NDTnet 1998 Aug, Vol.3 No.8

Full-Text - Abstract

Materials characterization by the backscattered ultrasonic signal in the time domain has been widely used [1], and recently, frequency domain analysis has a growing interest. This paper deals with the theoretical background of cast iron characterization by the backscattered spectrum. The formulation takes account of the scattered power by graphite precipitates and the associated attenuation by them (first order multiple scattering). The model of scattering used was proposed by Ying and Truel [2] for an elastic sphere in an isotropic elastic solid for incident wavelength much larger than the scatter diameter (Rayleigh domain). Numerical values for the cast iron case are analyzed and it was found that the graphite dimension and concentration could be readily evaluated by the analysis of the backscattered spectrum. Figure 1 illustrates the effect of scattering and attenuation on the spectrum for two graphite sizes. The transducer bandwidth must be as wide as possible to cover much of the cast iron range of microstructures.

Figure 1 - Theoretical spectrum of the backscattered ultrasonic signal for two graphite sizes

1 . Goebbels, K Research Techniques Non Destructive Testing, 1980, 4: 87-157.
2. Ying, C. F. and Truel, R. J. Appl. Phys. 1956, 27: 1086-1097

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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