CN202330358U - SH0 electromagnetic acoustic transducer for detecting defects of plate structure - Google Patents
SH0 electromagnetic acoustic transducer for detecting defects of plate structure Download PDFInfo
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- CN202330358U CN202330358U CN2011204691301U CN201120469130U CN202330358U CN 202330358 U CN202330358 U CN 202330358U CN 2011204691301 U CN2011204691301 U CN 2011204691301U CN 201120469130 U CN201120469130 U CN 201120469130U CN 202330358 U CN202330358 U CN 202330358U
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Abstract
The utility model provides an SH0 electromagnetic acoustic transducer for detecting defects of a plate structure, belonging to the field of nondestructive testing. The SH0 electromagnetic acoustic transducer for detecting the defects of the plate structure can be used for the defect detection of sheet materials of an iron magnetic material, profile steel and pipelines, particularly defect detection of plate structures, by exciting through a magneto-constriction effect and receiving ultrasonic guide waves SH0 (horizontal shearing) waves. The SH0 electromagnetic acoustic transducer comprises a transducer shell (4), a magnet array (3) and a coil (2) which are embedded into the shell of the transducer, a nickel belt (1) covering the surface of the coil, and a connector (6) which is embedded into the transducer shell and is connected with the coil. When the SH0 electromagnetic acoustic transducer is used, one transducer is used for receiving and one transducer is used for sending. The transducer is contacted with an object to be detected without a coupling agent, the detection process is simple and efficient, and the SH0 electromagnetic acoustic transducer is applicable to requirements of field detection of engineering.
Description
Technical field
The utility model belongs to supersonic guide-wave Non-Destructive Testing field, through magnetostrictive effect excitation and reception supersonic guide-wave SH0 horizontal shear wave, can be used for the defects detection, particularly plate structure defects detection of sheet material, shaped steel and the pipeline of ferrimagnet.
Background technology
As a kind of lossless detection method fast and efficiently, the supersonic guide-wave technology is widely used in the Nondestructive Evaluation and the health monitoring of various engineering structure (like plate, pipe and bar).Conventional ultrasound piezoelectric transducer often needs the good coupling between couplant realization and the measured piece, and the surface quality of measured piece is had relatively high expectations, and is difficult to be applicable to the detection of high temperature, motion and rough surface.The EM coupling of utilizing that late 1960s grows up produces hyperacoustic method, can realize contactless ultrasound wave defects detection.(Electromagnetic Acoustic Transducer EMAT), is the core apparatus that electromagnetic acoustic detects to electromagnet ultrasonic changer; Have the surface noncontact of transducer and medium, need not to add the characteristic of acoustic couplant; Can save processing procedures such as lacquer, oxide that surface of the work deoiled, have good reproducibility, detection speed is high, be fit to dynamically; Advantages such as high temperature detection; Receive acoustics and Non-Destructive Testing each side personnel's concern day by day, through the development of decades, the electromagnet ultrasonic changer technology has progressively got into the commercial Application stage.Its application detects and the high temperature thickness measuring from cut deal, train wheel, develops into various fields such as weld seam detection, rod iron detection, steel pipe detection, railway track detection, compound substance detection.
The theoretical foundation of electromagnet ultrasonic changer mainly is two kinds of effects, and a kind of is Lorentz force, and another kind is magnetostriction.When the coil that is loaded with the alternation exciting current during near tested metal surface; To go out eddy current at the metal internal induction; If exist a quiescent biasing magnetic field this moment, because Lorentz mechanism will produce the acting force of alternation in metal, the power of this variation will inspire ultrasound wave.Detection based on only suitable ferromagnetics of the EMAT of magnetostriction mechanism or magnetic material because the alternation effect in magnetic field changes the magnetic material volume, thereby forms the vibration of material internal, and finally outwards will vibrate with the ultrasound wave form and propagate.EMAT is a reversible transducer simultaneously, and it can be used to receive ultrasound wave.
