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Laser ultrasonic technology and its applications

Magnitude and nature of sound waves. ~ Application of this technology to show the first 17 out of physics and wave propagation of body waves to detect internal defects and shake the sample structure. Interfere with the sample surface is detected directly measured as a Michelson interferometer in the mirror Xiao, principles,[link widoczny dla zalogowanych], shown in Figure 4 Journal of focused laser beam irradiation surface of the sample, the incident laser beam reflected by the surface and with the light source isolated from the reference beam interference occurs, so that the occurrence of beam shift out of the detector shift. To measure the vibration displacement of the sample. If the reference in the introduction of shift system Xiao constitutes heterodyne detector, it actually has more frequency bands, can be detected on the rough surface, and the environment, has strong anti-interference ability vibration. Figure 4 Ultrasound examination oak interference optical system 6 emblem ultrasound technology introduces the week here in the light body of Che ultrasonic nondestructive testing of materials and evaluation. Conventional ultrasonic testing, ultrasonic pulse and the sample directly from the piezoelectric coupling Taiwan Sheng transducer or pressure generated. The transducer bandwidth limitations and the vase itself transducer coupled with the specimen, the sound effects, unlikely to produce a very narrow single ultrasonic pulse. Laser ultrasonic piezoelectric transducers to overcome the disadvantages of ultrasonic testing of opium. Non-contact laser ultrasonic method can not fling detection of objects, the laser emission Juan Tan to the distance between the keys can be achieved 10rz), and laser hair Cambodia to do very small. It can detect objects one can not close, such as high temperature,[link widoczny dla zalogowanych], high pressure, toxic or radioactive and other harsh environments of various objects. Without any coupling the laser ultrasonic Taiwan Jing, so. Coupling Taiwan Taiwan Jing volatility and reliability of vehicles and the matching problem does not exist. Be detected on the test site and also will limit the temperature of material removed. Reported the laser ultrasonic pulse width narrow, up to 1ns, catch a blind impulse of magnitude up to the width of the zygomatic things GHz, while the corresponding cross section only a few meters long. Greatly enhanced the ability of small defects Juan exploration. In addition, the laser ultrasonic testing parts of the requirements to be reduced. For those surface roughness, curvature and geometry of complex objects could be detected. The object with laser ultrasound can also be single-sided thickness measurement of non-connected Zha. In solids, using conventional ultrasound velocity measurement accuracy is about the absolute O. 2%, but the use of laser ultrasonic measurement accuracy can be improved 1O times. Thin materials can also be detected and Juan thick. 7 Results Cambodian language has many outstanding features of laser ultrasound. The development and application is quite optimistic. But there are some pressing problem. First, the ultrasonic energy from the laser energy conversion efficiency J. To increase the intensity of light induced ultrasound. Can increase the energy of laser radiation, but not too much, otherwise it will damage the surface of Juan key. Optical sound transfer to improve efficiency. Can also improve the efficiency of light absorption, light scattering less manpower base, preliminary research on apes in the sample surface coatings of different liquids. Flooded layer can enhance the absorption of light energy. Second,[link widoczny dla zalogowanych], detection sensitivity of ultrasonic signal light emblem�� same title. If the optical detection of laser ultrasonic signal is particularly high sensitivity, which in turn can reduce the excitation of laser ultrasonic signals do work requirements. As the limitations of the transducer testing, not suitable for Taiwan, ultrasonic signal detection of light logo, it should be made the morning school detection, optical detection method is particularly suitable for Taiwan in the short pulse laser generated broadband ultrasound. However, the various optical detection sensitivity than the transducer is low, thereby increasing the sensitivity of optical detection is one of the current development trends. If the above two issues have been resolved, the laser ultrasonic technique will be more widely used. 8 �� Covent more 11nAC. Soft dPhy5RevL seven c ��, 19B4,[link widoczny dla zalogowanych], 53 (6); 5602 terephthalic and so on. Tian Li, 1994.23 (4) :227 - 2303zaphW,[link widoczny dla zalogowanych], etl1. ApplP} L VII c ��, 1982,40 ~ 3104AD, etdApplPhys. 1992. B54: 765 Yin Qing glass and so on. Photoacoustic thermal technology ugly its application. Beijing: Science Press l991 (on the next page 39) As the above calculation of the soil system entropy eliminate time and space conditions, crop species and their natural factors {electronic puppets soil fertility evaluation. Thus comparability. Evaluation of soil fertility in this way, only reflects the structural condition of the soil, but also reflects the level of the input energy is available. Soil fertility evaluation to achieve ecological and economic benefits of Chi Taiwan, which for the evaluation of soil fertility, fertilizer provides scientific guidance and ten new ways and means. 4 �� 1 Chen Po Covent more brother. Speech densely populated areas of farmland under the Yangtze River ecosystem structure Yuk consumption drum Jiangsu Agricultural College, 1987.8 (2) :33-382 Wang Xudong, Hu Tian-Tian, Zhang and so on. Department of loess soil paste of the original Yu-Po, the study of arid areas of sleep students. 1996,14 (3): 16 ~ 19