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in particular, roughness and waviness. A new algorithm of surface’s interferograms
processing is elaborated for selection of these components. This allows reconstructing and
analyzing surface reliefs of materials and structural elements with an error of no more than
5 nm.
Based on the proposed method, recommendations for the creation and production of
an optical 3D profilometer device have been developed. The created device possesses such
characteristics as fast recording and retrieval of surface relief with 11-14 grades of finish
according to ISO 25178-2:2012; extraction of the relief components, in particular,
roughness and waviness, variable area of observation, determination of geometric
parameters of roughness and waviness using arbitrary profile and (or) all observed surface
area.
The proposed method and corresponding equipment were used during the monitoring
of objects subjected to fatigue cyclic loads. Due to this method and the created equipment,
the fatigue process zone sizes near the stress concentrator were estimated. Additional
analysis of the observed area roughness changes allows predicting the site of a fatigue crack
initiation long before its appearance on the surface.
Also with the help of the proposed interferometric means a number of experimental
studies of the effect of hydrogen on the steel surfaces with different structures have been
carried out. According to the results of experiments, it was found that the effect of hydrogen
on steels with different structures is different. Blisters were created and the roughness
increased on the surfaces of studied steels, however the blister sizes, their density and
dynamics of changes were different for each material. Information on the time changes of

the steel surfaces with different structures after the action of hydrogen on them is necessary
to develop recommendations for materials to produce friction pairs and appropriate
lubricants, as well as to predict the service life of structural elements operating in working
environments.
In order to predict the surface roughness parameters of titanium alloy details after their
chemical-thermal treatment (nitriding and boriding), the influence of these technological
processes on the change in roughness was studied. In particular, for titanium ВТ 1-0 it was
found that the level of initial roughness and the temperature of the technological process
also influenced on the change in roughness. The surface roughness of details before and
after technological processes was estimated by non-contact method. It is established that
the surface roughness after chemical-heat treatment increases on average by two classes.

Key words: phase-shifting interferometry, surface relief, surface roughness, fatigue
process zone, fatigue crack, blisters.