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Electromagnetics and Photonics

Materials properties

Ames Laboratory Publications

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Full-Text Articles in Physics

Microstructure And Magnetic Properties Of As-Quenched And Heat-Treated (Nd,Dy)Feb Powders Produced By High Pressure Gas Atomization, John E. Snyder, Chester C.H. Lo, X. Fang, B. Kriegermeier, David C. Jiles Apr 1999

Microstructure And Magnetic Properties Of As-Quenched And Heat-Treated (Nd,Dy)Feb Powders Produced By High Pressure Gas Atomization, John E. Snyder, Chester C.H. Lo, X. Fang, B. Kriegermeier, David C. Jiles

Ames Laboratory Publications

The magnetic properties and microstructures of a series of as-quenched and heat-treated inert gas atomized (IGA) rare-earth rich (Nd,Dy)–Fe–B particles have been investigated. Heat treatment was found to substantially improve magnetic properties, with effects most pronounced in samples with higher Dy content and higher total rare earth (RE) content. The as-quenched particles consisted of an underquenched dendritic-like structure with the majority phase RE2Fe14B, and a fine network of RE-rich material between the grains. The heat-treated particles showed a change in microstructure which correlated with magnetic property changes. Particles which showed little change in magnetic properties showed no ...


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 ...


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.


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 ...


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.