The first chapter is the development history and advantages of ultrasonic phased array detection technology.
1. 1 development of ultrasonic phased array detection technology
In the 1920s, Soviet scientist S.J.Slkolov began to study ultrasonic imaging. Since then, due to various technical reasons, the research progress of ultrasonic imaging has been slow. With the rapid development of electronic technology and computer technology, the research and application of ultrasonic imaging have been greatly promoted. At present, in the field of nondestructive testing, there are mainly the following ultrasonic testing imaging methods that have been developed or are being studied.
1. scanning ultrasonic imaging: pulse ultrasonic echo (actually, the ultrasonic transducer converts the waveform of ultrasonic echo into electrical signal) can be displayed on the display screen in different display modes, including A-scan, B-scan, C-scan, P-scan and F-scan.
2. Ultrasonic holography: Based on the principle of wavefront reconstruction, that is, the pattern (hologram) formed by the interference of object wave and reference wave, and then the image of the object is obtained through the reconstruction process of inverse diffraction integration. Early ultrasonic holography imitated the principle of optical holography and used liquid level imaging. At present, the active research method of acoustic holography is scanning acoustic holography, which can be roughly divided into laser beam scanning acoustic holography and computer reconstruction acoustic holography.
3. Ultrasonic microscope: a system and technology for high-resolution imaging detection of acoustic discontinuities (such as defects, mechanical properties or microstructure changes) inside objects by using sound waves. Its principle is to irradiate the sample with high-frequency (working frequency can be as high as 2GHz) ultrasonic waves to form the distribution of micro-acoustic parameters of the sample and obtain high-resolution images of the surface and near-surface structure of the measured object.
4. Ultrasonic CT: Computed tomography is an ultrasonic imaging technology developed from X-ray CT. It uses a beam of ultrasonic waves to illuminate the object in different azimuth angles in turn, and at the same time detects the scattered wave of the target in the object (that is, projection), and then calculates the reconstructed image of the target through projection. At present, there are two main types of ultrasonic CT: transmission type and reflection type, and there are two theories of image reconstruction, namely, ray theory and diffraction theory.
5.ALOK ultrasonic imaging (amplitude and Lauf zeit orts kurven) technology, namely amplitude-propagation time-position curve technology. Using the amplitude-propagation time-position curve, the echo information from the defect is identified from the callback signal by the methods of propagation time compensation and signal superposition, and the noise signal is removed, and the defect image displayed in B mode is given.
6. Diffraction propagation time technology (TOFD): A technology that relies on the diffraction wave generated by the interaction between ultrasonic wave and defect end to detect and quantitatively detect defects, which can display a-scan, d-scan and b-scan gray-scale images.
7. Synthetic Aperture Focusing Technology (SAFT): An ultrasonic detection technology with high spatial resolution by using a small aperture transducer and low working frequency, which can work in the near field and realize three-dimensional imaging.
8. Ultrasonic phased array imaging: By controlling the time delay of the excitation (or reception) pulse of each array element in the array transducer, the phase relationship of the acoustic wave emitted (or received) by each array element when it reaches (or comes from) a certain point in the object is changed, so as to realize the change of focus and beam direction, thus completing phased array beam synthesis and forming an imaging scan line. It can image A-scan, B-scan, C-scan, P-scan and 3D-scan.
Up to now, ultrasonic phased array technology has a development history of nearly 20 years. Initially, it was mainly used in the medical field. In medical ultrasound imaging (as shown in figure 1- 1), phased array transducer is used to quickly move the sound beam to image the examined organ (as shown in figure 1-2), while high-power ultrasound uses its controllable focusing characteristics to locally heat the tumor, thus heating the target tissue and reducing the power absorption of non-target tissue. Firstly, the complexity of the system, the complexity of wave propagation in solid and the high cost limit its application in industrial nondestructive testing. However, with the rapid development of electronic technology and computer technology, ultrasonic phased array technology is gradually applied to industrial nondestructive testing.
Figure 1- 1 medical phased array equipment figure 1-2 organ examination
In recent years, ultrasonic phased array technology has attracted more and more attention because of its flexible beam deflection and focusing performance. Due to the comprehensive application of piezoelectric composite material, controllable nanosecond pulse signal, data processing and analysis, software technology and computer simulation in the field of ultrasonic phased array imaging, ultrasonic phased array detection technology has developed rapidly and is gradually applied to the field of industrial nondestructive testing.
In terms of ultrasonic phased array imaging detection instruments and equipment, foreign countries are committed to developing phased array detection systems and equipment, such as SONOTRON NDT Company of Israel, R/D TECH Company of Canada, GE Company of the United States, OLYMPUS Company of Japan, SONATEST Company of the United Kingdom and British Technology Design Company. And successfully developed in the field of nondestructive testing in all walks of life.
Job application. At the same time, many companies in China are studying ultrasonic phased array detection equipment, such as Guangzhou Dopp Electronic Technology Co., Ltd., Shantou Ultrasonic Research Institute, Wuhan Zhongke Innovation Technology Co., Ltd., etc. These equipment have been put into production and promoted in the market gradually.
Advantages of 1.2 ultrasonic phased array detection
Compared with other nondestructive testing methods, ultrasonic phased array testing has the following advantages:
1) electronically controls the focusing and scanning of sound beam, and the detection speed is doubled;
① The direction of ultrasonic beam can be changed freely;
② The focus can be adjusted, even dynamically focused;
③ Ultrasonic sector scanning or line scanning can be realized when the probe is fixed;