CN105548358A - One-dimensional element nondestructive inspection method based on time reversal and multi-mode effect - Google Patents

Abstract

The invention relates to the field of nondestructive testing of elements and signal processing, in particular to a one-dimensional element nondestructive inspection method based on time reversal and multi-mode effect. The method comprises the steps that a receiving and transmitting sensor used for transmitting and receiving a signal is arranged at one end of a steel rod of which the length is 10 times larger than the diameter; the amplitude and time delay of a first-time echo signal caused by the multi-mode effect are obtained according to the frequency dispersion characteristic in a solid, and then mode components of the first-time echo signal are obtained; the reversal time T containing all waveform information is selected, and time reversal treatment is performed on a firstly-received echo in the time [0,T] in a time domain; the signal treated through time reversal is taken as excitation to be transmitted into the steel rod through a transmitting element, the waveform components of the echo signal received again are analyzed, and a focus signal of a damage signal is obtained. According to the method, the damage signal can be effectively focused for waveform distortion which is caused by the complex multi-mode effect and is in a one-dimensional element.

Description

A kind of one dimension component nondestructive means based on time reversal and multi-modal effect

Technical field

The present invention relates to component Non-Destructive Testing and signal transacting field, specifically a kind of one dimension component nondestructive means based on time reversal and multi-modal effect.

Background technology

Lossless detection is most important method in modern project detection technique.In recent years, Applicative time inverting method carries out solid material damage check and becomes the new research direction of of lossless detection.Time reversal is a kind of method be incorporated into by the phase conjugation in optics in acoustics, and this theory is greatly developed in ultrasonic bulk wave field.Time reversal, the research in more than 40 years of technology was mainly used in underwater sound field of acoustics, and when great many of experiments is verified, anti-mirror can be used for target detection under complicated marine environment and location.

At present, time reversal, method still concentrated on the simple plate construction of reflection case and sheet-metal duct at the large quantity research of material failure field of detecting.Stress wave transportation law in one dimension component is complicated, there is multiple modalities composition.Therefore, apply prior art to solve one dimension component lossless detection and there is following problem: an anti-research of detecting a flaw when being existing adopts the form of sensor array mostly.And one dimension component is subject to the restriction of single-ended sensor, cause the signal aliasing of reception serious; Two is that current one dimension component damage detection method is confined to qualitative detection more, still lacks quantitative theoretical foundation.

A kind of nondestructive means based on time reversal and multi-modal effect under the present invention proposes the one dimension component environment of single array element sensor condition; The 10 cycle single audio frequency sine pulses choosing Hanning window modulation, as detectable signal, are closed by the transmitting-receiving of steel pole end and put sensor receiving and transmitting signal; With time inverting method process damage signal, solve the problem of the serious distortion that multi-modal effect is brought in one dimension component, achieve and the focusing of damage signal is amplified.

Summary of the invention

In order to overcome above-mentioned existing methodical deficiency, the object of the present invention is to provide a kind of one dimension component nondestructive means based on time reversal and multi-modal effect.

The object of the present invention is achieved like this:

Comprise the steps:

(1) length be greater than diameter dimension ten times steel pole one end place transmitting-receiving conjunction put sensor for launching and receiving signal, utilize the propagation characteristic of stress wave in steel pole, in transmitting, unit sentences longitudinal L (0,1) mode is emitted through 10 cycle single audio frequency sinusoidal signals of Hanning window modulation in steel pole, it there occurs MODAL TRANSFORMATION OF A through the effect of border and internal injury in communication process, generate new mode, include longitudinal mode, mode of flexural vibration and torsion mode;

(2) steel pole is as solid waveguide, amplitude and the time delay of the echoed signal first caused due to multi-modal effect can be obtained according to the Dispersion in solid, obtain the mode composition of echoed signal first, the amplitude maximum of waveform received first according to reception unit and the ratio of the amplitude maximum of driving pulse, obtain the system responses of this channel;

(3) select the reversing time T containing all shape informations, time domain carries out time reversal processing to receiving echo first within the time [0, T];

(4) using time anti-after signal again launch into steel pole by transmitting unit as excitation, analyze the echoed signal waveform component again received, obtain the focus signal of damage signal.

