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  • 1
    Electronic Resource
    Electronic Resource
    s.l. ; Stafa-Zurich, Switzerland
    Key engineering materials Vol. 280-283 (Feb. 2007), p. 1779-1782 
    ISSN: 1013-9826
    Source: Scientific.Net: Materials Science & Technology / Trans Tech Publications Archiv 1984-2008
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: By the use of comprehensive transformation criterion and the method of weight function, the fracture enhancement of mixed-mode II-III crack in transformation toughened ceramics is predicated. The theoretical expressions of the toughening effect for both the stationary and steady-state growing crack are given respectively. The results show there is no toughening effect for the stationary crack and the toughening effect for the steady-state growing crack is associated with themodulus of elasticity, the width of transformation and its volume fraction
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  • 2
    Electronic Resource
    Electronic Resource
    s.l. ; Stafa-Zurich, Switzerland
    Key engineering materials Vol. 348-349 (Sept. 2007), p. 549-552 
    ISSN: 1013-9826
    Source: Scientific.Net: Materials Science & Technology / Trans Tech Publications Archiv 1984-2008
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: When failure occurs in material, it is often occurs by fracture along some grain boundariesand often by the micro-segregation of embrittling impurity to the grain boundaries. In the presentwork, the non-equilibrium grain-boundary segregation (NGS) kinetics of phosphorus and the temperembrittlement at the same solution treatment and different isothermal holding temperature in steel2.25Cr1Mo are studied. The NGS kinetics curves of phosphorus at the same solution temperature(1050 oC )and different isothermal holding temperature (540 oC and 600 oC) are given. Experimentalresults provide a direct evidence of NGS kinetic model and show that the grain boundary segregationconcentrations of phosphorus for specimen isothermal holding at 540 oC are higher than those at 600oC. The peak values of AES patterns of solute atoms for specimen isothermal holding at 540 oC arealso higher than those at 600 oC. It is therefore concluded that the lower the isothermal holdingtemperature, the higher the segregation concentration of phosphorus at the grain-boundaries, and alsothe higher the degree of embrittlement
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  • 3
    Electronic Resource
    Electronic Resource
    s.l. ; Stafa-Zurich, Switzerland
    Key engineering materials Vol. 361-363 (Nov. 2007), p. 1173-1176 
    ISSN: 1013-9826
    Source: Scientific.Net: Materials Science & Technology / Trans Tech Publications Archiv 1984-2008
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Osteoblasts were perceived as pivotal cells, recognized as the cells that control both the formativeand the resorptive phases of the bone remodeling cycle. Osteoblasts were an essential requirement forosteoclastogenesis though expressing or secreating bioactive osteoclast-differentiation-regulatory proteins,osteoclast differentiation factor (ODF)was the most important factor among these, ODF participate nearly inevery step of differentiation and activation of osteoclasts. In addition, intercellular adhesion molecule-1(ICAM-1)and its receptors LFA-1 play a role in osteoclast development by affecting adhesion betweenstromal cells and osteoclast progenitors before the occurrence of ODF-ODF receptor signaling. However, itis not clear about the relationship between ODF, ICAM-1 expression of osteoblasts and differentiation stateof osteoblasts. So,the aim of this study was to investgate whether the expression of ODF, ICAM-1 dependedon the stage of osteoblastic differentiation from rat bone marrow mesenchymal stem cells(rBMSCs). Theviability of rBMSCs is reduced significantly by osteogenic inducement as differentiating into osteoblasts,ALPase activity of OS-treated rBMSCs was enhanced obviously within 9 days , declined subsequently andrecovered nearly the original level at day 14. Expression of ODF is enhanced with osteogenic differentiationguadully. whereas, expression of ICAM-1 is activated at OS-treated day 6, then keeping at a stable level.This study indicated that rBMSCs undergoing osteogenic inducement was an ideal model for studying thedifferentiation and maturation of osteoblasts. During the early stage of differentiation along osteoblasts fromstem cells to osteocytes, rBMSCs or Osteoprogenitor react somewhat differently from osteoblasts,suggesting the ability of osteoblasts to regulating differentiation and maturation of osteoclasts have beenimproved with osteogenic culture
