CN103792287A - Large-area structural damage detection method based on Lamb wave - Google Patents

Large-area structural damage detection method based on Lamb wave Download PDF

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Publication number
CN103792287A
CN103792287A CN201410020701.1A CN201410020701A CN103792287A CN 103792287 A CN103792287 A CN 103792287A CN 201410020701 A CN201410020701 A CN 201410020701A CN 103792287 A CN103792287 A CN 103792287A
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damage
signal
mode
lamb
geodesic
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CN201410020701.1A
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武湛君
高进
刘科海
郑跃滨
王奕首
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Dalian University of Technology
Beijing Institute of Astronautical Systems Engineering
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Dalian University of Technology
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Abstract

The invention discloses a large-area structural damage detection method based on a Lamb wave. The large-area structural damage detection method based on the Lamb wave comprises the following steps: arranging a Lamb wave exciting device on a to-be-detected point of a to-be-detected structure; exciting a narrow band signal by a function generator and a power amplifier, controlling the band width range of the narrow band signal to be at the frequency band lower than the set A1 mode cut-off frequency, loading the excited narrow band signal to a mobile probe, generating a single A0 mode Lamb wave the frequency value of which is less than the A1 mode cut-off frequency on the to-be-detected structure, and receiving the Lamb wave signal by the mobile probe so as to acquire a Lamb wave echo signal f containing the damage structual information; collecting signals on residual to-be-detected points on the to-be-detected structure sequentially according to the mode, and collecting the response signal fm of the single A0 mode structure; and carrying out signal processing on the collected response signal fm to obtain a damage image, positioning the position of the damage of the to-be-detected structure, and estimating the damage situation of the structure.

