CN100399595C - Wheeled Scanning Probes for Scanning Imaging Devices - Google Patents

Abstract

The invention discloses a wheel-type scanning probe used for a scanning imaging device. The probe includes a cylindrical support body and a hollow wheel shaft nested in the cylinder; the outer surface of the support body is embedded with transducer units at equal intervals; Two extraction electrodes. The wheel shaft is provided with two electrode sliders, which are respectively connected to the two lead-out electrode brushes through the electrode compression spring; each of the two electrode sliders has an electrode lead wire that is led out of the wheel shaft through the hollow part of the wheel shaft; the transducer unit is composed of Composed of piezoelectric blocks and non-piezoelectric blocks; piezoelectric blocks and non-piezoelectric blocks are placed alternately; the upper and lower surfaces of the transducer unit are covered with upper electrodes and lower electrodes, respectively, and the two lead-out electrodes corresponding to the transducer unit connect. The wheel-type scanning probe used in the scanning imaging device provided by the invention can be used for the ultrasonic non-destructive testing of solid materials, including the quality evaluation of the bonding interface.

Description

Wheeled Scanning Probes for Scanning Imaging Devices

technical field

The invention relates to a probe for scanning imaging devices, in particular to a wheel-type scanning probe for scanning imaging devices.

Background technique

The traditional multi-channel imaging technology uses ultrasonic longitudinal wave probes to form a straight probe array or a wheel probe array to electronically scan and image the detection object. Due to the existence of wave mode conversion in solids, the traditional longitudinal wave phased array technology will encounter additional interference when used in the detection of solid media. In addition, in the detection of liquid interlayer and zero-gap debonding at the bonding interface, ultrasonic longitudinal waves cannot be used to detect.

Compared with longitudinal wave, shear wave detection has its unique advantages. It can be seen from the propagation theory that the scattering and reflection characteristics of pure shear waves in complex dielectric materials such as anisotropy are relatively simple, and the detection of shear waves has the effect that longitudinal waves cannot achieve. Under the condition of the same frequency, the wavelength of the shear wave is almost twice as small as that of the longitudinal wave, so the reflected energy of the shear wave is relatively much larger for defects of the same size. At the same time, in the detection of liquid interlayers in the bonding interface defects, the sensitivity of shear waves is much higher than that of longitudinal waves.

Although in ultrasonic testing of welds, shear wave array probes are sometimes used (Roy, O.Mahaut, S.Casula, O.Development of a smart flexible transducer to inspect component of complex geometry: modeling and experiment, AIP Conference Proceedingsno.615A: 908 -14, 2002), however, the array elements that make up the probe array directly radiate longitudinal waves, and then obliquely incident on the coupling interface, using wave mode conversion to generate shear waves in the detection medium. This use of wave mode conversion technology affects the efficiency of generating shear waves, and is often accompanied by longitudinal waves or surface waves to affect the detection. There is also the use of electromagnetic acoustic technology to generate SH transverse waves to measure the thickness of metal plates ^[2] , but the equipment is relatively complicated, the detection conditions are high, and it is only suitable for ferromagnetic media. At present, there is no product that can actually be used for small equivalent defect detection. . Transverse waves can also be generated using other methods ([1]. Murray, PRDewhurst, RJLaser/EMAT measurement systems for ultrasound B-scan imaging, Sensors and their Applications XI. Proceedings of the Eleventh Conference on Sensors and their Applications: 169-74, 2001; [ 2]. Every, AGSachse, W. Imaging of laser-generated ultrasonic waves in silicon, Physical Review B (Condensed Matter), vol.44, no.13: 6689-99, 1 Oct.1991Language: English; [3]. Wang Chenghao , Qiao Donghai, Research on Acoustic Beam Focusing Produced by Fresnel Array on Solid Surface, Acta Acoustica Sinica, Vol.24, No.4, 1999, pp351-356), but it is often accompanied by longitudinal waves, and cannot obtain pure shear wave radiation sound field.

