CN101839893B - Lamb wave virtual time reversal method with high spatial resolution - Google Patents
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- CN101839893B CN101839893B CN201010166891XA CN201010166891A CN101839893B CN 101839893 B CN101839893 B CN 101839893B CN 201010166891X A CN201010166891X A CN 201010166891XA CN 201010166891 A CN201010166891 A CN 201010166891A CN 101839893 B CN101839893 B CN 101839893B
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- 238000000034 method Methods 0.000 title claims abstract description 40
- 235000019687 Lamb Nutrition 0.000 title claims abstract description 30
- 230000006378 damage Effects 0.000 claims abstract description 87
- 238000012545 processing Methods 0.000 claims abstract description 5
- 238000012544 monitoring process Methods 0.000 claims description 45
- 230000005284 excitation Effects 0.000 claims description 35
- 230000004044 response Effects 0.000 claims description 16
- 230000008569 process Effects 0.000 claims description 11
- 230000003862 health status Effects 0.000 claims description 5
- 238000005086 pumping Methods 0.000 claims description 5
- 230000003321 amplification Effects 0.000 claims description 4
- 238000003199 nucleic acid amplification method Methods 0.000 claims description 4
- 238000010606 normalization Methods 0.000 claims description 3
- 208000027418 Wounds and injury Diseases 0.000 abstract description 11
- 208000014674 injury Diseases 0.000 abstract description 11
- 230000000694 effects Effects 0.000 abstract description 3
- 238000012806 monitoring device Methods 0.000 abstract 1
- 238000005516 engineering process Methods 0.000 description 8
- 230000036541 health Effects 0.000 description 5
- XAGFODPZIPBFFR-UHFFFAOYSA-N aluminium Chemical compound [Al] XAGFODPZIPBFFR-UHFFFAOYSA-N 0.000 description 4
- 229910052782 aluminium Inorganic materials 0.000 description 4
- 239000004411 aluminium Substances 0.000 description 4
- 230000002708 enhancing effect Effects 0.000 description 4
- 230000007246 mechanism Effects 0.000 description 4
- 230000002463 transducing effect Effects 0.000 description 4
- 238000000605 extraction Methods 0.000 description 3
- 230000008859 change Effects 0.000 description 2
- 239000011159 matrix material Substances 0.000 description 2
- 238000004088 simulation Methods 0.000 description 2
- 230000002123 temporal effect Effects 0.000 description 2
- 206010061245 Internal injury Diseases 0.000 description 1
- 238000003491 array Methods 0.000 description 1
- 230000021615 conjugation Effects 0.000 description 1
- 238000011161 development Methods 0.000 description 1
- 238000010586 diagram Methods 0.000 description 1
- 239000006185 dispersion Substances 0.000 description 1
- 230000001771 impaired effect Effects 0.000 description 1
- 239000000463 material Substances 0.000 description 1
- 239000000203 mixture Substances 0.000 description 1
- 230000003287 optical effect Effects 0.000 description 1
- 230000001902 propagating effect Effects 0.000 description 1
- 238000011160 research Methods 0.000 description 1
- 230000000630 rising effect Effects 0.000 description 1
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Abstract
The invention provides a lamb wave virtual time reversal method with a high spatial resolution. The method comprises the following steps: (1) a piezoelectric array consisting of n piezoelectric chips is arranged on a structure to be tested, (2) an injury scattering path transfer function is obtained, (3) multipath injury scattering signals are obtained and (4) focused and strengthened injury scattering signals are obtained through virtual time reversal processing. Compared with the prior art, the invention has the technical effects: (1) complex physical time reversal operation is unnecessary, the requirement on a monitoring device is low, and the operation is easy, (2) the multipath injury scattering signals are focused and strengthened at the corresponding injury part, boundary reflection and noise are prohibited and the signal-to-noise ratio of the injury scattering signals is improved effectively, and (3) the time domain of the wave crest of Lamb wave and the spatial resolution ratio of injury focus wave crest is improved.
