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ABSTRACT
Semak P. M. Evaluation the condition of the material surface layers by
measuring the velocity of surface Rayley waves with different frequencies -
Manuscript.
The thesis is submitted for Ph.D. degree in technical sciences, speciality
05.02.10 - diagnostics of materials and constructions - Karpenko Physico-Mechanical
Institute, Lviv, 2020.
The dissertation work is aimed at solving important scientific and technical
problems of materials and designs diagnostics, namely – development of methods for
estimating the inhomogeneous near-surface layer of material for thickness based on
measuring the propagation speed of Rayleigh waves with different frequencies.
Degradation and almost all types of material processing begin with the
modification of the surface layer, and then change the properties of the material on
the internal volume of the sample (we are talking about mechanical processing, in
particular hardening, thermal, flooding, coating). Naturally, the urgent task is to
estimate the parameters of the inhomogeneous near-surface layer of material in
thickness. To solve this problem, it is adequate to use surface acoustic Rayleigh
waves at different frequencies. This is due to the fact that the depth of penetration of
the surface acoustic Rayleigh wave depends on the frequency of the probing signal,
and the speed, attenuation and "structure" of the Rayleigh wave are associated with
mechanical, thermal and other characteristics of the surface layer of material in which
it (wave) is propagating. Therefore, it is possible to obtain information about the state
of the surface layer of the material in thickness based on the speed, attenuation and
other parameters of Rayleigh waves at different frequencies.
An analytical review and systematic analysis of literature sources about modern
methods and means of measuring the parameters of surface acoustic Rayleigh waves
was done. Restriction on the use of surface acoustic Rayleigh waves of different
frequencies to determine the parameters of inhomogeneous near-surface layers in
thickness was set.
