CN105738478B - Imaging method is detected based on the steel plate Lamb wave that linear array focal time is inverted - Google Patents

Imaging method is detected based on the steel plate Lamb wave that linear array focal time is inverted Download PDF

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CN105738478B
CN105738478B CN201610047917.6A CN201610047917A CN105738478B CN 105738478 B CN105738478 B CN 105738478B CN 201610047917 A CN201610047917 A CN 201610047917A CN 105738478 B CN105738478 B CN 105738478B
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mrow
msub
defect
focusing
array
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CN105738478A (en
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涂君
宋小春
邱公喆
李羽可
熊芝
陈涛
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Hubei University of Technology
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    • GPHYSICS
    • G01MEASURING; TESTING
    • G01NINVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
    • G01N29/00Investigating 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
    • G01N29/04Analysing solids
    • G01N29/07Analysing solids by measuring propagation velocity or propagation time of acoustic waves
    • GPHYSICS
    • G01MEASURING; TESTING
    • G01NINVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
    • G01N2291/00Indexing codes associated with group G01N29/00
    • G01N2291/02Indexing codes associated with the analysed material
    • G01N2291/023Solids
    • G01N2291/0234Metals, e.g. steel
    • GPHYSICS
    • G01MEASURING; TESTING
    • G01NINVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
    • G01N2291/00Indexing codes associated with group G01N29/00
    • G01N2291/10Number of transducers
    • G01N2291/106Number of transducers one or more transducer arrays

Abstract

The present invention relates to a kind of steel plate Lamb wave detection imaging method inverted based on linear array focal time.One group of ultrasonic phase array sensor array is excited according to certain rule, the focusing at sound wave any point in large area sheet material is realized;Time reversal processing is carried out to the echo-signal comprising defect information, and transmitting in ultrasonic phase array sensor array is loaded into using the signal after processing as new wave source, secondary focusing of the sound wave in fault location is realized;The amplitude focused view at the fault location secondary focusing moment is set up, large area plate defect is imaged.This method combines ultrasonic phase array focus deflection method the rejection characteristic and time reversal of SATT in the self-focusing characteristic of fault location, breaches the limitation that Conventional temporal reversion defect imaging technology is difficult to be used for quickly detecting large area sheet material.

Description

Steel plate Lamb wave detection imaging method based on linear array focusing-time reversal
Technical field
The invention belongs to Ultrasonic Nondestructive technical field, and in particular to one kind is anti-based on linear array focusing-time The steel plate Lamb wave detection imaging method turned.
Background technology
Ultrasonic phase array focus deflection theory shows, as long as exciting one group by relatively independent piezoelectricity according to certain rule The ultrasonic phase array sensor array of chip composition, it is real with regard to the wave beam that each array element is launched can be made superposition, deflection and other effects occur Focusing of the existing sound wave at any point;Thus ultrasonic phase array focus deflection method can be such that acoustic energy assembles in certain area, press down Decay of the sound wave processed in communication process.
Fig. 1 is focusing ultrasonic wave schematic diagram, and one group of probe is first excited according to two ends, and the time sequencing excited behind centre swashs One group of ultrasonic wave is encouraged out, then the situation of superposition occurs in the ultrasonic wave that each probe is motivated during propagating forward, makes Wave surface it is less and less, energy is increasingly concentrated, and is finally focused on a bit, that is, realizes the focusing of ultrasonic wave.
Fig. 2 is that ultrasonic wave deflects schematic diagram, one group of probe is first excited according to left end, the time sequencing excited after right-hand member swashs One group of ultrasonic wave is encouraged out, then the situation of superposition occurs in the ultrasonic wave that each probe is motivated during propagating forward, makes Wave surface is less and less, energy is increasingly concentrated, and wave surface can be deflected to certain direction, finally be focused on a bit, i.e., Realize the deflection focusing of ultrasonic wave.
Time reversal acoustic theory shows, defect in propagation process of sound wave similar one new passive wave source to sensor The initial sonic waves of excitation are reflected, while producing new conversion mode, are carried out by the echo-signal received to sensor Time reversal processing, and it is loaded into transmitting in model using the signal after processing as new wave source, you can realize sound wave in defect The self-focusing at place.
