherein, described permanent magnet magnetic patch is used for the constant bias magnetic field being parallel to drive coil wire at ferromagnetism sheet material Surface Creation; The drive coil of described electromagnetic acoustic drive coil is three-back-shaped coil, is provided with the first wiring point and the second wiring point in described three-back-shaped coil; Passed in described three-back-shaped coil by the sinusoidal wave train of impulses formed of continuous print as excitation by described first wiring point and described second wiring point, under the acting in conjunction in the alternating magnetic field produced by alternating excitation electric current and constant bias magnetic field, launching perpendicular to winding wire and constant bias magnetic field, frequency is the supersonic guide-wave of f '.
Preferably, under described characteristic frequency f ', the phase velocity of 1 rank pattern is 2 times of the phase velocity of 0 rank pattern, and when sound source initial phase is identical and sound source spacing is 1 times of wavelength of 0 rank pattern, 0 rank pattern is enhanced, and 1 rank pattern is suppressed.
Preferably, the described characteristic frequency f ' based on described supersonic guide-wave, determines the characteristic parameter of described electromagnetic acoustic drive coil, to build described probe, specifically comprises: based on the characteristic frequency f ' of described supersonic guide-wave, determines the wavelength of 0 rank pattern guided wave; According to the wavelength of described 0 rank pattern guided wave, determine the characteristic parameter of described electromagnetic acoustic drive coil.
Preferably, described electromagnetic acoustic drive coil characteristic parameter specifically: wire pitch W=λ
0, conductor width B≤λ
0/ 2, conductor length 2 λ
0≤ L≤10 λ
0; Wherein, λ
0it is the wavelength of 0 rank pattern guided wave in described supersonic guide-wave.
By one or more technical scheme of the present invention, the present invention has following beneficial effect or advantage:
The invention discloses a kind of method for designing of electromagnetic acoustic incentive probe, according to the acoustic propagation principle in solid panel, the i.e. propagation law of SH type guided wave, determine characteristic frequency, then probe is excited according to this Frequency Design electromagnetic acoustic, the method achieve the enhancing of SH type 0 rank pattern guided wave in plate and the suppression of 1 rank pattern guided wave, achieve lower of characteristic frequency and excite the simplification of guided wave mode, improve signal to noise ratio (S/N ratio) thus effectively improve detection probability and the quantified precision of defect.
Accompanying drawing explanation
Fig. 1 is that in the embodiment of the present invention, electromagnetic acoustic excites probe schematic diagram;
Fig. 2 is the implementation step figure of the method for designing of embodiment of the present invention electromagnetic acoustic incentive probe;
Fig. 3 is embodiment of the present invention SH template phase velocity of wave dispersion curve;
Fig. 4 is embodiment of the present invention electromagnetic acoustic drive coil schematic diagram.
Embodiment
In order to make the application the technical staff in the technical field more clearly understand the application, below in conjunction with accompanying drawing, by specific embodiment, technical scheme is described in detail.
Main enforcement principle of the present invention is: according to the acoustic propagation principle in solid panel, and namely the propagation law of SH (Shear Horizontal, horizontal shear) type guided wave, determines characteristic frequency, then excites probe according to this Frequency Design electromagnetic acoustic.Wherein, electromagnetic acoustic excites probe to be made up of permanent magnet magnetic patch 1 and electromagnetic acoustic drive coil 2, as shown in Figure 1, electromagnetic acoustic drive coil 2 is placed between the N pole of permanent magnet magnetic patch 1 and S pole, and permanent magnet magnetic patch 1 is parallel to the constant bias magnetic field of drive coil wire at ferromagnetism sheet material Surface Creation.
Please refer to Fig. 2 below, the implementation step of the method for designing of the electromagnetic acoustic incentive probe based on magnetostrictive effect provided by the invention is as follows:
S1, according to the propagation law of SH type supersonic guide-wave in plate, determines the characteristic frequency f ' of supersonic guide-wave, and wherein, under characteristic frequency f ', the phase velocity of 1 rank pattern is 2 times of the phase velocity of 0 rank pattern.