The utility model is intended on the theoretical foundation of electromagnet ultrasonic changer; Develop a kind of novel supersonic guide-wave SH0 EMAT; Utilize magnetostrictive effect; In the ferromagnetic plate structure, encourage and receive the SH0 horizontal shear wave of single mode, utilize flaw echo to judge corrosion position and extent of corrosion.The SH0 ripple be particle vibration all at the ripple that is arranged in the plane that is parallel to aspect, have the advantages that velocity of wave does not change basically in the different-thickness plate, velocity of wave is stable; No frequency dispersion, transmission coefficient also are higher than other wave modes far away, a little less than the decay; Be beneficial to long distance detecting, it is less that the SH0 ripple is influenced by material surface, and with crackle, border effect MODAL TRANSFORMATION OF A does not take place basically; And the sound field that the SH0 transducer produces, the acoustic beam spread angle is little, and is easy to control; Testing result does not receive the influence of structure boundary, and shortcomings such as MODAL TRANSFORMATION OF A take place easily for multi-modal, frequency dispersion, the border that can well overcome like Lamb wave.Theoretical and experiment shows; This novel supersonic guide-wave SH0 EMAT can be to the defects detection of carrying out of sheet material, shaped steel and the pipeline of ferrimagnet; The particularly detection of plate structure defective, testing process is simple, efficient, adapts to the requirement that engineering site detects.
Summary of the invention
The purpose of the utility model provides a kind of SH0 EMAT that can practical application; Being mainly used in the ferromagnetic plate fault of construction detects; And then obtain defective locations and defect size, can carry out economy, quick and effectively detection to the ferrimagnet plate structure that is in the different medium environment.
The utility model is to solve the problems of the technologies described above the technical scheme that is adopted to be: comprise nickel strap 1, coil 2, ndfeb magnet array 3, shell 4 and joint 6; Be placed with ndfeb magnet array 3 in the shell 4, the width of each piece magnet is wavelength half the of the SH0 ripple that goes out of transducer excitation in the ndfeb magnet array 3; Magnet array 3 fits tightly at thickness direction and 2 one surfaces of coil, and the lead that coil 2 is drawn is connected with the joint that is embedded in transducer enclosure 46; Be covered with nickel strap 1 on coil 2 another surfaces.
Ndfeb magnet array 3 array center overlap with coil 2 centers.
Described transducer enclosure 4 is the metal material of aldary or other electromagnetic screen.
Said transducer winding 2 adopts pcb board or manual coiling, becomes the racetrack wiring, but and arranging multiplayer (being generally front-back two-sided wiring).
Said nickel strap bottom area covers coil and whole magnet array, and thickness should be thin as far as possible.Suggest thickness≤0.15mm.
Said SH0 EMAT, magnet array 3 thickness directions are DOM, array center overlaps with coil 2 centers.When combination back transducer was placed on the ferromagnetic plate structure, coil 2, magnet array 3 fitted tightly with plate structure.
The result of use of the utility model is: this transducer encourages, receives and respectively use a transducer in use, and when transducer was placed on the tested ferromagnetic plate, coil, magnet array and workpiece fitted tightly.Through impulse function generator Energizing cycle pulse signal after power amplification to encouraging transducer; Produce the SH0 ripple by magnetostriction principle; The SH0 ripple is propagated in ferromagnetic plate and is met end face or defective and return by receiving transducer and receive and on oscillograph, show in real time, confirms endface position or defect size, position through echo time and amplitude.Transducer contacts with workpiece and need not couplant, and detection is simple, efficient, but Rapid Realization plate structure section and defects detection.
Description of drawings
Fig. 1 is the product assembling synoptic diagram of SH0 EMAT;
Fig. 2 be the SH0 EMAT along A-A cross-sectional view among Fig. 1;
Fig. 3 is a SH0 EMAT STRUCTURE DECOMPOSITION synoptic diagram;
SH wave dispersion curve in the long band steel of the thick 4m of Fig. 4: 6mm, this curve shows: in 0～0.31MHz frequency range, can encourage single mode SH0 ripple.Constant and the frequency-independent of SH0 wave-wave speed, theoretical velocity of wave is the no dispersion phenomenon of 3260m/s (relating to parameters such as speed and density of material, elastic modulus).Therefore when design SH0 wave transducer; Should select the frequency of centre frequency below 310kHz; The too high SH1 mode horizontal shear wave that then motivates easily of frequency is differentiated multi-modal being difficult to of pumping signal, and underfrequency then encourages the SH0 wave-wave long bigger; Detect the limited ability of defective, suggestion transducer centre frequency is chosen between the 250kHz-310kHz.
