CN204044114U - A kind of ring-shaped ultrasonic array energy transducer - Google Patents

Abstract

The utility model discloses an annular ultrasonic array transducer, which comprises a shell, an annular piezoelectric crystal array and an acoustic resistance matching layer arranged in the shell; the annular piezoelectric crystal array is composed of a plurality of concentric annular piezoelectric crystals according to the prescribed The upper and lower surfaces of the annular piezoelectric crystal are connected with electrodes respectively, and the annular piezoelectric crystal connected to the electrodes is the vibration element; the electrode facing the concrete detection surface is set on the acoustic resistance matching layer, and the electrode facing away from the concrete detection surface is arranged on the acoustic resistance matching layer. A pad sound-absorbing layer is provided between the electrode and the shell. The annular ultrasonic array transducer of the utility model overcomes the lack of lateral resolution of the single vibration element system, adopts the annular array transducer with fewer vibration elements to form a high-resolution focused sound field, and has high lateral resolution for the grouting quality of the prestressed pipeline. High-rate detection and identification, improve detection signal-to-noise ratio and sensitivity.

Description

A circular ultrasonic array transducer

technical field

The utility model belongs to the technical field of ultrasonic nondestructive testing, in particular to an annular ultrasonic array transducer.

Background technique

In prestressed concrete structures, the quality of prestressed pipe grouting directly affects the bearing capacity and durability of the overall structure, and the effective detection of pipe grouting quality is a problem that engineers generally care about. Using the ultrasonic method to detect the quality of prestressed pipe grouting is the same as the basic principle of detecting the internal defects of concrete. Using the ultrasonic transmission method or ultrasonic echo method to obtain the characteristic parameters of ultrasonic propagation in concrete, such as sound velocity, amplitude, and frequency, through the analysis of these parameters Changes to judge the quality of concrete.

Concrete is a mixed material composed of cement, sand, and coarse aggregate. When ultrasonic waves propagate in concrete, the sound beam is reflected, scattered, and absorbed. The ultrasonic energy attenuates greatly, and the penetration depth is small, and it decays exponentially with the increase of frequency. . Traditional ultrasonic non-destructive testing devices generally use a single vibrating element transducer and choose a lower operating frequency. This type of device has poor lateral resolution and can only detect decimeter-level grouting defects, and defect location is difficult, which has some shortcomings . In order to improve the detection lateral resolution, high-frequency waves with high frequency and good beam directivity should be selected. Therefore, in the quality detection of prestressed pipeline grouting, high lateral resolution and large detection depth form a contradiction.

Therefore, people consider the sound beam focusing technology to make the ultrasonic beam emitted by the transducer converge within a certain range. Due to the convergence of the sound beam, the penetration and echo are enhanced, the detection sensitivity is improved, and the resolution is also improved. Currently, phased array technology is usually used for electronic focusing. Phased array transducers mainly include linear arrays, two-dimensional arrays, and annular phased arrays. Ultrasonic phased array technology has been widely used in biomedicine and other fields, but it is less used in concrete detection.

The circular phased array sound field is completely axisymmetric and has excellent axial focusing ability. The annular phased array can form a high-resolution focused sound field when the number of vibrators is less than that of linear array and area array transducers, reducing the production cost due to the excessive number of channels, while simplifying the circuit and control system. Therefore, the annular phased array transducer can be applied to the quality detection of prestressed pipeline grouting, and the resolution and sensitivity of detection can be improved.

Contents of the invention

Aiming at the above-mentioned defects existing in the prior art, the utility model provides an annular ultrasonic array transducer, which can form a high-resolution focused sound field to detect and identify the high lateral resolution of the grouting quality of the prestressed pipeline, so as to improve the detection Signal-to-noise ratio and sensitivity.

A ring-shaped ultrasonic array transducer, including a shell and a ring-shaped piezoelectric crystal array and an acoustic resistance matching layer arranged in the shell; the ring-shaped piezoelectric crystal array consists of multiple (generally 4 to 8) concentric ring-shaped The piezoelectric crystals are arranged according to the specified spacing; the upper and lower surfaces of the annular piezoelectric crystals are respectively connected with electrodes, and the annular piezoelectric crystals connected to the electrodes are the vibration elements; the electrodes facing the concrete detection surface are arranged in the acoustic resistance matching On the upper layer, a pad sound-absorbing layer is provided between the electrode facing away from the concrete detection surface and the shell.

