A NEW METHOD TO ENHANCE THE RESOLUTION OF ULTRASONIC TESTING
Yan-Rongming*, Zhou-Guangping and Qiu-Wenbin *Shenzhen Airlines, P. R. China Nanchang Institute of Aeronautic Technology
Keywords: digital signal processing, spectrum, cross correlation, resolution, ultrasonic testing
ABSTRACT
The theory and technology to enhance the resolution of ultrasonic testing by means of digital signal processing technique is introduced in this paper. A microcomputer with 20MHz sampling frequency is used to sample and then process the signals which are obtained by a conventional analog ultrasonic flaw detector with a 2.5MHz longitudinal wave probe. The experiment results show:
The far-field resolution (the ability to distinguish two flaws closely spaced in the direction of the wave propagation) may be improved by spectrum analysis (two narrow slots which is 2mm wide respectively and 2mm apart may be distinguished clearly);
The up-surface resolution (the ability to discover flaw near to the test surface) may be enhanced by cross correlation analysis (a 1mm diameter flat-bottomed hole which bottom is 2.5mm deep from the up-surface may be detected easily);
The bottom-surface resolution (the ability to discover flaw near to the opposite surface of the workpiece) may be a improved by cross correlation analysis also (a crack which is 3mm deep from the bottom surface may be detected easily).
Publication Source: Trends in NDE Science & Technology; Proceedings of the 14th World Conference on Non-Destructive Testing, New Delhi, 8-13 December 1996.Vol. 4, pages 2165 - 2168 Publisher:Ashgate Publishing Company
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