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Full-Text Articles in Physics

Novel Mechanisms For Solid-State Processing And Grain Growth With Microstructure Alignment In Alnico-8 Based Permanent Magnets, Aaron G. Kassen, Emma M. H. White, Liangfa Hu, Wei Tang, Lin Zhou, Matthew J. Kramer, Iver E. Anderson Jan 2018

Novel Mechanisms For Solid-State Processing And Grain Growth With Microstructure Alignment In Alnico-8 Based Permanent Magnets, Aaron G. Kassen, Emma M. H. White, Liangfa Hu, Wei Tang, Lin Zhou, Matthew J. Kramer, Iver E. Anderson

Ames Laboratory Accepted Manuscripts

An estimated 750,000 new hybrid electric and plug-in battery vehicles, most with permanent magnet synchronous alternating current (PMAC) drive motors, took to the road in 2016 alone. Accompanied by 40% year over year growth in the EV market significant challenges exist in producing large quantities of permanent magnets (on the order of tens of millions) for reliable, low-cost traction motors [IE Agency, Energy Technology Perspectives (2017)]. Since the rare earth permanent magnet (REPM) market is essentially 100% net import reliant in the United States and has proven to have an unstable cost and supply structure in recent years, a ...


Recycled Sm-Co Bonded Magnet Filaments For 3d Printing Of Magnets, Helena A. Khazdozian, J. Sebastian Manzano, Kinjal Gandha, Igor I. Slowing, Ikenna C. Nlebedim Jan 2018

Recycled Sm-Co Bonded Magnet Filaments For 3d Printing Of Magnets, Helena A. Khazdozian, J. Sebastian Manzano, Kinjal Gandha, Igor I. Slowing, Ikenna C. Nlebedim

Ames Laboratory Accepted Manuscripts

Recycling of rare earth elements, such as Sm and Nd, is one technique towards mitigating long-term supply and cost concerns for materials and devices that depend on these elements. In this work recycled Sm-Co powder recovered from industrial grinding swarfs, or waste material from magnet processing, was investigated for use in preparation of filament for 3D printing of bonded magnets. Recycled Sm-Co powder recovered from swarfs was blended into polylactic acid (PLA). Up to 20 vol.% of the recycled Sm-Co in PLA was extruded at 160°C to produce a filament. It was demonstrated that no degradation of magnetic properties ...


Gd5(Si,Ge)4 Thin Film Displaying Large Magnetocaloric And Strain Effects Due To Magnetostructural Transition, Ravi L. Hadimani, Joao H. B. Silva, Andre M. Pereira, Devo L. Schlagel, Thomas A. Lograsso, Yang Ren, David C. Jiles, Joao P. Araújo Jan 2015

Gd5(Si,Ge)4 Thin Film Displaying Large Magnetocaloric And Strain Effects Due To Magnetostructural Transition, Ravi L. Hadimani, Joao H. B. Silva, Andre M. Pereira, Devo L. Schlagel, Thomas A. Lograsso, Yang Ren, David C. Jiles, Joao P. Araújo

Ames Laboratory Publications

Magnetic refrigeration based on the magnetocaloric effect is one of the best alternatives to compete with vapor-compression technology. Despite being already in its technology transfer stage, there is still room for optimization, namely, on the magnetic responses of the magnetocaloric material. In parallel, the demand for different magnetostrictive materials has been greatly enhanced due to the wide and innovative range of technologies that emerged in the last years (from structural evaluation to straintronics fields). In particular, the Gd5(Six Ge1−x)4 compounds are a family of well-known alloys that present both giant magnetocaloric and colossal magnetostriction effects. Despite their ...


