Page 27 - НАЦІОНАЛЬНА АКАДЕМІЯ НАУК УКРАЇНИ

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диагностирования не более 11%.
Ключевые слова: ферромагнитный материалл, доменная стенка, магнитное
поле, магнитоупругая акустическая эмиссия, математическая модель, информа-
тивные параметры сигнала, алгоритмы оценки, методика диагностирования, нап-
ряженное состояние.

ABSTRACT

Melnyk N. P. Development of the method of magnetoelastic acoustic emission for
the state diagnostics of long-term exploitation of the ferromagnetic construction
elements. – 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 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.
Based on the energy approach, a mathematical model of motion of 90° domain wall
during the ferromagnetic re-magnetization is developed. The relation ship between
parameters of the jump of 90° domain wall and the parameters of the MAE signal and the
tested ferromagnetic material is established.
Distinct features of the MAE signal are found, in particular, the random occurrence of

individual events in time, time boundedness, and amplitude randomness. The model of the
MAE signal in the framework of statistical model of the random impulse flow is
developed. The impulse, time and spectral characteristics of the pulse signal at the output
of the primary piezoelectric converter are singled out.
Informative parameters of the MAE signal and algorithms for their estimation
together with an experimental verification have been proposed and substantiated. High
sensitivity of these parameters to structural changes of ferromagnetic material, influence of
physico-chemical and mechanical factors, parameters of the re-magnetizing field is
revealed.
Based on the proposed informative parameters of the MAE signal, the technique for
diagnostic of the stress state of ferromagnetic materials is developed and its experimental
testing on long-term exploited pipe steels is carried out. This technique makes it possible
to identify areas of residual stresses and in practice provide an error less than 11%.
Keywords: ferromagnetic material, domain wall, magnetic field, magnetoelastic
acoustic emission, mathematical model, information parameters of the signal, evaluation
algorithms, diagnostic method, stress state.