In simple terms, i.e., one group of ultrasonic wave is motivated simultaneously with one group of ultrasonic probe, according to Huygen's principle, works as ultrasound Ripple pops one's head in the ultrasonic wave launched as the ultrasonic source of active when reaching defect in flat board, defect can be considered as one it is passive Ultrasonic source outwards launches ultrasonic wave, and this is that our imaginations there may be a video camera, records the super of defect transmitting Sound wave reaches the process of each ultrasonic probe, and this process is referred to as the ultrasonic signal with defect information by ultrasonic probe The process of reception.Then we turn the image recorded around projection, i.e., shown from piece Caudad head, at this moment we can see The process for emitting and being focused in fault location to one group of ultrasonic signal from probe, and first receive the probe of ultrasonic wave after the meeting Motivate ultrasonic wave, after receive the probe of ultrasonic wave and can first motivate ultrasonic wave, i.e., after the arriving first of so-called signal hair and after arrive First send out, this process is referred to as process of the ultrasonic wave in fault location self-focusing.And the process for turning image around projection is to visiting The echo-signal that head is received carries out the process of time reversal processing.
Fig. 3 is the schematic diagram of time reversal, and solid line represents the ultrasound sent from ultrasonic probe as active wave source in figure Ripple reaches the process of defect, and this group of sound wave is to encourage simultaneously;Dotted line represents the ultrasound that defect is launched as passive wave source in figure The process that ripple echo-signal is received by ultrasonic probe;Figure chain lines represent to carry out ultrasonic echo signal (dotted line is represented) It is re-loaded in ultrasonic probe and is launched after time reversal, in the process of fault location self-focusing.
Because ultrasonic wave is decayed comparatively fast in communication process, therefore the defect time reversal imaging technique of comparative maturity at present It is many that mode is laid using circular workpiece formula sensor array as shown in Figure 3;But this sensor lays mode and there is following office Limit:
(1) number of sensors of arrangement is more, data processing complex;
(2) because sensor array column wrap workpiece is arranged, therefore the size of detection workpiece is limited, is not suitable for large-scale workpiece Detection.
At present, using more laid around workpiece formula sensor array the flat-panel defect time reversal imaging technique of comparative maturity Mode.This sensor array lays mode can only be with being detected, to big in certain thickness and the significant structural member of defect The detection of type component can only be realized by a series of scanning, thus can not realize the efficient quick detection to large-scale plate.
The content of the invention
The purpose of the present invention is to be directed to the deficiencies in the prior art, and ultrasonic phase array focus deflection method is declined to sound wave The rejection characteristic and time reversal subtracted combines in the self-focusing characteristic of fault location, it is proposed that based on linear array focusing- The steel plate Lamb wave detection imaging method of time reversal.
The present invention technical solution be:A kind of steel plate Lamb wave detection based on linear array focusing-time reversal Imaging method, one group of ultrasonic phase array sensor array is excited according to certain rule, realizes that sound wave is appointed in large area sheet material Anticipate the focusing of a bit;Time reversal processing is carried out to the echo-signal comprising defect information, and using the signal after processing as new Wave source be loaded into model launch, realize secondary focusing of the sound wave in fault location;Set up the width at the defect secondary focusing moment It is worth focused view, large area plate defect is imaged.
Ultrasonic phase array focus deflection theory shows, as long as exciting one group by relatively independent piezoelectricity according to certain rule The ultrasonic phase array sensor array of chip composition, it is real with regard to the wave beam that each array element is launched can be made superposition, deflection and other effects occur Focusing of the existing sound wave at any point.Thus ultrasonic phase array focus deflection method can be such that acoustic energy assembles in certain area, press down Decay of the sound wave processed in communication process.
Time reversal acoustic theory shows, defect similar one new passive wave source (Huygens in propagation process of sound wave Principle) initial sonic waves of sensor excitation are reflected, while producing new conversion mode, pass through what sensor was received Echo-signal carries out time reversal processing, and is loaded into transmitting in model using the signal after processing as new wave source, you can real Self-focusing of the existing sound wave in fault location.
The inventive method is linear array focusing-time reversal (Linear Array Focusing Time Reversal, is abbreviated as LAFTR) ultrasound detection imaging method, ultrasonic exciting-reception is used as using linear array focusing probe Sound source, binding time inversion technique realizes the accurately image of defect in component.The as shown by data of table two, with being sensed using array Result when device is directly carried out obtained by anti-imaging is compared, the steel plate Lamb wave detection based on linear array focusing-time reversal Preferably, its positional precision improves 30%~50% to the imaging effect of imaging method, and geometric accuracy improves 26%~130%.
