Chapter I ultrasound phased array detection technology development history and advantages
1.1 ultrasound phased array detection technology development history
The 20th century In the 1920s, the Soviet scientist S.J. Slkolov has begun the study of ultrasound imaging. Subsequently, due to various technical reasons, ultrasonic imaging research progress was slow. Later, with the rapid development of electronic technology and computer technology, the research and application of ultrasonic imaging has been greatly promoted. At present, in the field of nondestructive testing, ultrasonic detection imaging methods that have been developed or are being studied are mainly the following.
1, scanning ultrasound imaging: pulsed ultrasound echo (actually ultrasound echo through the ultrasound transducer converted to electrical signal waveform) in the display can be displayed by different ways, including A-type, B-type, C-type, P-type, F-type scanning display.
2, ultrasound holography: based on the principle of wavefront reconstruction, that is, through the interference of the object wave and the reference wave formed by the pattern (hologram), and then after the reconstruction process of the anti-diffraction integral, to obtain the image of the object. Early ultrasonic holography mimicked the principle of optical holography, using a liquid surface imaging method. The more actively researched acoustic holography method is scanning acoustic holography, which is broadly divided into two categories: laser beam scanning acoustic holography and computer reconstruction acoustic holography.
3, ultrasound microscopy: the use of acoustic waves on the object within the acoustic discontinuity (such as defects, mechanical properties or microstructural changes, etc.) for high-resolution imaging and detection of the system and technology. The principle is to irradiate the sample with high-frequency (operating frequency can be as high as 2GHz) ultrasound, the formation of samples of the micro-acoustic parameters of the distribution, can be measured on the surface of the object and the near-surface structure of the high-resolution image.
4, ultrasound CT: computerized tomography ultrasound imaging, it is borrowed from the X-ray CT and the development of ultrasound imaging technology. It uses a beam of ultrasound waves sequentially along different azimuths to irradiate the object, and at the same time to detect the object in the target scattered waves (i.e., projection), and then by the projection to calculate the inverse reconstruction of the target's image. At present, there are two main types of ultrasound CT, transmission type and reflection type, and there are two theories of image reconstruction, ray theory and diffraction theory.
5, ALOK ultrasound imaging (amplituden and laufzeit orts kurven) technology, that is, amplitude - propagation time - position curve technology. The use of amplitude - propagation time - position curve, through the propagation time compensation and signal superposition method, from the callback signal to identify the echo information from the defect and remove the noise signal, and can give a B-type display of the defect image.
6, diffraction propagation time technology (TOFD): rely on ultrasonic and defect end interaction of the diffraction wave issued by the defect to detect defects and its quantitative detection technology, and can give the A-type scanning display and the D-scan, B-scan grayscale image display.
7, synthetic aperture focusing technology (SAFT): the use of small aperture transducer and lower operating frequency, in order to obtain high spatial resolution of an ultrasonic detection technology, can work in the near-field area, and can realize the characteristics of three-dimensional imaging.
8, ultrasound phased array imaging: by controlling the array transducer in each array element excitation (or receive) pulse time delay, change by the array element emission (or receive) sound waves to reach (or from) the object at a certain point in the phase relationship to realize the focus point and the change in the orientation of the acoustic beam, so as to complete the phased-array beam synthesis, the formation of imaging scanning line of the technology can be given to the A-type, B-type, C-type, P-type and 3D scanning imaging. type A, B, C, P and 3D scanning imaging.
To date, ultrasound phased array technology has nearly 20 years of development history. Initially, it was mainly used in the medical field, medical ultrasound (see Figure 1-1) imaging with a phased array transducer to rapidly move the sound beam to the examined organ for imaging (see Figure 1-2), and high-power ultrasound to use its controllable focusing characteristics of the local heating thermotherapy for cancer treatment, so that the target tissues are warmed up and to reduce the absorption of power in non-target tissues. Initially, the complexity of the system, the complexity of fluctuation propagation in solids, and the high cost have limited its application in industrial nondestructive testing. However, with the rapid development of electronics and computer technology, ultrasonic phased array technology has been gradually applied to industrial nondestructive testing.
Figure 1-1 Medical phased array equipmentFigure 1-2 Organ inspection
In recent years, ultrasonic phased array technology has attracted more and more attention with its flexible beam deflection and focusing performance. Due to the piezoelectric composite materials, nanosecond pulse signal can be controlled, data processing analysis, software technology and computer simulation and other high-tech in the field of ultrasonic phased array imaging in the comprehensive application of ultrasonic phased array inspection technology can be rapid development, and gradually applied to the field of industrial non-destructive testing.
In terms of ultrasonic phased array imaging detection equipment, there are Israel SONOTRON NDT company, Canada R/D TECH company, the United States GE company, Japan OLYMPUS company, the United Kingdom SONATEST company, the United Kingdom Technology Design company, etc. committed to research and development of phased array inspection system equipment, and has been in the All walks of life in the field of non-destructive testing has been successful
Application. At the same time, there are also many companies in the domestic research on ultrasonic phased array inspection equipment, such as Guangzhou Doppler Electronic Technology Co.
1.2 Advantages of Ultrasonic Phased Array Inspection
Ultrasonic Phased Array Inspection has the following advantages in comparison with other non-destructive testing methods:
1) Adopting the electronic method to control the focusing and scanning of the acoustic beam, and the inspection speed is improved exponentially:
1) The direction of the ultrasonic beam can be freely changed;
2) The focal point can be adjusted and even realize dynamic Focus;
3) the probe can be fixed to realize the ultrasonic fan scanning or line scanning;