FIFTH CANADIAN CONFERENCE ON NONDESTRUCTIVE ... - IAEA

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FLAW CHARACTERIZATION USING THE TIME-OF-FLIGHT METHOD AND
ULTRASONIC FREQUENCY ANALYSIS
V.K. Mak
EnzKgij, Mitiei and Re.ioun.ce.i, Ottawa, Ontanio
ABSTRACT
The time-of-flight method and ultrasonic frequency analysis are valuable tools
for measuring the sizes and shapes of defects. Experiment work was carried
out using both methods simultaneously to measure the diameter and orientation
of circular rods with diameters ranging from 2 mm to 7 mm. A 5 MHz broadband
transducer was used as a transmitter/receiver. Each rod was immersed in a
water bath and located in the far field region of the transducer. The difference
in travel time (At) from opposite edges of the circular rod was measured.
Sound waves diffracted from the circular scatterer were analyzed at
the same time to yield a frequency spectrum and the spacing between consecutive
frequency maxima (Af) was determined. The measurements were repeated by
changing the orientation of the transducer, Both methods have the capability
to determine independently the diameter and orientation of the circular rods.
It was also shown that the product AtAf is approximately equal to 1. Time and
frequency are mutually complementary variables. The two parameters can reinforce
each other in terms of the information each one produces. A merger
of the time-of-flight method and ultrasonic frequency analysis will provide a
powerful nondestructive testing method in the future.