Description
Technical field
The present invention relates to a kind of Lamb wave virtual time reversal method of high spatial resolution, belong to the engineering structure health monitoring technical field.
Background technology
The engineering structure health monitoring technology is a kind of online, dynamic, real-time monitoring technology, and it obtained high speed development in recent years and in the safety of engineering structure and reliability assessment, was bringing into play the effect that becomes more and more important.The Lamb ripple can be grown propagation and all responsive to body structure surface and internal injury as the supersonic guide-wave of propagating in a kind of plate structure because of it, obtains increasingly extensive concern in the monitoring structural health conditions field.At present, based on Lamb wave structure health monitoring technology, particularly initiatively Lamb ripple monitoring technology has become a research focus.This technology can be divided into 4 processes: 1. with specific signal excitation piezoelectric element, in structure, excite Lamb ripple signal; 2. the propagation of Lamb ripple signal in material; 3. adopt piezoelectric sensor or other sensor to receive Lamb ripple signal at the diverse location of structure; 4. the Lamb ripple transducing signal that receives is carried out analyzing and processing, extract the damage characteristic parameter.
The Lamb velocity of wave propagation is very fast and have a Dispersion; Multipath propagation that complex boundary causes in the practical structures and on-the-spot noise make in the Lamb transducing signal that more weak damage scattered signal is submerged probably originally; Have a strong impact on follow-up damage characteristic parameter extraction, reduced the reliability of monitoring result.So the signal to noise ratio (S/N ratio) that improves the damage scattered signal is active Lamb ripple monitoring technology is badly in need of solution in practical applications a difficult problem.
Time reversal (being called phase conjugate in the frequency domain), method was developed by the phase conjugation method of optical field; After being meant that sensor receives the signal of sound source emission; Reload anti-Secondary Emission when carrying out on the corresponding sensor to transducing signal time reversal, promptly arrive first the back and send out, the back is to sending out earlier.This method can make signal on time and space, be compensated automatically, thereby realizes that at the wave source place self-adaptation focuses on.Damage, particularly damage can be considered the secondary wave source, utilizes the time reversal method can realize that multipath damage scattered signal focuses on enhancing at corresponding injury region, improves its signal to noise ratio (S/N ratio).
Lamb wave time-reversal method in the present existing engineering structure health monitoring; Mainly have following two weak points: (1) transmits and receives owing to the physical time counter-rotating relates to twice signal; Operating process is comparatively loaded down with trivial details; To having relatively high expectations of monitoring equipment, in actual engineering, directly carry out the physical time counter-rotating and have certain degree of difficulty; (2) some researchers have proposed a kind of time-reversal focusing method that comes alternative physical operation time reversal with signal operation; Like Chinese patent 200710133882.9 disclosed methods; Its damage scattered signal that focuses on enhancing is shown in Fig. 5 b, because this method is directly carried out computing to Lamb ripple damage scattered signal, so can increase the focus wave peak width; Reduce its spatial resolution, limited the application of this method under the poly-injury situation.
Summary of the invention
The object of the invention overcomes the weak point of prior art; A kind of high spatial resolution virtual time reversal method is provided; Can need not to carry out complicated physical time reverse turn operation and just can realize signal focus, can keep the focus wave peak width again, improve its spatial resolution.
