CN102608220B - Multi-basic frequency combined SH0 model electromagnetic acoustic transducer - Google Patents
Multi-basic frequency combined SH0 model electromagnetic acoustic transducer Download PDFInfo
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- CN102608220B CN102608220B CN 201210004883 CN201210004883A CN102608220B CN 102608220 B CN102608220 B CN 102608220B CN 201210004883 CN201210004883 CN 201210004883 CN 201210004883 A CN201210004883 A CN 201210004883A CN 102608220 B CN102608220 B CN 102608220B
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Abstract
The invention discloses a multi-basic frequency combined SH0 model electromagnetic acoustic transducer, belonging to the field of nondestructive detection. The multi-basic frequency combined SH0 model electromagnetic acoustic transducer is composed of a signal input BNC (Bayonet Nut Connector), a signal output BNC, a pulse electromagnet power supply BNC, a magnet fixing plate, a protective shell, a pulse electromagnet and a folded coil; the folded coil is put in a groove on the bottom of the protective shell; the pulse electromagnet is arranged in the protective shell; the magnet fixing plate is arranged on the pulse electromagnet; a cover plate of the protective shell is arranged at the uppermost end of the protective shell; and the signal input BNC, the signal output BNC and the pulse electromagnet power supply BNC are fixed on the cover plate. The signal input BNC and the signal output BNC are respectively connected into terminals on the upper and lower surfaces of the folded coil; and the pulse electromagnet power supply BNC is connected to a winding of the pulse electromagnet. Compared with an equivalent periodic coil EMAT (Electro Magnetic Acoustic Transducer), the transducer provided by the invention can pay attention to the information of a plurality of frequency points and can replace a plurality of EMATs with different frequencies to carry out frequency sweeping.
Description
Technical field
The invention belongs to the Non-Destructive Testing field, be specifically related to a kind of SH0 mode Electromagnetic Acoustic Transducer (EMAT, Electromagnetic Acoustic Transducer) of many dominant frequency combinations.
Background technology
Horizontal shear wave (SH ripple) is a kind of supersonic guide-wave of propagating in plate structure, and its propagation characteristic is very tempting in the guided wave context of detection.SH only produces the shear direction vibration that is parallel to the plate face in plate, when running into the interface consistent with its particle vibration direction reflex time takes place, and MODAL TRANSFORMATION OF A does not take place the SH ripple.In addition, the zeroth order mode of SH ripple is frequency dispersion not, and velocity of propagation is lower, has higher spatial resolution under the equal instrument condition.Thereby the SH ripple is widely used in all kinds of defects detection and monitoring structural health conditions of plate.
EMAT is the sonac with periodic distribution structure, is convenient to very much produce in-plane displacement, therefore often is used to produce in test specimen the SH ripple.Its characteristics are that sensor always optionally encourages or receive the wavelength mode consistent with its distribution cycle.By the coil form be installed with the displacement that DISTRIBUTION OF MAGNETIC FIELD collocation can motivate different directions on the test specimen surface.Therefore, the coil form is the key of EMAT design with the design that is installed with magnetic field.Fig. 1 is SH ripple EMAT commonly used.
Coil:
For the scissoring vibration that produces the SH ripple is provided, the coil of SH ripple EMAT adopts inflection molded lines circle usually, when feeding the electric current of alternation in the coil, produce the moving field of alternation on the surface of ferromagnetism test specimen, this moving field with by being installed with the static magnetic field reciprocation that magnet produces, in the surperficial or nearly superficial layer of test specimen, produce the vibration of shearing and to direction (left and right directions among the figure) propagation that coil extends, namely formed the SH ripple.
Coil width has determined the aperture of sensor, thereby has determined the beam width of the sound wave that sensor motivates.When coil width was more big, the acoustic beam that sensor motivates was more concentrated, and sensor directive property is more good; When coil width more hour, the acoustic beam that sensor motivates is diffusing all the more, and is more big with the zone that equidistant lower sensor covers.But the design of coil width should consider simultaneously sensor directive property demand and by increase bias magnet that coil width brings away from (being just reducing of biased magnetic field strength).
Coil period has determined the wavelength of the sound wave that sensor can encourage and receive, and the wavelength of sound wave is coil period.Current opposite in direction in the coil in adjacent two line segments, its spacing should be half of wavelength.When tested material is determined, the frequency of its sound wave that can encourage and receive that coil period is then corresponding.Periodicity just because of coil is arranged, and has realized the mode selectivity of EMAT.