Described 10 cycles single audio frequency sinusoidal signal s (t) being emitted through Hanning window modulation in steel pole, λ and μ is for drawing close constant, ρ is density of material, ▽ is Laplacian, represent acoustic wave movement track with p (r, t), δ is impulse function, then after transmitting unit encourages to transponder pulse in steel pole, the stress wave propagation pattern in steel pole is:

$(\mathrm{\λ}+\mathrm{\μ})\·\▿\▿p(r,t)+\mathrm{\μ}{\▿}^{2}p(r,t)-\mathrm{\ρ}\frac{{\∂}^{2}p(r,t)}{\∂t^2}=s\left(t\right)\·\mathrm{\δ}(r-r_m).$

The multiple modalities composition that the described mode composition obtaining echoed signal first causes due to component border and internal injury, its velocity of wave is different, and the echo G receiving unit's reception is the superposition of the signal with different amplitudes and time delay:

$G(r,\mathrm{\ω})=\underset{L_i}{\Σ}{a}_{L_i}(r,\mathrm{\ω})e^{-{\mathrm{jk}}_{L_i}r}+\underset{T_i}{\Σ}{a}_{T_i}(r,\mathrm{\ω})e^{-{\mathrm{jk}}_{T_i}r}+\underset{F_i}{\Σ}{a}_{F_i}(r,\mathrm{\ω})e^{-{\mathrm{jk}}_{F_i}r}$

Wherein ω is the center angular frequency of stress wave, represent signal amplitude wave number and the velocity of propagation of rotational symmetry compressional wave respectively, represent the ultrasonic guided wave signals amplitude of axisymmetric torsion ripple, wave number and velocity of propagation respectively, represent the ultrasonic guided wave signals amplitude of asymmetric modes ripple, wave number and velocity of propagation respectively.Each mode composition is that this mode is reflected back the superposition of waveform through damage surface and terminal surface respectively.

Described carry out time reversal processing comprise receiving echo first: for steel pole model, if the pumping signal frequency domain presentation of incidence is S (ω), receive the signal V that unit receives first ₁frequency domain can be expressed as:

$V_1(r,\mathrm{\ω})=S\left(\mathrm{\ω}\right)\·G(r,\mathrm{\ω})=S\left(\mathrm{\ω}\right)\left(\underset{L_i}{\Σ}{a}_{L_i}\right(r,\mathrm{\ω})e^{-{\mathrm{jk}}_{L_i}r}+\underset{T_i}{\Σ}{a}_{T_i}(r,\mathrm{\ω})e^{-{\mathrm{jk}}_{T_i}r}+\underset{F_i}{\Σ}{a}_{F_i}(r,\mathrm{\ω}\left)e^{-{\mathrm{jk}}_{F_i}r}\right)$

Choose the time interval [0, T] comprising all shape informations, echoed signal will carry out operation time reversal, for the signal V again encouraged first in [0, T] ₁' frequency domain representation is:

$V_1^{\′}(r,\mathrm{\ω})=S^{*}\left(\mathrm{\ω}\right)G^{*}(r,\mathrm{\ω})=S^{*}\left(\mathrm{\ω}\right)\left(\underset{L_i}{\Σ}{a}_{L_i}\right(r,\mathrm{\ω})e^{{\mathrm{jk}}_{L_i}r}+\underset{T_i}{\Σ}{a}_{T_i}(r,\mathrm{\ω})e^{{\mathrm{jk}}_{T_i}r}+\underset{F_i}{\Σ}{a}_{F_i}(r,\mathrm{\ω}\left)e^{{\mathrm{jk}}_{F_i}r}\right).$

The echoed signal waveform component that described analysis receives again comprises: system responses H is

H(ω)＝V ₁'(r,ω)/V ₁(r,ω)

The echo again received is on frequency domain:

Z(ω)＝S ^*(ω)H(ω)H ^*(ω)＝S ^*(ω)H(ω) ²。

Beneficial effect of the present invention is:

The distortion of the waveform that the present invention can cause for the multi-modal effect of one dimension component inside complexity, focal damage signal effectively.

Accompanying drawing explanation

Fig. 1 is algorithm flow chart of the present invention.

Fig. 2 is the multi-modal propagation model figure of stress wave in one dimension solid element.

Fig. 3 is the echoed signal oscillogram received first.

Fig. 4 is the focused echo signal again received.

Concrete implementing measure

Below in conjunction with accompanying drawing, the present invention is described further.

One dimension component has the restriction of single-ended sensor, the present invention proposes the one dimension component stress ripple nondestructive means based on time reversal and multi-modal effect, it is characterized in that step is as follows: for one dimension component, choose the steel pole that length is greater than diameter dimension ten times, place a transmitting-receiving conjunction in one end of steel pole and put sensor array element, after the first transponder pulse excitation of transmitting, according to the propagation characteristic of stress wave in one dimension steel stock, mode composition is carried out to the echo receiving unit's reception and analyzes.Choose the reversing time T comprising all shape informations, time domain carries out time reversal processing to the echoed signal first received, using time anti-after signal be again emitted in steel pole by transmitting unit as excitation, analyze the echo waveform again received, obtain method time reversal significant focusing and amplification effect in multi-modal propagation conditions.