Analysis Of Ringing Effects Due To Magnetic Core Materials In Pulsed Nuclear Magnetic Resonance Circuits, Neelam G. Prabhu Gaunkar, N. R. Y. Bouda, Ikenna C. Nlebedim, Ravi L. Hadimani, I. Bulu, K. Ganesan, Y. Q. Song, Mani Mina, David C. Jiles Jan 2015

Analysis Of Ringing Effects Due To Magnetic Core Materials In Pulsed Nuclear Magnetic Resonance Circuits, Neelam G. Prabhu Gaunkar, N. R. Y. Bouda, Ikenna C. Nlebedim, Ravi L. Hadimani, I. Bulu, K. Ganesan, Y. Q. Song, Mani Mina, David C. Jiles

Electrical and Computer Engineering Publications

This work presents investigations and detailed analysis of ringing in a non-resonant pulsednuclear magnetic resonance (NMR) circuit. Ringing is a commonly observed phenomenon in high power switching circuits. The oscillations described as ringing impede measurements in pulsed NMR systems. It is therefore desirable that those oscillations decay fast. It is often assumed that one of the causes behind ringing is the role of the magnetic core used in theantenna (acting as an inductive load). We will demonstrate that an LRC subcircuit is also set-up due to the inductive load and needs to be considered due to its parasitic effects. It ...


Phenomenological Modelling Of First Order Phase Transitions In Magnetic Systems, Yevgen Melikhov, Ravi L. Hadimani, Arun Raghunathan Jan 2014

Phenomenological Modelling Of First Order Phase Transitions In Magnetic Systems, Yevgen Melikhov, Ravi L. Hadimani, Arun Raghunathan

Electrical and Computer Engineering Publications

First order phase transitions may occur in several magnetic systems, with two structural phases having different magnetic properties each and a structural transition between them. Here, a novel physics based phenomenological model of such systems is proposed, in which magnetization is represented by the volumetric amounts of ferromagnetism (described by extended Jiles-Atherton theory) and paramagnetism (described by the Curie-Weiss law) in respective phases. An identification procedure to extract material parameters from experimental data is proposed. The proposed phenomenological approach was successfully applied to magnetocaloric Gd5(Six Ge 1−x)4 system and also has the potential to describe the behavior ...


Examination Of The Relationship Between The Parameters Of Barkhausen Effect Model And Microstructure Of Magnetic Materials, Chester C.H. Lo, S. J. Lee, L. C. Kerdus, David C. Jiles May 2002

Examination Of The Relationship Between The Parameters Of Barkhausen Effect Model And Microstructure Of Magnetic Materials, Chester C.H. Lo, S. J. Lee, L. C. Kerdus, David C. Jiles

Center for Nondestructive Evaluation Publications

A relationship between the parameters of a hysteretic-stochastic process model of the Barkhausen effect (BE) and the microstructural features of a series of ferritic/pearlitic steel samples has been identified. The root-mean-square values and pulse height distributions of the experimental and modeled BE signals showed similar dependence on the pearlite content. The correlation length parameter ξ of the model, which represents the range of interaction of domain walls with pinning sites, was found to obey ξ=AVfDf+BVpDp where Vf(Vp)and Df(Dp) are the volume fraction and grain size of ferrite (pearlite).


Composite Magnetostrictive Materials For Advanced Automotive Magnetomechanical Sensors, R. William Mccallum, Kevin W. Dennis, David C. Jiles, John E. Snyder, Y. H. Chen Apr 2001

Composite Magnetostrictive Materials For Advanced Automotive Magnetomechanical Sensors, R. William Mccallum, Kevin W. Dennis, David C. Jiles, John E. Snyder, Y. H. Chen

Ames Laboratory Publications

In this paper we present the development of a composite magnetostrictive material for automotive applications. The material is based on cobaltferrite,CoO⋅Fe2O3, and contains a small fraction of metallic matrix phase that serves both as a liquid-phasesintering aid during processing and enhances the mechanical properties over those of a simple sinteredferrite ceramic. In addition the metal matrix makes it possible to braze the material, making the assembly of a sensor relatively simple. The material exhibits good sensitivity and should have high corrosion resistance, while at the same time it is low in cost.


