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  • 1
    Digitale Medien
    Digitale Medien
    Study on High Performance Warm Compacted Fe-2Ni-2Cu-1Mo-1C Powder Metallurgy Materials (2007)
    s.l. ; Stafa-Zurich, Switzerland
    Key engineering materials Vol. 353-358 (Sept. 2007), p. 1621-1624 
    Details
    ISSN: 1013-9826
    Quelle: Scientific.Net: Materials Science & Technology / Trans Tech Publications Archiv 1984-2008
    Thema: Maschinenbau
    Notizen: 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
    Materialart: Digitale Medien
    URL: http://www.tib-hannover.de/fulltexts/2011/0528/01/55/transtech_doi~10.4028%252Fwww.scientific.net%252FKEM.353-358.1621.pdf
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  • 2
    Digitale Medien
    Digitale Medien
    Effect of Nozzle Type and Abrasive on Machinablity in Micro Abrasive Air Jet Machining of Glass (2007)
    s.l. ; Stafa-Zurich, Switzerland
    Key engineering materials Vol. 359-360 (Nov. 2007), p. 404-408 
    Details
    ISSN: 1013-9826
    Quelle: Scientific.Net: Materials Science & Technology / Trans Tech Publications Archiv 1984-2008
    Thema: Maschinenbau
    Notizen: 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
    Materialart: Digitale Medien
    URL: http://www.tib-hannover.de/fulltexts/2011/0528/01/55/transtech_doi~10.4028%252Fwww.scientific.net%252FKEM.359-360.404.pdf
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  • 3
    Digitale Medien
    Digitale Medien
    The Toughening Action of Comprehensive Transformation on Mixed Mode II-III Ceramics (2007)
    s.l. ; Stafa-Zurich, Switzerland
    Key engineering materials Vol. 280-283 (Feb. 2007), p. 1779-1782 
    Details
    ISSN: 1013-9826
    Quelle: Scientific.Net: Materials Science & Technology / Trans Tech Publications Archiv 1984-2008
    Thema: Maschinenbau
    Notizen: 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
    Materialart: Digitale Medien
    URL: http://www.tib-hannover.de/fulltexts/2011/0528/01/49/transtech_doi~10.4028%252Fwww.scientific.net%252FKEM.280-283.1779.pdf
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  • 4
    Digitale Medien
    Digitale Medien
    Expression of ODF and ICAM-1 of Bone Marrow Mesenchymal Stem Cells is Enhanced with Osteogenic Differentiation (2007)
    s.l. ; Stafa-Zurich, Switzerland
    Key engineering materials Vol. 361-363 (Nov. 2007), p. 1173-1176 
    Details
    ISSN: 1013-9826
    Quelle: Scientific.Net: Materials Science & Technology / Trans Tech Publications Archiv 1984-2008
    Thema: Maschinenbau
    Notizen: 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
    Materialart: Digitale Medien
    URL: http://www.tib-hannover.de/fulltexts/2011/0528/01/56/transtech_doi~10.4028%252Fwww.scientific.net%252FKEM.361-363.1173.pdf
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  • 5
    Digitale Medien
    Digitale Medien
    Effect of Isothermal Holding Temperature on NGS Kinetics of Phosphorus and Temper Embrittlement (2007)
    s.l. ; Stafa-Zurich, Switzerland
    Key engineering materials Vol. 348-349 (Sept. 2007), p. 549-552 
    Details
    ISSN: 1013-9826
    Quelle: Scientific.Net: Materials Science & Technology / Trans Tech Publications Archiv 1984-2008
    Thema: Maschinenbau
    Notizen: 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
    Materialart: Digitale Medien
    URL: http://www.tib-hannover.de/fulltexts/2011/0528/01/55/transtech_doi~10.4028%252Fwww.scientific.net%252FKEM.348-349.549.pdf
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  • 6
    Digitale Medien
    Digitale Medien
    Thermal Fatigue Life Prediction of Ni Base Alloy Ceramic Composite Coating (2007)
    s.l. ; Stafa-Zurich, Switzerland
    Key engineering materials Vol. 280-283 (Feb. 2007), p. 1775-1778 
    Details
    ISSN: 1013-9826
    Quelle: Scientific.Net: Materials Science & Technology / Trans Tech Publications Archiv 1984-2008
    Thema: Maschinenbau
    Notizen: 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
    Materialart: Digitale Medien
    URL: http://www.tib-hannover.de/fulltexts/2011/0528/01/49/transtech_doi~10.4028%252Fwww.scientific.net%252FKEM.280-283.1775.pdf
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  • 7
    Digitale Medien
    Digitale Medien
    A Study on Erosion Mechanisms of Quartz Crystals Polished by Micro Abrasive Waterjet (2007)
    s.l. ; Stafa-Zurich, Switzerland
    Advanced materials research Vol. 24-25 (Sept. 2007), p. 195-199 
    Details