Each vibration element receives the delayed pulse signal provided by the external equipment, and converts the signal into an ultrasonic signal, and the generated ultrasonic signal is incident on the concrete, and reflected at the position where the grouting of the prestressed pipe embedded in the concrete is not full, forming an echo Signal; each vibration element receives the echo signal, converts the echo signal into an electrical signal, and outputs it.

The ring-shaped piezoelectric crystal adopts piezoelectric ceramics.

The thickness of the annular piezoelectric crystal is λ/2, the thickness of the acoustic resistance matching layer is an odd multiple of λ/4, and λ is the wavelength of ultrasonic waves.

Wires are welded on the electrodes for transmitting electrical signals.

The material of the pad sound-absorbing layer is made of epoxy resin plus tungsten powder, or ferrite powder plus rubber powder.

The shell is used to fix the internal components of the transducer and protect the internal components. There must be acoustic isolation between the internal components and the shell, and rubber materials can be used to prevent signal interference caused by shell vibration.

In order to reduce the signal lines connected between the transducer and external equipment, the vibration element is connected with an electronic switch.

During the transmission process, each vibration element is excited according to a certain timing, so that the ultrasonic signals emitted by each vibration element are superimposed to form a new wave front, and the transmission focus is realized; during the reception process, according to the feedback received by each vibration element Based on the phase difference between the wave signals, the electrical signals output by each vibration element are phase-shifted and synthesized to achieve receiving focus.

During the transmitting process, by changing the delay time configuration of the delayed pulse signal, the focal length changes with the delay time; during the receiving process, according to the distance of the ultrasonic echo, the electrical signals output by each vibration element are sequentially put into the corresponding receiving Delay for dynamic focus. In practical applications, the focal length can be selected according to the embedding depth of the prestressed pipeline, without replacing the annular ultrasonic array transducer.

In order to improve the lateral resolution in the near-field area, the variable aperture technology is adopted: invest less inner ring vibration elements in the near-field, and the annular ultrasonic array transducer receives echo signals with a smaller aperture; appropriately increase the input in the far-field The outer ring vibrator and the ring ultrasonic array transducer receive echo signals with a larger aperture.

Compared with the prior art, the utility model has the following beneficial technical effects:

(1) The annular ultrasonic array transducer of the utility model overcomes the lack of lateral resolution of the single vibration element system, and adopts the annular array transducer with a small number of vibration elements to form a high-resolution focused sound field. High lateral resolution detection and identification, improve detection signal-to-noise ratio and sensitivity.

(2) The annular ultrasonic array transducer of the utility model forms a concentrated sound field, the sound energy is concentrated, and the transmission distance in the concrete is long, thereby increasing the detection depth range.

(3) The annular ultrasonic array transducer of the utility model can realize the dynamic focusing of the sound field by controlling the time delay, and the focus can be automatically adjusted according to the buried depth of the actual prestressed pipeline without replacing the transducer.

(4) The structure of the annular ultrasonic array transducer of the utility model is simple, and the system cost is low, which is equivalent to the cost of the traditional single-vibrator transducer detection device.

Description of drawings

Fig. 1 is a schematic structural diagram of the annular ultrasonic array transducer of the present invention.

Fig. 2 is a cross-sectional view of the annular piezoelectric crystal array of the present invention.

Fig. 3 is a schematic diagram of focusing of the annular ultrasonic array transducer of the present invention.

Fig. 4 is a schematic diagram of dynamic focusing of the annular ultrasonic array transducer of the present invention.

Fig. 5 is a schematic diagram of receiving echo signals with a variable aperture of the annular ultrasonic array transducer of the present invention.

Detailed ways

In order to describe the utility model more specifically, the technical solutions of the utility model will be described in detail below in conjunction with the accompanying drawings and specific embodiments.

FIG. 1 is a structural diagram of an annular ultrasonic array transducer, which is mainly composed of an annular piezoelectric crystal array 1 , an acoustic resistance matching layer 2 , an electrode 3 , a pad sound-absorbing layer 4 , a wire 5 and a housing 6 .

