D.G. Lee
,
K.C. Jang
,
J.M. Kuk
,
I.S. Kim
金属学报(英文版)
Rotary bending fatigue tests were carried out with two kinds of materials, S43C and S50C, using the front engine and front drive shaft (FF shaft) of vehicle. The specimens were induction hardened about 1.0mm depth from the specimen surface, and the hardness value on the surface was about HRC56-60. The tested environment temperatures were -30, 25 and 80℃ in order to look over effect of the induction hardening and the environmental temperatures on the fatigue characteristics. The fatigue limit of induction hardened specimens increased more about 45% than non-hardened specimens showing that the endurances of S43C and S50C were 98.1 and 107.9MPa in non-hardened samples, 147.1 and 156.9MPa in hardened samples respectably. The maximum tensile and compressive stress on the small circular defect was about +250 and -450MPa respectively when circular defect is situated on top and bottom. The fatigue life increased 80, 25 and -30℃ in order regardless of hardening. In comparison of the fatigue lives on the basis of tested result at 25℃, the fatigue lives of non-hardened specimens decreased about 35%, but that of hardened specimens decreased about only 5% at 80℃ more than at 25℃. And fatigue life of non-hardened and hardened specimens were about 110% and 120% higher at -30℃ than that of 25℃. Based on the result of stress distribution near the defect, the tensile and compressive stress repeatedly generated by load direction were the largest on the small circular defect due to the stress concentration.
关键词:
induction hardening
,
null
,
null
Physica B-Condensed Matter
Similar to the cases of 3d(n) ions in 4-fold (or 8-fold) and 6-fold cubic coordinations, a simple and uniform method that calculates the spin-lattice coupling coefficients G11 and G44 for those ions in the more complex 12-fold cubic coordination from the derivatives of zero-field splittings in low symmetries with respect to the distinct structural parameters has been established. Through this method, the analytic expressions of G11 and G44 for 3d5 ions in this cubic coordination based on various mechanisms and models have been given. The results are rather different from those in 4-fold (or 8-fold) and 6-fold cubic coordinations. As an example, the coefficients G11 and G44 for Fe3+ in K+ site ( 12-fold cubic coordination) as well as Ta5+ site (6-fold cubic coordination) of KTaO3 crystal are studied from the important spin-orbit coupling mechanism. When we compare these results with the experimental findings, it appears that the Fe3+ ion is in a Ta5+ site, and not in a K+ site as shown by some researchers.
关键词:
s-6-state ions;symmetry;formulas
Communications in Theoretical Physics
By successively taking into account various interactions for d(2) ions in trigonally distorted cubic crystal fields, detailed analyses, derivations and calculations of the zero-field splitting (ZFS) and g factors of the ground state have been carried out; and their physical essentials and origins have been clearly revealed. The mistakes and shortcomings in some references have been corrected and improved. The calculated results are in excellent agreement with experimental data and much better than those of previous work. It is found that both the combined action of the trigonal field and spin-orbit interaction and the interaction between the ground state and excited states are quite necessary for causing ZFS of the ground state, and both the spin-orbit interaction and the admixture between the ground state and excited states are necessary for causing the deviation of g factors of the ground state from spin-only values.
关键词:
zero-field splitting;g factors;d(2) ions;crystal field;combined;action;admixture of wavefunction
Journal of Physics and Chemistry of Solids
The g-shifts Ag( = g-g(s), where g(s) approximate to 2.0023 is the free-ion value) of the isoelectronic 3d(3) series Cr3+. Mn4+ and Fe5+ in SrTiO3 crystals are calculated from the high-order perturbation formula based on the cluster approach for 3d3 ion in cubic octahedral site. The formula includes not only the contribution from the crystal-field (CF) mechanism, but also that from the charge-transfer (CT) mechanism (which is omitted in the CF theory). From the calculations, it is found that the contribution Delta g(CT) from the CT mechanism in sign is contrary to the corresponding Delta g(CF) from the CF mechanism and the relative importance of CT mechanism (characterized by vertical bar Delta g(CT)/Delta g(CF)vertical bar) increases with the increasing valence state (and hence the atomic number) of 3d(3) ion. The positive g-shift Delta g of SrTiO3:Fe5+ is due mainly to the contribution of CT mechanism. So, for the explanations of g factors of the high valence state 3d" ions (e.g. Mn4+ and Fe5+) in crystals, the contributions from both CF and CT mechanisms should be taken into account. (c) 2005 Elsevier Ltd. All rights reserved.
关键词:
oxides;crystal fields;electronic paramagnetic resonance;optical;properties;electron-paramagnetic-resonance;atomic screening constants;scf;functions;luminescence;parameters;spectra;temperature;manganese;lattices;csmgbr3
Physica B-Condensed Matter
The perturbation formula of g factor for 3d(7) ion in cubic octahedral crystals has been obtained from a cluster approach. In the formula, the parameters related to the configuration interaction and the covalency reduction effect can be obtained from the optical spectra of the crystal under study and so no adjustable parameters are applied. From the formula, the g factors for Co2+ in fluoroperovskites LiBaF3, KMBF3, KZnF3 and CsCdF3 are calculated. The calculated results are in agreement with the observed values. The g factor following the order of LiBaF3 : Co2+ < KMgF3 : Co2+ < KZnF3: Co2+ < CsCdF3 : Co2+ is also explained. (C) 2000 Elsevier Science B.V. All rights reserved.
关键词:
electron paramagnetic resonance;crystal- and ligand-field theory;Co2+;LiBaF3;KMgF3;KZnF3;CsCdF3;perovskite;transition;impurities;crystals
Zeitschrift Fur Naturforschung Section a-a Journal of Physical Sciences
This paper presents a cluster approach to the calculation of the g factors for 3d(7) ions in cubic octahedral crystals, in which the parameters related to the configuration interaction and the covalency reduction effects are obtained from optical spectra of the studied crystals, and so no adjustable parameters are applied. From the approach, the g factors for MgO:Co2+ and CaO:Co2+ are calculated. The calculated results show good agreement with the observed values. The experimental values of g < 4.333 (the first order value in absence of configuration and covalency interactions) for MgO:Co2+ and g > 4.333 for CaO:Co2+ are also explained.
关键词:
electron paramagnetic resonance (EPR);crystal-field theory;Co2+ ion;MgO;CaO
