CN106124635A - For the piezoelectric transducer of pipe ultrasonic guide wave flaw detection and control method thereof and application - Google Patents
For the piezoelectric transducer of pipe ultrasonic guide wave flaw detection and control method thereof and application Download PDFInfo
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- CN106124635A CN106124635A CN201610669377.5A CN201610669377A CN106124635A CN 106124635 A CN106124635 A CN 106124635A CN 201610669377 A CN201610669377 A CN 201610669377A CN 106124635 A CN106124635 A CN 106124635A
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- G—PHYSICS
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- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N29/00—Investigating 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
- G01N29/22—Details, e.g. general constructional or apparatus details
- G01N29/24—Probes
- G01N29/2437—Piezoelectric probes
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- G—PHYSICS
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- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N29/00—Investigating 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
- G01N29/34—Generating the ultrasonic, sonic or infrasonic waves, e.g. electronic circuits specially adapted therefor
- G01N29/346—Generating the ultrasonic, sonic or infrasonic waves, e.g. electronic circuits specially adapted therefor with amplitude characteristics, e.g. modulated signal
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
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- G01N2291/028—Material parameters
- G01N2291/0289—Internal structure, e.g. defects, grain size, texture
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N2291/00—Indexing codes associated with group G01N29/00
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Abstract
The invention discloses a kind of piezoelectric transducer for pipe ultrasonic guide wave flaw detection and control method thereof and application.The piezoelectric transducer of the present invention uses the upper surface of n curved surface transducing Slab element to be bonded in the lower surface of flexible substrates equably, the upper surface of each curved surface transducing Slab element is plane, lower surface is curved surface, be close to the outer surface of tested pipeline as work surface, n curved surface transducing Slab element in parallel is around the outer surface one week along tested pipeline；Encourage at tested pipeline and receive zeroth order torsion guided wave T (0,1) of single mode；The piezoelectric transducer energy conversion efficiency that the present invention proposes is high, volume small size is compact, it is possible to directly against being combined in pipe surface, be highly suitable for pipeline health monitoring, it is anticipated that the present invention will promote the development of pipeline health monitoring based on supersonic guide-wave effectively.
Description
Technical field
The present invention relates to intellectual material and structural health monitoring technology, be specifically related to a kind of for pipe ultrasonic guide wave flaw detection
Piezoelectric transducer and control method and application.
Background technology
Pipeline, as a kind of important means of transport, plays irreplaceable effect in the field such as oil, chemical industry.Cut-off
In the end of the year 2013, China builds natural gas line and exceedes 60,000 kilometers, and crude oil pipeline exceedes 2.6 ten thousand kilometers, and it is public that processed oil pipeline exceedes 20,000
In, pipeline has become the important infrastructure concerned the life-blood of the national economy.In recent years, due to burn into accidental injury, abrasion etc. because of
Element, domestic and international pipe safety Frequent Accidents, cause huge Loss of Life and property.Therefore, pipeline integrity detects and comments
Valency has great importance.The features such as lossless detection method based on supersonic guide-wave has detecting distance far due to it, low cost,
Have become as the important technical of pipeline integrity detection.At present, pipeline inspection technology based on supersonic guide-wave also mainly goes out
In the laboratory research stage, it is possible to the most few for instrument and the system of actual industrial pipe detection.One main reasons is that
Pipeline guided wave has multi-modal, the complex characteristics of high frequency dispersion.With external diameter as 100mm, as a example by the aluminum pipe of wall thickness 3mm, arrive at 0kHz
In the range of 200kHz, total more than more than 50 guided wave modal axially propagated.Each frequency correspond to two with
On guided wave modal.If the guided wave of single mode cannot be motivated, from numerous guided waves, identify the echo letter relevant with defect
Breath will be faced with the difficulty being difficult to overcome.On the other hand, except zeroth order reverses guided wave T (0,1) outward, all of pipeline guided wave all has
The most serious Dispersion, i.e. velocity of wave change along with the change of frequency.It is the most all to use window function due to guided wave
The special waveform excitation of modulation, Dispersion makes excitation waveform become distortion along with the increase of ripple propagation distance, leads simultaneously
Wave-amplitude is decayed rapidly, thus is difficult to distance detection.The guided wave the most how encouraging single mode and non-frequency dispersion is pipe
The problem that road Guided waves is most crucial.
