| ABSTRACT: | DAMAGE AND MAGNETIC PARAMETERS OF STEEL AFTER PLASTIC
DEFORMATION UNDER HYDROSTATIC PRESSURE
E. Gorkunov, S. Smirnov, and S. Rodionova.
Institute of Engineering Science, Russian Academy of Sciences (Urals Branch), Yekaterinburg,
Russia.
Plastic deformation of steel parts in course of production followed by severe operation conditions can
result in metal discontinuity. Generation of microdefects is followed by partial relaxation of plastic
energy.
The purpose of this study is to study the feasibility of magnetic inspection for monitoring metal
structure damage. Measurements were made on carbon steel with 0.2% C. To slow down the
generation of microdefects, the samples were subjected to tension in a test chamber with hydrostatic
pressure ranging from 0.1 to 500 MPa. Magnetic parameters were obtained from minor hysteresis
loops measured by the ballistic method. Accumulation of microdefects was evaluated by the change in
the density of strained metal.
The sophisticated experimental procedure has made it possible to separate alterations of magnetic
parameters induced by the growth in the degree of strain from those caused by density loss due to the
accumulation of microdefects. Magnetic parameters have been shown to depend upon two competing
processes – hysteresis parameters increase with the number of pinning points for domain wall
movement, but they tend to decrease due to the loss of magnetoelastic energy in local areas of elastic
relaxation.
The research conducted reveals a relation of remanent induction Br and coercive force Hc to strain
degree, density variation and the analytical parameters of the damage mechanics. The relationship
obtained may be used for magnetic inspection of complex technical systems. By estimating the current
value of damage and the loading conditions in operation, one can predict the residual lifetime of a steel
part in terms of an appropriate model of the mechanics of damage.
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