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The thesis is submitted for Ph.D. degree in technical sciences, speciality 05.02.10 –

Diagnostics of Materials and Constructions (132 – Materials Science). – Karpenko

Physico-Mechanical Institute of the National Academy of Sciences of Ukraine, Lviv,

2019.

The dissertation is aimed at solving the significant scientific and technical problem

consists in the development of the method for diagnostic of the condition of the long-

term exploited ferromagnetic elements of constructions on the parameters of the signal

of magnetoelastic acoustic emission (MAE). This method is based on the analysis of the

mechanism of generation of the MAE, selection and substantiation of the statistical

model of the registered signal, development of effective algorithms for processing the

result of the received signals as well as the method for diagnostic of ferromagnetic

objects.

Today in the industrial complex of Ukraine, a relevant problem is the diagnostics

of the condition of metal products and structural elements, as well as equipment, which

has completed its design resource and needed replacement. Most of equipment in the

industrial sector is made from steels that are ferromagnetic materials. Contacting during

long-term exploitation with a medium which contains hydrogen or hydrogen sulfide,

undergoing temperature changes, environmental influences and natural factors, and also

stresses influences, ferromagnetic materials are degraded losing their strength properties
and characteristics.

To improve the quality of technical diagnostics of the state of the materials from
which these products are made, it is necessary to develop and apply new methods and

means of non-destructive testing. A perspective diagnostic method is the MAE method,

which occurs during the re-magnetization of the ferromagnet and is associated with the

jump motion of non-180° domain walls.

The dissertation presents a mathematical model of motion of non-180° domain

wall during the ferromagnetic re-magnetization based on the energy approach is

developed. The relation ship between parameters of the jump of non-180° domain wall

and the parameters of the MAE signal and the tested ferromagnetic material is

established.