Author M. AbdelKarim
,
M. Mizuno and N. Ohno\= Department of Mechanical Engineering
,
Nagoya University Chikusaku
,
Nagoya 4648603
,
Japan Manuscript received 18 October 1998
金属学报(英文版)
In the previous paper, in order to express steadystate ratchetting, the present authors extended the cyclic plasticity model proposed by Ohno and Wang (1993), and the validity of the extended model was discussed on the basis of uniaxial ratchetting experiments of 316FR steel at room temperature. In the present paper, the validity of the extended model is discussed further on the basis of nonproportional experiments of IN738LC at 850 such as multiaxial ratchetting, multiaxial cyclic stress relaxation, circular cyclic straining with strain hold, and so on. Predictions based on the OhnoWang model as well as the ArmstrongFrederick model are also given for the sake of comparison. It is shown that the extended model is capable of simulating the nonproportional experiments accurately, and especially that the extended model can predict much less steadystate ratchetting than the ArmstrongFrederick model. It is also shown that the extended model provides almost the same predictions as the OhnoWang and th
关键词:
dynamic recovery
,
null
,
null
,
null
,
null
T.A. Popovich
,
O.V. Arestov
,
A.A.Popovich
,
A.S. Kuchma
材料科学技术（英文）
Mossbauer spectrometry was used to study the peculiarity of formation of nonequilibrium phase in Fe-Ti and Fe-Ti-N systems by mechanical alloying. Mossbauer spectra of powders show the formation of nonequilibrium crystalline phase and intermetallic compounds during a mechanical alloying process depending on the alloy composition and the milling time.
关键词:
Mehdi Ebrahimian-Hosseinabadi Fakhredin Ashrafizadeh Mohammadreza Etemadifar Subbu S. Venkatraman
材料科学技术（英文）
In this paper, preparation of nano-biphasic calcium phosphate (nBCP), mechanical behavior and load-bearing of poly (lactide-co-glycolide) (PLGA) and PLGA/nBCP are presented. The nBCP with composition of 63/37 (w/w) HA/β-TCP (hydroxyapatite/β-tricalcium phosphate) was produced by heating of bovine bone at 700°C. Composite scaffolds were made by using PLGA matrix and 10-50 wt% nBCP powders as reinforcement material. All scaffolds were prepared by thermally induced solid-liquid phase separation (TIPS) at -60°C under 4 Pa (0.04 mbar) vacuum. The results of elastic modulus testing were adjusted with Ishai-Cohen and Narkis models for rigid polymeric matrix and compared to each other. PLGA/nBCP scaffolds with 30 wt% nBCP showed the highest value of yield strength among the scaffolds. In addition, it was found that by increasing the nBCP in scaffolds to 50 wt%, the modulus of elasticity was highly enhanced. However, the optimum value of yield strength was obtained at 30 wt% nBCP, and the agglomeration of reinforcing particles at higher percentages caused a reduction in yield strength. It is clear that the elastic modulus of matrix has the significant role in elastic modulus of scaffolds, as also the size of the filler particles in the matrix.
关键词:
Scaffold
Metallurgical and Materials Transactions a-Physical Metallurgy and Materials Science
The influence of solution temperature on the microstructure and mechanical properties of TMW-4M3 superalloy has been investigated. Comparisons of mechanical properties have also been made between the heat-treated TMW-4M3 variants and the commercial U720Li. The key microstructural variables examined were grain size and the volume fraction and size of the strengthening gamma' precipitates that control the mechanical properties of these alloys. By increasing the solution temperature from 1373 K to 1393 K (1100 A degrees C to 1120 A degrees C), the volume fraction of primary gamma prime dropped from 16.9 pct to 14.5 pct, whereas the average grain size increased from 8.7 mu m to 10.6 mu m. Compared with an alloy with a smaller grain size, the alloy with a larger grain size exhibited superior resistances to creep and fatigue crack growth without the expense of reduced tensile strength and low-cycle fatigue resistance. This suggested that a higher solution temperature may benefit TMW-4M3 in terms of superior overall properties. The greater overall properties of TMW-4M3 variants than that of commercial U720Li were also demonstrated experimentally. The possible explanations for the improvement of mechanical properties were discussed.