High spatial resolution virtual time reversal method of the present invention may further comprise the steps:
(1) treating to arrange the piezoelectric-array that N piezoelectric patches formed on the geodesic structure;
(2) obtain damage scattering path transport function: through random waveform card takes place and send a step signal, after power amplification, be loaded into piezoelectric patches P as excitation
iOn, in treating geodesic structure, produce Lamb ripple broadband monitor signal; Another piezoelectric patches P
jGather the response signal of structure under faulted condition and health status respectively as sensor, these two kinds of response signals are carried out difference operation to obtain the monitoring path P
i-P
jIn step excitation under the damage scattered signal, the damage scattered signal is carried out obtaining monitoring path P after derivative operation and the normalization processing
i-P
jIn damage scattering path transport function h
Ij, choose different excitations and sensor respectively and carry out aforesaid operations, obtain the damage scattering path transport function h in all monitoring paths in the piezoelectric-array
Ij
(3) obtain multipath damage scattered signal: be loaded into piezoelectric patches P to pumping signal as excitation
iOn, another piezoelectric patches P
jThen gather respectively and treat the response signal of geodesic structure under faulted condition and health status, these two kinds of response signals are carried out difference operation to obtain the monitoring path P as sensor
i-P
jIn multipath damage scattered signal w
Ij, choose different excitations and sensor respectively and carry out identical operations, obtain the multipath damage scattered signal w in all monitoring paths in the piezoelectric-array
Ij
(4) virtual time reversal is handled: the damage of the multipath in the step (3) scattered signal w
IjCarry out obtaining time reversal w '
Ij, selected another piezoelectric patches P
k, to the multipath damage scattered signal w ' of elapsed time counter-rotating
IjAnd the damage scattering path transport function h that asks for of step (2)
IkCarry out convolution and summation operation:
Realize the physical time Umklapp process, obtain corresponding to the monitoring path P
i-P
kThe damage scattered signal S2 that strengthens of focusing
Ik, select different piezoelectric patches P respectively
iAnd P
kCarry out identical operations all damage scattered signals of monitoring paths are focused on enhancement process, wherein, N>=3,1≤i≤N, 1≤j≤N, j ≠ i, 1≤k≤N, k ≠ i, and k ≠ j.
Preferably, in the Lamb wave virtual time reversal method of high spatial resolution of the present invention, said piezoelectric-array is made up of 8 piezoelectric patches.
Among the present invention, let one of them piezoelectric patches P earlier
iIn structure, excite Lamb ripple monitor signal to encourage first as excitation, other piezoelectric patches P
jReceive the structural response signal as sensor.Reload corresponding sensor P separately to response signal after time reversal then
jOn anti-secondary excitation when carrying out, adopt the change first reception mechanism different this moment with conventional fixed reception mechanism, promptly select other piezoelectric patches P
kReplace original excitation P
iAs sensor receive structure the time response signal under the anti-secondary excitation, thereby accomplish twice excitation and reception.
Principle of work of the present invention is theoretical according to Signals & Systems, regards each the bar monitoring path in the piezoelectric-array as a system that is made up of excitation, sensor and tested structure.The input and output side of this system then corresponds respectively to the input and output part as two piezoelectric patches of excitation and sensor; Input signal is Lamb wave excitation signal, and the convolution algorithm between this pumping signal and the said system transport function is then corresponding to Lamb wave excitation and sensing process in every monitoring path.So; As long as obtain every damage scattering path transport function and multipath damage scattered signal in the monitoring path, can realize twice excitation and sensing process in the physical time Umklapp process just then the damage scattered signal after transport function and the elapsed time counter-rotating is carried out convolution algorithm.Theoretical according to time reversal; Though in excitation first, reach sensor through multipath by the produced simultaneously scattered signal of damage; But this multipath damage scattered signal has temporal correlation; The time they compensate its time along original travel path backpropagation meeting respectively automatically after the anti-Secondary Emission, thereby arrive injury region simultaneously and the homophase stack take place, realize focusing on and strengthen.Other part then respectively since the linear reflective character on border and the randomness of noise decay with superimposed through non-; So this method need not to carry out the signal to noise ratio (S/N ratio) that complicated physical time reverse turn operation just can improve the damage scattered signal, shown in Fig. 5 a and 5c.With existing time reversal method for congregating compare, the present invention at first obtains damaging the scattering path transport function, has avoided directly damage scattered signals to two different monitorings paths to carry out crest that convolution the causes problem that broadens.Comparison diagram 5b and 5c find out easily; The width of handling the damage focusing crest that obtains through the inventive method is significantly less than the crest width that adopts existing time-reversal focusing method to obtain; Thereby make two adjacent damage focus wave peak energy obviously distinguish, improved monitoring capability for adjacent damage.And; The time anti-secondary excitation in; Adopt the change first reception mechanism different with conventional fixed reception mechanism; Promptly select for use other piezoelectric patches replace original excitation receive structure the time anti-secondary excitation response signal down, changed the distance between the excitation and sensor in twice excitation, thus can keep damage the focusing crest temporal information so that follow-up damage characteristic parameter extraction.
