A NEW MODEL OF PERMANENT MAGNET MATERIALS FOR COMPUTER AIDED DESIGN

In Computer Aided Design (CAD) permanent magnet materials are assumed to be either magnetically isotropic or ideally anisotropic. In this paper we present a new calculation of the reversible and irreversible processes which are analysed on the basis of a simple texture function

Discussion de la Question III : Conception des ouvrages de protection

Chapon J., Tenaud R., Carbonnel P. Discussion de la Question III : Conception des ouvrages de protection. In: L'hydraulique et la maitrise du littoral. Problèmes côtiers posés par le mouvement des sédiments et la pollution. Dix-huitièmes journées de l'hydraulique. Marseille, 11-13 septembre 1984. Tome 6, 1984

sexhy experimental results on pressure dynamics from head-on reflections of hydrogen flames

International audienceIn the past few years, CEA has been fully involved at both experimental and modeling levels in projects related to hydrogen safety in nuclear and chemical industries, and has carried out a test program using the experimental bench SSEXHY (Structure Submitted to an EXplosion of HYdrogen) in order to build a database of the deformations of simple structures following an internal hydrogen explosion. Different propagation regimes of explosions were studied, varying from detonations to slow deflagrations. During the experimental campaign, it was found that high-speed deflagrations, corresponding to relatively poor hydrogen-air mixtures, resulted in higher specimen deformation compared to those related to detonations of nearly stoichiometric mixtures. This paper explains this counter-intuitive result from qualitative and quantitative points of view. It is shown that the overpressure and impulse from head-on reflections of hydrogen flames corresponding to poor mixtures of specific concentrations could have very high values at the tube end

sexhy experimental results on pressure dynamics from head-on reflections of hydrogen flames

International audienceIn the past few years, CEA has been fully involved at both experimental and modeling levels in projects related to hydrogen safety in nuclear and chemical industries, and has carried out a test program using the experimental bench SSEXHY (Structure Submitted to an EXplosion of HYdrogen) in order to build a database of the deformations of simple structures following an internal hydrogen explosion. Different propagation regimes of explosions were studied, varying from detonations to slow deflagrations. During the experimental campaign, it was found that high-speed deflagrations, corresponding to relatively poor hydrogen-air mixtures, resulted in higher specimen deformation compared to those related to detonations of nearly stoichiometric mixtures. This paper explains this counter-intuitive result from qualitative and quantitative points of view. It is shown that the overpressure and impulse from head-on reflections of hydrogen flames corresponding to poor mixtures of specific concentrations could have very high values at the tube end

MÖSSBAUER STUDY OF COMPOUNDS RCo4-xFexB AND RFe4B

Compounds of the form RCo4-xFexB are ferromagnetic for R = Pr, Nd, Sm (x < 2) and ferrimagnetic for R = Er, Tm, Lu, with Tc ∼ 500 - 600 K. 57Fe Mössbauer spectra yield their magnetization directions, which depend both on the R.E. anisotropy and on the transition metal anisotropy

DETERMINATION OF THE DEGREE OF CRYSTALLITES ORIENTATION IN PERMANENT MAGNETS BY X-RAY SCATTERING AND MAGNETIC MEASUREMENTS

Les aimants permanents sont essentiellement des composés ferromagnétiques et uniaxiaux. Certains aimants sont élaborés en frittant des poudres préalablement orientées et comprimées sous champ. La valeur de 1'induction rémanente Br dépend directement du degré d'alignement des cristallites et nous présentons dans cet article deux méthodes quantitatives différentes pour le déterminer. L'analyse aux rayons X permet de comparer les intensités des réflexions de Bragg pour les différentes valeurs de l'angle entre une direction [hkl] et l'axe cristallographique principal. L'analyse magnétique permet de comparer les courbes d'aimantation expérimentales et celles calculées, pour différentes distributions statistiques des orientations des grains. Les deux méthodes ont été appliquées à des aimants Nd-Fe-B et SmCo5. Elles révèlent que la désorientation des particules dans ces systèmes conduit à une réduction d'environ 10 % de l'induction rémanente.Permanent magnet compounds are basically ferromagnets with uniaxial anisotropy. In different cases, the magnets are elaborated by sintering of powders previously oriented and compressed under field. The value of the remanent induction Br is directly dependent on the degree of crystallites alignment, and we present in this paper two different quantitative methods to determine it. X-ray analysis involves the comparison of the intensities of Bragg reflections, for different values of the angle of a direction [hkl] with respect to the unique crystallographic axis of the compound. Magnetic analysis involves the comparison between experimental magnetization curves and calculated ones for different statistical distributions of crystallites orientations. Both methods were applied to NdFeB and SmCo5 magnets. They reveal that the misorientation of particles in these systems leads to a reduction of the remanent induction by about 10 %