Contents of the invention

The purpose of the present invention is to overcome the shortcomings of the scanning imaging device in the prior art that the probe cannot directly emit shear waves, thus having low efficiency and limiting its application, and by designing a transducer unit that can directly generate shear waves, thereby providing a kind for The wheeled scanning probe of the scanning imaging device.

Technical scheme of the present invention is:

A wheeled scanning probe for scanning imaging devices, the probe includes a cylindrical support body 1 and a hollow wheel shaft 7 nested in the cylinder; the outer surface of the support body 1 is embedded with transducer units 2 at equal intervals, and the The transducer unit 2 is a cuboid, and its length direction is parallel to the axis of the support body 1; the transducer unit 2 is provided with two lead-out electrodes 8 on the inner surface of the support body 1 corresponding to the radial direction of the support body 1; the axle 7 is provided with Two electrode sliders 9 are respectively brush-connected to the two lead-out electrodes 8 through electrode compression springs 10; each of the two electrode sliders 9 has an electrode lead wire 11 drawn out to the outside of the wheel shaft 7 through the hollow part of the wheel shaft 7; The transducer unit 2 is composed of piezoelectric blocks 3 and non-piezoelectric blocks 4; the piezoelectric blocks 3 and non-piezoelectric blocks 4 are alternately placed; the upper and lower surfaces of the transducer unit 2 are covered with upper electrodes 5 and lower electrodes respectively. The electrodes 6 are respectively connected to two lead-out electrodes 8 corresponding to the transducer unit 2 .

The support body 1 and the axle 7 are connected by bearings or direct friction. The width of the transducer unit 2 is less than or equal to λ/2, and its thickness is less than or equal to λ/2, where λ is equal to the wavelength of the sound wave to be emitted. The distance between adjacent transducer units 2 is greater than or equal to the minimum distance required to isolate the coupled vibration between transducer units. The polarization direction of the piezoelectric block 3 is along the length direction or width direction of the transducer unit 2 . The probe also includes a protective film arranged on the sound radiation surface of the transducer unit 2 and a backing arranged on the back of the transducer unit 2 .

In actual use, the wheel-type scanning probe provided by the present invention can be connected to the transmitting/receiving circuit part of the scanning imaging device in the prior art through multiple bundles of high-frequency shielded cables, thereby forming a complete multi-channel scanning imaging device.

The advantage of the wheel-type scanning probe used for scanning imaging devices provided by the present invention is that the probe can directly generate pure shear waves, avoiding energy loss or other interference caused by wave mode conversion, and avoiding the effects of sound wave mode conversion in solids. Using this probe, not only can use the electronic phase control technology to realize the electronic scanning of the vertical pure shear wave acoustic beam on the solid material, but also detect the liquid interlayer and zero-gap debonding at the bonding interface.

The wheel-type scanning probe used in the scanning imaging device provided by the invention can be used for the ultrasonic non-destructive testing of solid materials, including the quality evaluation of the bonding interface.

Description of drawings

Fig. 1 (a) is the front view of wheel type scanning probe of the present invention;

Fig. 1 (b) is the side view of wheel type scanning probe of the present invention;

Fig. 2 is a schematic structural view of the transducer unit in Fig. 1;

Figure 3 is a structural schematic diagram of another transducer unit

4 is a schematic structural view of the mechanical part of the scanning imaging device using the wheel scanning probe of the present invention;

5 is a schematic structural view of the electronic part of the scanning imaging device using the wheel scanning probe of the present invention;

Graphic description:

Support body 1 Transducer unit 2 Piezoelectric block 3 Non-piezoelectric block 4

Upper electrode 5 Lower electrode 6 Axle 7 Lead-out electrode 8

Electrode slider 9 Electrode compression spring 10 Electrode lead wire 11

Detailed ways

Below in conjunction with accompanying drawing and specific embodiment the present invention is described in further detail:

Figure 1 is a schematic structural view of the wheel-type scanning probe, Figure 1(a) is a front view, and Figure 1(b) is a side view. The probe as a whole includes a cylindrical support body 1 made of epoxy resin material and a hollow wheel shaft 7 nested in the cylinder, which are connected by bearings or direct friction. A plurality of transducer units 2 are embedded at equal intervals around the outer surface of the support body 1, and the distance between adjacent transducers is 2 mm. The transducer unit 2 is in the shape of a cuboid, and its length direction is parallel to the axis of the support body 1 . Each transducer unit 2 corresponds to two lead-out electrodes 8 , and the lead-out electrodes 8 are located on the inner surface of the support body 1 and are in the same radial direction of the support body 1 as the corresponding transducer unit 2 . Two electrode sliders 9 are arranged on the wheel shaft 7, and are respectively connected to the two lead-out electrodes 8 through electrode compression springs 10 in a brush-like manner; each of the two electrode sliders 9 has an electrode lead wire 11 drawn out through the hollow part of the wheel shaft 7 to Axle 7 outside.

A kind of structure of transducer unit 2 is as shown in Figure 2, and its width is 0.8 millimeters, and thickness is 1.1 millimeters, and length is 10 millimeters, and the wavelength of this transducer unit 2 emission sound waves is 3 millimeters (corresponding to detection body is case of metallic steel). The upper and lower surfaces of the transducer unit 2 are respectively covered with an upper electrode 5 and a lower electrode 6 , and these two electrodes are used to connect with two lead-out electrodes 8 corresponding to the transducer unit 2 . The transducer unit 2 is composed of three piezoelectric blocks 3 and four non-piezoelectric blocks 4 placed alternately, and its polarization direction is along the length direction of the transducer unit 2; the piezoelectric block 3 uses piezoelectric materials, which can be zirconium titanium Lead acid piezoelectric ceramics, such as PZT-5A and PZT-4, can also be used with other series of piezoelectric materials such as barium titanate, lead metaniobate, potassium sodium niobate, lead titanate piezoelectric ceramics or quartz crystal. The material of the non-piezoelectric block is epoxy such as E-51, or other bisphenol A type epoxy such as E-44 or E-55.

The transducer unit 2 can also have another configuration, as shown in Figure 3, it is composed of 7 piezoelectric blocks 3 and 7 non-piezoelectric blocks 4 placed alternately, and its polarization direction is along the width of the transducer unit 2 direction.

The sound radiation surface of the transducer unit 2 is provided with a protective film (not shown) made of epoxy resin plus 280 mesh corundum, wherein the corundum can also be replaced by insulating material micropowder such as silicate micropowder or corundum micropowder. The back of the transducer unit 2 is provided with a backing (not shown) of epoxy plus metal powder, for example plus tungsten powder.

The scanning imaging device using the wheel-type scanning probe of the present invention includes an electronic part and a mechanical part. The mechanical part is shown in Figure 4, and the electronic part is shown in Figure 5. A wheel-type probe scanning mechanism composed of a wheel-type scanning probe and a scanning frame. The scanning frame is composed of supporting guide rails, scanning frame base, stepping motor, and cable connector. The scanning frame base is installed on the supporting guide rail, and can move along the rail under the drive of the stepping motor. The wheel-type scanning probe is installed under the base, and the scanning frame can apply a certain pressure load to the wheel-type scanning probe. The cable connector connects the electrode leads 11 from the wheel-type scanning probe, the drive/control line of the stepping motor with the transmitting/receiving circuit of the electronic part, and the scanning control drive circuit respectively, wherein the electrode leads 11 use high-frequency coaxial shielded cables.

The electronic part includes transmitting circuit, receiving circuit, A/D conversion circuit, industrial control computer, display, printer. The scanning system includes a scanning control driving circuit and a scanning driving device. The industrial control computer is responsible for equipment control, waveform processing, identification, classification and imaging. The transmitting circuit is responsible for generating the high-voltage pulse signal to drive the piezoelectric transducer, usually the transmitting pulse amplitude is ≥200 volts, and the rising edge/falling edge is ≤10 nanoseconds. The receiving circuit is responsible for amplifying the received signal and sending it to the A/D conversion circuit. Usually, the amplifier bandwidth in the receiving circuit is ≥15 MHz, the gain is ≥64 decibels, and the gain control range is ≥74 decibels. The A/D conversion circuit adopts a waveform acquisition card, uses a sampling frequency not less than 20 MHz to collect echo signals and stores them in a dual-port memory, and finally sends the collected waveform data to an industrial control computer for processing and display. The display is used for menu-based operation of the equipment system, real-time monitoring of echo signal waveforms and display of imaging results. The printer completes the function of printing out imaging results and related parameters.

