CN100344968C - Excitation of single non-axial-symmetric pipe line guide mode and pipeline no-demaged detection method - Google Patents

Abstract

The present invention discloses a method for exciting a relatively pure non-axisymmetrical pipeline guided wave F(1, 3) mode by utilizing piezoelectric transducers and using the mode for pipeline non-destructive flaw detection. The top end and the bottom end of the outer wall of a pipeline are respectively and symmetrically provided a piezoelectric transducer, the annular direction expansion angle of each transducer is 120 DEG C, the two transducers can be excited reversely in the axial direction, and the exciting frequency is controlled in the range in which the color dispersion is weak and the propagation velocity is rapid on a group velocity dispersion curve. The excited pure F(1, 3) mode is used for the non-destructive flaw detection of pipelines. The present invention provides the method for exciting a relatively pure non-axisymmetrical guided wave F(1, 3) mode by utilizing piezoelectric transducers for the first time. The color dispersion of similar L(0, 2) mode and F(1, 3) mode in a fixed frequency band is small, the propagation velocity is rapid, and therefore, the waveform after the flaw reflection is simple, and the present invention is suitable for analyzing characteristic flaws.

Description

A kind of method of carrying out the pipeline nondestructive examination that excites of utilizing single non-rotational symmetry pipeline guided wave mode

One, technical field

The present invention relates to a kind of method of pipeline nondestructive examination, especially excite the method for utilizing single non-rotational symmetry pipeline guided wave mode F (1,3) to carry out the pipeline nondestructive examination.

Two, background technology

Compare with traditional single-point Ultrasonic Detection or formation method, ultrasonic guide wave flaw detection has efficiently, implements advantages such as convenience and cost are low.The research that utilizes supersonic guide-wave to carry out the defect of pipeline detection is the heat subject in Non-Destructive Testing field.

At present, the research that utilizes rotational symmetry longitudinal vibration guided wave mode to carry out the defect of pipeline detection has obtained remarkable progress.Its core concept is that piezoelectric transducer was placed along one week of pipeline, thereby excite simple rotational symmetry L (0,2) mode detection defect of pipeline, because this pattern is in certain lower frequency band of frequency, on-dispersive and velocity of propagation are the fastest, levy defective surely so its waveform behind defect reflection simply is beneficial to analysis.But there are following two major defects in this method: when (a) detecting at the scene, for pipeline placed side by side and that spacing is less, often can't place transducer along one week of pipeline, thereby be difficult to inspire simple L (0,2) pattern; (b) L (0,2) pattern is only relatively responsive to the defect of pipeline that distributes along hoop, and is insensitive to the defect of pipeline that distributes vertically.

Because non-rotational symmetry pattern is propagated forward in pipeline twist, so compare with the rotational symmetry pattern, it is responsive more to the defective that distributes vertically.But the research that utilizes non-rotational symmetry pattern to carry out the defect of pipeline detection does not have big progress for a long time, one of its reason is to be difficult to as activation axis symmetry guided wave, inspire more simple non-rotational symmetry pattern, otherwise the waveform complexity that inspires is difficult to analyze.

Three, summary of the invention

The present invention proposes a kind of method of utilizing more simple non-rotational symmetry guided wave F (1, the 3) pattern of piezoelectric transducer rate of induced polarization, and the method is used for the pipeline nondestructive examination.

With rotational symmetry longitudinal vibration guided wave L (0,2) mode class seemingly, also in certain frequency band, chromatic dispersion is little and velocity of propagation is fast for F (1,3) pattern, so its waveform behind defect reflection is simple, is beneficial to analysis and levies defective surely.

The present invention seeks to realize like this: respectively place a piezoelectric transducer symmetrically on pipeline outer wall top and bottom, the hoop start point of transducer is 120 degree, and two transducers are anti-phase vertically to be excited, simultaneously stimulating frequency is controlled at F (1,3) chromatic dispersion is weak and in the scope that velocity of propagation is fast on the GVD (Group Velocity Dispersion) curve of pattern, thereby inspire simple F (1,3) pattern.Simple F (1, the 3) pattern that utilization of the present invention inspires is carried out the pipeline nondestructive examination.