In this embodiment, the annular piezoelectric crystal array is composed of four mutually independent concentric annular piezoelectric crystals arranged at specified intervals. Piezoelectric crystals are composite materials, generally piezoelectric ceramic materials, and are used to convert electrical pulses into ultrasonic frequency mechanical devices. Vibration, and the mechanical vibration of the received echo is converted into an electrical signal, and the thickness of the piezoelectric crystal is 1/2 of the ultrasonic wavelength λ.

The upper and lower surfaces of each piezoelectric crystal are respectively connected to the positive and negative electrodes, and the piezoelectric crystal connected to the positive and negative electrodes is called a ring vibrating element, which is the basic component of an ultrasonic transducer.

The front end of the piezoelectric vibrator, that is, the side facing the concrete detection surface, is provided with an acoustic resistance matching layer, and materials with insulation, low attenuation coefficient and wear resistance should be selected. On the one hand, its function is to protect the piezoelectric vibrator from being worn; on the other hand, it makes the ultrasonic beam energy transmit as much as possible into the concrete structure. The geometric dimensions and acoustic impedance of the acoustic resistance matching layer must meet the matching conditions, and the thickness is taken as an odd multiple of 1/4 ultrasonic length, and its acoustic impedance Z2 satisfies the following formula:

${\mathrm{<span\; class="notranslate">\; Z</span>}}_{\mathrm{<span\; class="notranslate">\; 2</span>}}<span\; class="notranslate">\; =</span>\sqrt{{\mathrm{<span\; class="notranslate">\; Z</span>}}_{\mathrm{<span\; class="notranslate">\; 1</span>}}{\mathrm{<span\; class="notranslate">\; Z</span>}}_{\mathrm{<span\; class="notranslate">\; 3</span>}}}$

In the formula: Z ₁ is the acoustic impedance of the piezoelectric crystal material, and Z ₃ is the acoustic impedance of the concrete material.

Since the piezoelectric crystal emits ultrasonic waves to both ends, a pad sound-absorbing layer needs to be added on the back. The sound-absorbing material is generally made of epoxy resin plus tungsten powder or ferrite powder plus rubber powder for attenuation and absorption. The piezoelectric crystals back-radiate the ultrasonic energy so that it does not bounce back and forth inside the transducer.

The housing is used to hold and protect the internal components of the transducer. There must be acoustic isolation between the internal components and the shell, which can be isolated by rubber materials to prevent the signal from being disturbed by the vibration of the shell.

Fig. 2 is a schematic cross-sectional view of a ring-shaped ultrasonic array transducer with four vibrating elements. Each ring adopts a concentric and equal-area design scheme to ensure that the electrical impedance and sensitivity of each vibrating element are close.

Under the premise of ensuring a certain transducer size, when the number of vibrators is small, the area of a single vibrator is large, and the mutual interference between vibrators is small, but the amplitude of the side lobe is also increased; when the number of vibrators increases, the mutual interference between vibrators increases. Large, increasing the complexity and instability of the control circuit. Therefore, according to the testing requirements and conditions, the annular ultrasonic array transducer can be designed as different series of 4 to 8 circular vibrator elements.

If the distance between the vibrators is too small, the mutual interference between the vibrators will increase, and it will cause inconvenience to the processing and production of the transducer; Energizer size increases. Therefore, it is more suitable for the distance between the vibration elements to be less than 1/2 wavelength.

The parameters of the annular piezoelectric crystal array (4 vibration elements) in this embodiment are shown in Table 1:

Table 1

The selection of the operating frequency of the annular ultrasonic array transducer should be made according to the requirements of different detection depths and lateral resolution. The higher the frequency and the shorter the wavelength, the better the beam directivity and high lateral resolution, but the attenuation also increases proportionally, which reduces the detection depth and affects the signal-to-noise ratio. Therefore, a lower operating frequency should be selected, and the operating frequency in this embodiment is between 50 kHz and 250 kHz.

Figure 3 shows a schematic diagram of the electronic focusing of the annular ultrasonic array transducer. The ultrasonic phased array detection technology is realized by precisely controlling the delay of each vibration element signal, which is the core technology in the ultrasonic phased array detection.