Longitudinal mode guided wave L (0,2) is prone to excite due to it, and has less frequency dispersion in certain frequency range,
Thus be the most studied the most extensive, the also guided wave modal of relative maturity.But longitudinal wave guide mode has footpath due to it
To displacement, when pipe interior or outside exist liquid, part guided wave energy can be leaked in liquid, thus have a strong impact on
Detecting distance.Comparing longitudinal mode guided wave L (0,2), zeroth order is reversed guided wave T (0,1) and is had obvious advantage.Zeroth order reverses guided wave
T (0,1) is the guided wave modal of unique non-frequency dispersion in pipeline.Simultaneously because zeroth order reverses guided wave T (0,1) only has tangential displacement, and
Liquid can not bear shearing, therefore guided wave energy will not be leaked in the liquid that pipeline is transported.Therefore zeroth order reverse guided wave T (0,
1) at pipeline integrity detection field, there is important application prospect.But the zeroth order of single mode can be encouraged at present to reverse and lead
The transducer of ripple T (0,1) is also little, significantly limit the application in pipeline integrity detection of T (0,1) guided wave.The most
In succession it is suggested through there being two classes to reverse wave guide energy converter, and is successfully realized business application.One class is with South West USA academy
(Southwest Research Institute) is the electromagnet ultrasonic changer of the research and development of representative
(U.S.Pat.No.6429650B1).This transducer is by leading to alternating current at coil, thus forms alternating magnetic field, alternating magnetic field
Cause ferromagnetic material to be deformed by magnetostrictive effect, thus form guided wave in the duct.But electromagnet ultrasonic changer
Need to apply a stronger bias magnetic field, thus the volume of transducer is relatively large.Additionally, electromagnet ultrasonic changer energy turns
Change efficiency low, thus need stronger driving source to improve signal to noise ratio.Above-mentioned factor makes electromagnet ultrasonic changer be only used for
Non-Destructive Testing and be not suitable for monitoring structural health conditions.Another kind of is the dry coupling of research and development with Imperial College of Britain as representative
Piezoelectric transducer (A.Demma, P.Cawly and M.Lowe, The reflection of the fundamental
torsional mode from cracks and notches in pipes,J.Acoust.Soc.Am.114(2),2003)。
The units such as China National Offshore Oil Corporation have also been developed similar dry coupling piezoelectric transducer (ZL 201010605979.7).Dry coupling
Piezoelectric transducer is by circumferentially thickness shear piezoelectric patches, thus realizes reversing excitation and the reception of guided wave.But thickness is cut
Hobbing electric transducer in the case of being not added with pressure, simple shear is tended in deformation, thus detrusion is difficult to effectively transmit
On pipeline.Pressue device makes dry coupling piezoelectric transducer volume bigger.On the other hand, thickness shear type piezoelectric transducer resonance
Frequency is higher, typically much higher than the driving frequency of guided wave, thus transducer cannot encourage near resonant frequency and improve energy
Conversion efficiency.Above-mentioned 2 make dry coupling piezoelectric transducer also be only suitable for pipeline non-destructive testing and are not suitable for the healthy prison of pipeline
Survey.
Compared with pipeline non-destructive testing, pipeline health monitoring technique can the safe condition of real-time prediction pipeline, energy simultaneously
Enough save manpower and time cost, from but the study hotspot in Present Domestic Outer Tube integrity detection field and trend.Therefore
The transducer of pipeline health monitoring it is suitable in the urgent need to research and development.Li Faxin seminar of Peking University latest developments are cut in a kind of face
Cutting new piezoelectric transducer (ZL 201620284659.9), this transducer can motivate the water of single mode in slab construction
Straight snips cuts guided wave modal (SH0), but improper is directly used in pipeline, and this transducer dimensions is little and energy conversion efficiency is high, therefore suitable
Conjunction structural health checks.Due to the horizontal shear guided wave modal (SH0) in slab construction on waveform configuration with zero in pipeline
Rank are reversed guided wave modal (T (0,1)) and are similar to, and the torsion being therefore hopeful to develop on this basis suitable channel health monitoring is led
Wave piezoelectric transducer, and then promote the development of pipeline health monitoring.
Summary of the invention
For the current wave guide energy converter lacking applicable pipeline health monitoring, the present invention proposes one can be in the duct
Excitation and receive single mode zeroth order and reverse the piezoelectric transducer of guided wave T (0,1), this transducer has that lightweight, size be little and energy
The feature that conversion efficiency is high, is suitable for pipeline health monitoring.
It is an object of the present invention to propose a kind of piezoelectric transducer for pipe ultrasonic guide wave flaw detection.
The piezoelectric transducer for pipe ultrasonic guide wave flaw detection of the present invention includes: n curved surface transducing Slab element and one
Flexible substrates；Wherein, the upper surface of each curved surface transducing Slab element is plane, is bonded in the lower surface of flexible substrates, curved surface
The upper surface of transducing Slab element be shaped as rectangle, four sides are perpendicular to upper surface, and lower surface is curved surface, and curved surface is along thickness
The projection in direction and upper surface congruence, the curvature of curved surface is consistent with the outer surface curvature of tested pipeline, and lower surface is as work surface；
Curved surface transducing Slab element uses the piezoelectric after polarization, and polarised direction, along the chord length direction of work surface, has piezoelectric modulus
d24；Two the relative sides parallel with polarised direction are electrode surface；The upper surface of n curved surface transducing Slab element glues equably
Being connected on the lower surface of flexible substrates, the polarised direction orientation of n curved surface transducing Slab element is consistent；N curved surface transducing Slab element is same
The electrode surface of side is respectively adopted a wire and is electrically connected an electrode column, thus n curved surface transducing Slab element is in parallel；Work
Time, the work surface of each curved surface transducing Slab element is close to the outer surface of tested pipeline, is evenly distributed on the following table of flexible substrates
N the curved surface transducing Slab element in face is uniformly distributed along the outer surface circumference of tested pipeline, and around outside tested pipeline
One week, surface；It is respectively arranged at two ends with locking mechanism in flexible substrates, the two ends of flexible substrates is connected solid by locking mechanism
Fixed so that piezoelectric transducer forms the annular linked into an integrated entity the outer surface being fixed on tested pipeline；Piezoelectric transducer conduct
The supersonic guide-wave of brake excitation tested pipeline, or the supersonic guide-wave of tested pipeline is received as sensor；As brake
Time, the pumping signal that signal generator sends, after power amplifier amplifies, is connected to two electrode columns, and excitation n is bent simultaneously
Face transducing Slab element, produces inplane shear by the d24 pattern of inverse pressure point effect at work surface and deforms, and applies to carry to tested pipeline
Lotus, motivates supersonic guide-wave；During as sensor, the supersonic guide-wave of tested pipeline causes the work of each curved surface transducing Slab element
Detrusion in the generating plane of face, thus form dielectric displacement, n song in parallel by the d24 pattern of direct piezoelectric effect at electrode surface
Face transducing Slab element, by after signal averaging, is connected to preamplifier by electrode column and amplifies, by data acquisition digital simulation
A/D card is transferred to signal processing analysis system, and n is the natural number of >=2.