Fig. 5: the SH0 EMAT detects band steel defective device synoptic diagram;
Fig. 6: the SH0 EMAT detects the long band of 4m defective band steel and receives oscillogram;
Among the figure: 1, nickel strap, 2, the PCB coil, 3, magnet array, 4, transducer enclosure; 5, nut, 6, BNC connector, 7, the cross pan head screw, 8, the impulse function generator; 9, excitation terminal impedance coupling, 10, SH0 ripple electromagnetic sound excitation transducer, 11, SH0 ripple electromagnetic sound receiving transducer, 12, the receiving-end impedance coupling; 13, digital oscilloscope, 14, computing machine, 15, band steel.
Embodiment
Through specific embodiment the utility model is done further to detail below, be without loss of generality, detected object adopts the band steel plate structure (hereinafter to be referred as band steel) of 4000 * 60 * 5 (mm of unit), and density is 7.9g/cm
3, Poisson ratio is 0.31.Fig. 4 has provided SH wave dispersion curve in the long band steel of the thick 4m of 5mm of above-mentioned parameter.Detecting other plate structures (like aluminium sheet) can adjust accordingly transducer parameters according to this instance.Following examples be descriptive be not determinate, can not limit the protection domain of the utility model with this.
Like Fig. 1, Fig. 2, SH0 EMAT shown in Figure 3 is mainly by nickel strap 1, PCB coil 2, ndfeb magnet array 3, shell 4, BNC connector) constitute.Be placed with ndfeb magnet array 3 in the shell 4, the width D of each piece magnet is wavelength half the of the SH0 ripple that goes out of transducer excitation.Magnet array 3 fits tightly at thickness direction and coil 2 upper surfaces, and the lead that coil 2 is drawn is connected with the joint that is embedded in transducer enclosure 46; Be covered with nickel strap 1 at coil 2 lower surfaces, and fastening with screw 7.
The width D of the magnet of instance magnet array 3 is wavelength half the of the SH0 ripple that goes out of transducer excitation.Design transducer frequency 270KHz can get according to SH0 theoretical velocity of wave 3260m/s in band steel, and the wavelength of SH0 ripple is 12mm, and then adopting the magnet width is 6mm.
Instance transducer winding 2 adopts pcb board to make, and front-back two-sided wiring becomes racetrack layout, thickness of slab 0.5mm, coil effective dimensions 40mm * 20mm.
Said SH0 EMAT, magnet array 3 thickness directions are DOM, array center overlaps with pcb board coil 2 centers.When transducer was placed on the band steel, the coil 2, the magnet array 3 that are coated with nickel strap fitted tightly with band steel.
According to the characteristics of band steel, in the present embodiment transducer parameters carried out the selection of the following aspects: transducer enclosure, PCB coil parameter, array magnet parameter and nickel strap parameter.
1, transducer enclosure design
Transducer enclosure adopts aldary (brass, copper component concentration >=68%).The SH0 transducer receives signal and often is mingled with space low frequency electromagnetic undesired signal; Can make the signal to noise ratio (S/N ratio) variation; Brought difficulty to detection, do not received the interference of low frequency magnetic field, can place this device in the shielding case of processing with metallic copper for making the SH0 transducer; The magnetic line of force is mainly through the little screen layer of magnetic resistance, thereby protection places the interior device of shell not receive the influence of external magnetic field.Advantages such as aldary is cheap, and high intensity, electric conductivity and thermal conductivity are arranged, and processing characteristics and corrosion stability are good, and satisfy shielding requirements, so transducer enclosure 4 adopts copper alloy made.For magnet array center and PCB hub of a spool closely are harmonious, transducer architecture design draw-in groove is accurately located to guarantee magnet and PCB coil, and leaves spatial margin, so that place impedance matching electric capacity.
