An Effect of Nonferromagnetic Gaps on the Magnetic Properties of Stacks of Steel Plates with Different Values of Magnetic Hardness: I. A Closed Circuit

Stacks of steel plates having different values of magnetic hardness and separated with nonferromagnetic gaps are investigated. The coercive force and the residual magnetic induction of a stack measured in a closed magnetic circuit depend on the layout of the plates in the stack and on the thickness of nonmagnetic gaps between them.__________Translated from Defektoskopiya, Vol. 41, No. 3, 2005, pp. 55–62.Original Russian Text Copyright © 2005 by Gorkunov, Mitropol’skaya, Povolotskaya.Dedicated to the Anniversary of the 100th Birthday of Corresponding Member of the Russian Academy of Sciences M. N. Mikheev     

Estimating the deformation state of single-and two-layer ferromagnetic materials on the basis of their magnetic characteristics

Magnetic characteristics measured along and perpendicularly to the tensile-stress direction for single-and two-layer specimens made of steel Ct3cΠ and steel 45 that were subjected to various heat treatments are studied at different degrees of deformation. Measuring the magnetic characteristics perpendicularly to the tension direction is shown to be more informative from the point of view of estimating the degree of deformation, while the use of a four-pole transducer allows determination of the direction.     

Coercive-force and eddy-current testing of the abrasive wear resistance of quenched and tempered hypereutectoid carbon steels: II. Steels subjected to different quenching regimes,subzero treatment,and tempering after high-temperature quenching

The effects of the carbon concentration in martensite from 0.70 to 1.35 wt %, the presence of up to 70 vol % residual austenite, the degree of coagulation, and the volume fraction of tempering carbides on the specific features of the application of eddy-current and magnetic methods for testing abrasive wear resistance are studied. The case of high-carbon (0.83–1.53 wt % C) steels quenched from 790–1200° C, treated with cold at ?196°C, and tempered in the temperature range 75–700°C is considered.     

Application of magnetic and electromagnetic-acoustic methods for assessing plastic deformations under cyclic loading of annealed intermediate-carbon steel

The influence of cyclic loading of annealed steel 45 during low-cycle fatigue on changes in its magnetic characteristics, in particular, the coercive force and the residual magnetic induction, for the major and minor magnetic-hysteresis loops and on changes in the propagation velocity of a longitudinal acoustic wave is studied. The sensitivity of the considered physical characteristics to the value of plastic deformation stored under cyclic loading in the region of both large and small strains is determined. The residual mechanical properties displayed after cyclic loading are determined, and the steady-state correlations between the coercive force measured on minor hysteresis loops in weak fields (the Rayleigh region) and the remanent clongation are obtained. The possibility of monitoring the stored plastic deformation and assessing the residual life of a material during its cyclic loading from the values of its magnetic parameters is shown.     

Magnetic inspection of fatigue degradation of a high-carbon pearlitic steel

The effect of high-cycle fatigue loading of U10 steel specimens with a fine-lamellar pearlite structure that were a annealed for a short time on the character of variations of the tangential component of the magnetic induction vector of specimens in a residual-magnetization state has been studied. It was found that fatigue loading up to major fatigue-crack formation leads to an increase in the tangential component of the magnetic induction vector and to nonuniformity of the magnetic induction distribution along the length of a specimen. This is due to the spheroidization of cementite plates, which occurs in U10 steel specimens under a fatigue load. Major fatigue-crack formation is accompanied by the appearance of a clearly pronounced peak in the distribution of the tangential component of the magnetic induction vector. The magnetic measurement technique that was used allows us to record both structural changes and cracks that result from the fatigue degradation of high-carbon-pearlitic steel.     

Internal Demagnetization Factor for Porous Ferromagnets in Remagnetization Process

Computational and experimental methods of determining the internal demagnetization factor of porous ferromagnetic materials are compared. The effect of the porosity, the shape of pores, and the magnetizing field strength on the demagnetization factor of model porous materials are considered. It is established experimentally that the internal demagnetization factor is subjected to hysteresis when the porous materials are remagnetized along the magnetic hysteresis loop.     

A speckle-interferometric setup for contactless measurements of the velocity of rayleigh ultrasonic waves

The velocity of a Rayleigh wave was determined by measuring its propagation time between two Iaser-illuminated small areas of a rough surface. It is sh own that, if a Rayleigh wave passes over these areas, a photodiode twice detects signals proportional to the surface displacement in the speckle overlap region. In contrast to the previous variant, signal-distorting reflections are eliminated in the instrument. A sample holder excluding adjustment of the interferometer upon a change in the object size has been manufactured. A new technique for determining the time interval between two signals is used. The instrument operates at a frequency of 5 MHz, and the distance between the areas is adjusted in the range 5–100 mm. The rms deviation of the velocity from the average value for ten measurements is 8 × 10–4.     

Effect of Deviation from Coaxiality between the Directions of Magnetization and Mechanical Strain on the Results of Magnetic Testing of Elastic Strain in Steels

The magnetoelastic effect in steels that are in the states of coercive force and residual magnetization in the saturation hysteresis loop is studied. The regularities of changes in the residual magnetization and coercive force under uniaxial tensioning and compression of specimens of 30KhGSA steel magnetized along the direction of strain application are established. It is shown that a variation in the direction of magnetization and complication of the strain pattern result in considerable deviations in the character of changes in the magnetic forces determined by a ferroprobe-type coercive force meter for elastically strained plates from St3 and R6M5 steels and for an St3 beam.     

Magnetic Acoustic Emission in Ferromagnetic Materials. 3: Effect of Structural Changes on Magnetic Acoustic Emission (Review Article)

This part of the review is devoted to effects of structural changes in multiply alloyed ferromagnetic materials on parameters of magnetoelastic acoustic emission.     

Features of magnetization curves of assemblies including steel rods with different magnetic properties

Samples composed of four and nine steel rods with different magnetic properties have been studies. The values of shape permeability of the samples have been found, and it has been proven that the composition of a composite sample can be determined on the base of the differential magnetic permeability of the sample versus external magnetic field with due account of the shape permeability, whereas positions of peaks on the differential permeability versus internal magnetic field yield information about properties of rods included in the sample.