The upper surface of curved surface transducing Slab element is rectangle, and the length of side along flexible substrates length direction is long limit a, along soft
The length of side in property base widths direction is minor face b, and the minimum thickness i.e. peak of work surface of curved surface transducing Slab element is away from upper surface
Distance be h, meet
The a length of L of flexible substrates, width is W, and thickness is H, meets b≤W≤4b, 0.1h≤H≤4h.Flexible substrates
Length is equal to the outer perimeter of tested pipeline, and flexible substrates has certain elasticity, thus enables to n song by locking mechanism
Face transducing Slab element is securely around the outer surface of tested pipeline.
The piezoelectric of curved surface transducing Slab element uses PZT pottery, ferroelectric ceramics or the piezoelectric monocrystal of ferroelectric type；If adopting
With pottery, its residual polarization during polarization, should be made to reach maximum；According to the piezoelectric monocrystal of ferroelectric type, then polarization time it is ensured that its
There is bigger piezoelectric coefficient d 24.Flexible substrates uses low elastic modulus, and elastomeric material, such as rubber.
When piezoelectric transducer is used as brake excitation supersonic guide-wave, signal generator produces the excitation letter of window function modulation
Number, signal center frequency is f0, signal frequency width is [fmin,fmax], this frequency band is referred to as working band.For suppression high order mode
Torsional wave, fmaxShould be less than tested pipeline and reverse the single order cut-off frequency of guided wave；For the product of bending wave in the range of rejection band
Raw, quantity n of curved surface transducing Slab element should be greater than tested pipeline [0, fmax] bending guided wave modal occurs in frequency band range
High circumference order.The velocity of wave of the torsional wave that piezoelectric transducer excites is cg, wavelength is λ=cg/f0.For making piezoelectric transducer have
Higher energy conversion efficiency, the minor face b of preferred curved surface transducing Slab element meets: 0.25 λ≤b≤0.6 λ.Meet above-mentioned pass
The piezoelectric transducer of system, at the mid frequency f of working band0Place encourages the zeroth order of single mode to reverse guided wave T (0,1).
In like manner, when piezoelectric transducer is used as sensor reception supersonic guide-wave, the mid frequency receiving signal is f0, signal frequency
Rate width is [fmin,fmax], this frequency band is referred to as working band.For suppressing the torsional wave of high order mode, fmaxShould be less than tested pipeline
Reverse the single order cut-off frequency of guided wave；For the generation of bending wave in the range of rejection band, quantity n of curved surface transducing Slab element should be big
In tested pipeline [0, fmax] the interior the highest circumference order bending guided wave modal appearance of frequency band range.Piezoelectric transducer receives
The velocity of wave of torsional wave is cg, wavelength is λ=cg/f0.For making piezoelectric transducer have higher energy conversion efficiency, preferably bent
The minor face b of face transducing Slab element meets: 0.25 λ≤b≤0.6 λ.Meet the piezoelectric transducer of above-mentioned relation, at working band
Mid frequency f0Place receives the zeroth order of single mode and reverses guided wave T (0,1).
The piezoelectric transducer of the present invention can be at the mid frequency f of working band0Place's filtering bending guided wave modal, and only connect
Receive and reverse guided wave.