The coil period number is more big, and the acoustic wave energy that sensor can motivate is more big, but simultaneously can the time motivate signal the time domain width lengthen, thereby reduced the time domain resolving power that detects.When running into the defective of meeting nearer, signal is understood mutual superposition, is difficult to differentiate.
Magnet:
EMAT adopts permanent magnet that bias magnetic field is provided usually.This mode is simple and convenient, but exists not enough in actual applications.When sensor frequency lower (coil period is bigger), for equally distributed magnetic field is provided, need select the bigger magnet of volume for use.This will cause sensor too heavy, and detected object return during for ferrimagnet be not easy to mobile.
The design of above coil and magnet has caused SH ripple EMAT commonly used in the deficiency that receives in signal amplitude, time domain resolving power and the sensor dirigibility.
Summary of the invention
In order to solve the shortcoming in existing EMAT reception signal amplitude, time domain resolving power and the sensor dirigibility, a kind of SH0 mode Electromagnetic Acoustic Transducer of many dominant frequency combinations.
This sensor is made up of signal input BNC connector 1, signal output BNC connector 2, impulse mgnet power supply BNC connector 3, magnet fixed head 4, protecting sheathing 5, impulse mgnet 6 and inflection molded lines circle 7, as shown in Figure 2.Inflection molded lines circle 7 places in containment vessel 5 bottom recesses, and containment vessel inside is equipped with impulse mgnet 6, is magnet fixed head 4 on it.The top at protecting sheathing is the cover plate of protecting sheathing, and signal input BNC connector 1, signal output BNC connector 2 and impulse mgnet power supply BNC connector 3 are fixedly arranged on it.
Described magnet fixed head 4, purpose are to fix two blocks of electromagnet, to guarantee that under the effect of high-intensity magnetic field two electromagnet can adhesive.
Described protecting sheathing 5 provides protection for whole sensor.Signal input BNC connector 1, signal output BNC connector 2 and impulse mgnet power supply BNC connector 3 place the protecting sheathing top.Magnet fixed head 4 places protecting sheathing inside with impulse mgnet 6, and inflection molded lines circle is fixed in the groove of protecting sheathing bottom, as shown in Figure 3.In order to characterize the distribution of each element of enclosure, the protecting sheathing among Fig. 3 is simplified model, and the real protection shell should comprise the pit, groove of particular design so that fixed pulse electromagnet and inflection molded lines circle.
Described impulse mgnet 6, for having the impulse mgnet of square iron core, require magnetic direction under magnet evenly and direction vertically downward/upwards, the direction in the magnetic field that two impulse mgnets produce is opposite, as shown in Figure 3.During work, pulse signal of excitation in the coil of impulse mgnet, its width should be greater than pumping signal.Two impulse mgnets can form a direction is pointed to another impulse mgnet by an impulse mgnet bias magnetic field on the test specimen surface.The number of turn of impulse mgnet and electrical current should design according to required biased magnetic field strength.
Described inflection molded lines circle 7 is fixed in the groove of protecting sheathing 5 bottoms.The coil period of described inflection molded lines circle 7 is also unequal, but changes according to certain rules, and coil is printed on the printed circuit board (PCB), and upper epidermis aligns from beginning to end with the coil that following top layer is printed, but its regularity of distribution is opposite, as shown in Figure 4.
The principle of work of the sensor of common inflection molded lines circle as shown in Figure 5, this type of sensor utilization be the magnetostrictive effect of material.Permanent magnet or electromagnet form bias magnetic field B on the test specimen surface
0, when feeding electric current in the coil, electrified wire can be set out magnetic field B at the test specimen surface induction
m, moving field and bias magnetic field quadrature meet the producing method of maximum shear, and both magnetic field of closing is B
HIf when material was negative magnetostriction material (as nickel etc.), under the influence of bias magnetic field, the lattice of material was compressed, shown in figure among Fig. 5.At this moment, if introduce the moving field that electrified wire produces, then lattice can be shown in two figure about among Fig. 5.When feeding the electric current of alternation in the inflection molded lines circle, just produced reciprocal scissoring vibration, thereby formed the SH ripple.The current opposite in direction of two adjacent leads in the inflection molded lines circle, the moving field direction of its generation is opposite, thereby the half-wavelength of the sound wave that produces is always consistent at interval therewith.