On The Temperature Dependence Of Multiple- And Single-Scattering Contributions In Magnetic Exafs, H. Wende, F. Wilhelm, P. Poulopoulos, K. Baberschke, J. W. Freeland, Y. U. Idzerda, A. Rogalev, Deborah L. Schlagel, Thomas A. Lograsso, D. Arvanitis Sep 1999

On The Temperature Dependence Of Multiple- And Single-Scattering Contributions In Magnetic Exafs, H. Wende, F. Wilhelm, P. Poulopoulos, K. Baberschke, J. W. Freeland, Y. U. Idzerda, A. Rogalev, Deborah L. Schlagel, Thomas A. Lograsso, D. Arvanitis

Ames Laboratory Conference Papers, Posters, and Presentations

We demonstrate that the temperature dependence of structural as well as magnetic fluctuations can be probed by the use of the Magnetic Extended X-ray Absorption Fine Structure (MEXAFS) spectroscopy. We compare those to the dynamic disorder as probed by the EXAFS. Here we present temperature-dependent MEXAFS investigations carried out at the L-edges of a thin Fe film and a Gd single crystal. By comparing the experimental results to ab initio calculations the single-scattering contributions are separated from multiple-scattering contributions. It is found that the multiple-scattering contributions are enhanced for the MEXAFS compared to the normal EXAFS.


Application Of The Preisach And Jiles–Atherton Models To The Simulation Of Hysteresis In Soft Magnetic Alloys, M. Pasquale, G. Bertotti, David C. Jiles, Y. Bi Apr 1999

Application Of The Preisach And Jiles–Atherton Models To The Simulation Of Hysteresis In Soft Magnetic Alloys, M. Pasquale, G. Bertotti, David C. Jiles, Y. Bi

Ames Laboratory Publications

his article describes the advances in unification of model descriptions of hysteresis in magnetic materials and demonstrates the equivalence of two widely accepted models, the Preisach (PM) and Jiles–Atherton (JA) models. Recently it was shown that starting from general energy relations, the JA equation for a loop branch can be derived from PM. The unified approach is here applied to the interpretation of magnetization measured in nonoriented Si–Fe steels with variable grain size ⟨s⟩, and also in as-cast and annealed Fe amorphous alloys. In the case of NO Fe–Si, the modeling parameter k defined by the volume ...


Monitoring Fatigue Damage In Materials Using Magnetic Measurement Techniques, Chester C.H. Lo, F. Tang, Y. Shi, David C. Jiles, S. B. Biner Apr 1999

Monitoring Fatigue Damage In Materials Using Magnetic Measurement Techniques, Chester C.H. Lo, F. Tang, Y. Shi, David C. Jiles, S. B. Biner

Center for Nondestructive Evaluation Publications

Measurements of hysteresis and Barkhausen effect (BE) have been made on 0.1 wt % C Fe–C alloys subjected to strain-controlled fatigue at various strain amplitudes. A relationship between the fatigue lifetime and strain amplitude was observed. The hysteresis properties of the samples cycled at different strain amplitudes were found to vary systematically with expended fatigue life. These properties showed significant changes in the initial and final stages of fatigue, while between these stages they remained stabilized. In the stable stage the remanence was found to decrease, whereas the coercivity increased with increasing strain amplitude. Variations in BE signal during ...


Effect Of The Elastic Modulus Of The Matrix On Magnetostrictive Strain In Composites, Y. Chen, John E. Snyder, Carl R. Schwichtenberg, Kevin W. Dennis, D. K. Falzgraf, R. William Mccallum, David C. Jiles Feb 1999

Effect Of The Elastic Modulus Of The Matrix On Magnetostrictive Strain In Composites, Y. Chen, John E. Snyder, Carl R. Schwichtenberg, Kevin W. Dennis, D. K. Falzgraf, R. William Mccallum, David C. Jiles

Ames Laboratory Publications

The effect of the matrix material on the magnetostriction of composites containing highly magnetostrictive particles has been studied. Experimental results showed that the elastic modulus of the matrix is an important factor determining the bulk magnetostriction of the composite. For a series of composites with the same volume fraction of magnetostrictive particles but different matrix materials, the bulk magnetostriction was found to increase systematically with decreasing elastic modulus of the matrix. A modeltheory for the magnetostriction of such composites has been developed, based on two limiting assumptions: uniform strain or uniform stress inside the composite. The theory was then used ...


