NDTnet 1998 Aug, Vol.3 No.8

Abstract

The acousto-optic technique is based on the interaction of laser light with ultrasound and is focusing on the phase difference between the incident and the reflected ultrasound. From numerical calculations it is seen that even for low frequency ultrasound, the phase information is extremely sensitive to specific characteristics of the material when ultrasound is incident in a critical angle of the investigated material. The phase information as well as the critical angle detection is obtained using laser light. The diffraction area appearing when light is diffracted by ultrasound can be separated into two regions: the optical near field and the optical far field. From the acousto-optic theories it is known that the near field diffraction zone obtains an exact image of the ultrasonic field, so when the phase is altered by changes in the physical properties of the material, the acousto-optic technique can measure it A systematic study has been carried out on hardened steel bars and copper plates with varying grain sizes respectively to measure the hardness profile or changes in the microstructure in a nondestructive way and to control/evaluate the grain size of copper plates. This study opens new markets for the AO-technique to control the microstructural quality of products for which NDT is the only way allowed to achieve this information.

Abstract Source:
Book of Abstracts, 7th European Conference on Non-Destructive Testing, 26-29 May 1998, ISBN: 87-986898-0-00

Full-Text Source:
Proceedings of the 7th European Conference on Non-Destructive Testing, 26-29 May 1998, ISBN:

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