2, the PCB coil parameter is selected
For realizing that the band steel corrosion detects the function that special-purpose SH0 transducer produces the SH0 ripple that mode is single, energy is big, directive property is good.Make characteristics in conjunction with pcb board, coil arrangement adopts the front-back two-sided layout of racetrack, increases coil turn, and makes transducer architecture compact; Select in live width and distance between centers of tracks parameter, under the CF, different live widths and distance between centers of tracks all can produce single mode SH0 ripple; Live width and spacing densification then energy are big more, consider the pcb board processing technology, and this transducer instance adopts live width 0.2mm; Distance between centers of tracks 0.2mm, the number of turn 46 circles, the PCB coil of plate length * wide * thick=50 * 30 * 0.5 (mm of unit).
3, the selection of magnet size
Design theory according to transducer; The transducer of the design SH0 ripple that mode is single, energy is big, directive property is good, the magnetic line of force that magnet produces should wrap up the PCB coil uniformly, makes the magnetic field of generation uniform and stable and have enough static magnetic field strength; Therefore magnet array back magnetization direction area should be slightly larger than PCB coil useful area; Array center and PCB hub of a spool are harmonious, and guarantee to make up when afterwards transducer is placed on the band steel, and the PCB coil, magnet and the band steel that are coated with nickel strap fit tightly.Be wavelength half the of the SH0 ripple that goes out of transducer excitation by the magnet width D, design transducer frequency 270KHz, SH0 in the band steel conductor theoretical velocity of wave 3260m/s, then the wavelength of SH0 ripple is 12mm, promptly the magnet width is 6mm.12 of this transducer instance selection length * wide * thick=20 * 6 * 10 (mm of unit) Surface field 4500 Gausses' Nd-Fe-B permanent magnets.
4, nickel strap parameters of choice
In order to produce the good signal of signal to noise ratio (S/N ratio), motivate single S H0 ripple, nickel strap thickness should approach (thickness≤0.15mm) as far as possible.Area covers whole magnet array.This transducer instance nickel strap thickness is 0.15mm.
In addition, in the present embodiment in order to realize that better signal to noise ratio (S/N ratio) will realize impedance matching.Present embodiment select electric capacity be 7.4nF as SH0 wave transducer impedance matching original paper, terminal adopts BNC connector 6.
Utilize the transducer after parameter is confirmed, a kind of method with SH0 ripple electromagnetic acoustic Non-Destructive Testing band steel plate structure be provided:
(1) as shown in Figure 5, place SH0 ripple electromagnetic sound excitation transducer 10 and SH0 ripple electromagnetic sound receiving transducer 11 on the band steel 15 length direction central axis.SH0 ripple electromagnetic sound excitation transducer 10 is connected with excitation terminal impedance coupling 9; Excitation terminal impedance coupling 9 is connected with impulse function generator 8; SH0 ripple electromagnetic sound receiving transducer 11 is connected with receiving-end impedance coupling 12; Receiving-end impedance coupling 12 is connected with digital oscilloscope 13, and computing machine 14 is connected with digital oscilloscope 13.SH0 ripple electromagnetic sound excitation transducer is placed band steel right-hand member termination (the transducer center is concordant with end face), and SH0 ripple electromagnetic sound receiving transducer is positioned at the place apart from SH0 ripple electromagnetic sound excitation transducer 0.5m, and the artificial defect simulated defect is positioned at the place apart from band steel left end 1m.
