NDTnet 1998 Aug, Vol.3 No.8

Abstract

To charakterise the scattering behaviour of different materials, especially from liquid dispersion, conventional ultrasound equipment in the frequency range of approximately 5 MHz was used. The control of all components and the evaluation of the results is realized by a PC and a "Lab View" based program. Many calculations are necessary, to provide information about the important parameters required in order to evaluate the necessary data include:
damping
scattering coefficient
loss factor
frequency dependence.

The equipment detects the backscattering signal in impuls-echo mode from the specimen. To reduce statistical deviation more then 30 single measurements were averaged. Diverse routines search for a part of the A picture, where the scattering signal remains undisturbed from echos especially from surfaces, membranes or interfaces. In this area the amplitude of the scattering signal can be described with an exponential function

y=a*exp(x) , with damping,
x delay,
a amplitude.

After the parameters of the transducer have been determined by a reference measurement, the program fits the mean scattering curve with an exponential function and calculates a and .

Another routine transforms every A picture within a frequency domain, averages and smoothes the frequency response. The damping of the various frequencies in the ultrasound wave is dependend on the size and nature of the scattering particles. The maximum of the the calculated frequency response will be shifted to lower frequencies and the differences to the reference curve of the transducer gives information about the structure of the scattering particles.

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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