And what adopt among the present invention is the SH0 mode coil of many dominant frequency combination, improves in the principle of common inflection molded lines circle, and its principle as shown in Figure 6.The coil period of the SH0 mode inflection molded lines circle of many dominant frequency combinations is also unequal, because coil is always selected the excitation wavelength sound wave corresponding with coil period, so the coil of unequal-interval can go out the SH0 mode of different wave length at the test specimen underexcitation.Because SH0 mode is frequency dispersion not, the SH velocity of wave propagation unanimity of each frequency, therefore the sequencing that only need when designing excitation with receiving coil different coil period be distributed is corresponding, can finish the frequency modulation (PFM) to coil.The SH ripple of each frequency is inner independent propagation of test specimen, (one swashs one when receiving pattern, adopts on two pcb boards two coils of distribution in the same way, during the self excitation and self receiving pattern and excitation and the distribution of receiving coil are consistent, adopt two coils that oppositely distribute on the same pcb board, as shown in Figure 6).Therefore, each frequency SH wave propagation distance equates, thereby the travel-time also equates.On the time domain, each frequency SH ripple can be in identical time point stack.
The present invention has the following advantages,
1) the SH ripple of each frequency superposes at synchronization, has increased the amplitude that receives signal greatly, and shortens the time domain width of signal when increasing amplitude, can obtain higher time domain resolving power;
2) the coil EMAT with the cycle of grade compares, and the present invention can pay close attention to the information of a plurality of Frequency points simultaneously, and by signal post-processing, can substitute the EMAT that utilizes a plurality of different frequencies carries out frequency sweep;
3) owing to the frequency band of sensor can be adjusted according to design, and can in time domain, improve signal amplitude by the compressed signal width, thus lower to the requirement of pumping signal, adopt pulse excitation or sine-wave excitation to get final product.This greatly reduces the requirement to detecting instrument.
4) because sensor adopts impulse mgnet that bias magnetic field is provided, thereby sensor can not adsorb ferrimagnet when not switching on, and has improved the dirigibility of sensor greatly.
Below in conjunction with description of drawings and embodiment the present invention is described in further detail.
Description of drawings
Fig. 1: the structural drawing of common SH ripple inflection molded lines circle EMAT
Fig. 2: sensor wiring layout
Fig. 3: sensor internal structural drawing
Fig. 4: loop construction synoptic diagram
Fig. 5: inflection molded lines circle fundamental diagram
Fig. 6: working sensor schematic diagram
Fig. 7: self excitation and self receiving detection system synoptic diagram
Fig. 8: one swashs one receives the detection system synoptic diagram
Fig. 9: the SH0 mode EMAT experiment self excitation and self receiving signal graph of many dominant frequency combinations
Figure 10: the SH0 mode EMAT experiment one of many dominant frequency combinations swashs one and receives signal graph
Among the figure, 1-signal input BNC connector, 2-signal output BNC connector, 3-impulse mgnet power supply BNC connector, 4-magnet fixed head, 5-protecting sheathing, 6-impulse mgnet, 7-inflection molded lines circle.
Embodiment
Concrete implementation step of the present invention comprises:
A kind of is that magnetostriction materials or surface are covered with in the plate of magnetostriction materials in material; excitation produces the Electromagnetic Acoustic Transducer of the SH0 ripple of single many dominant frequency combinations, is made up of signal input BNC connector 1, signal output BNC connector 2, impulse mgnet power supply BNC connector 3, magnet fixed head 4, protecting sheathing 5, impulse mgnet 6 and inflection molded lines circle 7.
Processing and assembling process:
Protecting sheathing 5 is covering and the support of whole sensor; long 70mm; wide 50mm, high 15mm is processed by engineering plastics; the thick 3mm of upper top; be processed with the BNC connector hole on it, the bottom has long 65mm, and the dark groove of the 1mm of wide 45mm is with fixing inflection molded lines circle circuit board; have through hole in wiring place, be convenient to coil and BNC connector wiring.
Inflection molded lines circle 7 in the load map 2, its physical dimension is long 65mm, wide 45mm, the PCB circuit board of thick 0.5mm, tangible as inflection molded lines circle in the central area of circuit board, adjacent two conductor spacings of coil spacing, its current opposite in direction is changed to 2mm from 5mm, totally 13 sections.