(2) it is adjustable in 1～20 scope to produce one-period by impulse function generator 8; Centre frequency adjustable square-wave signal in 0～1MHz scope; In 0～1MHz scope, change frequency; Excitation makes SH0 ripple electromagnetic sound excitation transducer 10 produce signal energies in this scope, to be in maximal value, and the frequency of corresponding this moment is 0.27MHz, then is chosen for impulse function generator frequency of operation.The intensity of square-wave signal and gain etc. all can exert an influence to supersonic guide-wave.In this enforcement, by impulse function generator produce power grade 10, gain 50db, frequency is the square-wave signal in 5 concussion cycles of 0.27MHz;
(3) pumping signal is through excitation terminal impedance coupling 9 excitation SH0 ripple electromagnetic sound excitation transducers 10, excitation SH0 ripple in band defective band steel 15;
(4) the SH0 ripple signal of excitation is propagated in band steel 15, and after defective and grounded screen end reflections, SH0 ripple electromagnetic sound receiving transducer 11 shows at digital oscilloscope 13, and stores computing machine 14 into through ethernet port through receiving impedance matching 12;
(5) through analyzing the time that the reflection echo that receives in the signal arrives acceptance point, confirm defective locations in the band steel 15.Tell among Fig. 6 for the first time that echo is a direct wave, crest time location 0.158ms (under this experiment condition with each ripple bag time to peak as signal initial and time of arrival the position since in the oscillogram zero point be that radiofrequency signal rises and sends out a point; Be not time to peak, during actual computation, get radiofrequency signal and delay about 0.008ms as actual leading zero's position; The above-mentioned crest time is through revising, down together), echo is the band steel flaw echo for the second time; Crest time location 1.751ms, echo is the second trip echo of defective after the reflection of right side for the third time, crest time location 2.070ms; The 4th time echo is the left side echo; Crest time location 2.376ms, the 5th echo is the second trip echo of left side echo through the right side, crest time location 2.693ms.。By the 4th right side echo (crest is obvious, is convenient to differentiate) and direct wave mistiming 2.218ms, and the respective distances 7000mm of institute, can calculate and this time test actual SH0 velocity of wave is 3156m/s, with theoretical velocity of wave relative error be 3.2%.By actual velocity of wave and the anti-defective locations that pushes away of echo time for the second time, (1.751ms * 3156m/s+500mm)/2, record defective apart from its right end face 3013mm is merely 0.4% with actual range 3000mm relative error.In like manner, also can pass through echo time checking defective locations for the third time---apart from its right end face 3016mm, be merely 0.5% with actual range 3000mm relative error.Utilize a little less than the SH0 wave reflection echo attenutation, can also differentiate defect size according to the amplitude of defect waves bag.
Through experimental verification; This supersonic guide-wave SH0 transducer can rapidly and efficiently detect the band steel defective, and this transducer cost is low, good stability and can reusing; The measurement result accuracy is high; Favorable repeatability, testing process is convenient and swift, adapts to the requirement that actual engineering site detects.
Claims (3)
1. a SH0 EMAT that is used for the plate structure defects detection is characterized in that: comprise nickel strap (1), coil (2), ndfeb magnet array (3), shell (4) and joint (6); Be placed with ndfeb magnet array (3) in the shell (4), the width of each piece magnet is wavelength half the of the SH0 ripple that goes out of transducer excitation in the ndfeb magnet array (3); Magnet array (3) fits tightly at thickness direction and (2) surfaces of coil, and the lead that coil (2) is drawn is connected with the joint that is embedded in shell (4) (6); Be covered with nickel strap (1) on another surface of coil (2).
