CN202052686U

CN202052686U - Low-frequency single-mode lamb wave energy transducer

Info

Publication number: CN202052686U
Application number: CN2011200782566U
Authority: CN
Inventors: 焦敬品; 张永强; 宋国荣; 何存富; 吴斌
Original assignee: Beijing University of Technology
Current assignee: Beijing University of Technology
Priority date: 2011-03-23
Filing date: 2011-03-23
Publication date: 2011-11-30
Anticipated expiration: 2021-03-23

Abstract

The utility model relates to a low-frequency single-mode lamb wave energy transducer, which is used for exciting and receiving low-frequency single A0-mode lamb waves in a plate structure and further realizing the large-range defect detection of the plate structure and belongs to the technical field of nondestructive testing. The low-frequency single-mode lamb wave energy transducer comprises a piezoelectric chip 2, an energy transducer positive electrode lead wire 4 and an energy transducer negative electrode lead wire 5. A back liner 1 and a front liner 3 are pasted at the upper side and the lower side of the piezoelectric chip, the energy transducer positive electrode lead wire 4 and the energy transducer negative electrode lead wire 5 are respectively led out from a positive electrode and a negative electrode of the piezoelectric chip and are respectively connected with the back liner 1 and the front liner 3 of the energy transducer. The low-frequency single-mode lamb wave energy transducer has the advantages that the center frequency of the piezoelectric chip is reduced through the pasting of the back liner and the front liner, the low-frequency single-mode lamb wave energy transducer can work in a low frequency range, and in addition, single A0-mode lamb waves can be excited.

Description

A kind of low frequency single mode Lamb wave transducer

Technical field:

The utility model relates to a kind of low frequency single mode Lamb wave transducer, is used for the excitation of the single A0 mode of plate structure medium and low frequency Lamb wave and receives, and then realize plate structure defects detection on a large scale, belongs to technical field of nondestructive testing.

Background technology:

In the plate structure defects detection, often use the PZT (piezoelectric transducer) excitation to receive Lamb wave, to realize the detection and the location of defective.But Lamb wave has the multimode state property, promptly has the different mode of a plurality of group velocitys, comprises symmetry each rank mode S0, S1 etc., antisymmetry each rank mode A0, A1 etc.When PZT (piezoelectric transducer) was done excitation usually, the multimode state property that receives echo can influence the identification of flaw echo, the accuracy that influence detects.If therefore can realize the excitation of the single mode of Lamb wave in the plate, can improve detection efficiency to a great extent.

When the excitation transducer is operated in the scope under the A1 mode cut-off frequency (below about 100kHz), along perpendicular to the vibration of the direction of plate, and wavelength is during much larger than transducer diameter, except that A0 mode, other mode can not be energized or energy very little, at this moment can think and only encourage A0 mode Lamb wave.The operating frequency position of common piezoelectric patches often is higher than this scope, and the centre frequency of piezoelectric patches is relevant with the material of piezoelectric patches and size, for example, diameter 5mm, thickness 2mm, the PZT-5H piezoelectric patches centre frequency of thickness direction vibration is 1MHz.If make the piezoelectric patches centre frequency is 100kHz, and the thickness of piezoelectric patches will reach 20mm.Obviously, reducing centre frequency by the thickness that increases piezoelectric patches is infeasible in practical operation.

The utility model content:

The low frequency single mode Lamb wave transducer that the utility model proposes under the situation that does not change the piezoelectric patches size, reduces centre frequency, realizes the single A0 mode of low frequency Lamb wave transducer designs.

A kind of low frequency single mode Lamb wave transducer as described in Figure 1, comprises piezoelectric patches 2, transducer positive wire 4, transducer negative wire 5.Bonding backing 1 and preceding lining 3 in the top and bottom of piezoelectric patches.Positive wire 4, the transducer negative wire 5 of transducer are drawn from the both positive and negative polarity of piezoelectric patches respectively, link to each other respectively with preceding lining 3 with the backing 1 of transducer.

Backing uses brass material, and preceding lining uses the SiO2 foamed material.

Bonding between backing 1, piezoelectric patches 2 and the preceding lining 3 by epoxide-resin glue.

Low frequency single mode Lamb wave transducer described in the utility model by having pasted backing and preceding lining, has reduced the centre frequency of piezoelectric patches, can be operated in (about 100kHz is following) in the lower frequency range, and motivate single A0 mode Lamb wave.