S2, based on the characteristic frequency f ' of supersonic guide-wave, determines the characteristic parameter of electromagnetic acoustic drive coil, to build probe.
When determining characteristic parameter, concrete way is: based on the characteristic frequency f ' of supersonic guide-wave, determines the wavelength of 0 rank pattern guided wave; According to the wavelength of 0 rank pattern guided wave, determine the characteristic parameter of electromagnetic acoustic drive coil.Electromagnetic acoustic drive coil characteristic parameter is specifically: wire pitch W=λ
0, conductor width B≤λ
0/ 2, conductor length 2 λ
0≤ L≤10 λ
0.Wherein, λ
0it is the wavelength of 0 rank pattern guided wave in supersonic guide-wave.
Specifically, electromagnetic acoustic drive coil of the present invention is according to following acoustic propagation principle design:
1) guided wave, in solid panel
Be the sheet material of H for thickness, shear wave velocity is VS, and excitation SH type guided wave, then lead phase velocity of wave V
pfor:
In formula 1, f is frequency, n be guided wave mode exponent number (n=0,1,2 ...).
2), the superposition of ripple
Consider (x direction) two row plane waves of propagating in the horizontal direction, the position of sound source is respectively x1 and x2, and this two train waves frequency is identical, amplitude is identical, and initial phase is zero, and two train waves can describe with following formula:
Wherein k=2 π/λ is wave number, and λ=V/f is wavelength, and ω=2 π f is angular frequency, and f is frequency, and V is acoustic wave phase velocity degree.The sound field of other positions, according to the superposition principle of ripple, can be obtained by formula 2 and formula 3:
Can show that the amplitude size of total sound field is determined by the distance between sound source by formula 4, the distance between them | x
1-x
2| when being the even-multiple of half-wavelength, amplitude is maximum, and when being the odd-multiple of half-wavelength, amplitude is minimum.Therefore, if need to strengthen sound field, so allow the distance between sound source be the integral multiple of wavelength, otherwise, if in order to weaken sound field, so allow the distance between sound source be the odd-multiple of half-wavelength.
According to the superposition principle of ripple, simultaneously according to the propagation law (as shown in Figure 3) of SH type guided wave in plate, a certain characteristic frequency f'(5 can be obtained by formula 1), the phase velocity V of 1 rank pattern guided wave (that is: the curve of 4 representatives) under this frequency
p00 rank pattern guided wave (that is: the straight line of 3 representatives) phase velocity V
p12 times.
V in formula 5
p0be that 0 rank pattern leads phase velocity of wave.
Frequency f ' under, the wavelength of 0 rank pattern guided wave and 1 rank pattern guided wave is respectively:
If select two sound sources, its spacing is λ
0, stimulating frequency is f ', and initial phase is identical.For 0 rank pattern, the distance between two sound sources is just in time the integral multiple of its wavelength, so 0 rank pattern is strengthened.Now, for 1 rank pattern, the distance between two sound sources is just in time the odd-multiple of its half-wavelength, and namely 1 rank pattern is suppressed.And analyzed from above-mentioned theory, sound source width can not be greater than λ
0/ 2.
In sum, strengthen 0 rank pattern, suppress in the embodiment of 1 rank pattern, the initial phase of sound source is identical (in order to easy analysis, initial phase can be all allowed to be 0 degree), then when sound source distance is even-multiple (integral multiple of wavelength) of half-wavelength, sound field strengthens; When sound source distance is the odd-multiple of half-wavelength, sound field weakens.Due under selected characteristic frequency f, the phase velocity of 1 rank pattern is 2 times of the phase velocity of 0 rank pattern, and namely under this frequency, the wavelength of 1 rank pattern is 2 times of 0 rank pattern wavelength.Therefore, when selecting the identical sound source of initial phase and sound source spacing is 1 times of wavelength (i.e. the half-wavelength of 1 rank pattern) of 0 rank pattern, 0 rank pattern is enhanced, and 1 rank pattern is suppressed.
