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examined and the influence of residual after welding stresses in the vicinity of the

welded joint and stressed areas of the control objects on the change of the amplitude of

signals of magneto-elastic acoustic emission is evaluated.

At the based of the development of the MAE method in the dissertation are the

following the scientific results.

The mechanism of generation of magnetoelastic acoustic emission is analyzed,

which allows us to associate the signal parameters with the characteristics of the studied

ferromagnetic material and singled out its characteristic features such as random occur-

rence of individual events in time, time boundedness, and randomness of amplitude.

A pulsed model of the recorded signal is developed based on an analysis of the

mechanism of generation ofmagnetoelastic acoustic emission, which takes into account

its characteristic features and in addition to measure traditional ones, allows for using

statistical characteristics, in particular, the parameters of the amplitude and time

distribution functions.

The informative parameters of the MAE signal are substantiated and algorithms for

their estimation are proposed. Based on theseresults it is established at the first time

thatthe amplitude of the pulses of the MAE signal is distributed according to the

exponential law, which makes it possible to use its parameter as informative in the

diagnostic of ferromagnetic objects.
The impact of re-magnetization conditions on the change of signals parameters

ofmagnetoelastic acoustic emission is established. This makes it possible to develop
means and algorithms for stabilization of the re-magnetization current amplitude and the

re-magnetisation field inductionthat optimizes the signal registration procedure and

ensures the comparability of diagnostic results.

A new applied technique to diagnosing the stress state of feromagnetic materials

by the damping parameter of the exponential distribution of the amplitudes of the MAE

signal is developed. This technique is experimentally tested on long-exploitation pipe

steels, which allows for more accurate estimation of residual stresses in the material.

The practical significance of the obtained results is that the based on theoretical

and experimental examination, a relevant scientific and technical problem which