It is theoretical according to the deflection of phase array focusing shown in Fig. 4, one group is excited by relatively independent piezo crystals according to certain rule The ultrasonic phase array sensor array of piece composition, can make launching beam superposition, deflection and other effects occur, realize sound wave any one The focusing of point, so as to strengthen energy of the sound wave in focal zone.
The ultrasonic phase array sensor array is classified as linear array transducer, there is N+1 array element, if acoustic beam is F in depth, Deflection angle completes focus deflection for θ position, then the focusing delay time t needed for sensor iiFor:
Wherein, d is array element spacing,For the velocity of sound, θ is deflection angle.
It is that the focusing to any point P (x, y) in detection object can be achieved using above-mentioned formula, sensor array element 0, sensing Device array element N and focus point P (x, y) constitute a triangle, and the triangle encloses region and is considered as effective detection area.
If wanting to realize the complete detection to large area sheet material, only need to suitably choose multiple focus points is focused.Such as The power of fruit ultrasonic array is sufficiently large, and focus point P can be with chosen distance ultrasonic array unlimited distance, therefore our law theory On can realize the quick detection to unlimited large-area sheet material.If existing defects in effective detection zone, due to each sensor It is different from the distance of defect, thus from excitation ultrasonic wave to the time received needed for the echo-signal comprising defect information also not phase Together.
Time reversal refers to sensor after echo-signal is received, and carries out time reversal processing to it, is then made It is loaded into model and launches for new wave source, realizes and sent out after the arriving first of signal, it is rear to first sending out.
Time reversal acoustic theory shows, defect in propagation process of sound wave similar one new passive wave source to sensor The initial sonic waves of excitation are reflected, while producing new conversion mode, are carried out by the echo-signal received to sensor Time reversal processing, and it is loaded into transmitting in model using the signal after processing as new wave source, you can realize sound wave in defect The self-focusing at place.
Specific steps using the large area sheet material defect imaging recognition methods of above-mentioned technical proposal include:
Step 1:Region to be scanned is subjected to discretization, by focusing on array probe timesharing along different angular emissions ultrasound Ripple, is A at the time of each probe transmitting ultrasonic wavem,i, its subscript represents i-th in m-th of scanning area probe;
Step 2:Setting alarm defect threshold value, extracts B at the time of array probe receives defect reflection echom,i, calculate anti- Turn time delay Δ Tm,i, interception time window length Lm,i
Step 3:By interception time window length Lm,iInverted signal f when interior signal progress time reversal obtainsm,i, and add again I-th of probe is loaded onto, then realizes secondary focusing moment F in fault locationm,i
Step 4:Set up in secondary focusing Fm,iEach pixel on amplitude focused view K, the K figure at moment corresponds to mould Each construction unit in type;
Step 5:Scanning area is divided into h × g grid, by grid element center point echo amplitude Km,pIt is approximately whole net The echo amplitude of lattice, sets up two-dimensional pixel matrix P
P∝(Km,p)h×g
Wherein image pixel value maximum is defect.
Further, inversion delay time Δ T in the step 2m,iCalculation formula be:
Time window length Lm,iCalculation formula be:
Lm,i=Bm,i+ΔTm,N-i
Further, secondary focusing moment F is realized in fault location in the step 3m,iCalculation formula be:
Fm,i=Lm,i-(Am,i+Bm,i)/2。
Further, for each construction unit, arbitrary image unit P (x in the step 4p,yp) in Fm,iTime at moment Wave amplitude is represented by:
Wherein, Ns is the number of sampled signal, AiFor i-th of sensor performance difference of compensation and monitoring signals energy attenuation Amplification coefficient, amplification coefficient takes normalization coefficient;V is the velocity of sound;xi、yiFor the coordinate of i-th of sensor.
Further, ultrasonic phase array sensor array is made up of relatively independent piezoelectric chip, in Active Lamb Wave In anti-imaging process, one group of piezoelectric sensor element is first constituted into piezoelectric-array, the pattern received entirely in excitation using sending out entirely.
