V. N. Kostin

Portable instruments for multiparameter magnetic evaluation of material structures

The principles of operation and capabilities of portable computerized testing facilities of the MMT and SIMTEST series, which are intended for multiparameter magnetic evaluation of the structure of ferromagnetic articles of different dimensions, are described.

Possibilities of magnetic inspection of plastic deformations preceding failures of low-carbon steels constructions

The possibility of magnetic inspection of plastic deformations preceding the failure of strained steel constructions was studied by locally magnetizing them with an attachable electromagnet. Field dependences of the differential magnetic permeability of a plate made of steel 09Γ2 on the applied and residual stresses were determined. Critical fields of 90° and 180° domain-wall motion at different degrees of deformation were calculated using a model taking into account the contribution of these domain walls to magnetization reversal processes. Dependences of the coercive force and residual magnetization of the plate on the applied and residual stresses, which were measured using a SIMTEST portable magnetic measuring system, are reported.

Irreversible changes in the magnetization as indicators of stressed-strained state of ferromagnetic objects

The changes in the magnetic properties of low-carbon steels connected with reversible and irreversible magnetization reversal processes under the action of elastic stresses are studied. It is shown that, on the curve of return from the coercive force, the maximal irreversible increment in the magnetization corresponds to the zero values of applied stresses. The application of compressive stresses leads to a sharp decrease in the irreversible component of the magnetization increment. Tensile stresses influence slightly the proportion between reversible and irreversible processes. New possibilities for the multiparametric quasi-static evaluation of stressed-strained states of ferromagnetic objects are revealed.

Magnetic and magnetoacoustic testing parameters of the stressed–strained state of carbon steels that were subjected to a cold plastic deformation and annealing

A complex of magnetic and magnetoacoustic properties of cold-deformed and annealed (at different temperatures) steels with carbon contents of 0.2 (20 steel) and 0.7% (70 steel) was investigated. It was established that as the annealing temperature of these steels increases up to 700°C, the values of the parameters that are related to the intensity of irreversible magnetization-reversal processes monotonically increase. It is shown that the coercive force of 70 steel changes nonmonotonically under variations in the annealing conditions and cannot be a testing parameter. Among quasi-statically measured magnetic parameters for testing the annealing procedure, the residual induction and the coercivereturn induction can be used. The structural sensitivities of such parameters of the magnetoacoustic emission (MAE) as the amplitude, the fundamental frequency, and the field of the MAE maximum were investigated. It is shown that the MAE maximum amplitude and field correlate with the residual magnetic induction of the substance of the investigated steels and can be used in the diagnostics.

Multiparameter Methods for Structural Analysis of Steel Articles Using the Magnetic Properties of Substances

The potentialities of multiparameter testing for the determination of the physical and mechanical properties of steel articles based on measurements of the magnetic characteristics of the substance have been shown. The most likely testing parameters have been determined. Information about a small portable MMT-2 magnetic multitester, which allows rapid measurements of the relative magnitudes of the magnetic properties of a substance to be taken, is presented.

Simulation of field and inductance spatial distribution in locally magnetized massive objects and optimization of U-shaped transducer design

The field and magnetic-inductance spatial distributions in plates that differ in geometric dimensions and magnetic properties, which were magnetized locally by U-shaped electromagnets of different standard sizes, were calculated using the finite element method. The magnetic-flux side scattering, which impedes the magnetization, was estimated qualitatively. Recommendations on designing magnetizing instruments, which are characterized by low side scattering, are given.

Measurements of Relative Magnetic Parameters of Materials in Tested Components Incorporated in Closed Circuits

The paper is dedicated to the feasibility of measurements of magnetic parameters of tested components incorporated in closed circuits with ferromagnetic transducers in the capacity of magnetic flux meters and the technique based on the conversion of the measured flux to a magnetic field intensity in an opening of a certain configuration made in the magnetic conductor of an applied electromagnet.

The topography of the field and flux inside and above the surfaces of ferromagnetic plates during their contact and contactless magnetization

Modeling and experimental studies of the spatial distributions of the field and flux inside and above the surface of ferromagnetic plates of different dimension types, which were locally magnetized by U-shaped electromagnets, were performed. It was established that the location of a magnetic inhomogeneity in the interpole zone of an electromagnet substantially affects the results of a local measurement of the coercive force using a demagnetization current. It is shown that the presence of a gap in the magnetic circuit impairs the magnetization of the interpole zone of an object to a higher degree than the magnetization of the near-pole zone. Recommendations on the concentration of the magnetic flux in the interpole zone via a decrease in the interpole distance of the electromagnet are given. Possible locations of internal-field probes that provide local measurements of the magnetic properties of a substance are determined.

On new possibilities for making local measurements of the coercive force of ferromagnetic objects

The possibility of reducing the influence of both the gap in a transducer-object combined circuit and the shape of tested objects on the results of local measurements of their coercive force is investigated. It is shown that additional measurements of the maximum magnetic flux in the circuit and the tangential component of the magnetic field on the surface of the tested area of the object, which is retained after the magnetizing current is turned off, allow a substantial decrease in the corresponding errors.

Local measurement of the coercive-return induction in the presence of a gap in the transducer-object combined circuit

The possibilities of making local measurements of the coercive-return induction of ferromagnetic objects of different dimensions in a closed combined transducer-object circuit and in the presence of a nonmagnetic gap in this circuit are investigated.