The concrete steps of the method are:

(1) length be greater than diameter dimension ten times steel pole one end place transmitting-receiving conjunction put sensor for launching and receiving signal.The sinusoidal single audio frequency pulse signal in 10 cycles through Hanning window modulation of source emission is represented with s (t), λ and μ is for drawing close constant, ρ is density of material, ▽ is Laplacian, δ is impulse function, represent acoustic wave movement track with p (r, t), following rule is followed in the propagation of stress wave in steel pole:

$(\mathrm{\λ}+\mathrm{\μ})\·\▿\▿p(r,t)+\mathrm{\μ}{\▿}^{2}p(r,t)-\mathrm{\ρ}\frac{{\∂}^{2}p(r,t)}{\∂t^2}=s\left(t\right)\·\mathrm{\δ}(r-r_m)---\left(1\right)$

(2) in steel pole, multi-modal effect propagation model is as shown in Figure 2.10 cycles single audio frequency sine pulse signal s (t) of being modulated by Hanning window are with longitudinal L (0,1) mode is from transmitting elementary excitation to steel pole, receiving the echoed signal of unit's place's reception as shown in Figure 3 first, if the pumping signal frequency domain presentation of incidence is S (ω), be the superposition that the stress wave of different modalities arrives the signal of impaired loci to be detected:

$V_1(r,\mathrm{\ω})=S\left(\mathrm{\ω}\right)\·G(r,\mathrm{\ω})=S\left(\mathrm{\ω}\right)\left(\underset{L_i}{\Σ}{a}_{L_i}\right(r,\mathrm{\ω})e^{-{\mathrm{jk}}_{L_i}r}+\underset{T_i}{\Σ}{a}_{T_i}(r,\mathrm{\ω})e^{-{\mathrm{jk}}_{T_i}r}+\underset{F_i}{\Σ}{a}_{F_i}(r,\mathrm{\ω}\left)e^{-{\mathrm{jk}}_{F_i}r}\right)---\left(2\right)$

Wherein represent signal amplitude wave number and the velocity of propagation of rotational symmetry compressional wave respectively, represent the ultrasonic guided wave signals amplitude of axisymmetric torsion ripple, wave number and velocity of propagation respectively, represent the ultrasonic guided wave signals amplitude of asymmetric modes ripple, wave number and velocity of propagation respectively.Each mode composition is that this mode is reflected back the superposition of waveform through damage surface and terminal surface respectively.

(3) choose the reversing time T comprising all shape informations, in time T, in time domain, time reversal processing is carried out to echoed signal.By time anti-after following signal again encourage:

$V_1^{\′}=(r,\mathrm{\ω})=S^{*}\left(\mathrm{\ω}\right)G^{*}(r,\mathrm{\ω})=S^{*}\left(\mathrm{\ω}\right)\left(\underset{L_i}{\Σ}{a}_{L_i}\right(r,\mathrm{\ω})e^{{\mathrm{jk}}_{L_i}r}+\underset{T_i}{\Σ}{a}_{T_i}(r,\mathrm{\ω})e^{{\mathrm{jk}}_{T_i}r}+\underset{F_i}{\Σ}{a}_{F_i}(r,\mathrm{\ω}\left)e^{{\mathrm{jk}}_{F_i}r}\right)---\left(3\right)$

(4) receive unit again to receive as Fig. 4, follow following rule:

$\begin{array}{c}{V}_2\left(t\right)=\frac{1}{2\mathrm{\π}}{\∫}_{-\mathrm{\∞}}^{\mathrm{\∞}}{S}^{*}\left(\mathrm{\ω}\right)G^{*}(r,\mathrm{\ω})e^{j\mathrm{\ω}t}d\mathrm{\ω}\\ =\frac{1}{2\mathrm{\π}}s(-t)\[\underset{L_i}{\Σ}{a}_{L_i}^2+\underset{T_i}{\Σ}{a}_{T_i}^2+\underset{F_i}{\Σ}{a}_{F_i}^2\]+\frac{1}{2\mathrm{\π}}\underset{Li}{\Σ}{a}_{L_i}\underset{Ti}{\Σ}{a}_{T_i}\underset{Fi}{\Σ}{a}_{F_i}\\ \left\{\begin{array}{c}\hat{s}\[r\left(\underset{L_i}{\Σ}\frac{1}{c_{L_i}}+\underset{T_i}{\Σ}\frac{1}{c_{T_i}}+\underset{F_i}{\Σ}\frac{1}{c_{F_i}}\right)-t\]+\hat{s}\[r\left(\underset{L_i}{\Σ}\frac{1}{c_{L_i}}-\underset{T_i}{\Σ}\frac{1}{c_{T_i}}+\underset{F_i}{\Σ}\frac{1}{c_{F_i}}\right)-t\]+\\ \hat{s}\[r\left(-\underset{L_i}{\Σ}\frac{1}{c_{L_i}}+\underset{T_i}{\Σ}\frac{1}{c_{T_i}}+\underset{F_i}{\Σ}\frac{1}{c_{F_i}}\right)-t\]\end{array}\right\}\end{array}---\left(4\right)$

When guided wave because exciting of injury region produces longitudinal L mode, when reversing T mode and bending F mode, after elapsed time reversion process, the echoed signal time of the time reversal that initialize signal excitation place obtains can divide two parts: one is be in zero moment point amplitude pumping signal time designature echoed signal, the amplitude of this part signal is the superposition of three kinds of different modalities race signal amplitudes square, and the amplitude comparing direct-detection signal alters a great deal, and is presented as the main crest signal of amplitude maximum in whole data-signal; Another part of formula the amplitude size that these moment occur is pumping signal time designature, can obtain conclusion, the amplitude of this part signal will not be significantly less than zero moment amplitude, not superposition, only exists as side-lobe signal.So under the condition of single-sensor array element, time reversal, method can realize focusing and the amplification of damage signal in the multi-modal model of one dimension component guided wave.

Based on an one dimension component stress ripple nondestructive means for time reversal and multi-modal effect, its concrete steps are as follows:

(1) analyzing long is 1500mm, diameter is the propagation characteristic of stress wave in the steel one dimension component of 20mm, calculate amplitude and the time delay numerical value from launching the multi-modal signal generated through the effect of border and damage after unit launches, thus determine the transport function of channel.

(2) the 10 cycle single audio frequency sine pulse signals being emitted through Hanning window function modulation encourage as initial detecting.Find that the existence of multiple modalities causes waveform aliasing serious to echoed signal analysis first, damage signal is also difficult to differentiate.Altogether ten groups of analysis of simulation experiment are carried out to ten different damage surface-rod area ratios.

(3) choosing the reversing time T comprising all shape informations is 1.5ms, the echoed signal received first is carried out in [0, T] interval the time reversal processing in time domain.Specific implementation method is: the time domain echoed signal of reception is done Fourier transform, then get conjugation on frequency domain, then carries out Fourier inversion to getting the signal after conjugation, obtains the excitation for again launching.

(4) after elapsed time reversion is also launched again, the echoed signal again received has the significantly main correlation peak of focusing at injury region, and other partial amplitude are relatively very little, are distributed in main peak value both sides and form secondary lobe, and Shi Fanhou relative to time anti-before signal to noise ratio (S/N ratio) improve 0.5dB.

The invention discloses a kind of one dimension component nondestructive means based on time reversal and multi-modal effect, establish the multi-modal propagation model of damage signal based on time reversal under the one dimension component environment of single array element sensor condition, and the single injury in component has been carried out to focusing and the amplification of signal.

Claims (5)

1., based on an one dimension component nondestructive means for time reversal and multi-modal effect, it is characterized in that, comprise the steps:

(1) length be greater than diameter dimension ten times steel pole one end place transmitting-receiving conjunction put sensor for launching and receiving signal, utilize the propagation characteristic of stress wave in steel pole, in transmitting, unit sentences longitudinal L (0,1) mode is emitted through 10 cycle single audio frequency sinusoidal signals of Hanning window modulation in steel pole, it there occurs MODAL TRANSFORMATION OF A through the effect of border and internal injury in communication process, generate new mode, include longitudinal mode, mode of flexural vibration and torsion mode;

(2) steel pole is as solid waveguide, amplitude and the time delay of the echoed signal first caused due to multi-modal effect can be obtained according to the Dispersion in solid, obtain the mode composition of echoed signal first, the amplitude maximum of waveform received first according to reception unit and the ratio of the amplitude maximum of driving pulse, obtain the system responses of this channel;

(3) select the reversing time T containing all shape informations, time domain carries out time reversal processing to receiving echo first within the time [0, T];

(4) using time anti-after signal again launch into steel pole by transmitting unit as excitation, analyze the echoed signal waveform component again received, obtain the focus signal of damage signal.