Description

A kind of large area structure damage detecting method based on Lamb ripple
Technical field
The present invention relates to structure lossless detection method, be specifically related to single A 0mode guided wave and the method for quick that traditional Dynamic Non-Destruction Measurement combines, relate in particular to a kind of large area structure damage detecting method based on Lamb ripple.
Background technology
Be applied to the metal of engineering or composite structure and will bear complexity, the effect such as fatigue load, accidental shock load for a long time, easily produce and be difficult for observed damage, thereby develop relevant structure Dynamic Non-Destruction Measurement and enjoy attention always.Existing structural damage detection technology, comprise speckle-shearing interferometry, infrared thermal imaging, eddy current, ultrasound wave, the technology such as acoustic emission, in structure Non-Destructive Testing, can bring into play certain effect, but most of technology only can detect by single-point, need to structurally carry out traversal search, when particularly large area structure detection, often wastes time and energy.
For the tabular structure of large area, the detection technique based on guided wave (being commonly referred to Lamb ripple in plate, shell structure) becomes study hotspot in recent years, and its good propagation characteristic has improved detection efficiency greatly.At present, most Lamb damage monitoring methods all adopts adhered or embedded type sensor excitation reception Lamb ripple, using health signal as reference signal, subtract each other by response signal and the reference signal of current state, the scattered signal obtaining is assessed structural damage situation.But under true environment; while gathering health signal; in structure, may there is damage; and in the acquisition interval time of current response signal and health signal, the inner and exterior conditions of structure, as ambient temperature and humidity, external vibration; aging and Boundary Conditions in Structures of sensor etc.; can change unavoidably, the degree of impairment that the scattered signal that conventionally can cause extracting can not reaction structure, causes mistake to examine and fails to pinpoint a disease in diagnosis.
In prior art, the damage detecting method of structure is existed to following problem mostly: Lamb ripple exists symmetrical mode and asymmetric mode, prior art adopts narrow band frequency control mode more, but is still difficult to suppress completely, causes the difficulty of damage check; Lamb ripple and damaging action complexity, be difficult to the details such as shape, type of damage to carry out accurate evaluation by signal; Sensor position is fixed, and need large quantity sensor to cover the whole geodesic structure for the treatment of, and bonding interface and sensor life-time is lower than structural life-time, after damage, can not replace in time.
Summary of the invention
The problem existing according to prior art, the invention discloses a kind of large area structure damage detecting method based on Lamb ripple: the method adopts the damage detecting method based on Lamb ripple to position the damage of large area structure, by harmless single-point detection technique, damage status is assessed again, is comprised the following steps:
S1: treating to set up rectangular coordinate system on geodesic structure, select multiple tested points;
S2: the Lamb wave excitation device with portable probe is set at a tested point place;
S3: adopt function generator and power amplifier to excite narrow band signal, the bandwidth range of this narrow band signal is controlled at lower than the A setting 1the frequency range of mode cutoff frequency, is loaded into portable probe by the narrow band signal exciting upper, is treating that on geodesic structure, producing frequency values is less than A 1the single A of mode cutoff frequency 0mode Lamb ripple, portable probe receives Lamb ripple signal, obtains the Lamb ripple echoed signal f containing damaged structure information 1;
S4: complete successively the signals collecting for the treatment of to remain on geodesic structure tested point according to the mode of S2, S3, collect single A 0modal structure response signal f m;
S5: by the response signal f collecting mcarry out signal processing and obtain damage image, this damage for the treatment of geodesic structure is carried out to location, position, the situation of the damage to structure is assessed.
Described Lamb wave excitation device comprises portable probe, and the end of described portable probe is connected with multiple piezoelectric chips, is connected with shearing effect inhibition layer on described piezoelectric chip, and described portable probe is connected with treating geodesic structure by shearing effect inhibition layer.
Described shearing effect inhibition layer suppresses portable probe and treats the shearing effect of geodesic structure, suppresses symmetrical mode Lamb ripple, encourages single A 0mode Lamb ripple.
Described shearing effect inhibition layer is the lubricated interface being made up of railway grease, lubricant or lubricating oil.
Owing to having adopted technique scheme, a kind of large area structure damage detecting method based on Lamb ripple provided by the invention, adopt the damage detecting method based on Lamb ripple to position the damage on large area structure, detailed situation (the shape to damage by harmless single-point detection technique (as ultrasonic, infrared etc.) again, type, the order of severity etc.) assess.There is following beneficial effect:
1, damage detecting method disclosed by the invention has improved the detection efficiency of traditional single-point Non-Destructive Testing by the large area structure detectability of guided wave, the accuracy of detection that has improved damage by traditional single-point detection technique, has made up the shortcoming that can not obtain detailed damage information in guided wave damage check.