The impulse mgnet 6 of packing into, impulse mgnet 6 be by long 60mm, wide 10mm, and the strip iron core of high 10mm is outer to be that 20 winding constitutes around the number of turn.
The magnet fixed head of packing into.BNC connector is fixed in the protecting sheathing top cover; the following top layer terminals that connect signal input BNC connector 1 and inflection molded lines circle 7; connect signal output BNC connector 2 and 7 times top layer terminals of inflection molded lines circle, connect the winding of impulse mgnet power supply BNC connector 3 and impulse mgnet 6.Cover plate that the BNC connector protecting sheathing the is housed threaded hole by 4 drift angles of shell is fixed on the protecting sheathing.
Using method:
Typical case's detection system is made up of signal generator, power amplifier, sensor, prime amplifier and digital oscilloscope as shown in Fig. 7 and Fig. 8, and wherein Fig. 7 is the signal of self excitation and self receiving detection system, and Fig. 8 is a sharp receipts detection system signal.
When adopting self excitation and self receiving to arrange, signal generator produces the rect.p. that pulsewidth is 1 μ s, and behind power amplifier, in the input pickup, sensor is positioned on the nickel plate of the about 1m of a block length, wide 120mm, thick 1mm.Sound wave is back and forth propagated at plate width direction, and the end face echo of reception receives via sensor, outputs to digital oscilloscope via the change-over circuit of power amplifier inside and shows.
When adopting one to swash a receipts layout, signal generator produces the rect.p. that pulsewidth is 1 μ s, behind power amplifier, in the input stimulus sensor, receiving sensor is positioned at apart from the about 300mm of stimulus sensor place, and the signal of reception outputs to digital oscilloscope via preposition amplification and shows.
Reception signal when the SH0 mode EMAT that many dominant frequency that are Fig. 9 and Figure 10 make up adopts self excitation and self receiving and to swash a receipts pattern.Can see, when the distribution that is distributed in drive coil of receiving coil is consistent (the even echo and that comprises the self excitation and self receiving pattern swashs a receipts pattern), signal is compressed in time domain, and amplitude is bigger, the time domain resolving power is better, has realized mentality of designing of the present invention.
Claims (5)
1. the SH0 mode Electromagnetic Acoustic Transducer of dominant frequency more than kind combination, by signal input BNC connector (1), signal output BNC connector (2), impulse mgnet power supply BNC connector (3), magnet fixed head (4), protecting sheathing (5), impulse mgnet (6) and inflection molded lines circle (7) are formed; Inflection molded lines circle (7) places in containment vessel (5) bottom recesses, and containment vessel inside is equipped with impulse mgnet (6), is magnet fixed head (4) on it; The top at protecting sheathing is the cover plate of protecting sheathing, and signal input BNC connector (1) is fixedly arranged on the cover plate, signal output BNC connector (2), impulse mgnet power supply BNC connector (3); Signal input BNC connector (1), signal output BNC connector (2) inserts the terminals of inflection molded lines circle top and bottom respectively, and impulse mgnet power supply BNC connector (3) is connected to the winding of impulse mgnet; In order to the impulse mgnet (6) of bias magnetic field that vertical direction is provided for producing the opposite strip electromagnet of magnetic direction, two not adhesives of impulse mgnet; The coil period of described inflection molded lines circle (7) is unequal.
2. according to the SH0 mode Electromagnetic Acoustic Transducer of a kind of many dominant frequency combinations described in the claim 1, it is characterized in that: described protecting sheathing (5) is engineering plastics.
3. according to the SH0 mode Electromagnetic Acoustic Transducer of the combination of a kind of many dominant frequency described in the claim 1, it is characterized in that: described impulse mgnet (6) is for having the impulse mgnet of strip iron core, require magnetic direction under magnet evenly and direction vertically downward or upwards; During work, pulse signal of excitation in the coil of impulse mgnet, its width should be greater than the pumping signal of inflection molded lines circle (7).
4. according to the SH0 mode Electromagnetic Acoustic Transducer of the combination of the described a kind of many dominant frequency in the claim 1, it is characterized in that: coil is printed on the printed circuit board (PCB) in the described inflection molded lines circle (7), upper epidermis aligns from beginning to end with the coil that following top layer is printed, but its regularity of distribution is opposite.