The piezoelectric transducer of the present invention is used as brake and only encourages the principle of torsion guided wave T (0,1) of single mode as follows:
After excitation transducer is arranged on tested pipeline, n curved surface transducing Slab element is uniformly distributed along tested pipeline circumference；When n
When curved surface transducing Slab element is encouraged by AC signal simultaneously, curved surface transducing Slab element is owing to the d24 pattern of inverse piezoelectric effect is in work
Make face and produce inplane shear deformation, thus form the most equally distributed shear stress at tested pipeline；Owing to curved surface changes
The quantity of energy Slab element is more than the highest circumference order of bending wave in working frequency range interior conduit so that adjacent curved surface transducing plate list
The half-wavelength of guided wave is reversed in the gap of unit less than encouraging, such that it is able to approximate thinks that piezoelectric transducer is applied to tested pipeline
On load be axisymmetric loads circumferentially；Bending guided wave modal is non-axisymmetry mode, therefore axisymmetric loads will not swash
Send out bending guided wave modal；On the other hand, the main displacement of longitudinal axis Guided is axial along tested pipeline, does not has circumferential position
Moving, the axisymmetric loads hence along circumference only understands excitement of torsional guided wave；The frequency of pumping signal is cut at the single order of torsional wave again
Only below frequency, therefore zeroth order torsional wave T (0,1) of single mode can only be excited.In like manner, the piezoelectric transducer of the present invention is used as to pass
The principle that sensor only receives torsional wave is as follows: when having torsional wave in tested pipeline, and torsional wave is only along tested pipeline circumference
Displacement component, and be uniformly distributed along tested pipeline circumference, circumferentially displaced component causes the work of each curved surface transducing Slab element
Detrusion in the generating plane of face, thus form dielectric displacement by the d24 pattern of direct piezoelectric effect at electrode surface；Have in tested pipeline
During bending wave, although bending wave is containing circumferentially displaced component, but circumferentially distributed uneven along tested pipeline, and therefore transducer is only
There is small part piezoelectric patches can form dielectric displacement；Owing between n curved surface transducing Slab element, circuit is in parallel, therefore the signal detected
Actually being approximately equal to the average of n curved surface transducing Slab element signal, therefore the bending wave signal of superposition will be the faintest, thus
Realize the function of filtering bending ripple.In real work, use and actively produce a pumping signal determining frequency, then pass through
Detect the echo-signal after this pumping signal and defect effect, as receiving signal, realize the location of defect and the knowledge of size
Not.Therefore the present invention as sensor time, sensor can be designed according to the frequency receiving signal in advance, receive signal and be in work
Make frequency band, thus realize only receiving zeroth order and reverse the function of guided wave T (0,1).
Further object is that the control that a kind of piezoelectric transducer for pipe ultrasonic guide wave flaw detection is provided
Method.
The piezoelectric transducer of the present invention is as the supersonic guide-wave of brake excitation tested pipeline, or receives as sensor
The supersonic guide-wave of tested pipeline.
The piezoelectric transducer of the present invention is as the control method of the supersonic guide-wave of brake excitation tested pipeline, including following
Step:
1) upper surface of n curved surface transducing Slab element is bonded in the lower surface of flexible substrates, n curved surface transducing plate equably
The polarised direction orientation of unit is consistent；The electrode surface of the homonymy of n curved surface transducing Slab element is respectively adopted a wire electricity even
Connect an electrode column, thus n curved surface transducing Slab element is in parallel；The work surface of each curved surface transducing Slab element is close to tested
The outer surface of pipeline, is evenly distributed on n the curved surface transducing Slab element of lower surface of flexible substrates along the appearance of tested pipeline
Face circumference is uniformly distributed, and around the outer surface one week along tested pipeline；By being arranged on the padlock machine at flexible substrates two ends
The two ends of flexible substrates are connected fixing by structure so that piezoelectric transducer forms the annular linked into an integrated entity and is fixed on tested pipeline
Outer surface；
2) signal generator produces the pumping signal of window function modulation, after power amplifier amplifies, by electrode column, with
N the curved surface transducing Slab element that Shi Jili is in parallel, curved surface transducing Slab element produces at work surface due to the d24 pattern of inverse piezoelectric effect
Detrusion in dough, thus form the most equally distributed shear stress at tested pipeline；
3) quantity of curved surface transducing Slab element is more than the highest circumference order of bending wave in working frequency range interior conduit so that phase
The half-wavelength of guided wave is reversed in the gap of adjacent curved surface transducing Slab element less than encouraging, thus piezoelectric transducer is applied to measured tube
Load on road is axisymmetric loads circumferentially；Bending guided wave modal is non-axisymmetry mode, therefore axisymmetric loads will not
Excite bending guided wave modal；
4) axial along tested pipeline of the displacement that longitudinal axis Guided is main, does not has circumferentially displaced, circumferentially
Axisymmetric loads only understands excitement of torsional guided wave；The frequency of pumping signal is below the single order cut-off frequency of torsional wave again, therefore only
Zeroth order torsional wave T (0,1) of single mode can be excited.