High spatial resolution virtual time reversal method of the present invention has following technique effect with respect to prior art:
(1) need not to carry out complicated physical time reverse turn operation, lower to the requirement of monitoring equipment, simple;
(2) can realize that multipath damage scattered signal focuses on enhancing and suppresses edge reflection and noise at corresponding injury region, has effectively improved the signal to noise ratio (S/N ratio) of damage scattered signal;
(3) can keep the time domain width at Lamb wave-wave peak, improve the spatial resolution that damage focuses on crest.
Description of drawings
Fig. 1 is the distribution situation of piezoelectric patches and damage;
Fig. 2 is the step excitation signal;
Fig. 3 is the monitoring path P
4-P
8Damage scattered signal under the middle step excitation;
Fig. 4 is the monitoring path P
4-P
8In damage scattering path transport function;
Fig. 5 a is the monitoring path P
1-P
2In multipath damage scattered signal;
Fig. 5 b is the monitoring path P after the time-reversal focusing method processing of adopting in the background technology
1-P
2In the damage scattered signal;
Fig. 5 c is the monitoring path P that adopts after method of the present invention is handled
1-P
2In the damage scattered signal.
Embodiment
Come the present invention is done further detailed description below in conjunction with accompanying drawing and embodiment.
This instance adopts LY-21CZ aluminium sheet common in the engineering structure as treating geodesic structure; Be of a size of 1000mm * 1000mm * 2mm; In aluminium sheet, be furnished with the piezoelectric-array that 8 piezoelectric patches P1～P8 forms; Come two microlesion D1 and D2 in the model configuration through placing two pairs of circular magnet that attract each other (diameter 10mm, thick for 3mm).With the aluminium sheet center is that true origin is set up rectangular coordinate system, and then piezoelectric patches is seen Fig. 1 and table 1 respectively with the distribution situation and the position thereof of damage in coordinate system.Monitoring equipment is made up of waveform generation and data acquisition system (DAS), power amplifier and matrix switch controller.Wherein, The waveform generation blocks with the LAI200-ISA random waveform in the data acquisition system (DAS), signal amplifies card and the PCI-9812 data collecting card is realized the generation of Lamb wave excitation waveform, the amplification of transducing signal and the acquisition function of signal respectively; Power amplifier strengthens pumping signal to enlarge the monitoring range of Lamb ripple in structure, and the matrix switch controller is then monitored the path according to pre-determined scanning policy selection accordingly.