For example, sheet material parameters,acoustic is H=20mm, V
sthe phase velocities dispersion curve of the SH type guided wave of=3200m/s as shown in Figure 3.As can be seen from Figure 3, there is the guided wave of 0 rank pattern and 1 rank pattern, two kinds of patterns in 0kHz ~ 200kHz frequency range, 0 rank pattern is led phase velocity of wave and frequency and is had nothing to do, i.e. not frequency dispersion.1 rank pattern guided wave normal dispersion, namely phase velocity reduces with the increase of frequency, and trends towards medium shear wave velocity V gradually
s.According to the superposition principle of ripple, simultaneously according to the propagation law of SH type guided wave in plate, can obtain a certain characteristic frequency f'=92376Hz by formula 1, under this frequency, 1 rank pattern leads 2 times that phase velocity of wave is 0 rank pattern guided wave phase velocity, is 6400m/s.If select two sound sources, its spacing is the wavelength X of 0 rank pattern guided wave
0=34.64mm, stimulating frequency is f', and initial phase is identical.For 0 rank pattern, the distance between two sound sources is just in time the integral multiple of its wavelength, so 0 rank pattern is strengthened.Now, for 1 rank pattern, the distance between two sound sources is just in time the odd-multiple of its half-wavelength, and namely 1 rank pattern is suppressed.And analyzed from above-mentioned theory, sound source width can not be greater than λ
0/ 2=17.32mm.
Electromagnetic acoustic based on printed circuit board (PCB) excites drive coil, wherein, and wire pitch W=λ
0=34.64mm, conductor width B≤λ
0/ 2=17.32mm, for reducing diffraction effect, conductor length L=2 λ
0~ 10 λ
0.A, b are wiring point, are positioned at (symmetry of guarantee system) on oo ' axle.From drive coil a, b wiring point place passes into the train of impulses be made up of several sine waves of continuous print, under the alternating magnetic field of alternating excitation electric current generation and the acting in conjunction of constant bias magnetic field, drive coil produces the SH type supersonic guide-wave perpendicular to winding wire and bias magnetic field.
Electromagnetic acoustic drive coil of the present invention adopts printed circuit board (PCB) or flexible PCB to make, as shown in Fig. 4 and Fig. 1, the drive coil of electromagnetic acoustic drive coil is three-back-shaped coil, wherein, hollow line is same-phase sound source, is provided with the first wiring point a and the second wiring point b in three-back-shaped coil; In three-back-shaped coil, the train of impulses that is made up of several sine waves of continuous print is passed into as excitation by the first wiring point a and the second wiring point b; Under the acting in conjunction of the alternating magnetic field produced by alternating excitation electric current and constant bias magnetic field, launch the SH type supersonic guide-wave perpendicular to winding wire and bias magnetic field.
By one or more embodiment of the present invention, the present invention has following beneficial effect or advantage:
The invention discloses a kind of method for designing of electromagnetic acoustic incentive probe, according to the acoustic propagation principle in solid panel, the i.e. propagation law of SH type guided wave, determine characteristic frequency f, then probe is excited according to this Frequency Design electromagnetic acoustic, the method achieve the enhancing of SH type 0 rank pattern guided wave in plate and the suppression of 1 rank pattern guided wave, achieve lower of characteristic frequency and excite the simplification of guided wave mode, improve signal to noise ratio (S/N ratio) thus effectively improve detection probability and the quantified precision of defect.
Although described the preferred embodiment of the application, one of ordinary skilled in the art once obtain the basic creative concept of cicada, then can make other change and amendment to these embodiments.So claims are intended to be interpreted as comprising preferred embodiment and falling into all changes and the amendment of the application's scope.
Obviously, those skilled in the art can carry out various change and modification to the application and not depart from the spirit and scope of the application.Like this, if these amendments of the application and modification belong within the scope of the application's claim and equivalent technologies thereof, then the application is also intended to comprise these change and modification.