5. according to the SH0 mode Electromagnetic Acoustic Transducer of the combination of the described a kind of many dominant frequency in the claim 1, it is characterized in that: its assembling process is, the inflection molded lines circle (7) of packing in protecting sheathing (5) bottom, the electromagnet (6) of in protecting sheathing (5), packing into, the magnet fixed head (4) of packing into is with fixed magnet; BNC connector is fixed in the protecting sheathing top cover, connects BNC connector and the signal wire of inflection molded lines circle (7) and the winding of BNC connector and impulse mgnet (6); The top board that BNC connector protecting sheathing (5) will be housed is fixed on the protecting sheathing by the threaded hole of 4 drift angles of shell.
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| Application Number | Priority Date | Filing Date | Title |
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| CN 201210004883 CN102608220B (en) | 2012-01-09 | 2012-01-09 | Multi-basic frequency combined SH0 model electromagnetic acoustic transducer |
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| CN 201210004883 CN102608220B (en) | 2012-01-09 | 2012-01-09 | Multi-basic frequency combined SH0 model electromagnetic acoustic transducer |
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| CN102608220B true CN102608220B (en) | 2013-08-21 |
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| Publication number | Priority date | Publication date | Assignee | Title |
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| CN103837606B (en) * | 2014-03-14 | 2016-06-08 | 厦门大学 | The method that the electromagnet ultrasonic changer of polyphase structure and ultrasonic high-efficiency excite |
| CN104198594A (en) * | 2014-06-11 | 2014-12-10 | 北京工业大学 | Multiple-main-frequency combined torsional-mode electromagnetic acoustic array sensor |
| CN112305065B (en) * | 2020-09-16 | 2024-02-02 | 北京工业大学 | SH production 0 Periodic electromagnet array electromagnetic acoustic transducer for wave guide |
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| US6041656A (en) * | 1995-10-31 | 2000-03-28 | Dunegan; Harold L. | Transducer for measuring acoustic emission events |
| JP2003274488A (en) * | 2002-03-18 | 2003-09-26 | Chuo Seisakusho Ltd | Electromagnetic ultrasonic wave probe |
| CN101701809A (en) * | 2009-11-12 | 2010-05-05 | 哈尔滨工业大学 | Electromagnetic ultrasonic thickness gauge and measurement method thereof |
| CN101706266A (en) * | 2009-11-12 | 2010-05-12 | 哈尔滨工业大学 | Impulse electromagnet for electromagnetic acoustic transducer |
| CN101706476A (en) * | 2009-11-12 | 2010-05-12 | 哈尔滨工业大学 | Electromagnetic ultrasonic automatic flaw detection method for plates and device thereof |
| CN101713642A (en) * | 2009-11-12 | 2010-05-26 | 哈尔滨工业大学 | Electromagnetic ultrasonic probe |
| CN202757915U (en) * | 2012-01-09 | 2013-02-27 | 北京工业大学 | Multi-main-frequency combined SH0-mode electromagnetic acoustic transducer |
Family Cites Families (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JPS59173750A (en) * | 1983-03-23 | 1984-10-01 | Mitsubishi Electric Corp | Plate wave transmitter and receiver |
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Patent Citations (7)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US6041656A (en) * | 1995-10-31 | 2000-03-28 | Dunegan; Harold L. | Transducer for measuring acoustic emission events |
| JP2003274488A (en) * | 2002-03-18 | 2003-09-26 | Chuo Seisakusho Ltd | Electromagnetic ultrasonic wave probe |
| CN101701809A (en) * | 2009-11-12 | 2010-05-05 | 哈尔滨工业大学 | Electromagnetic ultrasonic thickness gauge and measurement method thereof |
| CN101706266A (en) * | 2009-11-12 | 2010-05-12 | 哈尔滨工业大学 | Impulse electromagnet for electromagnetic acoustic transducer |
| CN101706476A (en) * | 2009-11-12 | 2010-05-12 | 哈尔滨工业大学 | Electromagnetic ultrasonic automatic flaw detection method for plates and device thereof |
| CN101713642A (en) * | 2009-11-12 | 2010-05-26 | 哈尔滨工业大学 | Electromagnetic ultrasonic probe |
| CN202757915U (en) * | 2012-01-09 | 2013-02-27 | 北京工业大学 | Multi-main-frequency combined SH0-mode electromagnetic acoustic transducer |
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