When each ring vibrator is excited by a pulse signal of the same frequency, the sound waves generated are coherent waves. The sound pressure amplitude of some points in the space is enhanced due to the in-phase superposition of sound waves, and the sound pressure amplitude of other points is reduced due to the anti-phase cancellation of sound waves. Weaken, thus forming a stable ultrasonic field in space.

Considering that the ultrasonic beams emitted by each crystal array unit are focused on the position with a distance F in the axial direction, that is, the focal point O, in order to make the ultrasonic waves emitted by each array unit reach the focal point O at the same time, the distance between the focal point and each crystal unit must be calculated first. The amount of time delay applied to each unit is controlled based on the calculated distance difference and the propagation velocity of the ultrasonic wave in the concrete medium. The transmitting pulse generator generates high-voltage pulse signals with different delays to excite the corresponding vibration elements, and precisely controls the ultrasonic signals of different vibration elements to reach the target focus point O at the same time. At the focus point O, the sound beams of each vibration element are superimposed to obtain the largest sound beam signal.

The receiving process is the reverse process of the transmitting process; firstly, the target focus point is set, and the external receiver accurately delays the echo signals of different vibration elements according to the time difference between the target focus point O reaching different vibration elements, so that the The echo signals are added to concentrate the energy of multiple echo signals to obtain a larger echo signal amplitude.

Usually the reflection signal that meets the delay requirement on the sound path can be focused and strengthened. For some random reflection interference signals and noise, because they are not reflected according to specific reflection rules, they will not be superimposed. Therefore, useful reflection signals will be strengthened, interference signals will be suppressed, and the signal-to-noise ratio will be improved.

In actual detection, the embedding depth of the prestressed pipe is different, and the distance D from the transducer changes. At this time, the time delay of each ring is changed so that the focal length F is always equal to D, and the radiation sound field is always focused on the prestressed pipe. At the embedding depth of the stress pipe, dynamic focusing is realized, as shown in Figure 4. By controlling the time delay and amplitude of the transmitted signal on each vibration element to perform scanning imaging and dynamic focusing, the grouting quality inspection of prestressed pipelines with different embedding depths can be realized without changing the transducer.

The use of a vibration element array to combine transmission and reception increases the aperture of the sound source and improves the resolution of the far field. However, as the aperture increases, the diameter of the sound beam also increases in the near field area, which reduces the lateral resolution of the near field. . In response to this problem, the technique of changing the aperture is used to obtain good resolution in the near and far fields, as shown in Figure 5. When the detection target is relatively close, the central disk and fewer ring vibration elements are used to receive near-field echo signals to improve the lateral resolution of the near-field area. As the depth of the detection target increases, the outer ring vibration elements receive more Far-field echo signal to improve far-field lateral resolution.

In addition, this embodiment can also support the transmission and reception of signals by a single central disk vibration element without changing the software and hardware, that is, the detection mode of the single vibration element transducer.

The embodiments of the present utility model have been described above, which are only examples. Within the scope of not departing from the gist of the present utility model, omissions, additions, and changes can be made, and implemented in other ways. These changes should also be regarded as the scope of protection of the present utility model Inside.

Claims (5)

1. a ring-shaped ultrasonic array energy transducer, is characterized in that: comprise shell and the ring piezoelectric crystal array be located in shell and acoustic resistance matching layer; Described ring piezoelectric crystal array is rearranged by the spacing of multiple concentric ring piezoelectric crystal according to regulation; The upper and lower surface of described ring piezoelectric crystal is connected to electrode, and the ring piezoelectric crystal of connecting electrode is unit of shaking; Electrode towards concrete NDT face is located on acoustic resistance matching layer, is provided with pad absorbent treatment dorsad between the electrode in concrete NDT face and shell.

2. ring-shaped ultrasonic array energy transducer according to claim 1, is characterized in that: described ring piezoelectric crystal adopts piezoelectric ceramics.

3. ring-shaped ultrasonic array energy transducer according to claim 1, is characterized in that: the thickness of described ring piezoelectric crystal is λ/2, and the thickness of described acoustic resistance matching layer is the odd-multiple of λ/4, and λ is ultrasound wave wavelength.

4. ring-shaped ultrasonic array energy transducer according to claim 1, is characterized in that: described electrode is welded with wire.

5. ring-shaped ultrasonic array energy transducer according to claim 1, is characterized in that: described unit of shaking is connected with electronic switch.