Key Engineering Materials Vol. 339

Abstract: Simulation of the velocity field of solid-liquid flow inside and outside the abrasive water jet nozzle was studied by the computational fluid dynamics software(CFD). The velocity field of the flow in the abrasive water jet (AWJ) nozzle was obtained. The results indicate that the swirl is produced in the nozzle and the abrasives are all distributed along the inner surface of the nozzle. The velocity at the center of the outlet face is the highest, while it is smallest at the both edge. The dispersion of the flow is happened when it flows out of the nozzle, but the flow velocity away from the outlet at a distance of about 4 times of the outlet diameter changes little. The fillet diameter, the inner cone angle, the length of mixing tube of the nozzle greatly affect the field of two-phase flow. The velocity of outlet increases with an increase in the fillet diameter, the flow becomes ease when the cone angle decreases, the mixing tube hampers the two-phase flowing.

Abstract: A new method is given to determine the load distribution factor Kβ of involute gears. Compared with the old method, the new one gives up some improper assumptions such as linear load distribution along gear tooth width. While considering the effects of bearing deformations, gear manufacture and assembly errors, gear axial force and gear tooth run-in on Kβ, the paper calculates Kβ according to “Load- Deformation Coordination” of gear tooth. Practical examples show that this method is more accurate, more effective than old ones.

Abstract: Cathodic-anodization process was performed to treat titanium sheets to improve biocompatible performance. Grazing incident X-ray diffraction, transmission electron microscopy, scanning electron microscopy and electrochemical measurement were used to evaluate the influence of hydrogen on the formation of nanoporous TiO2. Multimeshworked and nanoporous TiO2 was observed after treatment with cathodic-anodization process. The nanoporous oxide layer is hard to form without nano-TiH2. The nano-TiH2 plays an important role in forming multimeshworked and nanostructured TiO2 layer. Hydrogen charging by cathodization is believed to enhance the formation of nanoporous oxide film and thus promote biocompatibility.

Abstract: In this report, nanopatterns consisting of an organic polymer film were fabricated using a simple detachment method. The method used a patterned ultraviolet (UV) curable poly(urethane acrylate) (PUA) as a mold and an organic polymer layer as a template material. A thin film was prepared by spin coating and then annealed below the glass transient temperature while in physical contact with the PUA mold. The polymer layer in contact with the mold was detached due to the difference in adhesion force, resulting in a well-defined nanoarray of the polymer template. Nanopatterns as small as 70 nm lines were fabricated using this approach.

Abstract: As demand for complex precision parts increase, the existing fabrication methods such as MEMS, and LIGA technology have technical limitations with regard to high precision, high aspect ratio, and high complexity. A microstereolithography technology based on DMDTM(Digital Micromirror Device) can meet these demands. DMD enables a system to handle dynamic patterns. In this technology, the same standard format of the conventional rapid prototyping system, the STL file, is used, and 3D parts are fabricated by stacking layers that are sliced as 2D section from STL file. Whereas in conventional methods, the resin surface is cured by scanning laser beam spot according to the section shape, but in this research, we used an integral process which enabled the resin surface to be cured by one irradiation. In this paper, we dealt with the dynamic pattern generation and DMD operation to fabricate microstructures. Firstly, the microstereolithography apparatus and process were discussed. Secondly, the DMD operation according to mirror tilting, and optimal mounters for DMD and reflecting mirror according to light path were described. And thirdly, complex 3D microstructures were demonstrated.

Abstract: Bridge-type flexure hinge is a classical flexure amplification mechanism. The amplification ratio and stiffness are the key parameters in an amplification mechanism. Elastic mechanics was used to analyze the input and output stiffness of bridge-type amplification mechanism in relation to the translational and rotational stiffness of the flexure pivots. The result showed that the stiffness model can explain well the outer characteristic of bridge-type flexure hinge.

Abstract: The present paper describes the highly efficient and precise ELID grinding method and presents a discussion on the ELID grinding process and the grinding characteristics of several kinds of ceramic materials. The following conclusions are obtained; (1) Good ground surface roughness and accuracy are achieved using the #4000 metal-bonded grinding wheel in through-feed centerless grinding for ZrO2 optical fiber ferrules. (2) Efficient and precise grinding of spherical lens molds with cup wheels using the ELID CG-grinding process was proposed and tested in the present study. (3) The ELID grinding method can be used to fabricate machined surfaces exhibiting desirable characteristics for hard AlN ceramics. The ELID ground AlN demonstrated a surface hardness and sliding characteristics that were superior to those of the polished series. These advantages may be attributable to the diffusion phenomenon of the oxygen element produced by the ELID grinding.

Abstract: The paper presents a micro-fluidics cooling system which is designed on a silicon substrate including a micro-pump, two temperature sensors, a flow sensor and some microchannels. To design the cooling system optimally, a finite element model is built. The temperature distribution on the silicon substrate is analyzed using the model. Moreover, the quantitative relation is given of the temperature distribution, flow velocity and driving capability of the micro pump. Consequently, the structure parameters and design requirements of the cooling system are obtained.

Abstract: Interpolation approximation is used in the design of Pin-jointed Four-bar Linkages with corresponding angular displacements of grounded links to realize approximately a given function. First Four-bar linkage position equations with parameters to be determined are established；then the paper sets up the relationships between given function and approximation function；finally it chooses Chebychev interpolation points to determine the approximation function. Angular error analysis is also conducted. A design example is given for reference in the end.

Abstract: The machining performance of Al2O3 ceramics is studied by abrasive waterjet (AWJ) milling experiment. The machined surface characteristics and the effect of process parameters on machined surface quality are analyzed. The results showed that the nozzle traverse speed and traverse feed have a strong effect on the machined surface quality. The effect of process parameters on material volume removal rate and the milling depth is also researched. The results indicated that the material volume removal rate and the milling depth would be increased at the milling conditions of higher water pressure and bigger standoff distance. However, the milling depth will decrease at the milling conditions of higher traverse speed and higher traverse feed, and the material volume removal rate has a complex variation.