Generalization Of Hysteresis Modeling To Anisotropic Materials, A. Ramesh, David C. Jiles, Y. Bi Apr 1997

Generalization Of Hysteresis Modeling To Anisotropic Materials, A. Ramesh, David C. Jiles, Y. Bi

Materials Science and Engineering Publications

An extension to the model of hysteresis has been presented earlier which included the effect of anisotropy in the modeling of the anhysteretic magnetization curves of uniaxially anisotropic single crystalline materials. Further exploration of this extension shown here considers different kinds of crystal anisotropy in materials. Theory considers that the differential susceptibility at any given field is determined by the displacement of the prevailing magnetization from the anhysteretic magnetization. Thus, it has been shown that the effect of anisotropy on magnetic hysteresis in materials can be incorporated into the model of hysteresis through the anisotropic anhysteretic. This extension is likely ...


Dependence Of Energy Dissipation On Annealing Temperature Of Melt–Spun Ndfeb Permanent Magnet Materials, Z. Gao, David C. Jiles, Daniel J. Branagan, R. William Mccallum Apr 1996

Dependence Of Energy Dissipation On Annealing Temperature Of Melt–Spun Ndfeb Permanent Magnet Materials, Z. Gao, David C. Jiles, Daniel J. Branagan, R. William Mccallum

Ames Laboratory Publications

A model of magnetic hysteresis which was developed originally for soft magnetic materials has been applied to melt–spun ribbons of Nd2Fe14B‐based material. The crucial ideas in the model description of hysteresis center on a dissipation of energy due to hysteresis which is proportional to the change in magnetization. The Nd2Fe14B material was melt–spun amorphous and then annealed for a period of 24 h at temperatures ranging from 700 to 950 °C. This resulted in different grain sizes, depending on annealing temperature. Consequently the hysteresis curves represent the properties of ...


The Magnetomechanical Effect In Electrolytic Iron, Michael K. Devine, David C. Jiles Apr 1996

The Magnetomechanical Effect In Electrolytic Iron, Michael K. Devine, David C. Jiles

Ames Laboratory Publications

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 ...


Frequency Dependence Of Hysteresis Curves In Conducting Magnetic Materials, David C. Jiles Nov 1994

Frequency Dependence Of Hysteresis Curves In Conducting Magnetic Materials, David C. Jiles

Ames Laboratory Publications

An extension of the hysteresis model has been developed that takes into account the effects on the hysteresis curves of eddycurrents in electrically conducting media. In the derivation presented it is assumed that the frequency of the applied field is low enough (or the thickness of the material medium small enough) that the skin effect can be ignored so that the magnetic field penetrates uniformly throughout the material. In this case, the dc hysteresis equation is extended by the addition of a classical eddy‐current‐loss term depending on (i) the rate of change of magnetization with time, (ii) the ...


Estimation Of Fatigue Exposure From Magnetic Coercivity, Z. J. Chen, David C. Jiles, J. Kameda May 1994

Estimation Of Fatigue Exposure From Magnetic Coercivity, Z. J. Chen, David C. Jiles, J. Kameda

Ames Laboratory Publications

An investigation of the effects of fatigue on A533B steel under constant load amplitude is reported in this paper. It was found that the plastic strain of the sample accumulated logarithmically with the number of stress cycles after initial fatigue softening. Based on the fact that plastic strain is often linearly related to the coercivity of material, at least for small changes of H c , a phenomenological relationship has been developed and tested to correlate the number of stress cycles to this magnetic parameter. This result represents the first successful attempt to relate the fatigue exposure directly to a magnetic ...


