CN102331455B - Engineering structure damage monitoring method based on active Lamb wave damage index - Google Patents

Abstract

The invention discloses an engineering structure damage monitoring method based on an active Lamb wave damage index. The method comprises the following steps of: (1) arranging piezoelectric chips on a structure to be monitored to form N piezoelectric monitoring paths; (2) acquiring benchmark signals of each monitoring path; (3) acquiring damage scattered signals of each monitoring path; (4) calculating a damage index of each monitoring path; and (5) judging the damage situation of the structure according to the calculated damage index. In the method, a piezoelectric exciter/sensor pair is applied to form the monitoring paths, the structure damage is judged by calculating the damage index of each monitoring path, a signal processing process is simple, damage characteristic parameters are convenient to extract, and the structure damage is obvious to indicate, so that the method is simple and easy to operate.

Description

A kind of engineering structure damage monitoring method based on the Active Lamb Wave damage index

Technical field

The invention belongs to the damage monitoring technology, relate to a kind of engineering structure damage monitoring method based on the Active Lamb Wave damage index.

Background technology

Means using the Lamb ripple as the plate structure damage check have had one phase longer history.At the 1980s to the nineties initial stage, people start the Lamb wave method is applied to the online health monitoring of plate structure.Plate structure damage monitoring method based on piezoelectric element and Active Lamb Wave is because the little damage such as the crackle in structure, delamination is responsive, it is the online damage monitoring method of plate structure that is considered at present effective and the most important, become one of focus of studying at present both at home and abroad, there is wide future in engineering applications.

Structure damage monitoring method based on Active Lamb Wave can be divided into Four processes substantially:

A) with specific signal excitation piezoelectric element (initiatively), and excite the Lamb signal in structure;

B) the Lamb signal is propagated in structure;

C) (or one group) piezoelectric sensor in other position receives the Lamb signal;

D) the Lamb signal received is analyzed, extracted the feature damage signal.

At present, the structure damage monitoring based on Active Lamb Wave has threshold method, oval localization method, Time-frequency Analysis, signal peak characteristic method, time reversal formation method etc., and these methods have the following disadvantages:

The signal processing complexity; Because the Lamb ripple has multi-mode, Dispersion, when signal is walked, the extraction accuracy is not high; Damaging diagnostic parameter extracts inconvenient; Accuracy of judgement degree to structural damage is not high; The damaging judge real-time is poor.

Summary of the invention

Purpose of the present invention: provide that a kind of accuracy is high, Real-Time Monitoring is good, easy to operate, the engineering structure damage monitoring method based on the Active Lamb Wave damage index.

Technical scheme of the present invention: a kind of engineering structure damage monitoring method based on the Active Lamb Wave damage index, it comprises the following steps:

Step 1: treating on geodesic structure to arrange that the piezoelectric patches array forms piezoelectricity monitoring path;

Step 2: the reference signal s that obtains every monitoring path ⁰(t):

Produce waveform by waveform generator by following formula, and the driver in the monitoring path of by power amplifier, encouraging the piezoelectric patches array to form, sensor in every monitoring path receives signal, and by the reference signal s in charge amplifier, every monitoring path of data acquisition processing system storage ⁰(t);

$s^0\left(t\right)=A[H\left(t\right)-H(t-n/f_c)](1-\mathrm{<figure-callout\; id="2"\; label="cos"\; filenames="HSA00000558193600011.png"\; state="\{\{state\}\}">cos</figure-callout>}\frac{2\mathrm{\&pi;}{f}_{c}t}{n})\sin 2\mathrm{\&pi;}{f}_{c}t$

In formula:

The amplitude modulation(PAM) of A-signal;

F _c-signal center frequency;

N-signal wave crest number;

H-Heaviside step function.

Step 3: the damage scattered signal a (t) that obtains every monitoring path:

Adopt the mode identical with step 2, the acquisition damage signal is s (t), damages scattered signal

a(t)＝s(t)-s ⁰(t)；

Step 4: obtain the damage index DI in every monitoring path,

$\mathrm{DI}={\left(\frac{\underset{\mathrm{ti}}{\overset{\mathrm{tf}}{\&Integral;}}\sqrt{a\left(t\right)+h\left(t\right)\mathrm{dt}}}{\underset{\mathrm{ti}}{\overset{\mathrm{tf}}{\&Integral;}}\sqrt{s^0\left(t\right)+h^0\left(t\right)\mathrm{dt}}}\right)}^{\text{\&alpha;}}$

In formula:

Ti-integration zero-time;

Tf-integration concluding time;

A (t)-damage scattered signal;

The Hilbert of h (t)-a (t) changes;

S ⁰(t)-reference signal;

H ⁰(t)-s ⁰(t) Hilbert changes;

α-gain factor, the span of general α is: (0,1];

Step 5: judgement structural damage situation,

According to the damage index DI size in every the monitoring path calculated, the damage status of judgement structure.

