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An approach to optimally determine the velocity of surface acoustic waves
distribution by creating a technique for carrying out the necessary measurements with
a variable step, using a contact transducer, is developed. The criterion of optimization
of the measurement step based on the characteristics of the research material and the
parameters of the measuring equipment is formulated. The method of achieving the
optimum measurement step is also proposed.
Methods for determining the distribution of the surface acoustic waves velocity
have been developed and created using an installation that allows measuring the
passage time of the surface acoustic waves with an error of several nanoseconds. The
developed methods have been tested during determination of the distribution of the
surface acoustic waves velocity in plastic deformed and hydrogenated low- carbon
steels.
It is experimentally found that the velocity of the surface acoustic waves
decreases in the case of plastic tensile deformation. It is also shown that the velocity
of surface acoustic waves decreases under hydrogenation from the gas phase.
Conducted studies of the porosity distribution show that with increasing the degree of
deformation the porosity increases, and the surface acoustic waves velocity decreases
too.
Key words: diagnostics, non-destructive testing, acoustic wave velocity, surface

acoustic waves, laser interferometry, piezoelectric transducers.