Further, the one side of ultrasound phase-control array sensor along large area sheet material is laid.
Further, the detection probe of sensor is that piezoelectric probe or EMAT pop one's head in.
Further, sensor array can also lay mode, area-type probe laying mode using arcuate probe.
The beneficial effects of the invention are as follows:Ultrasonic phase array focus deflection method is anti-to the rejection characteristic of SATT and time Robin combines in the self-focusing characteristic of fault location, it is proposed that based on ultrasonic phase array focus deflection theory and time reversal sound The large area sheet material material defect imaging recognition methods of theory, breaking through Conventional temporal reversion defect imaging technology can not be to large area The limitation that sheet material is used for quickly detecting.
Brief description of the drawings
Fig. 1 is that ultrasonic phase array focuses on schematic diagram.
Fig. 2 is ultrasonic wave deflection schematic diagram.
Fig. 3 is the schematic diagram of time reversal.
Fig. 4 is large area sheet material defect imaging recognition methods schematic diagram of the present invention.
Fig. 5 be the focusing delay time with when anti-focus on moment schematic diagram.
Fig. 6 is single-pass hole LAFTR detection models
Fig. 7 is simulation result figure.
Fig. 8 is damage scattered signal figure.
Inverted signal oscillogram when Fig. 9 is.
Anti- imaging results figure when Figure 10 is.
Figure 11 is double cutting LAFTR detection models.
Figure 12 (a) is instead imaged obtained imaging effect when directly being carried out using array-type sensor.
Steel plate Lamb waves of the Figure 12 (b) based on linear array focusing-time reversal detects the imaging effect of imaging method.
Embodiment
The present invention is described further below in conjunction with the accompanying drawings.
Embodiment 1, embodiment 2 by COMSOL finite element emulation softwares illustrate the modeling method of LAFTR ultrasound detections with And the influence of imaging is surveyed in reverse-examination during linear array focusing pair.
The single-pass hole LAFTR detection models of embodiment 1
Fig. 6 is single-pass hole LAFTR detection models, and steel plate length of side 300mm, due to using Lamb wave detection model, ignores plate Thick size simultaneously sets up two-dimensional model, and material is No. 45 steel, and its attribute is as shown in table 1.Center is provided with a diameter in plate ForThrough hole as defect to be detected, coordinate system, array-type sensor are set up using defect center as the origin of coordinates Steel plate side is arranged in, element number of array is 16 array elements, and array element is centrally located at (0,150) place, and array element spacing is 1/4 wavelength, and Pattern is received using full hair is complete.
The steel plate physical dimension of table 1 and material properties parameter
Using transient pulse function as excitation wave source, its expression formula is:
In formula:Pulse frequency centered on f;N is the wave number in driving pulse waveform.
Set transient state solve the time be:6.5×10-5S, solving step-length is:1/f/30, coil current amplitude is 10A.Pass through Calculate and solve, simulation result is as shown in Figure 7, it can be seen that:
(1) length shortens the wave surface of acoustic beam in the horizontal direction, it was demonstrated that can be with using the focus deflection technology of phased array Effectively improve ultrasonic beam energy in the propagation direction and then increase the detecting distance of acoustic beam in the propagation direction, so that full The detection demand of sufficient band large-scale metal sheet material;
(2) as a result of the focusing technology of phased array, the secondary lobe on wave surface direction is suppressed, and main beam narrows, The resolution ratio of defect can be improved;With reference to phased array deflection technique, so that the Multi-angle omnibearing detection to detecting object is realized, It is finally reached the purpose for expanding detection range.
When inverse processing analyze:In order to protrude flaw indication when anti-waveform in amplitude and be easy to focus on so that most The anti-imaging effect of terminal hour is obvious and readily identified defect, and detection signal is processed using differential mode, be that is to say sensor The signal subtraction that received signal is received with it on structural health model in defect model, it is possible to obtain defect Scattered signal, as shown in Figure 8.
The waveform received to each sensor carries out flaw indication interception, while anti-when being carried out in time window to it Inverted signal at that time is can be obtained by, as shown in Figure 9.By when it is anti-after signal reload to each sensor, with when inverted signal At the beginning of carve be zero moment point, so as to realize the secondary focusing in fault location.
