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Thesis for the scientific degree of Candidate of Technical Sciences (PhD) on

speciality 05.02.10 – diagnostics of materials and structures. – Karpenko Physico-

Mechanical Institute of the National Academy of Sciences of Ukraine, Lviv, 2021.

The new solution of the scientific and technical problem of monitoring the surfaces

of materials and structural elements that work under cyclic loads and in working

environment is proposed in the thesis. This solution is based on the analysis of the surface

relief changes on nano- and microlevels.

To solve this task, a three-step phase-shifting interferometry method and respective

means of its implementation are developed that allow retrieving the surface relief in speed

mode. It is proposed to analyze both the total retrieved surface relief and its components,

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