    ISSN: 1662-8985
    Quelle: Scientific.Net: Materials Science & Technology / Trans Tech Publications Archiv 1984-2008
    Thema: Maschinenbau
    Notizen: 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
    Materialart: Digitale Medien
    URL: http://www.tib-hannover.de/fulltexts/2011/0528/01/39/transtech_doi~10.4028%252Fwww.scientific.net%252FAMR.24-25.195.pdf
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  • 8
    Digitale Medien
    Digitale Medien
    Three-Dimensional Simulation of Liquid-Solid Two-Phase Flow Inside the Abrasive Water Jet Nozzle (2007)
    s.l. ; Stafa-Zurich, Switzerland
    Key engineering materials Vol. 329 (Jan. 2007), p. 329-334 
    Details
    ISSN: 1013-9826
    Quelle: Scientific.Net: Materials Science & Technology / Trans Tech Publications Archiv 1984-2008
    Thema: Maschinenbau
    Notizen: Three dimensional simulation of the velocity field of solid-liquid two-phase flow insidethe abrasive water jet nozzle was studied by the computational fluid dynamics software (CFD). Thecomplicated velocity field and vectorgraph of the flow in the abrasive water jet nozzle was obtained.In the course of the simulation, the Syamlal-O’Brien model was used to decide the inter-phase dragexchange coefficient. The velocity vectorgraph simulation results indicate that the highest flowspeed is occurred at the inlet of the mixing chamber and the flow speed is gradually decreased alongthe direction of the nozzle axis and got to the lowest speed at the outlet of the nozzle. And also theflow speed in the cross section of the mixing chamber is gradually reduced along the radialdirection of the cross section and got to the lowest speed in the verge of the chamber. Thecomparison of simulation result for the velocity field of water and abrasive exhibits that the velocityof water in the mixing chamber is three or four times higher than that of abrasive
    Materialart: Digitale Medien
    URL: http://www.tib-hannover.de/fulltexts/2011/0528/01/52/transtech_doi~10.4028%252Fwww.scientific.net%252FKEM.329.329.pdf
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  • 9
    Digitale Medien
    Digitale Medien
    Surface Characteristics of Ceramics Milled with Abrasive Waterjet Technology (2007)
    s.l. ; Stafa-Zurich, Switzerland
    Key engineering materials Vol. 329 (Jan. 2007), p. 335-340 
    Details
    ISSN: 1013-9826
    Quelle: Scientific.Net: Materials Science & Technology / Trans Tech Publications Archiv 1984-2008
    Thema: Maschinenbau
    Notizen: The surface characteristics of Si3N4 ceramics milled with abrasive waterjet millingtechnology is studied. The milled surface characteristics and the effect of process parameters onmilled surface roughness are analyzed. The results show that the milled surface roughness rangesbetween 0.55 and 1.1um at the milling conditions under consideration and is changed with thechange of process parameters. The milled surface roughness will be significantly decreased at themilling conditions of lower water pressure and larger lateral spacing. The effect of nozzle traversespeed on milled surface roughness is complex, but a traverse speed of 1000mm/min is the optimumspeed for AWJ milling Si3N4 ceramics. The milled surface roughness first decreases then increaseswith an enhancement of standoff distance from 10mm to 30mm, and it also significantly decreaseswith the increase in abrasive mesh. Therefore, the medium standoff distance of 20mm and finerabrasive are the optimum conditions for AWJ milling Si3N4 ceramics with the process parametersunder consideration
    Materialart: Digitale Medien
    URL: http://www.tib-hannover.de/fulltexts/2011/0528/01/52/transtech_doi~10.4028%252Fwww.scientific.net%252FKEM.329.335.pdf
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  • 10
    Digitale Medien
    Digitale Medien
    Effects of Mechanical Strain on Osteoblastic Precursor Cells in a Three-Dimensional Scaffold (2007)
    s.l. ; Stafa-Zurich, Switzerland
    Key engineering materials Vol. 330-332 (Feb. 2007), p. 1181-1184 
    Details
    ISSN: 1013-9826
    Quelle: Scientific.Net: Materials Science & Technology / Trans Tech Publications Archiv 1984-2008
    Thema: Maschinenbau
    Notizen: 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
    Materialart: Digitale Medien
    URL: http://www.tib-hannover.de/fulltexts/2011/0528/01/53/transtech_doi~10.4028%252Fwww.scientific.net%252FKEM.330-332.1181.pdf
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