The piezoelectric transducer of the present invention receives the control method of the supersonic guide-wave of tested pipeline as sensor, including following
Step:
1) upper surface of n curved surface transducing Slab element is bonded in the lower surface of flexible substrates, n curved surface transducing plate equably
The polarised direction orientation of unit is consistent；The electrode surface of the homonymy of n curved surface transducing Slab element is respectively adopted a wire electricity even
Connect an electrode column, thus n curved surface transducing Slab element is in parallel；The work surface of each curved surface transducing Slab element is close to tested
The outer surface of pipeline, is evenly distributed on n the curved surface transducing Slab element of lower surface of flexible substrates along the appearance of tested pipeline
Face circumference is uniformly distributed, and around the outer surface one week along tested pipeline；By being arranged on the padlock machine at flexible substrates two ends
The two ends of flexible substrates are connected fixing by structure so that piezoelectric transducer forms the annular linked into an integrated entity and is fixed on tested pipeline
Outer surface；
2), when having torsional wave in tested pipeline, torsional wave is only along the displacement component of tested pipeline circumference, and along quilt
Test tube road circumference is uniformly distributed, and circumferentially displaced component causes the work surface generation inplane shear of each curved surface transducing Slab element to become
Shape, thus form dielectric displacement by the d24 pattern of direct piezoelectric effect at electrode surface；When having bending wave in tested pipeline, bending wave
Though containing circumferentially displaced component, circumferentially distributed uneven along tested pipeline, and therefore transducer only has small part piezoelectric patches
Dielectric displacement can be formed；
3) in parallel between n curved surface transducing Slab element, the signal of detection is approximately equal to n curved surface transducing Slab element signal
Averagely, therefore the bending wave signal of superposition will be the faintest, and only torsional wave causes the electricity of n curved surface transducing Slab element in parallel
The dielectric displacement of pole-face, thus realize the function of filtering bending ripple；
4) it is connected to preamplifier by electrode column amplify, is transferred to signal processing analysis by data acquisition A/D card
System.
A further object of the present invention is the purposes providing a kind of piezoelectric transducer to be used as pipeline guided wave wave filter.
Advantages of the present invention:
The invention provides one can be in tested pipeline excitation and zeroth order torsion guided wave T (0,1) receiving single mode
Piezoelectric transducer, the piezoelectric transducer energy conversion efficiency that the present invention proposes is high, volume small size is compact, it is possible to directly fit
At pipe surface, it is highly suitable for pipeline health monitoring, it is anticipated that the present invention will promote pipe based on supersonic guide-wave effectively
The development of road health monitoring.
Accompanying drawing explanation
Fig. 1 is the schematic diagram that the piezoelectric transducer of the present invention is close on tested pipeline, and wherein, (a) is that stereochemical structure is shown
Being intended to, (b) is side view；
Fig. 2 is the schematic diagram of the curved surface transducing Slab element of the piezoelectric transducer of the present invention；
Fig. 3 is the expansion schematic diagram of the piezoelectric transducer of the present invention；
Fig. 4 be wall thickness be 3mm, external diameter is that the group velocity dispersion of the aluminum pipe of 100mm guided wave in the range of 0-250kHz is bent
Line；
Fig. 5 is the waveform configuration figure that zeroth order reverses guided wave T (0,1)；
Fig. 6 be the embodiment one of the piezoelectric transducer of the present invention be 3mm as brake at wall thickness, external diameter is 100mm's
Aluminum pipe mid frequency is the experimental result of 150kHz signal excitation T (0,1)；
Fig. 7 is the experimental result that the embodiment two of the piezoelectric transducer of the present invention receives supersonic guide-wave as sensor, super
Guided Waves uses the piezoelectric transducer excitation of 12 curved surface transducing Slab element, and wherein (a) is only 12 curved surface transducing Slab element
The oscillogram that receives as sensor of piezoelectric transducer, (b) is the piezoelectricity of 32 curved surface transducing Slab element with the present invention
The oscillogram that transducer receives as sensor.
Detailed description of the invention
Below in conjunction with the accompanying drawings, by specific embodiment, the present invention is expanded on further.
As it is shown in figure 1, the piezoelectric transducer of the present embodiment includes: n curved surface transducing Slab element 15 and a flexible substrates
12；The upper surface of n curved surface transducing Slab element 15 is bonded in the surface of flexible substrates 12 equably；N curved surface transducing Slab element
The electrode surface of homonymy be respectively adopted a wire and be electrically connected an electrode column, thus n curved surface transducing plate list after parallel connection
Unit is respectively connecting to positive electricity pole 17 and negative electrode lives 19；Work surface is close to the outer surface of tested pipeline 10, n curved surface transducing plate
Unit is uniformly distributed along the outer surface circumference of tested pipeline 10, and around the outer surface one week along tested pipeline.
The number of curved surface transducing Slab element is that n, n are more than tested pipeline 10 [0, fmax] frequency band range interior bending guided wave mould
The highest circumference order that state occurs.The length of flexible substrates 12 is equal to the outer perimeter of tested pipeline 10.
As in figure 2 it is shown, curved surface transducing Slab element 15 upper surface is plane, it is shaped as rectangle；Lower surface is curved surface, curved surface
Curvature is consistent with the outer surface curvature of tested pipeline 10.Lower surface is work surface, is close to the outer surface of pipeline 10 during work.Work
Make face to be congruent to the upper surface of transducing plate 15, the i.e. chord length of work surface along the projection of transducing plate 15 thickness direction and be equal to upper surface
Length of side a.Two relative sides that curved surface transducing Slab element 15 is parallel and vertical with upper surface with polarised direction are electrode surface.
