Open Access. Powered by Scholars. Published by Universities.®

Physics Commons

Open Access. Powered by Scholars. Published by Universities.®

Articles 1 - 7 of 7

Full-Text Articles in Physics

Lattice-Dynamical Study Of The Premartensitic State Of The Cu-Al-Be Alloys, Lluís Mañosa, Jerel L. Zarestky, Thomas A. Lograsso, Dwight W. Delaney, C. Stassis Dec 1993

Lattice-Dynamical Study Of The Premartensitic State Of The Cu-Al-Be Alloys, Lluís Mañosa, Jerel L. Zarestky, Thomas A. Lograsso, Dwight W. Delaney, C. Stassis

Ames Laboratory Publications

Neutron-scattering techniques have been used to study the premartensitic state of a family of Cu-Al-Be alloys, which transform from the bcc phase to an 18R martensitic structure. We find that the phonon modes of the TA2[110] branch have very low energies with anomalous temperature dependence. A slight anomaly at q=2/3 was observed; this anomaly, however, does not change significantly with temperature. No elastic peaks, related to the martensite structure, were found in the premartensitic state of these alloys. The results are compared with measurements, performed under the same instrumental conditions, on two Cu-Al-Ni and a Cu-Zn-Al ...


Enhanced Differential Magnetostrictive Response In Annealed Terfenol‐D, N. Galloway, M. P. Schulze, R. D. Greenough, David C. Jiles Aug 1993

Enhanced Differential Magnetostrictive Response In Annealed Terfenol‐D, N. Galloway, M. P. Schulze, R. D. Greenough, David C. Jiles

Ames Laboratory Publications

The field and pressure dependencies of the magnetostriction of Tb0.316Dy0.684Fe1.982 have been measured in a grain‐oriented rod after thermally annealing for 1 day at 850 °C and for 4 days at 950 °C in an argon atmosphere. The results of the heat treatment are a fivefold increase in the strain coefficient d 33(=dλ/dH) and a 100% increase in the maximum strain (λ). There was also an increase in the λ‐vs‐Hhysteresis. Under compressive uniaxial stress there was virtually no bulk change in magnetostrictive strain until the ...


Dynamical X-Ray Diffraction From An Icosahedral Quasicrystal, S. W. Kycia, Alan I. Goldman, Thomas A. Lograsso, Dwight W. Delaney, D. Black, M. Sutton, E. Dufresne, R. Brüning, B. Rodricks Aug 1993

Dynamical X-Ray Diffraction From An Icosahedral Quasicrystal, S. W. Kycia, Alan I. Goldman, Thomas A. Lograsso, Dwight W. Delaney, D. Black, M. Sutton, E. Dufresne, R. Brüning, B. Rodricks

Ames Laboratory Publications

We present direct evidence of dynamical diffraction of x rays from a quasicrystal. High-resolution x-ray-diffraction measurements of the Al-Pd-Mn face-centered icosahedral quasicrystal were performed, revealing a mosaic full width at half maximum of less than 0.001°. In a second experiment, the anomalous transmission of x rays (the Borrmann effect) was observed. These measurements show that nearly perfect quasicrystals may be grown to centimeter-size dimensions allowing x-ray techniques based upon dynamical diffraction to be brought to bear on the analysis of icosahedral structures.


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 ...