1. exciting of single non-rotational symmetry pipeline guided wave mode F (1,3)

When piezoelectric transducer places pipeline outer wall and axial vibration exciting guided wave, pipeline outer wall stressedly write as following form

s(b，θ，z，t)| _r＝b＝b ^-1f(θ)g(z)T(t)e _z (1)

When the pipeline endless, the axial vibration displacement of each point is on the pipe outer wall

$u_z(b,\mathrm{\θ},z,t)=\underset{0}{\overset{\∞}{\∫}}\mathrm{d\ξ}\underset{\mathrm{nm}}{\mathrm{\Σ}}\frac{{{\mathrm{\ϵ}}_1{\mathrm{\ϵ}}_2\left[R_{\mathrm{nm}}^z(b,\mathrm{\ξ},{\mathrm{\ω}}_{\mathrm{nm}})\right]}^2}{{{\mathrm{\ω}}_{\mathrm{nm}}}^2{M}_{\mathrm{nm}}}---\left(2\right)$

$\·{\∫}_0^{t}T\left(\mathrm{\τ}\right)\sin {\mathrm{\ω}}_{\mathrm{nm}}(t-\mathrm{\τ})\mathrm{d\τ}\·\cos \mathrm{n\θ}\·\cos \mathrm{\ξz}$

Wherein b is an external radius, and θ and z are respectively hoop and axial coordinate component, and t is the time, and ξ is a wave number, and ω is a circular frequency, and n is the hoop exponent number, and m is an order of model behind the given n, and T (t) is over time stressed by the pipe outer wall, and

$M_{\mathrm{nm}}=\mathrm{\&pi;}{\&Integral;}_a^b\mathrm{\&rho;}[{{\mathrm{<figure-callout\; id="2"\; label="R\; nm\; r"\; filenames="C20041001429300091.png,C20041001429300092.png"\; state="\{\{state\}\}">R</figure-callout>}}_{\mathrm{nm}r}^{}}^2+{R_{\mathrm{nm}}^{\mathrm{\&theta;}}}^2+{R_{\mathrm{nm}}^z}^2]\mathrm{rdr}---\left(3\right)$

${\mathrm{\&epsiv;}}_1={\&Integral;}_0^{2\mathrm{\&pi;}}f\left(\mathrm{\&theta;}\right)\cos \mathrm{n\&theta;d\&theta;}---\left(4\right)$

${\mathrm{\&epsiv;}}_2={\&Integral;}_{-\&infin;}^{\&infin;}g\left(z\right)\cos \mathrm{\&xi;zdz}---\left(5\right)$

R _Nm ^r, R _Nm ^θWith R _Nm ^zBe respectively the amplitude of intrinsic displacement component.F (θ), g (z) represent external force along hoop and axial distribution respectively.

If respectively place a piezoelectric transducer on pipeline outer wall top and bottom, the hoop start point of transducer is 120 °, and two transducers are anti-phase vertically excites, and then has

Formula (6) substitution formula (4) can be got

By formula (7) as can be known, rotational symmetry guided wave mode and n=2k, the non-rotational symmetry guided wave mode of 3k (k is a positive integer) is suppressed fully, so the pattern count of the guided wave that is excited in the pipeline significantly reduces.If further the stimulating frequency of control piezoelectric transducer then can only inspire the non-rotational symmetry guided wave mode of several low orders.If the transducer axial excitation, then the energy of F (1,3) pattern accounts in the waveform that inspires mainly.

The sine pulse of 8 cycle 65kHz is added the excitation signal of Hanning window processing back gained waveform as piezoelectric transducer, can judge that from formula (7) and GVD (Group Velocity Dispersion) curve map can only inspire F (1 this moment, 1), F (1,2), F (1,3) and these several patterns of F (5,1).In order to suppress F (1,1) better, F (1,2) and F useless patterns such as (5,1) adopt two groups of piezoelectric transducers and control the spacing of width and two groups of transducers of transducer.Can find that from the finite element method Simulation result waveform that inspires is quite simple F (1,3) pattern.

2.F (1,3) pattern is used in the pipeline Non-Destructive Testing

Pipeline length overall 17m in the numerical experiment, external diameter OD=88.7mm, wall thickness h=5.5mm, close constant μ=8.4 * 10 are drawn in Poisson ratio γ=0.28 ¹⁰N/m ², density p=7.8 * 10 ³Kg/m ³, excite transducer centre distance pipeline left end 8cm, receiving transducer centre distance pipeline left end 9m, defective is apart from pipeline left end 15m, and the transducer width is all 5.2cm.Transducer stimulating frequency f=65kHz, the pipeline left end adopts symmetrical boundary condition, and right-hand member adopts the restrained boundary condition.