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  • 4
    Electronic Resource
    Electronic Resource
    s.l. ; Stafa-Zurich, Switzerland
    Key engineering materials Vol. 359-360 (Nov. 2007), p. 404-408 
    ISSN: 1013-9826
    Source: Scientific.Net: Materials Science & Technology / Trans Tech Publications Archiv 1984-2008
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Micro abrasive jet machining (MAJM) is a high effective economical technology for threedimensional micro structure fabrications of brittle materials. It is widely used in the fabrication ofsemiconductors, electronic devices, micro electro-mechanical systems (MEMS), optical-electronicand optical devices, and medical instruments. In this paper, based on the experimental study ofMAJM for glass, the influences of the nozzle type/size and abrasive type on the material erosion rateand structure profile are analyzed. The results show that the rectangular nozzle can yield a moreaccurate and efficient machining performance due to reduced flux effect. By contrast, with roundnozzle all the cross section profiles of the machined patterns show rounded V-type shape. Therectangular nozzle is able to produce geometry with flat shape. The machining area is almostindependent of the abrasive hardness, and the erosion rate increases with the increase in the hardnessof the abrasive grits. The nozzle geometry is of great importance for machining accuracy and theefficiency
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  • 5
    Electronic Resource
    Electronic Resource
    s.l. ; Stafa-Zurich, Switzerland
    Key engineering materials Vol. 353-358 (Sept. 2007), p. 1621-1624 
    ISSN: 1013-9826
    Source: Scientific.Net: Materials Science & Technology / Trans Tech Publications Archiv 1984-2008
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Warm compacting and sintering behaviors of pre-mixed Fe-2Ni-2Cu-1Mo-1C powderswere studied. Results showed that green density increased with compacting temperature and thenfell slightly; the maximum green density was obtained at about 120°C. Green compact density andspring back effect of the pre-mixed powder increased gradually as the compacting pressureincreased. Sintered density first increased and then fell as the temperatures went up under differentsintering temperatures for 50 minutes, but the trends of sintering dilatation were first reduced andthen increased. Sintered density first reduced and then increased with the prolonged sintering timeat 1300°C, but the trends of dimension change after sintering were the very reverse. Tensile strength,elongation and hardness of the warm compacted Fe-2Ni-2Cu-1Mo-1C materials generally increasedas sintering temperature and sintering time went up
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  • 6
    Electronic Resource
    Electronic Resource
    s.l. ; Stafa-Zurich, Switzerland
    Advanced materials research Vol. 24-25 (Sept. 2007), p. 195-199 
    ISSN: 1662-8985
    Source: Scientific.Net: Materials Science & Technology / Trans Tech Publications Archiv 1984-2008
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: The potential of abrasive waterjet technology was investigated as a method to polishZ-blocks of synthetic quartz crystals. The polished surfaces were characterized by surfaceroughometer and scanning electron microscopy. The main factors affecting the surface roughness andthe erosion mechanisms related to material removal were analysed. It is found that abrasive mesh,water pressure and jet incidence angle are the main factors affecting the surface roughness. Bycontrast, the influence of traverse speed on the surface roughness is small. Under certain controlledconditions, the erosion mechanisms of synthetic quartz crystals are plastic flow, leaving a crack-freesurface by low-middle pressure micro abrasive waterjet
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  • 7
    Electronic Resource
    Electronic Resource
    s.l. ; Stafa-Zurich, Switzerland
    Key engineering materials Vol. 280-283 (Feb. 2007), p. 1775-1778 
    ISSN: 1013-9826
    Source: Scientific.Net: Materials Science & Technology / Trans Tech Publications Archiv 1984-2008
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Ni base alloy ceramic grain composite coating is used mostly in high temperature condition, so thermal fatigue failure will be easy. If the thermal expansion coefficients and elastic modulus of Ni base alloy and ceramic grain are different, there will be thermal stresses between grain and matrix in thermosyphon. The thermal stress will arouse the initiation and growth of thermal fatigue crack. We use Eshebly-Mori-Tanaka method to study the thermal stress field in matrix and grain. It can be shown that the more difference of thermal expansion coefficients between Ni base alloy and ceramic grain is, the bigger the thermal stress is. The thermal stress relates to volume fractions and elastic constants of Ni base alloy and ceramic grain. Based on low-cycle fatigue crack growth rate formation, the thermal fatigue life was computed. The bigger thermal stress is, the smaller thermal fatigue life is. Thermal life is anexponential function of crack initiation length and critical length