2, in damage detecting method disclosed by the invention, apply Lamb wave excitation device, adopt the movable type probe of this device to treat geodesic structure and carry out whole detection, improved the dirigibility and the maneuverability that detect, and reduced the requirement to checkout equipment.
3, damage detecting method disclosed by the invention has proposed single A 0mode Lamb wave excitation, method of reseptance, avoided the multi-modal interference of Lamb ripple, greatly improved the ability of guided wave damage monitoring.
Accompanying drawing explanation
In order to be illustrated more clearly in the embodiment of the present application or technical scheme of the prior art, to the accompanying drawing of required use in embodiment or description of the Prior Art be briefly described below, apparently, the accompanying drawing the following describes is only some embodiment that record in the application, for those of ordinary skills, do not paying under the prerequisite of creative work, can also obtain according to these accompanying drawings other accompanying drawing.
Fig. 1 is Lamb wave excitation device structural representation in the present invention;
Fig. 2 is the schematic diagram of portable probe excitation Lamb ripple in the present invention;
Fig. 3 is the single A collecting in the present invention 0mode Lamb ripple signal is processed schematic diagram;
Fig. 4 is that the check point in the embodiment of the present invention distributes and damage arranges schematic diagram;
Fig. 5 is damage check diagnostic result in the embodiment of the present invention.
In figure: 1. portable probe; 2. piezoelectric chip; 3. shearing effect inhibition layer; 4. body structure surface to be measured; 5. injury region; The A of Fig. 3 (a) for collecting 0the schematic diagram of mode Lamb wave response signal (normalization), the A of Fig. 3 (b) for extracting 0the schematic diagram of mode lamb ripple damage scattered signal, the A of Fig. 3 (c) for extracting 0mode lamb ripple damage scattered signal energy envelope schematic diagram; 6. the pumping signal for collecting; 7. the A for extracting 0mode damage scattered signal; 8. for edge reflection signal, being 9. pumping signal closing time, is 10. nearest border echo time of arrival.
Embodiment
For making technical scheme of the present invention and advantage clearer, below in conjunction with the accompanying drawing in the embodiment of the present invention, the technical scheme in the embodiment of the present invention is known to complete description:
The invention discloses a kind of large area structure damage detecting method based on Lamb ripple, adopt the damage check/monitoring method based on Lamb ripple to position the damage on large area structure, can't harm the detailed situation (shape of single-point detection technique (as ultrasonic, infrared etc.) to damage by tradition again, type, the order of severity etc.) assess
Comprise the following steps:
S1: first, treating to set up rectangular coordinate system on geodesic structure, then choose multiple tested points in this structure; Can select N check point, use respectively m (m=1~N) to represent;
S2: the Lamb wave excitation device with portable probe is set at a tested point place; Can start at m(m=1) start to detect;
S3: excite narrow band signal by function generator and power amplifier at this tested point place, the bandwidth range of the narrow band signal exciting is controlled to the frequency range lower than the A1 mode cutoff frequency of setting, the narrow band signal exciting is loaded into portable probe upper, is at this moment treating that on geodesic structure, producing frequency values is less than A 1the single A of mode cutoff frequency 0mode Lamb ripple, portable probe receives Lamb ripple signal, obtains the Lamb ripple echoed signal f1 containing damaged structure information.Before detection, the bandwidth range of narrow band signal is controlled at lower than the A setting 1the frequency range of mode cutoff frequency, A 1mode cutoff frequency is the frequency values calculating by theory according to physical dimension to be measured.Therefore in the process detecting, treating that on geodesic structure, only producing frequency values is less than A 1single A 0mode Lamb ripple.
S4: complete successively the signals collecting for the treatment of to remain on geodesic structure tested point according to the mode of S2, S3, collect single A 0modal structure response signal f m;
S5: by the response signal f collecting mcarry out signal processing and obtain damage image, this damage for the treatment of geodesic structure is carried out to location, position, the details (shape, type, the order of severity etc.) of the damage to structure is assessed.
Further, as shown in Figure 1: the Lamb wave excitation device of damage detecting method application disclosed by the invention comprises portable probe 1, the end of portable probe 1 is connected with multiple piezoelectric chips 2, on piezoelectric chip 2, be connected with shearing effect inhibition layer 3, described portable probe 1 is connected with treating geodesic structure by shearing effect inhibition layer 3.
Further, the portable probe 1 of described shearing effect inhibition layer 3 inhibition is treated the shearing effect of geodesic structure, suppresses symmetrical mode Lamb ripple, encourages single A 0mode Lamb ripple.
Further, described shearing effect inhibition layer 3 is the lubricated interfaces that are made up of railway grease, lubricant or lubricating oil.The effect of this shearing effect inhibition layer 3 is: suppress portable probe 1 and treat the shearing effect of geodesic structure, thereby suppress symmetrical mode Lamb ripple, thereby encourage single A 0mode Lamb ripple.
Embodiment:
Step 1: get an aluminium sheet test specimen (size: 1000mm × 1000mm × 3mm) as shown in Figure 4, a hole wound and an indentation are set respectively thereon, both coordinates as shown in Figure 4.Wherein, the diameter of hole wound is 20mm, and the long 30mm of indentation, wide 1.5mm.Individual (this example is 24) diverse location of N on selected aluminium sheet (L1, L2 ..., L24) and as check point, its distribution situation as shown in Figure 4, is measured the distance of each check point to nearest border, and note is Lb1,, Lb2 ..., Lb24.
Step 2: in a certain check point position, Lamb wave excitation device is as shown in Figure 1 set, portable probe 1 is connected by shearing effect inhibition layer 3 with aluminium sheet body structure surface 4, adopts railway grease as shearing effect inhibition layer in this example.
Step 3: the narrow band signal of excitation is loaded into the excitation end of portable probe 1, the bandwidth region of the narrow band signal of excitation is controlled at lower than A 1the frequency range of mode cutoff frequency, because shearing effect inhibition layer has suppressed symmetrical mode Lamb ripple, realizes single A thus 0mode Lamb wave excitation, that is to say A 0the frequency values of mode is to be all less than A 1the frequency values of mode.The receiving end of portable probe 1 gathers structural response signal simultaneously.In this example, adopt centre frequency 50kHz, the sinusoidal signal that the periodicity of Hanning window modulation is 5 is as pumping signal, and the frequency band of this pumping signal is lower than A on this aluminium sheet 1the initial cutoff frequency of mode, shearing effect inhibition layer 3 has suppressed the shearing effect of 1 pair of structure of portable probe, thereby obtains single A 0mode Lamb wave response signal.
Step 4: portable probe 1 is to next check point, as shown in Figure 2, repeating step 2 and step 3, the single A0 mode lamb ripple of new detection position excitation runs into damage 5 or border also will produce scattering, and the formula that is moved is popped one's head in and 1 collected.
Step 5: complete successively the collection of residue check point, obtain the single A of cluster (the present embodiment comprises 24 groups) 0mode Lamb wave response signal f m(m=1~N);
Step 6: the single A collecting 0mode Lamb wave response signal, first by normalization, is eliminated the difference of different check points;
Step 7: extract single A 0damage scattered signal note in mode Lamb wave response signal is D m, as shown in Figure 3.In the present embodiment, pass through pumping signal and damage scattered signal with echo extraction time of arrival 10 of nearest border closing time 9, as shown in Fig. 3 (a), wherein 6 is the pumping signal collecting, 7 A for extraction 0mode damage scattered signal, 8 is edge reflection signal.And pumping signal t closing time 1with nearest border echo t time of arrival 2calculate by following formula:
t 1 = L as V L + L s , t 2 = t 1 + 2 L bm V L
Wherein V lrepresent the A that encourages 0the group velocity of mode guided wave, L asrepresent the excitation end of portable probe 1 and the spacing of receiving end, L srepresent the time domain width of pumping signal, L bmfor the check point m that measures in step 1 is to the spacing on nearest border, the Lamb ripple motivating due to the inventive method is single A 0mode, has avoided the S that adopt in prior art more 0when Modal detection, V lget S 0the group velocity of mode, but the slower A of velocity of wave 0mode echo can not be effectively separated, thereby testing result is exerted an influence.And single A 0the group velocity of mode can, according to pumping signal centre frequency, be calculated Lamb wave dispersion curve and the acquisition of measuring velocity of wave by theory.
Step 8: adopt Hilbert method to extract damage scattered signal D menergy envelope figure, as shown in Fig. 3 (c), note is E m(t);
Step 9: structure mapping is become to image array, and the each pixel of image is corresponding with locations of structures, its pixel value characterizes the probability that damage appears in this point, can calculate by following formula:
P ( i , j ) = Σ m = 1 N W m E m ( t mij ) , m = 1,2 , · · · , N
Wherein, P (i, j) is the probability that the damage of pixel (i, j) position occurs, E m(t) for check point m records the envelope that damages scattered signal, t mijrepresent single A 0mode Lamb ripple propagates into pixel (i, j) and returns the receiving end required time of m position from the excitation end of check point m position.Can be calculated by following formula:
t mij = L m ad + L m ds V L + L s 2
Wherein with be respectively the excitation end of check point m position and the receiving end distance to pixel (i, j), and V lwith L srepresent respectively Lamb group velocity and pumping signal time domain width, in formula, latter one is the reference time, is to arrive initial time and the difference in peak value moment in order to compensate damage scattered signal.
Parameter W mfor weight coefficient, for compensating the performance difference between different responses, in this example, get 1;
Step 10: the testing result image of test specimen shown in Fig. 4 as shown in Figure 5, can accurately locate with indentation by hole wound;
Step 11: the damage position in guided wave diagnostic image 5 is carried out to traditional single-point Non-Destructive Testing, the detailed situation (shape, type, the order of severity etc.) of damage is assessed.
The above; it is only preferably embodiment of the present invention; but protection scope of the present invention is not limited to this; any be familiar with those skilled in the art the present invention disclose technical scope in; be equal to replacement or changed according to technical scheme of the present invention and inventive concept thereof, within all should being encompassed in protection scope of the present invention.