The hoop start point that excites transducer is 120 °, totally two groups, placed pipeline outer wall top section and end section symmetrically, the control transducer is vibrate in opposite phase vertically, and stimulating frequency is controlled at F (1,3) on the modal dispersion curve a little less than the chromatic dispersion, velocity of propagation fast and with the zone of other pattern apart from each other in, as the pipeline for above-mentioned geometry and material parameter, optional excitation frequency ranges is 60-90kHz, in the simulation below, choose stimulating frequency f=65kHz.If have defective in the pipeline, simple F (1, the 3) pattern that inspires produces transmitted wave with its generation interaction in communication process, and reflection configuration can utilize receiving transducer to receive.

F (1, the 3) pattern that is obtained by simulation can be observed through the waveform of different rings behind the length defect reflection, and along with the increase of hoop length, the wave-shape amplitude of reflection F (1,3) pattern becomes big.In addition, also can obviously observe the mode switch phenomenon that defective causes, extend angle θ through hoop ₀L (0,2) has appearred behind=90 ° the defect reflection, F (1,3) and F (2,3) isotype, because the mode propagation speed that other conversion produces is slow, thus can not consider, when the defective hoop extends angle θ ₀Increase to 180 °, do not occur F (2,3) pattern in the reflection wave, if the defective hoop extends angle θ ₀Continue to increase to 360 °, promptly defective is axisymmetric, can not change in the reflection wave to produce the rotational symmetry ripple.Can find that by the waveform of F (1,3) pattern behind the rotational symmetry defect reflection of different depth along with the increase of depth of defect, it is big that the amplitude of reflection configuration becomes gradually.

Give regularly when frequency, each pattern has a corresponding velocity of propagation, therefore arrives the time of acceptance point by each guided wave mode in the analysis reflection configuration, can judge in axial position defective.As can be known by above-mentioned numerical experiment, when defective distributes axisymmetricly, receiving transducer receives incident F (1 when t ≈ 1.84ms, 3) crest of pattern receives the crest that reflects F (1,3) pattern when t ≈ 4.21ms, mistiming Δ t ≈ 2.37ms, and centre frequency is when being 65kHz, the group velocity C of F (1,3) pattern _g≈ 5082m/s is according to l=C _g* Δ t can get receiving transducer and be about 6.02m apart from the distance 1/2 of defective, and very approaching apart from 6.00m with realistic simulation, error is 0.3% only, during actual measurement, can take multiple measurements and is averaged to reduce error.Again by top numerical simulation as can be known, behind the defect reflection of length, the reflection coefficient of each pattern is different in the reflection wave through different rings for F (1,3) pattern, therefore can make surely the hoop size of defective the reflection coefficient analysis of each pattern in the reflection wave and levying.

The present invention has proposed a kind of method of utilizing piezoelectric transducer to inspire more simple non-rotational symmetry guided wave F (1,3) pattern first.Be similar to L (0,2) pattern, also in certain frequency band, chromatic dispersion is little and velocity of propagation is fast for F (1,3) pattern, so its waveform behind defect reflection is simple, is beneficial to analysis and levies defective surely.But compare with L (0,2) pattern, F (1,3) pattern is to some defect of pipeline, and is as the defect of pipeline that distributes vertically, responsive more.The result who obtains from the finite element method simulation can judge that it is fully feasible utilizing non-rotational symmetry pipeline guided wave mode F (1,3) pipelines defective.