Measurements Of Magnetic Circuit Characteristics For Comprehension Of Intrinsic Magnetic Properties Of Materials From Surface Inspection, Z. J. Chen, Michael K. Devine, David C. Jiles May 1993

Measurements Of Magnetic Circuit Characteristics For Comprehension Of Intrinsic Magnetic Properties Of Materials From Surface Inspection, Z. J. Chen, Michael K. Devine, David C. Jiles

Ames Laboratory Publications

A transfer function is presented for calculating magnetic field and flux density inside a test material as a result of surface measurement. By considering flux leakage, we introduce a parameter η, called the leakage coefficient, which can be experimentally determined. It is introduced into the equations to make the transfer function more practical. The distribution of field inside a test material is then discussed in accordance with a surfacemagnetic charge model.


Magnescope: Applications In Nondestructive Evaluation, Michael K. Devine, David C. Jiles, A. R. Eichmann, David A. Kaminski, S. Hardwick May 1993

Magnescope: Applications In Nondestructive Evaluation, Michael K. Devine, David C. Jiles, A. R. Eichmann, David A. Kaminski, S. Hardwick

Ames Laboratory Publications

This paper describes recent results obtained with the Magnescope, which has been used on location in industrial environments and has successfully detected impending fatigue failure, creep damage, applied stress, and microstructural differences. It is concluded that the device provides a useful nondestructive method for evaluating the mechanical properties of materials through the measurement of their structure sensitive magnetic properties.


Analytic Model Calculation Of Magnetic Field In A Magnetic Half‐Space Due To Surface Magnetic Charge, Z. J. Chen, Madhav Rao Govindaraju, David C. Jiles May 1993

Analytic Model Calculation Of Magnetic Field In A Magnetic Half‐Space Due To Surface Magnetic Charge, Z. J. Chen, Madhav Rao Govindaraju, David C. Jiles

Ames Laboratory Publications

By analogy with electrostatic field, a simple analytic model is presented on the distribution of magnetic field inside a test material as a result of surface inspection with a magnetic probe. According to this model, the penetration depth of the magnetic field is defined and the permeability of the material at different depths is calculated. Finally, the magnetic flux inside the inspection head when placed on samples of different thicknesses is calculated and compared with experimental results.


Evaluation Of Fatigue Damage In Steel Structural Components By Magnetoelastic Barkhausen Signal Analysis, Madhav Rao Govindaraju, Andrew Strom, David C. Jiles, S. B. Biner, Z. J. Chen May 1993

Evaluation Of Fatigue Damage In Steel Structural Components By Magnetoelastic Barkhausen Signal Analysis, Madhav Rao Govindaraju, Andrew Strom, David C. Jiles, S. B. Biner, Z. J. Chen

Ames Laboratory Publications

This paper is concerned with using a magnetic technique for the evaluation of fatigue damage in steel structural components. It is shown that Barkhausen effect measurements can be used to indicate impending failure due to fatigue under certain conditions. The Barkhausen signal amplitude is known to be highly sensitive to changes in density and distribution of dislocations in materials. The sensitivity of Barkhausen signal amplitude to fatigue damage has been studied in the low‐cycle fatigue regime using smooth tensile specimens of a medium strength steel. The Barkhausen measurements were taken at depths of penetration of 0.02, 0.07 ...


Interpretation Of The Magnetization Mechanism In Terfenol‐D Using Barkhausen Pulse‐Height Analysis And Irreversible Magnetostriction, David C. Jiles, S. Hariharan May 1990

Interpretation Of The Magnetization Mechanism In Terfenol‐D Using Barkhausen Pulse‐Height Analysis And Irreversible Magnetostriction, David C. Jiles, S. Hariharan

Electrical and Computer Engineering Publications

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 ...


Pressure Cell For Magnetostrictive Measurements, Jerome E. Ostenson, Douglas K. Finnemore, David C. Jiles Feb 1989

Pressure Cell For Magnetostrictive Measurements, Jerome E. Ostenson, Douglas K. Finnemore, David C. Jiles

Ames Laboratory Publications

A pressure cell has been designed to study the magnetostrictive properties of a material as a function of both pressure and magnetic field. For changes in length on the order of 2000 ppm, it is necessary to have a substantial compliance in the pressure cell to retain a constant stress over the length of travel.