Description of drawings:

Fig. 1: low frequency single mode Lamb wave transducer schematic diagram

Fig. 2: experiment measuring system schematic

Fig. 3: experiment displacement-frequency response curve

Fig. 4: do excitation by transducer and receive the signal graph that obtains

Fig. 5: do excitation by piezoelectric patches and receive the signal graph that obtains

Among the figure: 1, transducer backing, 2, piezoelectric patches, 3, lining before the transducer, 4, the transducer positive wire, 5, the transducer negative wire, 6, detected plate structure, 7, the excitation transducer, 8, receiving transducer, 9, the signal excitation device, 10, signal receiving device

The specific embodiment:

Provide following examples below in conjunction with content of the present utility model:

A kind of low frequency single mode Lamb wave transducer as described in Figure 1, comprises piezoelectric patches 2, transducer positive wire 4, transducer negative wire 5.Bonding backing 1 and preceding lining 3 in the top and bottom of piezoelectric patches.Positive wire 4, the transducer negative wire 5 of transducer are drawn from the both positive and negative polarity of piezoelectric patches respectively, link to each other respectively with preceding lining 3 with the backing 1 of transducer.Piezoelectric patches 2 adopts diameter 6mm, and the PZT-5H piezoelectric patches of thickness 1mm, backing 1 are the thick brass of 6mm, and preceding lining is the thick SiO2 foam of 2mm.It is bonding to pass through epoxide-resin glue between backing 1, piezoelectric patches 2 and the preceding lining 3, and transducer is sticked on the detected plate structure 6 with epoxy resin.In plate, encourage Lamb wave by the pumping signal that loads different frequency, analyze the centre frequency of transducer, and with the mode of piezoelectric patches contrast excitation Lamb wave in plate of same size.

1. use diameter 6mm, the PZT-5H piezoelectric patches of thickness 1mm is pasted thick brass backing of 6mm and the thick SiO of 2mm ₂Lining is drawn the positive pole of transducer and the negative pole of transducer from the both positive and negative polarity of piezoelectric patches before the foam, makes transducer.

On the thick aluminium sheet of 3mm at a distance of 450mm place, paste two above-mentioned transducers with epoxy resin, be used separately as and encourage transducer 7 and receiving transducer 8.

3. receive virtual instrument equipment as signal excitation device 9 by the HS3 excitation, pumping signal is the sine wave in five cycles of Hanning window modulation, peak-to-peak value is 24V, both positive and negative polarity as excitation transducer 7 is linked to each other with the excitation source signal output channel, oscillograph links to each other to gather signal, measuring system such as Fig. 2 with the both positive and negative polarity that is used as the transducer that receives as signal receiving device 10.

4. the frequency of signal is by 10k-200k, and 10k changes at interval, under each frequency, gather a received signal, gather 20 signals altogether, according to transducer spacing and each modal waves spread speed, judge the through A0 mode in each signal, get peak-to-peak value, obtain the corresponding relation of peak-to-peak value and frequency.

5. peak-to-peak value-frequency data are showed with curve, obtain the curve map of amplitude with frequency change, as Fig. 3, the centre frequency of transducer is about 90kHz as can be seen from Figure.

6. get the received signal of 90kHz frequency excitation, as shown in Figure 4, the A0 mode velocity of wave of 90kHz is 2533m/s, and S0 mode velocity of wave is 5421m/s, and can calculate first direct wave by propagation distance and time is A0 mode.And the oscillogram when only doing excitation and receive with piezoelectric patches as shown in Figure 5, and can calculate first direct wave is S0 mode.

Designed as seen from the above transducer meets design requirement.

Claims

1. a low frequency single mode Lamb wave transducer comprises piezoelectric patches (2), transducer positive wire (4), transducer negative wire (5); It is characterized in that: at bonding backings in the top and bottom of piezoelectric patches (1) and preceding lining (3); The positive wire of transducer (4), transducer negative wire (5) are drawn from the both positive and negative polarity of piezoelectric patches respectively, link to each other respectively with preceding lining (3) with the backing (1) of transducer.

2. a kind of low frequency single mode Lamb wave transducer according to claim 1 is characterized in that: backing uses brass material, and preceding lining uses the SiO2 foamed material.

3. according to claim 1 or the described a kind of low frequency single mode Lamb wave transducer of claim 2, it is characterized in that: bonding between backing (1), piezoelectric patches (2) and the preceding lining (3) by epoxide-resin glue.