A permanent-magnet-based attached instrument used to inspect articles on the basis of their coercive force

An attached magnetic instrument that uses two permanent magnets to magnetize and demagnetize an article is considered. When one of the magnets is set at a fixed angle, the rotation angle of the other magnet is proportional to the coercive force of an article and is used as the tested parameter.     

Features of electromagnetic methods for testing the wear resistance of medium-carbon structural steel subjected to laser or bulk hardening and tempering

Features of applying attachable eddy-current transducers of two types (with a flat end surface and a protruding ferrite rod core with localities 5–6 and 3–4 mm in diameter, respectively) for testing the structural state, hardness, and abrasive wear resistance of structural steel 45X (0.45 mass % C and 0.85% Cr), which was hardened under the action of continuous laser radiation, have been studied. The feasibilities of the eddy-current and coercimetric techniques for evaluating the wear resistance of a medium-carbon steel subjected to laser or bulk hardening and tempering in the temperature range 75–600°C have been studied.     

Possibilities of Nondestructive Testing of Physico-Mechanical Characteristics of Hypereutectoid Carbon Steels with the Structures of Isothermal Austenite Decomposition

The possibilities of estimating the hardness, the wear resistance under abrasive action and sliding friction, the impact strength, and the internal stresses of the U9 steel (with 0.94% of carbon) with the initial fine-lamellar pearlite structure annealed at 650°C during 2–600 min on the basis of magnetic and electrical characteristics, readings of an eddy-current instrument, and parameters of electromagnetic-acoustic conversion are studied. A comparative analysis of the magnetic, electromagnetic, strength, and tribological characteristics of the U10 and U15 hypereutectoid steels (with 1% and 1.53% of carbon, respectively) subjected both to isothermal treatment at 330–650°C (with formation of pearlite and bainite structures) and to additional short-time annealing at 650°C is carried out.     

Possibility of Nondestructive Testing of Operational Heating of Contact Surfaces of Rolling Bearings

The coupling between variation of parameters of nondestructive testing and heating of rolling bearings associated with their operation regime in a helicopter reduction gear is demonstrated. The coercive force method and the eddy-current method of testing outer bearing rings made from ShKh15 steel are considered.     

Evaluating the Wear in Steel-Steel and Iron-Iron Friction Pairs by the Eddy-Current Method

Results of a study of steel-steel and iron-iron friction pairs by eddy-current and X-ray methods are reported. An eddy-current transducer is shown to yield a generalized characteristic of changes in the properties of a surface layer in the process of its wearing. Similar results are obtained by the X-ray investigation of the same layer. A correlation between readings of an eddy-current device and the magnitude of the linear wear in the contact zone of tribological coupling is shown to exist at the stage of steady-state and intensive wear.__________Translated from Defektoskopiya, Vol. 41, No. 4, 2005, pp. 17–24.Original Russian Text Copyright © 2005 by Gorkunov, Kharlamov, Kogan, Zadvorkin.Dedicated to the 100th Anniversary of the Birthday of Corresponding Member of the Russian Academy of Sciences M. N. Mikheev     

The influence of elastic deformations on the hysteresis properties of a two-layer ferromagnet composed of components with magnetostrictions of opposite signs

The influence of an elastic deformation that is produced by an uniaxial extension (compression) on the behavior of several magnetic characteristics of Armco iron and nickel, whose magnetostrictions have opposite signs, and a two-layer material composed of them was studied. The magnetic characteristics were measured both under the conditions of a closed magnetic circuit and using attachable transducers along and across the direction of an applied load. The results are explained from the standpoint of the formation of magnetic anisotropy, which is induced by the action of normal stresses. The results of measurements of the hysteresis and magnetostriction properties of the investigated materials are compared. The magnetic parameters of the investigated materials that monotonically change with an increase in the applied stresses are determined.     

Study of arrangement efficiency of hall sensors of an attachable magnetic instrument used for recording the coercive force of a local area of an article

The use as a tested parameter of a coercimeter of the demagnetizing current that is measured at the moment of zero crossing of the magnetic flux in the magnet core by Hall sensors arranged under the electromagnet poles is shown to have an advantage over the use of the demagnetizing current measured at equal readings of Hall sensors placed in the neutral plane of the electromagnet in the leakage flux at different distances from an article.     

The peculiarities of magnetic and eddy-current testing of quenched structural steel hardened by nanostructuring frictional treatment

This paper deals with the study of the potential of the magnetic and eddy-current methods for the assessment of the structural state of hardened wear-resistant layers on the surface of quenched medium-carbon structural steel 50 (0.51 wt % C) that is subjected to frictional treatment by a sliding hemispherical hard-alloy indenter. It is found that the presence of a thin ～220 μm hardened wear-resistant layer on the surface of quenched steel 50 can be verified by readings of an eddy-current instrument, as well as by values of the coercive force (for major and minor magnetic hysteresis loops) and the residual magnetic induction (for minor magnetic hysteresis loops if measurements are carried out in weak magnetic fields). The eddy-current method has the highest susceptibility to the structural transformations caused by frictional treatment.     

On the efficiency of application of magnetic and electrical parameters for nondestructive testing of crystal-lattice microdistortions in heat-treated carbon steels

The effect of crystal-lattice microdistortions that characterize residual stresses in heat-treated steels that contain 0.36, 0.62, and 0.75% carbon on their magnetic characteristics, in particular, magnetic Barkhausen noise parameters, electrical resistivity, and elastic wave propagation velocity, which was determined by the electromagnetic acoustic transformation (EMAT) method, was studied. The coercive force and number of Barkhausen jumps for hardened steels are shown to correlate, to a great extent, with the average grain size rather than with crystal-lattice mirodistortions. Crystal-lattice microdistortions induced in steels upon hardening from different temperatures correlate adequately with the root-mean-square magnetic Barkhausen noise (RMS BN) voltage. When estimating crystallattice microdistortions in articles made from carbon steels subjected to marquenching and subsequent tempering, the combined use of the coercive force (for steels after low- and medium-temperature tempering) and RMS BN voltage (for steels after high-temperature tempering) is most efficient. Such parameters as the number of Barkhausen jumps, electrical resistivity, and elastic wave propagation velocity are less sensitive to changes in crystal-lattice microdistortions (CLMs) in heat-treated carbon steels.     

The influence of the magnetoelastic effect on the hysteretic properties of medium-carbon steel during uniaxial loading

Hysteretic magnetic properties and longitudinal magnetostriction of planar specimens of air-hardened 45 steel were measured as functions of elastic tensile stresses along and perpendicular to the applied loading using a closed magnetic circuit and attachable transducers. Parameters that exhibit monotonic variations with increasing elastic tensile stresses, were found. It was shown that the maxima that were observed in the dependences of residual inductance and relative maximum magnetic permeability on applied stresses, as well as the minima that were observed in the dependences of the coercive force and demagnetizing current of an attachable electromagnet as measured with a sensor arranged along the tension axis on applied stresses, are related to the behavior of the magnetostriction curves of the steel under study.