Fig. 3 illustrates the expanded view of the piezoelectric transducer of the present invention.When transducer is pasted onto pipeline 10, due to substrate 12
For flexible material, therefore a strip can be launched into.When piezoelectric transducer needs to be close to tested pipeline 10, flexible substrates 12
Being connected by locking mechanism 14 head and the tail, flexible substrates has elasticity, makes piezoelectric transducer be enclosed within tested pipeline 10, such as Fig. 1 institute
Show.As seen from Figure 3, curved surface transducing Slab element is evenly distributed in flexible substrates 12 surface, and channel wire 18 realizes song
The circuit in parallel of face transducing Slab element.
Zeroth order torsional wave T (0,1) encouraged by further illustrating the transducer of the present invention is led in pipeline integrity detection
The advantage in territory, it is 3mm that Fig. 4 gives wall thickness, external diameter be the aluminum pipe of 100mm in 0 to 250kHz along aluminum pipe Propagation
The group velocity dispersion graph of a relation of supersonic guide-wave.It can be seen that the guided wave axially propagated in tested pipeline has three classes: a class
It is that (0, m), m is the modulus (m=1,2,3) of guided wave to axisymmetric longitudinal wave guide mode L, and another kind of is torsional axis pair
(0, m), also a class is that (N, m), N is the circumferential rank of guided wave to nonaxisymmetrical bending guided wave modal F to the torsion guided wave modal T claimed
Secondary (N=1,2,3).It can be seen that zeroth order reverses the guided wave modal that guided wave T (0,1) is unique non-frequency dispersion, i.e. its velocity of wave
Do not change along with the change of frequency.The non-Dispersion of T (0,1) can make waveform and the propagation of the pumping signal of guided wave
Speed keeps constant in communication process, thus improves the distance of detection, reduces the difficulty of signal analysis.Other direction,
Fig. 5 gives the waveform configuration figure that zeroth order reverses guided wave T (0,1).It can be seen that T (0,1) only has circumferentially displaced UθComponent, due to
Liquid can not bear detrusion, and the energy therefore reversing guided wave T (0,1) will not be leaked in liquid, thereby may be ensured that
Detecting distance, this makes T (0,1) be highly suitable for the pipeline of detection transport liquid.Further, Fig. 5 shows that zeroth order is reversed
The displacement component of guided wave T (0,1) is the most equally distributed along tested pipeline wall thickness, and this explanation T (0,1) ripple is to tested pipeline
Surface and internal defect have an identical detectivity, thus ensure that defect detection not by defect at the shadow of pipe wall position
Ring.
Embodiment one
The zeroth order encouraging single mode for further illustrating the piezoelectric transducer of the present invention reverses the effective of guided wave T (0,1)
Property, devise one for being 3mm at wall thickness, external diameter is the piezoelectric energy-conversion that 100mm aluminum pipe excitation zeroth order reverses guided wave T (0,1)
Device.Piezoelectric transducer design center frequency is 150kHz, uses the sinusoidal signal in five cycles of Hanning window modulation as excitation
Signal, therefore the highest frequency in working band is 210kHz.As shown in Figure 4, in 0～210kHz, bending guided wave F (N, 1) is
High circumference order is 31, and therefore the number of curved surface transducing Slab element is 32.Curved surface transducing Slab element uses the PZT-5H after polarization
Pottery, is shaped as square, and it is 1.9mm that the upper surface length of side is 6mm, minimum thickness h.Flexible substrates uses rubber, a length of
314mm, a width of 12mm, thickness is 2mm.In order to test conveniently, it is prepared for the piezoelectricity that quantity is 12 of curved surface transducing Slab element simultaneously
Transducer.
Fig. 6 illustrates and uses the piezoelectric transducer of 32 the curved surface transducing Slab element preparing gained as brake, uses center
Frequency is 150kHz, amplitude be the voltage of 20V be 3mm at wall thickness, external diameter be on 100mm aluminum pipe encourage T (0,1) experiment knot
Really.Signal uses the piezoelectric transducer that quantity is 12 of curved surface transducing Slab element to receive, due to the number of curved surface transducing Slab element
Less than the highest circumference order of bending guided wave F (N, 1), therefore this transducer can receive torsional wave and can receive again bending guided wave mould
State.Fig. 6 shows that the piezoelectric transducer of 32 curved surface transducing Slab element prepared by the present invention has successfully motivated single mode, height
Zeroth order torsional wave T (0,1) of signal to noise ratio, does not has any other mode of flexural vibration guided wave to be excited.Between excitation point and reception point
Interval 600mm, such that it is able to the velocity of wave of zeroth order torsional wave T (0,1) that the piezoelectric transducer calculating the present invention is encouraged is
In 3050m/s, with aluminum pipe, theoretical value 3099m/s of T (0,1) is closely.It can be seen that the zeroth order that the present invention is encouraged is reversed
Ripple T (0,1) waveform is completely the same with excitation signal waveforms, does not has any frequency dispersion.
Embodiment two
In the present embodiment, using the piezoelectric transducer of 32 curved surface transducing Slab element of preparation in embodiment one as sensing
Device.