Claims (4)
1. a method for designing for electromagnetic acoustic incentive probe, is characterized in that, described method comprises:
According to the propagation law of SH type supersonic guide-wave in plate, determine the characteristic frequency f ' of described supersonic guide-wave, wherein, under this characteristic frequency f ', the phase velocity of 1 rank pattern is 2 times of the phase velocity of 0 rank pattern;
Based on the characteristic frequency f ' of described supersonic guide-wave, determine the characteristic parameter of described electromagnetic acoustic drive coil, to build described probe;
Described probe is made up of permanent magnet magnetic patch and electromagnetic acoustic drive coil, and described electromagnetic acoustic drive coil is placed between the N pole of permanent magnet magnetic patch and S pole; Wherein, described permanent magnet magnetic patch is used for the constant bias magnetic field being parallel to drive coil wire at ferromagnetism sheet material Surface Creation; The drive coil of described electromagnetic acoustic drive coil is three-back-shaped coil, is provided with the first wiring point and the second wiring point in described three-back-shaped coil; Passed in described three-back-shaped coil by the sinusoidal wave train of impulses formed of continuous print as excitation by described first wiring point and described second wiring point, under the acting in conjunction in the alternating magnetic field produced by alternating excitation electric current and constant bias magnetic field, launching perpendicular to winding wire and constant bias magnetic field, frequency is the supersonic guide-wave of f '.
2. the method for claim 1, is characterized in that, under described characteristic frequency f ', when sound source initial phase is identical and sound source spacing is 1 times of wavelength of 0 rank pattern, 0 rank pattern is enhanced, and 1 rank pattern is suppressed.
3. the method for claim 1, is characterized in that, the described characteristic frequency f ' based on described supersonic guide-wave, determines the characteristic parameter of described electromagnetic acoustic drive coil, to build described probe, specifically comprises:
Based on the characteristic frequency f ' of described supersonic guide-wave, determine the wavelength of 0 rank pattern guided wave;
According to the wavelength of described 0 rank pattern guided wave, determine the characteristic parameter of described electromagnetic acoustic drive coil.
4. method as claimed in claim 3, is characterized in that, described electromagnetic acoustic drive coil characteristic parameter specifically:
Wire pitch W=λ
0, conductor width B≤λ
0/ 2, conductor length 2 λ
0≤ L≤10 λ
0; Wherein, λ
0it is the wavelength of 0 rank pattern guided wave in described supersonic guide-wave.
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| CN110174466A (en) * | 2019-05-29 | 2019-08-27 | 湖北工业大学 | A kind of electromagnetic acoustic incentive probe and its construction method |
| CN110333291A (en) * | 2019-07-24 | 2019-10-15 | 湖北工业大学 | A kind of adjustable electromagnet ultrasonic changer of SV wave deflection angle and its design method |
| CN110702789A (en) * | 2019-11-11 | 2020-01-17 | 北京航空航天大学 | Electromagnetic ultrasonic transducer |
| CN111256630A (en) * | 2020-02-27 | 2020-06-09 | 西北大学 | Method for rapidly measuring thickness of metal plate by utilizing electromagnetic ultrasonic guided wave frequency dispersion characteristic |
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| Publication number | Priority date | Publication date | Assignee | Title |
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| CN110333291A (en) * | 2019-07-24 | 2019-10-15 | 湖北工业大学 | A kind of adjustable electromagnet ultrasonic changer of SV wave deflection angle and its design method |
| CN110333291B (en) * | 2019-07-24 | 2020-06-12 | 湖北工业大学 | Electromagnetic ultrasonic transducer with adjustable SV wave deflection angle and design method thereof |
| CN110702789A (en) * | 2019-11-11 | 2020-01-17 | 北京航空航天大学 | Electromagnetic ultrasonic transducer |
| CN111256630A (en) * | 2020-02-27 | 2020-06-09 | 西北大学 | Method for rapidly measuring thickness of metal plate by utilizing electromagnetic ultrasonic guided wave frequency dispersion characteristic |
| CN111256630B (en) * | 2020-02-27 | 2021-05-11 | 西北大学 | Method for rapidly measuring thickness of metal plate by utilizing electromagnetic ultrasonic guided wave frequency dispersion characteristic |
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