Detect imaging effect analysis:Defect imaging result is as shown in Figure 10, it can be seen that steel plate central through hole defect can be with Blur-free imaging, it is that centre coordinate is (1,2) that testing result, which is shown, a diameter ofThrough hole.
2 pairs of cutting LAFTR detection models of embodiment
For further research using under linear array focus deflection technology when anti-imaging effect superiority, from complexity Defect is verified.
Coordinate system is set up using model center as the origin of coordinates, defect is set to two that length and width is respectively 5mm and 1mm Adjacent cutting, its centre coordinate is respectively (- 10,0), (10,0), as shown in figure 11.
Remaining parameter of model keeps constant;Figure 12 (a) is anti-when directly being carried out using array-type sensor to be imaged and do threshold The pixel or pixel value of threshold value are only showed more than in imaging effect figure after value processing, figure, threshold size is according to experiment using warp Test value;Figure 12 (b) is when being done focus deflection along -30 °, 0 and 30 ° of three direction respectively using array-type sensor and carried out respectively Anti- imaging, then does average superposition and does in the imaging effect figure after threshold process, figure being only showed more than by imaging results image The pixel or pixel value of threshold value, threshold size use empirical value according to experiment.To be contrasted, by the testing result of two methods Sieve is listed in Table 2, wherein amplitude highest point coordinates is exceeded as the imager coordinate of each defect with defect using in imaging results figure The number of pixels of threshold value is used as imaging size.
Anti- imaging results error (the unit when array of table 2 is with focus deflection:mm)
Compared with as shown by data, result when directly being carried out using array-type sensor obtained by anti-imaging, based on linear Preferably, its positional precision improves 30% to the imaging effect of the steel plate Lamb wave detection imaging method of array focusing-time reversal ~50%, geometric accuracy improves 26%~130%.
A kind of LAFTR ultrasound detections imaging method is applied to detection of the Lamb wave on large-sized sheet material, has by COMSOL Xian Yuan simulation softwares verify that beneficial effect is as follows to this technology:
(1) time reversal technology is detected applied to Lamb wave, can be good at avoiding frequency dispersion, multi-mode etc. unfavorable because Number, is realized to the secondary focusing of defect, and it is focused on, and amplitude is high, and effect is good, image clearly and defect is readily identified.
(2) method for arranging of array-type sensor compared to other method for arranging ensureing to the identification effect of defect and On the basis of last image quality, while the number of applications of sensor can be greatly reduced, testing cost is reduced, is more suitable for The detection of large-sized sheet material.
(3) the amplitude focusedimage set up based on the method can relatively accurately detect defect in ejecting plate, and it is to defect Position, size imaging results it is truer, can for the positioning of defect, it is qualitative, strong technical support is quantitatively provided.

Claims (6)

1. based on the big surface plate defect imaging recognition methods of Lamb wave, it is characterized in that being used as ultrasound using linear array focusing probe Wave excitation-reception sound source, the one side of linear array transducer along big surface plate is laid, according to certain one group of ultrasound of rule excitation Phased-array transducer array, realizes the focusing at sound wave any point in big surface plate;To the echo-signal comprising defect information Time reversal processing is carried out, and transmitting in model is loaded into using the signal after processing as new wave source, realizes sound wave in defect The secondary focusing at place;The amplitude focused view at the defect secondary focusing moment is set up, massive plate defect is imaged;Defect imaging The specific steps of identification include:
Step 1:Region to be scanned is subjected to discretization, by focusing on array probe timesharing along different angular emission ultrasonic waves, often It is A at the time of individual probe transmitting ultrasonic wavem,i, its subscript represents i-th in m-th of scanning area probe;
Step 2:Setting alarm defect threshold value, extracts B at the time of array probe receives defect reflection echom,i, calculate reversion and prolong Slow time Δ Tm,i, interception time window length Lm,i
Step 3:By interception time window length Lm,iInverted signal f when interior signal progress time reversal obtainsm,i, and be loaded onto again I-th of probe, then be F at the time of fault location realizes secondary focusingm,i
Step 4:Set up in secondary focusing Fm,iEach pixel on amplitude focused view K, the K figure at moment corresponds on model Each construction unit;
Step 5:Scanning area is divided into h × g grid, by grid element center point echo amplitude Km,pIt is approximately whole grid Echo amplitude, sets up two-dimensional pixel matrix P,
P∝(Km,p)h×g
It is defect in image pixel value maximum.