Fig. 7 (a) illustrates to encourage and use as brake at 150kHz with the piezoelectric transducer that transducing plate number is 12 and changes
Energy plate number is the ultrasonic guided wave signals of the piezoelectric transducer reception of 12.It can be seen that except zeroth order reverses guided wave T (0,1) outward,
Bending guided wave modal is also had to be excited out.Fig. 7 (b) illustrates when the pressure of 32 the curved surface transducing Slab element prepared by the present invention
When electric transducer is as sensor, only zeroth order torsion guided wave T (0,1) is detected, and bending guided wave modal is filtered.This
Show that the present invention can serve as filtered sensor, the complexity receiving signal can be reduced greatly, there is important application
It is worth.
It is finally noted that, publicize and implement the purpose of example and be that help is further appreciated by the present invention, but this area
Those of skill will appreciate that: without departing from the spirit and scope of the invention and the appended claims, various replacements and repairing
It is all possible for changing.Therefore, the present invention should not be limited to embodiment disclosure of that, and the scope of protection of present invention is with power
Profit claim defines in the range of standard.
Claims (10)
1. the piezoelectric transducer for pipe ultrasonic guide wave flaw detection, it is characterised in that described piezoelectric transducer includes: n
Curved surface transducing Slab element and a flexible substrates；Wherein, the upper surface of each curved surface transducing Slab element is plane, is bonded in soft
The lower surface of property substrate；The upper surface of described curved surface transducing Slab element be shaped as rectangle, four sides are perpendicular to upper surface, under
Surface is curved surface, and curved surface is congruent with upper surface, outside the curvature of curved surface is with tested pipeline along the projection of transducing plate thickness direction
Surface curvature is consistent, and lower surface is as work surface；Curved surface transducing Slab element use polarization after piezoelectric, polarised direction along
The chord length direction of work surface, has piezoelectric coefficient d 24；Two the relative sides parallel with polarised direction are electrode surface；N bent
The upper surface of face transducing Slab element is bonded in the lower surface of flexible substrates, the polarised direction of n curved surface transducing Slab element equably
Orientation is consistent；The electrode surface of the homonymy of n curved surface transducing Slab element is respectively adopted a wire and is electrically connected an electrode column, from
And n curved surface transducing Slab element is in parallel；During work, the work surface of each curved surface transducing Slab element is close to outside tested pipeline
Surface, n curved surface transducing Slab element of the lower surface being evenly distributed on flexible substrates is equal along the outer surface circumference of tested pipeline
Even distribution, and around the outer surface one week along tested pipeline；It is respectively arranged at two ends with locking mechanism, by button in flexible substrates
The two ends of flexible substrates are connected fixing by latch mechanism so that piezoelectric transducer forms the annular linked into an integrated entity and is fixed on tested
The outer surface of pipeline；Described piezoelectric transducer is as the supersonic guide-wave of brake excitation tested pipeline, or connects as sensor
Receive the supersonic guide-wave of tested pipeline；During as brake, the pumping signal that signal generator sends through power amplifier amplify after,
It is connected to two electrode columns, simultaneously n curved surface transducing Slab element of excitation, is produced at work surface by the d24 pattern of inverse pressure point effect
Detrusion in dough, to tested pipeline imposed load, motivates supersonic guide-wave；During as sensor, tested pipeline ultrasonic
Guided wave causes detrusion in the work surface generating plane of each curved surface transducing Slab element, thus by the d24 mould of direct piezoelectric effect
Formula forms dielectric displacement at electrode surface, and n curved surface transducing Slab element in parallel, by after signal averaging, is connected to preposition by electrode column
Amplifier amplifies, and is transferred to signal processing analysis system by data acquisition digital simulation A/D card, and n is the natural number of >=2.
2. piezoelectric transducer as claimed in claim 1, it is characterised in that the upper surface of described curved surface transducing Slab element is square
Shape, the length of side along flexible substrates length direction is long limit a, and the length of side along flexible substrates width is minor face b, and curved surface changes
The minimum thickness i.e. peak of work surface of the energy Slab element distance away from upper surface is h, meets
3. piezoelectric transducer as claimed in claim 2, it is characterised in that the width of described flexible substrates is W, and thickness is H, full
Foot b≤W≤4b, 0.1h≤H≤4h.
4. piezoelectric transducer as claimed in claim 1, it is characterised in that the length of described flexible substrates is equal to tested pipeline
Outer perimeter.
5. piezoelectric transducer as claimed in claim 1, it is characterised in that the piezoelectric of described curved surface transducing Slab element uses
PZT pottery, ferroelectric ceramics or the piezoelectric monocrystal of ferroelectric type；Described flexible substrates uses low elastic modulus.
6. piezoelectric transducer as claimed in claim 1, it is characterised in that described piezoelectric transducer is ultrasonic as brake excitation
Guided wave, the mid frequency of the pumping signal that signal generator produces is f0, signal frequency width is [fmin,fmax], this frequency band claims
For working band；fmaxThe single order cut-off frequency of guided wave is reversed less than tested pipeline；Quantity n of described curved surface transducing Slab element is big
In tested pipeline [0, fmax] the interior the highest circumference order bending guided wave modal appearance of frequency band range；Piezoelectric transducer excites
The velocity of wave of torsional wave is cg, wavelength is λ=cg/f0；The minor face b of described curved surface transducing Slab element meets: 0.25 λ≤b≤0.6 λ,
Described piezoelectric transducer is at the mid frequency f of working band0Place encourages the zeroth order of single mode to reverse guided wave T (0,1).