Claims (4)

1. the large area structure damage detecting method based on Lamb ripple, it is characterized in that: the method adopts the damage detecting method based on Lamb ripple to position the damage of large area structure, by harmless single-point detection technique, damage status is assessed again, is specifically comprised the following steps:
S1: treating to set up rectangular coordinate system on geodesic structure, select multiple tested points;
S2: the Lamb wave excitation device with portable probe is set at a tested point place;
S3: adopt function generator and power amplifier to excite narrow band signal, the bandwidth range of this narrow band signal is controlled at lower than the A setting 1the frequency range of mode cutoff frequency, is loaded into portable probe by the narrow band signal exciting upper, is treating that on geodesic structure, producing frequency values is less than A 1the single A of mode cutoff frequency 0mode Lamb ripple, portable probe receives Lamb ripple signal, obtains the Lamb ripple echoed signal f containing damaged structure information 1;
S4: complete successively the signals collecting for the treatment of to remain on geodesic structure tested point according to the mode of S2, S3, collect single A 0modal structure response signal f m;
S5: by the response signal f collecting mcarry out signal processing and obtain damage image, this damage for the treatment of geodesic structure is carried out to location, position, the situation of the damage to structure is assessed.
2. a kind of large area structure damage detecting method based on Lamb ripple according to claim 1, be further characterized in that: described Lamb wave excitation device comprises portable probe (1), the end of described portable probe (1) is connected with multiple piezoelectric chips (2), on described piezoelectric chip (2), be connected with shearing effect inhibition layer (3), described portable probe (1) is connected with treating geodesic structure by shearing effect inhibition layer (3).
3. a kind of large area structure damage detecting method based on Lamb ripple according to claim 2, be further characterized in that: described shearing effect inhibition layer (3) the portable probe of inhibition (1) is treated the shearing effect of geodesic structure, suppress symmetrical mode Lamb ripple, encourage single A 0mode Lamb ripple.
4. a kind of large area structure damage detecting method based on Lamb ripple according to claim 2, is further characterized in that: described shearing effect inhibition layer (3) is the lubricated interface being made up of railway grease, lubricant or lubricating oil.
CN201410020701.1A 2014-01-16 2014-01-16 Large-area structural damage detection method based on Lamb wave Pending CN103792287A (en)

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CN104965023A (en) * 2015-05-21 2015-10-07 江苏大学 Multi-modal guided-wave industrial pipeline diagnostic method
CN106596737A (en) * 2016-11-29 2017-04-26 大连理工大学 Lamb wave structure-based multi-mode signal separation method
CN108445079A (en) * 2018-03-07 2018-08-24 重庆大学 The coaxial mixing detection method in the same direction of Lamb wave of thin plate earlier damage
CN108536920A (en) * 2018-03-19 2018-09-14 上海理工大学 A method of calculating, which is lain, drips Lamb wave scattering coefficient

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CN104597083A (en) * 2015-01-13 2015-05-06 大连理工大学 Ultrasonic guided wave and electromechanical impedance-based mobile damage detection method
CN104597083B (en) * 2015-01-13 2017-01-18 大连理工大学 Ultrasonic guided wave and electromechanical impedance-based mobile damage detection method
CN104965023A (en) * 2015-05-21 2015-10-07 江苏大学 Multi-modal guided-wave industrial pipeline diagnostic method
CN106596737A (en) * 2016-11-29 2017-04-26 大连理工大学 Lamb wave structure-based multi-mode signal separation method
CN106596737B (en) * 2016-11-29 2019-12-27 大连理工大学 Multi-mode signal separation method based on Lamb wave structure
CN108445079A (en) * 2018-03-07 2018-08-24 重庆大学 The coaxial mixing detection method in the same direction of Lamb wave of thin plate earlier damage
CN108536920A (en) * 2018-03-19 2018-09-14 上海理工大学 A method of calculating, which is lain, drips Lamb wave scattering coefficient

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