Coordinate (the unit: mm) of table 1 piezoelectric patches and damage
The virtual time reversal method of present embodiment comprises the following steps:
(1) treating to arrange 8 piezoelectric patches composition piezoelectric-arrays on the geodesic structure, as shown in Figure 1;
(2) obtain damage scattering path transport function: through random waveform card takes place and send the step signal that rising edge shown in Figure 2 is 0.25us, after power amplification and channel selecting, be loaded into piezoelectric patches P as excitation
4On, another piezoelectric patches P
8Gather aluminium sheet response signal of (placement Simulation Damage) under reference state (not placing Simulation Damage) and faulted condition respectively as sensor, these two kinds of response signals are carried out difference operation to obtain the monitoring path P
4-P
8In step excitation under the damage scattered signal, as shown in Figure 3, this damage scattered signal is carried out obtaining monitoring path P after derivative operation and normalization are handled
4-P
8In damage scattering path transport function h
48Choose different excitations and sensor respectively and carry out aforesaid operations, thereby obtain all 28 damage scattering path transport function h that monitor paths in the piezoelectric-array
Ij, as shown in Figure 4;
(3) obtain multipath damage scattered signal: be loaded into piezoelectric patches P to pumping signal as excitation
iOn, another piezoelectric patches P
jThen gather the response signal of structure under faulted condition and health status respectively, these two kinds of response signals are carried out difference operation to obtain the monitoring path P as sensor
i-P
jIn multipath damage scattered signal w
Ij, as shown in Figure 5, choose different excitations and sensor respectively and carry out identical operations, thereby the multipath that obtains all monitoring paths in the piezoelectric-array damages scattered signal w
Ij
(4) virtual time reversal is handled: the damage of the multipath in the step (3) scattered signal w
IjCarry out obtaining time reversal w '
Ij, selected another piezoelectric patches P
k, to the multipath damage scattered signal w ' of elapsed time counter-rotating
IjAnd the transport function h that asks for of step (2)
IkCarry out convolution and summation operation:
Realize the physical time Umklapp process; The phase error that wherein causes because of the nuance of scattering position in order to eliminate the Lamb ripple and to run into same impaired loci; Before carrying out summation operation, ask for the envelope of corresponding signal earlier, this envelope is superposeed obtains corresponding to the monitoring path P then
i-P
kThe damage scattered signal S2 that strengthened of focusing
IkSelect different piezoelectricity P respectively
iAnd P
kCarry out identical operations and then can realize focusing enhancement process the damage scattered signal in all monitoring paths.
Because the monitoring path of piezoelectric-array is more, for for simplicity, with wherein representative monitoring path P
1-P
2Be example, because the existence of the multipath propagation of Lamb ripple damage scattered signal and random noise makes the scattered signal of two damage D1 and D2 almost be submerged, for follow-up damage characteristic parameter extraction has increased difficulty, shown in Fig. 5 a.Fig. 5 c then is the result through the method for the invention; Comparing the scattered signal that can find two damages with Fig. 5 a all obtains focusing on enhancing and has effectively suppressed edge reflection signal and noise; Improved the signal to noise ratio (S/N ratio) of damage scattered signal greatly; Thereby effectively improved its spatial resolution, can find out obviously that from Fig. 5 c two damages focus on crest.
Claims (2)
1. the Lamb wave virtual time reversal method of a high spatial resolution is characterized in that, comprises the following steps:
(1) treating to arrange the piezoelectric-array that N piezoelectric patches formed on the geodesic structure;
(2) obtain damage scattering path transport function: through random waveform card takes place and send a step signal, after power amplification, be loaded into piezoelectric patches P as excitation
iOn, in treating geodesic structure, produce Lamb ripple broadband monitor signal; Another piezoelectric patches P
jGather the response signal of structure under faulted condition and health status respectively as sensor, these two kinds of response signals are carried out difference operation to obtain the monitoring path P
i-P
jIn step excitation under the damage scattered signal, the damage scattered signal is carried out obtaining monitoring path P after derivative operation and the normalization processing
i-P
jIn damage scattering path transport function h
Ij, choose different excitations and sensor respectively and carry out aforesaid operations, obtain the damage scattering path transport function h in all monitoring paths in the piezoelectric-array
Ij
(3) obtain multipath damage scattered signal: be loaded into piezoelectric patches P to pumping signal as excitation
iOn, another piezoelectric patches P
jThen gather respectively and treat the response signal of geodesic structure under faulted condition and health status, these two kinds of response signals are carried out difference operation to obtain the monitoring path P as sensor
i-P
jIn multipath damage scattered signal w
Ij, choose different excitations and sensor respectively and carry out identical operations, obtain the multipath damage scattered signal w in all monitoring paths in the piezoelectric-array
Ij
(4) virtual time reversal is handled: the damage of the multipath in the step (3) scattered signal w
IjCarry out obtaining time reversal w '
Ij, selected another piezoelectric patches P
k, to the multipath damage scattered signal w ' of elapsed time counter-rotating
IjAnd the damage scattering path transport function h that asks for of step (2)
IkCarry out convolution and summation operation:
Realize the physical time Umklapp process, obtain corresponding to the monitoring path P
i-P
kThe damage scattered signal S2 that strengthens of focusing
Ik, select different piezoelectric patches P respectively
iAnd P
kCarry out identical operations, all damage scattered signals of monitoring paths are focused on enhancement process, wherein, N>=3,1≤i≤N, 1≤j≤N, j ≠ i, 1≤k≤N, k ≠ i, and k ≠ j.