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  • 8
    Electronic Resource
    Electronic Resource
    s.l. ; Stafa-Zurich, Switzerland
    Key engineering materials Vol. 330-332 (Feb. 2007), p. 1181-1184 
    ISSN: 1013-9826
    Source: Scientific.Net: Materials Science & Technology / Trans Tech Publications Archiv 1984-2008
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: It was well recognized that mechanical strain plays a crucial role in periodontal tissuesremodeling. The aim of this study was to investigate the effect of mechanical strain on osteoblasticprecursor cells in a collagen type I gel scaffold. Rat MSCs were isolated and cultured according tothe established method. Cells were induced with osteogenic medium, then seeded in a collagen typeI gel and mechanically stretched by application of cyclic biaxial strain 24h later. Strain cycle was setto 1 cycle/min (0.017Hz), and strain magnitude was set to 2%, 5%, 7% elongation. Cells werecollected in 0h, 3h, 6h, 9h, 12h, 24h and 48h respectively. ODF and ICAM-1 mRNA were analyzedby RT-PCR assay. The results shown that 2-7% elongation strain, either dynamic or static, inhibitedICAM-1and ODF expression of osteoblastic precursors, and the effects were relative tightly to strainmagnitude. The inhibition effects of dynamic strain loading group exceeded the corresponding staticstrain. This work suggested that appropriate mechanical strech may suppress differentiation ofosteoclasts through inhibiting expression of ICAM-1 and ODF. Application of mechanical stressmight have a beneficial effect on quantity of generated bone tissue and might be a important factorin tissue engineering of periodontal tissues
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  • 9
    Electronic Resource
    Electronic Resource
    s.l. ; Stafa-Zurich, Switzerland
    Key engineering materials Vol. 336-338 (Apr. 2007), p. 1301-1303 
    ISSN: 1013-9826
    Source: Scientific.Net: Materials Science & Technology / Trans Tech Publications Archiv 1984-2008
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: In the preparation of polymer-derived SiC fibers, nanochannels are believed to be formed in theearly pyrolysis stages due to loss of large volumes of pyrolysis gases. In this paper, small angle X-rayscattering (SAXS) was applied to the characterization and calculation of nanochannels in partiallypyrolyzedSiC fibers. The SAXS measurements showed that nanochannels with a radius of 1.0-20 nmwere formed for fibers heat-treated at 973K and 1173K. But their distributions were not continuous and atlower part of the distribution, a peak value was observed at about 1.2nm. This means if the nanochannelsare finely controlled, the partially-pyrolyzed SiC fibers have great potential application in the fields ofhydrogen storage, gas separation, and so on
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  • 10
    Electronic Resource
    Electronic Resource
    s.l. ; Stafa-Zurich, Switzerland
    Key engineering materials Vol. 336-338 (Apr. 2007), p. 2432-2435 
    ISSN: 1013-9826
    Source: Scientific.Net: Materials Science & Technology / Trans Tech Publications Archiv 1984-2008
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Recent experiment showed that nano-fibers composite ceramics, fabricated through SHSprocess, could acquire high toughening and strengthening. Composite ceramics are mainly composed offiber eutectic with random orientation, in which nanometer sized zirconia fibers are dispersed within thealumina matrix. First, it can be visualized that tensile force is transmitted from the matrix to thenano-fiber by means of shear stress that develop along the fiber- matrix interface. Then the shear stress onthe surface of the fiber eutectic is obtained. It related to the volume fraction and slenderness ratio of thenano-fibers, and external strain of the fiber eutectic. The maximum shear stress is at the ends of the fibereutectic perpendicular to applied tensile stress. As maximum shear stress on the surface of the fibereutectic is equal to the critical shear stress, the composite ceramics would crack. So the applied tensilestress on composite ceramics arousing the surface crack of the fiber eutectic is gotten
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