2. according to claim 1 be based on the big surface plate defect imaging recognition methods of Lamb wave, it is characterized in that anti-in step 2 Turn time delay Δ Tm,iCalculation formula be:
<mrow> <msub> <mi>&amp;Delta;T</mi> <mrow> <mi>m</mi> <mo>,</mo> <mi>i</mi> </mrow> </msub> <mo>=</mo> <mfrac> <mrow> <mo>(</mo> <msub> <mi>B</mi> <mrow> <mi>m</mi> <mo>,</mo> <mi>i</mi> </mrow> </msub> <mo>-</mo> <msub> <mi>B</mi> <mrow> <mi>m</mi> <mo>,</mo> <mn>0</mn> </mrow> </msub> <mo>)</mo> <mo>-</mo> <mo>(</mo> <msub> <mi>A</mi> <mrow> <mi>m</mi> <mo>,</mo> <mi>i</mi> </mrow> </msub> <mo>-</mo> <msub> <mi>A</mi> <mrow> <mi>m</mi> <mo>,</mo> <mn>0</mn> </mrow> </msub> <mo>)</mo> </mrow> <mn>2</mn> </mfrac> </mrow>
Time window length Lm,iCalculation formula be:
Lm,i=Bm,i+ΔTm,N-i
3. it is according to claim 1 be based on the big surface plate defect imaging recognition methods of Lamb wave, it is characterized in that in step 3 Fault location is F at the time of realizing secondary focusingm,iCalculation formula be:
Fm,i=Lm,i-(Am,i+Bm,i)/2。
4. according to claim 1 be based on the big surface plate defect imaging recognition methods of Lamb wave, it is characterized in that right in step 4 In each construction unit, arbitrary image unit P (xp,yp) in Fm,iThe echo amplitude at moment is expressed as:
<mrow> <msub> <mi>K</mi> <mrow> <mi>m</mi> <mo>,</mo> <mi>p</mi> </mrow> </msub> <mo>=</mo> <munderover> <mo>&amp;Sigma;</mo> <mrow> <mi>j</mi> <mo>=</mo> <mn>1</mn> </mrow> <mrow> <mi>N</mi> <mi>s</mi> </mrow> </munderover> <msub> <mi>A</mi> <mi>i</mi> </msub> <msub> <mi>f</mi> <mrow> <mi>m</mi> <mo>,</mo> <mi>i</mi> <mo>,</mo> <mi>j</mi> </mrow> </msub> <mrow> <mo>(</mo> <msub> <mi>L</mi> <mrow> <mi>m</mi> <mo>,</mo> <mi>i</mi> </mrow> </msub> <mo>-</mo> <mfrac> <msqrt> <mrow> <msup> <mrow> <mo>(</mo> <msub> <mi>x</mi> <mi>p</mi> </msub> <mo>-</mo> <msub> <mi>x</mi> <mi>i</mi> </msub> <mo>)</mo> </mrow> <mn>2</mn> </msup> <mo>+</mo> <msup> <mrow> <mo>(</mo> <msub> <mi>y</mi> <mi>p</mi> </msub> <mo>-</mo> <msub> <mi>y</mi> <mi>i</mi> </msub> <mo>)</mo> </mrow> <mn>2</mn> </msup> </mrow> </msqrt> <mi>&amp;nu;</mi> </mfrac> <mo>)</mo> </mrow> </mrow>
Wherein, Ns is the number of sampled signal, AiIt is that i-th sensor performance difference of compensation and monitoring signals energy attenuation are put Big coefficient, takes normalization coefficient;V is the velocity of sound;xi、yiFor the coordinate of i-th of sensor.
5. according to claim 1 be based on the big surface plate defect imaging recognition methods of Lamb wave, it is characterized in that ultrasound phase-control Array sensor array is made up of relatively independent piezoelectric chip, in active lamb ripples in anti-imaging process, first by one group of piezoelectricity Sensor element constitutes piezoelectric-array, the incentive mode received entirely in excitation using sending out entirely.
6. according to claim 1 be based on the big surface plate defect imaging recognition methods of Lamb wave, it is characterized in that sensor Detection probe is that piezoelectric probe or EMAT pop one's head in.
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