关键词:
ni-base superalloy;low-cycle fatigue;heat-treatment;cooling;precipitation;stainless-steel;yield strength;udimet 720li;creep;behavior;alloy
Journal of Materials Research
Bonding character, elastic mechanical parameters, ideal strengths, and atomistic shear deformation mechanisms of M(3)AlN (M = Zr and Hf) were studied by first-principles method. M(3)AlN exhibits layered chemical bonding character due to the alternately stacking of relatively soft AI-M and strong N-M covalent bonds. The second-order elastic constants and mechanical parameters of M(3)AlN were reported for the first time. The stress-strain relationships for different deformation modes were studied and the ideal shear and tensile strength were obtained. M(3)AlN ceramics are predicted to be "quasi-ductile" layered nitrides based on the low shear-modulus-to-bulk-modulus ratios, positive Cauchy pressure (c(12)-c(44)), and lower ideal shear strength compared to ideal tensile strength. Investigation of the atomistic shear deformation mechanism of M(3)AlN shows that stretching of soft Al-Hf bonds and relatively weak bridge N-Hf1 bonds dominate the shear deformation; while the rigid N-Hf2 bonds resist against the applied shear strain. Chemical bonding characteristics and shear deformation mechanism of M(3)AlN are similar with those of other "quasi-ductile" ceramics, such as MAX phases, LaPO(4) monazite, and gamma-Y(2)Si(2)O(7). The results further suggest that M(3)AlN nitrides should be quasi-ductile and damage tolerant.
关键词:
electronic-structure;ternary carbides;ceramics;optimization;zr2al3c4;systems;solids;ti2alc
Materials Science & Engineering C-Biomimetic Materials Sensors and Systems
Bamboo, one of the strongest natural structural composite materials, has many distinguishing features. It has been found that its reinforcement unit, hollow, multilayered and spirally-wound bast fiber, plays an extremely important role in its mechanical behavior. In the present work, on the basis of the study on bamboo bast fiber and wood tracheid, a biomimetic model of the reinforcing element, composed of two layers of helically wound fiber, was suggested. To detect the structural characteristics of such a microstructure, four types of macro fiber specimens made of engineering composites were employed: axially aligned solid and hollow cylinders, and single- and double-helical hollow cylinders. These specimens were subjected to several possible loadings, and the experimental results reveal that only the double-helical structural unit possesses the optimum comprehensive mechanical properties. An interlaminar transition zone model imitating bamboo bast fiber was proposed and was verified by engineering composite materials. In our work, the transition zone can increase the interlaminar shear strength of the composite materials by about 15%. These biomimetic structural models can be applied in the design and manufacture of engineering composite materials.
关键词:
bamboo;bast fiber;biomimetics;engineering composites
Y.B. Hou
金属学报(英文版)
In this paper, the PMMA films doped with N,N'-diphenyl-N,N'-di(m-tolyl)-benzidineand rubrene were fabricated by spin coating, and the effect of photooxidation onthe photoluminescence of the doped PMMA thin films was investigated. The resultsshowed that under the irradiation of 350nm UV light, N,N'-diphenyl-N,N'-di(m-tolyl)-benzidine can sensitized rubrene and results in the enhancement in the photooxrationof rubrene. The effect of photooxidation on the photoluminescence from rubrene w asmore obvious. Both lifetime measurement and in situ measurement of photolumines-cence showed that rubrene molecules exist in two chemical surroundings.
关键词:
photoluminescence
,
null
Journal of Magnetism and Magnetic Materials
Phase constitution and magnetic properties of Nd10Fe76B4M10 and Nd10Fe76B2M12 (M = Fe,Ti,V,Cr, Mn,Co and Al) alloys prepared by mechanical alloying and subsequent annealing have been systematically studied. It is found that the components of phases in the alloys critically depend on the additive transition metals M. In all the alloys, only the addition of Ti give significant enhancement to the permanent-magnetic properties. The increase of the Curie temperature in the Ti-doped alloys with an excessively low B content implies that part of the Ti atoms may occupy crystalline sites other than the Fe sites. In all the M additive alloys, with increasing content of the additive elements, the quantity of 1:7 phase increases and that of Nd2Fe14B-type phase decreases, (C) 2000 Elsevier Science B.V. All rights reserved.
关键词:
phase constitution;structure;magnetic properties;alloys;mechanical;alloying;nd;coercivity
HL. Huang
,
J.H Xing
,
G.L. Liu and G.Y Zhang(Department of Electrouic Science and Engineering
,
Liaoning University Shenyang 110036
,
China)(Department of Physics
,
Liaoning University Shenyang 110036
,
China)(Shenyang Polytechnic University Shenyan 110023
,
China)(Northeast Microelectronic Institute of Ministry of Electronic Industry Shenyang 110032
,
China)
金属学报(英文版)
The electronic structures of (CdSe)n/(ZnSe)m strained-lager soperfattice (SLS) were investigated by the recursion method in the tight-bindiop opproximation. The total,local, and partial density of states were calculated for n=1, m=5.The total density of states (TDOS) for bulk CdSe, ZnSe and n=1, 3, m=1, 3, 5, for SLS were investigated.Fermi energy, the band gap, the valence of an atom, and the ionization potential and the electron affinity were discassed.
关键词:
density of state
,
null
,
null
,
null
,
null