2. a kind of one dimension component nondestructive means based on time reversal and multi-modal effect according to claim 1, it is characterized in that: described 10 cycles single audio frequency sinusoidal signal s (t) being emitted through Hanning window modulation in steel pole, λ and μ is for drawing close constant, ρ is density of material for Laplacian, represent acoustic wave movement track with p (r, t), δ is impulse function, then, after transmitting unit encourages to transponder pulse in steel pole, the stress wave propagation pattern in steel pole is:

$(\mathrm{\λ}+\mathrm{\μ})\·\▿\▿p(r,t)+\mathrm{\μ}{\▿}^{2}p(r,t)-\mathrm{\ρ}\frac{{\∂}^{2}p(r,t)}{\∂t^2}=s\left(t\right)\·\mathrm{\δ}(r-r_m).$

3. a kind of one dimension component nondestructive means based on time reversal and multi-modal effect according to claim 1, it is characterized in that, the multiple modalities composition that the described mode composition obtaining echoed signal first causes due to component border and internal injury, its velocity of wave is different, and the echo G receiving unit's reception is the superposition of the signal with different amplitudes and time delay:

$G(r,\mathrm{\ω})=\underset{L_i}{\Σ}{a}_{L_i}(r,\mathrm{\ω})e^{-{\mathrm{jk}}_{L_i}r}+\underset{T_i}{\Σ}{a}_{T_i}(r,\mathrm{\ω})e^{-{\mathrm{jk}}_{T_i}r}+\underset{F_i}{\Σ}{a}_{F_i}(r,\mathrm{\ω})e^{-{\mathrm{jk}}_{F_i}r}$

Wherein ω is the center angular frequency of stress wave, represent signal amplitude wave number and the velocity of propagation of rotational symmetry compressional wave respectively, represent the ultrasonic guided wave signals amplitude of axisymmetric torsion ripple, wave number and velocity of propagation respectively, represent the ultrasonic guided wave signals amplitude of asymmetric modes ripple, wave number and velocity of propagation respectively.Each mode composition is that this mode is reflected back the superposition of waveform through damage surface and terminal surface respectively.

4. a kind of one dimension component nondestructive means based on time reversal and multi-modal effect according to claim 1, it is characterized in that described carry out time reversal processing comprise receiving echo first: for steel pole model, if the pumping signal frequency domain presentation of incidence is S (ω), receive the signal V that unit receives first ₁frequency domain can be expressed as:

$V_1(r,\mathrm{\ω})=S\left(\mathrm{\ω}\right)\·G(r,\mathrm{\ω})=S\left(\mathrm{\ω}\right)\left(\underset{L_i}{\Σ}{a}_{L_i}\right(r,\mathrm{\ω})e^{-{\mathrm{jk}}_{L_i}r}+\underset{T_i}{\Σ}{a}_{T_i}(r,\mathrm{\ω})e^{-{\mathrm{jk}}_{T_i}r}+\underset{F_i}{\Σ}{a}_{F_i}(r,\mathrm{\ω})e^{-{\mathrm{jk}}_{F_i}r})$

Choose the time interval [0, T] comprising all shape informations, echoed signal will carry out operation time reversal, for the signal V ' again encouraged first in [0, T] ₁frequency domain representation is:

$V_1^{\′}(r,\mathrm{\ω})=S^{*}\left(\mathrm{\ω}\right)G^{*}(r,\mathrm{\ω})=S^{*}\left(\mathrm{\ω}\right)\left(\underset{L_i}{\Σ}{a}_{L_i}\right(r,\mathrm{\ω})e^{{\mathrm{jk}}_{L_i}r}+\underset{T_i}{\Σ}{a}_{T_i}(r,\mathrm{\ω})e^{{\mathrm{jk}}_{T_i}r}+\underset{F_i}{\Σ}{a}_{F_i}(r,\mathrm{\ω})e^{{\mathrm{jk}}_{F_i}r}).$

5. a kind of one dimension component nondestructive means based on time reversal and multi-modal effect according to claim 1, it is characterized in that, the echoed signal waveform component that described analysis receives again comprises: system responses H is

H(ω)＝V′ ₁(r,ω)/V ₁(r,ω)

The echo again received is on frequency domain:

Z(ω)＝S ^*(ω)H(ω)H ^*(ω)＝S ^*(ω)|H(ω)| ²。