The value of described gain factor is 0.5.

Beneficial effect of the present invention: the engineering structure damage monitoring method that the present invention is based on the Active Lamb Wave damage index is carried out the structural loss monitoring by dissipation factor, its signal processing is simple, damaging diagnostic parameter extracts convenient, indication accuracy to structural damage is high, damaging judge is real-time, method is simple, is highly suitable for the Real-Time Monitoring for sheet metal crackle and composite thin plate damage, has larger actual application value.

The accompanying drawing explanation

Fig. 1 is the system schematic that the present invention is based on engineering structure damage monitoring method one better embodiment of Active Lamb Wave damage index;

Fig. 2 is the process flow diagram that the present invention is based on the engineering structure damage monitoring method of Active Lamb Wave damage index,

In figure, the 1-waveform generator, the 2-power amplifier, 3-piezoelectric patches array, 4-treats geodesic structure, 5-charge amplifier, 6-data acquisition processing system.

Embodiment

Below by embodiment, the present invention is described in further detail:

Refer to Fig. 1, it is the principle schematic that the present invention is based on engineering structure damage monitoring method one better embodiment of Active Lamb Wave damage index.The monitoring system that the present invention is based on the structure damage monitoring method of Active Lamb Wave damage index comprises waveform generator 1, power amplifier 2, piezoelectric patches array 3, treats geodesic structure 4, charge amplifier 5, data acquisition processing system 6.Described waveform generator 1 is connected with power amplifier 2 by wire.Driver in the monitoring path that power amplifier 2 forms with piezoelectric patches array 3 by wire is connected, and this piezoelectric patches array 3 is arranged on to be treated on geodesic structure 4.Sensor in the monitoring path is connected with charge amplifier 5 by wire; Charge amplifier 5 is connected with data acquisition processing system by wire.

In observation process, produced the Lamb ripple by system in treating geodesic structure 4, and be captured in the Lamb ripple for the treatment of that geodesic structure 4 monitored areas are propagated, the Lamb ripple signal collected is analyzed, and then the damage status of judgement structure.

Refer to Fig. 2, it is the process flow diagram that the present invention is based on the engineering structure damage monitoring method of Active Lamb Wave damage index, and the idiographic flow step of structure damage monitoring of the present invention is:

Step 1: treating on geodesic structure 4 to arrange that piezoelectric patches array 3 forms N bar piezoelectricity monitoring path;

In embodiment, for different structures to be monitored, piezoelectric patches array 3 has different arrangements and layout type, as the piezoelectric patches of metal and composite structure arranges that distance is different; Piezoelectric patches array 3 is arranged will cover monitored area, the zone that surpasses the piezoelectric patches array be monitoring less than; According to monitoring target, the layout of piezoelectric patches array 3 can be different, but must make to monitor covering monitored area, path, and density degree can be different;

Step 2: the reference signal s that obtains every monitoring path ⁰(t):

The waveform produced as shown in Equation (1) by waveform generator 1, and the driver in the monitoring path formed by power amplifier 2 excitation piezoelectric patches arrays 3; Sensor in every monitoring path receives signal, and by the reference signal s in charge amplifier 5, every monitoring path of data acquisition processing system 6 storage ⁰(t),

$s^0\left(t\right)=A[H\left(t\right)-H(t-n/f_c)](1-\mathrm{<figure-callout\; id="2"\; label="cos"\; filenames="HSA00000558193600011.png"\; state="\{\{state\}\}">cos</figure-callout>}\frac{2\mathrm{\&pi;}{f}_{c}t}{n})\sin 2\mathrm{\&pi;}{f}_{c}t---\left(1\right)$

In formula:

The amplitude modulation(PAM) of A-signal;

F _c-signal center frequency;

N-signal wave crest number;

H-Heaviside step function;

Step 3: the damage scattered signal a (t) that obtains every monitoring path:

Adopt the identical method of step 2, sensor in every monitoring path receives signal, and be s (t) by the damage signal in charge amplifier 5, every monitoring path of data acquisition processing system 6 storage, damage scattered signal a (t)=s (t)-s ⁰(t) (2);

