查看更多>>摘要：To improve the structural properties of engineering ceramics, carbon nanotubes have been used as a reinforcement phase to produce stronger ceramic matrix composites. This paper investigates the possible chemical bond formation between a carbon nanotube and alumina with the aid of quantum mechanics analysis. The cases with and without functionalizing the nanotubes were examined. The nanotubes were modeled by nanotube segments with hydrogen atoms added to the dangling bonds of the perimeter carbons. The cleaved ceramic (0001) surface was represented by an alumina molecule with the oxygen atoms on either end terminated with hydrogen. Methoxy radicals were used to functionalize the CNTs. The study predicts that covalent bonding between Al atoms on a cleaved single crystal alumina surface and C atoms on a nanotube are energetically favorable.
查看更多>>摘要：This paper presents a high-speed high-precision spindle system with hybrid ceramic bearing, along with its lubricant design and numerical calculation method. A green and viscosity controllable water based fluid as lubricant of the spindle was designed. Viscosities as a function of temperature were tested. Subsequently, numerical calculation was used to deduce a serious of bearing performances. Based on the results rate of the permeation of porous restrictor, some bearing structure parameters and relative optimum lubricant viscosity were determined. The results of thermal elastohydrodynamic simulation and rotor dynamic analysis indicate that the design of the hybrid ceramic bearing meets security and performance specifications. Finally the structure arrangement of the spindle system was finished.
查看更多>>摘要：This paper presents a stress analysis of the ceramic femoral heads of hip joint prostheses with different borehole shapes to evaluate their mechanical reliability in terms of stress concentration. Under the ideal loading conditions used for ceramic rupture tests specified by the ISO 7206-5 standard, a finite element (FE) modeling is performed to determine the tensile and hoop stress distributions in the ceramic femoral heads. Two borehole shapes that are currently used in the manufacturing industry for hip joint prostheses, namely the flat bottom and keyhole, were first studied. Two new borehole shapes, dome arc and dome ellipse, were then introduced by the authors in the paper to minimize the stress concentration. It was found that while the currently used borehole shapes lead to high tensile notch stresses at their critical corners causing possible fracture failure of ceramic heads, the authors' borehole designs can improve the mechanical reliability significantly. In addition, the effects of taper-bore contact length and their interface friction are investigated and discussed.
Mei LiuL.C. ZhangAndrew BrawleyPetar Atanackovic...
P.742-747页
查看更多>>摘要：This paper investigates residual stress of epitaxial silicon film on SOS thin film systems. The emphasis was to develop a method to obtain accurately the complete residual stress tensors. It was found that using the multiple asymmetric X-ray diffraction method to measure strains in 13 [hkl] directions, the complete residual stress tensors can be determined reliably. The results were verified by both the Raman Backscattering and the substrate curvature methods.
查看更多>>摘要：Aerospace industry is a value-added and technology integrated industry. Due to the investment of aerospace industry is high and the pay back period is long, the type of aircraft production belongs to make-to-order system. Business flows and process flows are complex inside the aerospace manufacturing industry. Quality, cost, delivery and flexibility are the fundamental requirements of aerospace manufacturing suppliers. The aerospace manufacturing suppliers have to coordinate those fundamental requirements and construct the model of production system with Continuous Improvement in the competitive market. This study integrates the concepts of Six Sigma, Theory of Constraint, Lean Production and Value Engineering, and allies the functional groups and system resources inside the aerospace manufacturing suppliers. Then develop the Production Improvement Model with Continuous Improvement to allocate the resources to construct a production system. Thereby, the aerospace manufacturing suppliers can strengthen the competitiveness in the dynamic aerospace market.
NETL
NSTL
Trans Tech Publications Ltd