Effects of Stress on the Magnetic Properties of Steels

As described in previous work [1], an applied uniaxial stress σ acts in some respects like an applied magnetic field operating through the magnetostriction λ

Magnetic imaging system for display of local variations of magnetic properties in magnetic material

A multiparameter magnetic imaging system and method to be used in the localized measurement of the magnetic properties of a material and the display of those properties in the form of a false color image indicating the occurrence of those properties across the surface of a sample specimen. The system includes an inspection probe to measure certain magnetic parameters across the surface of the specimen and means to determine a multiplicity of magnetic property values based on the measured data. The system also includes a visual display system which selectively displays the data relating to the determined magnetic properties in the form of a false color image indicating the presence and variation of these magnetic properties across the specimen surface

Method for deriving information regarding stress from a stressed ferromagnetic material

A non-destructive evaluation technique for deriving stress in ferromagnetic materials including deriving anhysteretic and hysteresis magnetization curves for the material in both unstressed and stressed states. The anhysteretic curve is expressed as a Langevin function. The stress is expressed as an equivalent magnetic field dependent on stress and change of magnetostriction with magnetization. By measurement of these bulk magnetic properties, stress can be derived

Multiparameter magnetic inspection system with magnetic field control and plural magnetic transducers

A multiparameter magnetic inspection system for providing an efficient and economical way to derive a plurality of independent measurements regarding magnetic properties of the magnetic material under investigation. The plurality of transducers for a plurality of different types of measurements operatively connected to the specimen. The transducers are in turn connected to analytical circuits for converting transducer signals to meaningful measurement signals of the magnetic properties of the specimen. The measurement signals are processed and can be simultaneously communicated to a control component. The measurement signals can also be selectively plotted against one another. The control component operates the functioning of the analytical circuits and operates and controls components to impose magnetic fields of desired characteristics upon the specimen. The system therefore allows contemporaneous or simultaneous derivation of the plurality of different independent magnetic properties of the material which can then be processed to derive characteristics of the material

Interpretation of the magnetization mechanism in Terfenol‐D using Barkhausen pulse‐height analysis and irreversible magnetostriction

The ternary alloy Dy0.7Tb0.3Fe1.9, known as Terfenol‐D, is a highly magnetostrictive alloy with magnetostriction coefficients along the principal crystallographic directions of λ1 1 1=1640×10−6and λ1 0 0≤100(±30)×10−6. The bulk magnetostriction λ is dependent on the state of magnetization M, on the original domain configuration, and on the texture of the material. This paper reports on Barkhausen measurements and magnetostriction. The pulse‐height distribution of Barkhausen emissions revealed events occurring at a specific amplitude which were stress dependent. The magnetostriction results gave a saturationmagnetostriction in excess of 2000 μ strain

The magnetomechanical effect in electrolytic iron

The effect of stress on the magnetization of high purity iron has been studied systematically at different locations on the M,H plane corresponding to a variety of magnetic states of the material. The results confirm earlier studies that show the sign of the derivative dM/dσ changes at different locations on the M,H plane, and can even change as a result of a monotonic increase of stress either in compression or tension. The observed behavior can be explained on the basis of a recent theory which predicts that the irreversible changes in magnetization resulting from changes in applied stress cause the magnetization to approach the anhysteretic magnetization curve at the given applied field strength

Thermal effects on the magnetic properties of titanium modified cobalt ferrite

The temperature dependence of the magnetic properties of titanium modified cobalt ferrite is presented. The change of maximum magnetization obtained at H ≈ 2.4 MA/m between any two temperatures increases systematically with composition, which is desirable for applications in devices. Variation in magnetocrystalline anisotropy and coercivity were different from previous studies on cation substituted cobalt ferrite. At lower concentrations, the effect of lower thermal energy dominated the effect of non-magnetic cation substitutions in controlling the anisotropy.The reverse was the case at higher concentrations. The temperature dependence of coercivity is dominated by the contribution of magnetocrystalline anisotropy to coercivity, while the compositional dependence of coercivity is dominated by microstructural contribution through the pinning of domain walls

System and method for non-destructive evaluation of surface characteristics of a magnetic material

A system and a related method for non-destructive evaluation of the surface characteristics of a magnetic material. The sample is excited by an alternating magnetic field. The field frequency, amplitude and offset are controlled according to a predetermined protocol. The Barkhausen response of the sample is detected for the various fields and offsets and is analyzed. The system produces information relating to the frequency content, the amplitude content, the average or RMS energy content, as well as count rate information, for each of the Barkhausen responses at each of the excitation levels applied during the protocol. That information provides a contiguous body of data, heretofore unavailable, which can be analyzed to deduce information about the surface characteristics of the material at various depths below the surface

Magnetic inspection probe for measurement of magnetic anisotropy

A magnetic inspection probe for use in the planar measurement of magnetic properties in two or more defined directions. The inspection probe includes a cup-shaped outer body, a centrally disposed central core, a field generating power coil, a flux coil for measuring magnetic induction and a plurality of field detection elements disposed in various known orientations. In use, the inspection probe of the present invention permits the detection and measurement of anisotropy of material characteristics in at least two directions across the plane of measurement

Core loss reduction in electrical steels through materials processing

Research has been conducted into the effects of laser scribing on the core losses of soft magnetic materials. Various types of lamination steels for use in electric motors and transformers were studied including iron based alloys containing carbon,silicon,nickel, and cobalt. The results show that the change in core losses for carbon,nickel, and cobalt alloys was small for the scribing conditions examined, but core loss reductions of up to 18% were achieved with iron–silicon alloys