Four, description of drawings

The pipeline synoptic diagram that Fig. 1 is placed side by side

Fig. 2 (a) L (0,2) pattern and the defective interaction synoptic diagram that distributes vertically; (b) F (1,3) pattern and the defective interaction synoptic diagram that distributes vertically

The GVD (Group Velocity Dispersion) curve that Fig. 3 pipeline guided wave is propagated, OD=88.7mm, h=5.5mm, γ=0.28, μ=8.4 * 10 ¹⁰N/m ², ρ=7.8 * 10 ³Kg/m ³

Fig. 4 (a) piezoelectric transducer is placed synoptic diagram; (b) piezoelectric transducer vibration synoptic diagram

During the radial vibration of Fig. 5 (a) piezoelectric transducer, F (1,1), F (1,2) and the transient state radial displacement amplitude of F (1,3) pattern and the relation of frequency; (b) during piezoelectric transducer axial vibration, F (1,1), F (1,2) and the transient state axial displacement amplitude of F (1,3) pattern and the relation of frequency

Fig. 6 is that the sine pulse of 8 cycle 65kHz adds Hanning window processing back gained waveform

Two groups of width of Fig. 7 are 5.2cm, and center distance is the waveform that the transducer of 16cm inspires, z=9m, θ=0 °

Fig. 8 F (1,3) mode excitation and echo receive model

Fig. 9 defective cross sectional representation.

Figure 10 F (1,3) pattern is through the waveform of different rings behind the length defect reflection, and depth of defect and wall ratio are 50%:(a) defective hoop length is 25% with pipe girth ratio; (b) defective hoop length is 50% with pipe girth ratio; (c) defective hoop length is 100% with pipe girth ratio

The waveform of Figure 11 F (1,3) pattern behind the rotational symmetry defect reflection: (a) depth of defect and wall ratio are 36%; (b) depth of defect and wall ratio are 64%

Embodiment:

Adopting two groups of hoop start points is 120 ° piezoelectric transducer, it is placed pipeline outer wall top section and end section symmetrically, the control transducer is vibrate in opposite phase vertically, and stimulating frequency is controlled on the GVD (Group Velocity Dispersion) curve of F (1,3) pattern a little less than the chromatic dispersion, velocity of propagation fast and with the zone of other pattern apart from each other in, as being respectively OD=88.7mm for geometry and material parameter, h=5.5mm, γ=0.28, μ=8.4 * 10 ¹⁰N/m ², ρ=7.8 * 10 ³Kg/m ³Pipeline, optional excitation frequency ranges is 60-90kHz.If have defective in the pipeline, simple F (1, the 3) pattern that inspires produces transmitted wave with its generation interaction in communication process, and reflection wave can utilize receiving transducer to receive.

Give regularly when frequency, each pattern has a corresponding velocity of propagation, therefore arrives the time of acceptance point by each guided wave mode in the analysis reflection configuration, can judge in axial position defective.Therefore F (1,3) pattern is behind the defect reflection of different depth and hoop length again, and the reflection coefficient of each pattern is different in the reflection wave, can make surely the degree of depth of defective and hoop length the reflection coefficient analysis of each pattern in the reflection wave and levying.

Claims (1)

1, a kind of pipeline nondestructive means of single non-rotational symmetry pipeline guided wave mode: utilize piezoelectric transducer to excite simple non-rotational symmetry guided wave F (1,3) pattern, and the method is used for the pipeline nondestructive examination; It is characterized in that respectively placing a piezoelectric transducer symmetrically on pipeline outer wall top and bottom, the hoop start point of transducer is 120 degree, and two transducers are anti-phase vertically to be excited, and simultaneously stimulating frequency is controlled on the GVD (Group Velocity Dispersion) curve a little less than the chromatic dispersion and in the fast scope of velocity of propagation, utilizes the simple F (1 that inspires, 3) the non-rotational symmetry guided wave of pattern carries out the pipeline nondestructive examination, for pipeline length overall 17m, external diameter OD=88.7mm, h=5.5mm, γ=0.28, μ=8.4 * 10 ¹⁰N/m ², ρ=7.8 * 10 ³Kg/m ³Pipeline, excite transducer centre distance pipeline left end 8cm, receiving transducer centre distance pipeline left end 9m, the transducer width is all 5.2cm; If have defective in the pipeline, simple F (1, the 3) pattern that inspires produces transmitted wave with its generation interaction in communication process, and reflection configuration can utilize receiving transducer to receive; Along with the increase of hoop length, the wave-shape amplitude of reflection F (1,3) pattern becomes big; By F (1,3) the non-rotational symmetry guided wave of pattern will interact with defective in communication process and produce reflection wave, and meeting emergence pattern conversion phenomena, utilize piezoelectric transducer can receive reflection configuration, analyze the time of each pattern arrival acceptance point in the reflection configuration and the reflection coefficient of each pattern, then the position and the size of defective are made sign.

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