Step 4: the damage index DI that calculates every monitoring path:

The Hilbert transform of definition signal x (t) is:

$h\left(t\right)=H\left(x\left(t\right)\right)=\frac{1}{\mathrm{\&pi;}}\underset{-\&infin;}{\overset{\&infin;}{\&Integral;}}\frac{x\left(\mathrm{\&tau;}\right)}{t-\mathrm{\&tau;}}\mathrm{\&pi;\&tau;},$

Utilize formula 3 to calculate the damage index DI in every monitoring path:

$\mathrm{DI}={\left(\frac{\underset{\mathrm{ti}}{\overset{\mathrm{tf}}{\&Integral;}}\sqrt{a\left(t\right)+h\left(t\right)\mathrm{dt}}}{\underset{\mathrm{ti}}{\overset{\mathrm{tf}}{\&Integral;}}\sqrt{s^0\left(t\right)+h^0\left(t\right)\mathrm{dt}}}\right)}^{\text{\&alpha;}}---\left(3\right)$

In formula:

Ti-integration zero-time;

Tf-integration concluding time;

A (t)-damage scattered signal;

The Hilbert of h (t)-a (t) changes;

S ⁰(t)-reference signal;

H ⁰(t)-s ⁰(t) Hilbert changes;

α-gain factor, the span of general α is: (0,1], the experience value is 0.5;

Step 5: the damage status of judgement structure:

According to the damage index DI size in monitoring path, just can judge the damage status in this monitoring path; DI is larger, shows that damage is more serious.

For example: at three reinforcements, strengthen in the compression test of lamination wallboard, with the debonding of the method monitoring reinforcement and covering, the test monitoring result is: DI is greater than at 0.5 o'clock, just has debonding between reinforcement and covering, and DI is larger, damages more serious.

The structure damage monitoring method that the present invention is based on the Active Lamb Wave damage index has proposed a kind of brand-new breakdown diagnosis method by the damage index DI of formula 3, wherein, the signal processing of loss index wants simple compared with prior art, energy calculating to signal is higher than the accuracy of prior art, lower than the False Rate of existing Active Lamb Wave monitoring method to the damage judgement on the monitoring path.With respect to prior art, signal processing of the present invention is simple, consuming time few, can obtain in real time damage index DI, indicate damage status, method is simple, can, for the Real-Time Monitoring of sheet metal crackle and composite thin plate damage, there is larger actual application value.

Claims (2)

1. the engineering structure damage monitoring method based on the Active Lamb Wave damage index, is characterized in that, comprises the following steps:

Step 1: treating on geodesic structure to arrange that the piezoelectric patches array forms piezoelectricity monitoring path;

Step 2: the reference signal s that obtains every monitoring path ⁰(t):

Produce waveform by waveform generator by following formula, and the driver in the monitoring path of by power amplifier, encouraging the piezoelectric patches array to form, sensor in every monitoring path receives signal, and by the reference signal s in charge amplifier, every monitoring path of data acquisition processing system storage ⁰(t);

In formula:

The amplitude modulation(PAM) of A-signal;

F _c-signal center frequency;

N-signal wave crest number;

H-Heaviside step function;

Step 3: the damage scattered signal a (t) that obtains every monitoring path:

Adopt the mode identical with step 2, the acquisition damage signal is s (t), damages scattered signal

a(t)＝s(t)-s ⁰(t)；

Step 4: obtain the damage index DI in every monitoring path,

$\mathrm{DI}={(\frac{\underset{\mathrm{ti}}{\overset{\mathrm{tf}}{\&Integral;}}\sqrt{a\left(t\right)+h\left(t\right)\mathrm{dt}}}{\underset{\mathrm{ti}}{\overset{\mathrm{tf}}{\&Integral;}}\sqrt{s^0\left(t\right)+h^0\left(t\right)\mathrm{dt}}})}^{\mathrm{\&alpha;}}$

In formula:

Ti-integration zero-time;

Tf-integration concluding time;

A (t)-damage scattered signal;

The Hilbert of h (t)-a (t) changes;

S ⁰(t)-reference signal;

H ⁰(t)-s ⁰(t) Hilbert changes;

α-gain factor, the span of general α is: (0,1];

Step 5: judgement structural damage situation,

According to the damage index DI size in every the monitoring path calculated, the damage status of judgement structure.

2. the engineering structure damage monitoring method based on the Active Lamb Wave damage index according to claim 1, it is characterized in that: the value of gain factor is 0.5.

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