When scanning starts, the transducer unit connected to the electrode slider on the cylinder is located directly under the cylinder and on the surface of the workpiece, while the other units are disconnected. At this time, the transmitting circuit sends out excitation electric pulses, and the transducer unit radiates transverse waves into the workpiece. When the receiving circuit receives the echo from the workpiece, the scanning control circuit sends a scanning signal, and the scanning driving circuit drives the scanning frame to move forward, and the cylinder rolls to the next transducer unit to enter a new scanning detection cycle. Therefore, in the present invention, the scanning speed should be small enough so that each working transducer unit can receive the echo signal of the farthest defect that may exist in the workpiece.

During the detection process, it is necessary to apply a shear wave coupling agent such as viscous honey on the surface of the workpiece, and apply a certain coupling pressure load. Therefore, suitable materials should be selected for the filling of the roller shaft and cylindrical support, the support guide rail, and the scanning frame. It has a certain strength.

In the scanning process of Fig. 4, the actual scanning area realized is a series of rectangular scanning areas arranged in parallel, and these areas provide the scanning coverage when using the device of the present invention for scanning imaging or the non-missing defects that can be achieved minimum size of .

Claims (7)

1. wheeled scanning head that is used for scanned imagery device, this probe comprise a cylindric supporter (1) and are nested in a hollow wheel shaft (7) in the tube; It is characterized in that supporter (1) outer surface equidistantly is embedded with transducer unit (2), transducer unit (2) is cuboid, the parallel axes of its length direction and supporter (1); Transducer unit (2) is provided with two extraction electrodes (8) along the inner surface of the radially pairing supporter of supporter (1) (1); Wheel shaft (7) is provided with two electrode slide blocks (9), and is connected with two extraction electrodes (8) electric brush type by electrode stage clip (10) respectively; Two electrode slide blocks (9) respectively have a contact conductor (11) to be drawn out to wheel shaft (7) outside by the hollow space of wheel shaft (7); Described transducer unit (2) is made up of piezoelectric blocks (3) and non-piezoelectric blocks (4); Described piezoelectric blocks (3) and non-piezoelectric blocks (4) are staggeredly placed; The upper and lower surface of transducer unit (2) is coated with top electrode (5) and bottom electrode (6) respectively, and corresponding with this transducer unit (2) respectively two extraction electrodes (8) connect.

2. the wheeled scanning head that is used for scanned imagery device according to claim 1 is characterized in that, adopts bearing class or direct friction formula connected mode between described supporter (1) and the wheel shaft (7).

3. the wheeled scanning head that is used for scanned imagery device according to claim 1 is characterized in that, the width of described transducer unit (2) is smaller or equal to λ/2, and its thickness is smaller or equal to λ/2, and wherein λ equals the wavelength of required emission sound wave.

4. the wheeled scanning head that is used for scanned imagery device according to claim 1 is characterized in that, the distance between adjacent transducer unit (2) is more than or equal to isolating the minimum range that coupled vibrations needs between transducer unit.

5. the wheeled scanning head that is used for scanned imagery device according to claim 1 is characterized in that the polarization direction of described piezoelectric blocks (3) is along the length direction or the Width of transducer unit (2).

6. the wheeled scanning head that is used for scanned imagery device according to claim 1 is characterized in that, also comprises the diaphragm that is arranged on described transducer unit (2) the acoustic radiation face.

7. the wheeled scanning head that is used for scanned imagery device according to claim 1 is characterized in that, also comprises the backing that is arranged on described transducer unit (2) back side.

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