2. the Lamb wave virtual time reversal method of high spatial resolution according to claim 1 is characterized in that, said piezoelectric-array is made up of 8 piezoelectric patches.
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Families Citing this family (12)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN102128881B (en) * | 2010-12-22 | 2012-06-27 | 南京邮电大学 | Method for monitoring Lamb wave engineering structural damage by utilizing signal decomposition |
| CN102323337B (en) * | 2011-06-13 | 2013-04-10 | 南京邮电大学 | Method for actively monitoring damage of engineering structure excited by adopting synthesis wave front |
| CN103105434B (en) * | 2013-01-17 | 2015-04-08 | 华南理工大学 | Elongated metal structure damage detecting method and system based on active acoustic emission method |
| CN104181235B (en) * | 2014-04-14 | 2017-03-15 | 中国商用飞机有限责任公司北京民用飞机技术研究中心 | A kind of acoustic emission imaging and passive imaging method and apparatus based on virtual time reversal |
| CN103971012B (en) * | 2014-05-20 | 2017-01-18 | 南京信息工程大学 | Lamb wave signal denoising method based on John Saris model and fractional differentiation |
| CN103954697B (en) * | 2014-05-20 | 2016-09-28 | 南京信息工程大学 | A kind of Lamb wave denoising method based on fractional order differential |
| CN104698086A (en) * | 2015-03-13 | 2015-06-10 | 哈尔滨工程大学 | Nondestructive flaw detection method for one-dimensional stress waves based on time inversion and multipath effects |
| CN105403622A (en) * | 2015-11-07 | 2016-03-16 | 哈尔滨理工大学 | Sheet material damage identifying and positioning method |
| CN107490602A (en) * | 2017-07-27 | 2017-12-19 | 华东理工大学 | A kind of damage real-time perception and early warning system for pressure vessel |
| CN108536920B (en) * | 2018-03-19 | 2022-05-31 | 上海理工大学 | Method for calculating lying droplet Lamb wave scattering coefficient |
| CN110332463A (en) * | 2019-06-14 | 2019-10-15 | 南京理工大学 | Pipeline structure damage monitoring system based on wireless sensor network |
| CN110568084B (en) * | 2019-09-19 | 2020-07-24 | 哈尔滨工业大学 | Method for extracting low signal-to-noise ratio guided wave signal reaching time suitable for guided wave transducer array |
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| US20050075846A1 (en) * | 2003-09-22 | 2005-04-07 | Hyeung-Yun Kim | Methods for monitoring structural health conditions |
| CN1978977A (en) * | 2006-12-01 | 2007-06-13 | 北京工业大学 | Supersonic guide-wave time reversion detection apparatus and method for defect of pipeline |
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|---|---|---|---|---|
| US20050075846A1 (en) * | 2003-09-22 | 2005-04-07 | Hyeung-Yun Kim | Methods for monitoring structural health conditions |
| CN1978977A (en) * | 2006-12-01 | 2007-06-13 | 北京工业大学 | Supersonic guide-wave time reversion detection apparatus and method for defect of pipeline |
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