2. SH0 EMAT as claimed in claim 1 is characterized in that: coil (2) adopts pcb board or manual coiling.
3. SH0 EMAT as claimed in claim 1 is characterized in that: ndfeb magnet array (3) center overlaps with coil (2) center.
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| Application Number | Priority Date | Filing Date | Title |
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| CN2011204691301U CN202330358U (en) | 2011-11-23 | 2011-11-23 | SH0 electromagnetic acoustic transducer for detecting defects of plate structure |
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| CN2011204691301U CN202330358U (en) | 2011-11-23 | 2011-11-23 | SH0 electromagnetic acoustic transducer for detecting defects of plate structure |
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| CN103822973A (en) * | 2014-02-26 | 2014-05-28 | 北京工业大学 | Omnidirectional shear-horizontal-mode magnetostrictive transducer |
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| CN106248790A (en) * | 2016-08-01 | 2016-12-21 | 北京工业大学 | A kind of non-metal board Lamb wave detection method based on Electromagnetic Acoustic Transducer |
| CN107271572A (en) * | 2017-07-31 | 2017-10-20 | 沈阳工业大学 | Electromagnetic acoustic sheet metal flaw detection transducer |
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| CN110471010A (en) * | 2019-09-18 | 2019-11-19 | 北京工业大学 | The SH of ferrimagnet Magnetostrictive curve0Mode supersonic guide-wave measurement method |
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| CN103822973A (en) * | 2014-02-26 | 2014-05-28 | 北京工业大学 | Omnidirectional shear-horizontal-mode magnetostrictive transducer |
| CN104198581A (en) * | 2014-09-01 | 2014-12-10 | 北京工业大学 | Lorentz force-based electromagnetic acoustic surface wave sensor with high signal to noise ratio |
| CN106248790A (en) * | 2016-08-01 | 2016-12-21 | 北京工业大学 | A kind of non-metal board Lamb wave detection method based on Electromagnetic Acoustic Transducer |
| US10605790B2 (en) * | 2016-08-08 | 2020-03-31 | Tsinghua University | Device and method for detecting defect in main shaft of wind turbine |
| CN109831922A (en) * | 2016-10-07 | 2019-05-31 | 通用电气(Ge)贝克休斯有限责任公司 | Improved downhole electromagnetic sonic transducer sensor |
| CN109831922B (en) * | 2016-10-07 | 2023-06-02 | 通用电气(Ge)贝克休斯有限责任公司 | Improved underground electromagnetic acoustic transducer sensor |
| CN107271572A (en) * | 2017-07-31 | 2017-10-20 | 沈阳工业大学 | Electromagnetic acoustic sheet metal flaw detection transducer |
| CN107271572B (en) * | 2017-07-31 | 2023-09-26 | 沈阳工业大学 | Electromagnetic ultrasonic metal sheet flaw detection transducer |
| CN110057913A (en) * | 2019-05-27 | 2019-07-26 | 上海市特种设备监督检验技术研究院 | A kind of horizontal shear wave transducer for coarse grain material weld seam detection |
| CN110618200A (en) * | 2019-08-28 | 2019-12-27 | 江苏大学 | Flexible probe of welding seam defect detection array sensor based on characteristic guided waves |
| CN110618200B (en) * | 2019-08-28 | 2022-04-26 | 江苏大学 | Flexible probe of welding seam defect detection array sensor based on characteristic guided waves |
| CN110471010B (en) * | 2019-09-18 | 2021-09-10 | 北京工业大学 | SH of magnetostriction curve of ferromagnetic material0Modal ultrasonic guided wave measuring method |
| CN110471010A (en) * | 2019-09-18 | 2019-11-19 | 北京工业大学 | The SH of ferrimagnet Magnetostrictive curve0Mode supersonic guide-wave measurement method |
| CN112305065A (en) * | 2020-09-16 | 2021-02-02 | 北京工业大学 | Production of SH0Guided wave periodic electromagnet array electromagnetic acoustic transducer |
| 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 |
| CN112730613A (en) * | 2020-12-21 | 2021-04-30 | 厦门大学 | Composite board bonding layer performance degradation evaluation method |
| CN114062495A (en) * | 2021-11-15 | 2022-02-18 | 中北大学 | Method and device for enhancing electromagnetic ultrasonic SH wave crossing weld joint defect detection capability |
| CN117233263A (en) * | 2023-11-15 | 2023-12-15 | 中北大学 | Narrow-sound-beam electromagnetic ultrasonic sensor and device for detecting defects in axial direction of pipeline |
| CN117233263B (en) * | 2023-11-15 | 2024-02-06 | 中北大学 | Narrow-sound-beam electromagnetic ultrasonic sensor and device for detecting defects in axial direction of pipeline |
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| C14 | Grant of patent or utility model | ||
| GR01 | Patent grant | ||
| CX01 | Expiry of patent term |
Granted publication date: 20120711 |
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| CX01 | Expiry of patent term |