7. piezoelectric transducer as claimed in claim 1, it is characterised in that described piezoelectric transducer is used as sensor and receives ultrasonic
Guided wave, the mid frequency receiving signal is f0, signal frequency width is [fmin,fmax], this frequency band is referred to as working band；fmaxLittle
The single order cut-off frequency of guided wave is reversed in tested pipeline；Quantity n of described curved surface transducing Slab element more than tested pipeline [0,
fmax] the interior the highest circumference order bending guided wave modal appearance of frequency band range；The velocity of wave of the torsional wave that piezoelectric transducer receives is
cg, wavelength is λ=cg/f0；The minor face b of described curved surface transducing Slab element meets: 0.25 λ≤b≤0.6 λ, described piezoelectric transducer
Mid frequency f at working band0Place receives the zeroth order of single mode and reverses guided wave T (0,1).
8. a piezoelectric transducer is as the control method of the supersonic guide-wave of brake excitation tested pipeline, it is characterised in that institute
State control method to comprise the following steps:
1) upper surface of n curved surface transducing Slab element is bonded in the lower surface of flexible substrates, n curved surface transducing Slab element equably
Polarised direction orientation consistent；The electrode surface of the homonymy of n curved surface transducing Slab element is respectively adopted a wire and is electrically connected one
Individual electrode column, thus n curved surface transducing Slab element is in parallel；The work surface of each curved surface transducing Slab element is close to tested pipeline
Outer surface, be evenly distributed on flexible substrates lower surface n curved surface transducing Slab element along tested pipeline outer surface week
To being uniformly distributed, and around the outer surface one week along tested pipeline；Will by being arranged on the locking mechanism at flexible substrates two ends
The two ends of flexible substrates connect fixing so that piezoelectric transducer forms the annular linked into an integrated entity and is fixed on outside tested pipeline
Surface；
2) signal generator produces the pumping signal of window function modulation, after power amplifier amplifies, by electrode column, swashs simultaneously
Encouraging n curved surface transducing Slab element of parallel connection, curved surface transducing Slab element produces face due to the d24 pattern of inverse piezoelectric effect at work surface
Interior detrusion, thus form the most equally distributed shear stress at tested pipeline；
3) quantity of curved surface transducing Slab element is more than the highest circumference order of bending wave in working frequency range interior conduit so that adjacent
The half-wavelength of guided wave is reversed in the gap of curved surface transducing Slab element less than encouraging, thus piezoelectric transducer is applied on tested pipeline
Load be axisymmetric loads circumferentially；Bending guided wave modal is non-axisymmetry mode, therefore axisymmetric loads will not excite
Bending guided wave modal；
4) axial along tested pipeline of the displacement that longitudinal axis Guided is main, does not has circumferentially displaced, axle pair circumferentially
Load is claimed only excitement of torsional guided wave；The frequency of pumping signal is below the single order cut-off frequency of torsional wave again, therefore can only swash
Zeroth order torsional wave T (0,1) of bill one mode.
9. a piezoelectric transducer receives the control method of supersonic guide-wave of tested pipeline as sensor, it is characterised in that institute
State control method to comprise the following steps:
1) upper surface of n curved surface transducing Slab element is bonded in the lower surface of flexible substrates, n curved surface transducing Slab element equably
Polarised direction orientation consistent；The electrode surface of the homonymy of n curved surface transducing Slab element is respectively adopted a wire and is electrically connected one
Individual electrode column, thus n curved surface transducing Slab element is in parallel；The work surface of each curved surface transducing Slab element is close to tested pipeline
Outer surface, be evenly distributed on flexible substrates lower surface n curved surface transducing Slab element along tested pipeline outer surface week
To being uniformly distributed, and around the outer surface one week along tested pipeline；Will by being arranged on the locking mechanism at flexible substrates two ends
The two ends of flexible substrates connect fixing so that piezoelectric transducer forms the annular linked into an integrated entity and is fixed on outside tested pipeline
Surface；
2), when having torsional wave in tested pipeline, torsional wave is only along the displacement component of tested pipeline circumference, and along measured tube
Road circumference is uniformly distributed, and circumferentially displaced component causes detrusion in the work surface generating plane of each curved surface transducing Slab element, from
And form dielectric displacement by the d24 pattern of direct piezoelectric effect at electrode surface；When having bending wave in tested pipeline, although bending wave contains
There is circumferentially displaced component, but circumferentially distributed uneven along tested pipeline, and therefore transducer only has small part piezoelectric patches to be formed
Dielectric displacement；
3) in parallel between n curved surface transducing Slab element, the signal of detection is approximately equal to the flat of n curved surface transducing Slab element signal
All, therefore the bending wave signal of superposition will be the faintest, and only torsional wave causes the electrode of n curved surface transducing Slab element in parallel
The dielectric displacement in face, thus realize the function of filtering bending ripple；
4) it is connected to preamplifier by electrode column amplify, is transferred to signal processing analysis system by data acquisition A/D card.
10. the piezoelectric transducer described in a claim 1 is used as the purposes of pipeline guided wave wave filter.
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