Advanced Materials Research Vols. 308-310

Abstract: How to design appropriate scaffold structure and mechanical environment for vitro culture of bone tissues are the focus of bone tissue engineering research. The mechanical properties of internal flow field within the scaffold are the most important factors in the scaffold design and cultivation. In order to identify the relationship between perfusion parameters, pore structure and the internal shear stress distribution, a computational scaffold model is proposed, which uses ellipsoid as the basic pore-making unit and uses major axis as the shape control parameter. Computational fluid dynamics simulation shows that the average shear stress on pore walls is linear with the major axis when the bone scaffold porosity is maintained in the same level, and the distribution of shear stress trends to be more uniform with the increase of the major axis. The experiments provide clear relationship between the structure parameter and the distribution of shear stress. And this can be used to improve the pore structure design.

Abstract: This paper proposes a robust approach to solve the complex problem of concurrent tolerance allocation. The optimal tolerances are allocated based on the adjusted nominal values of the dimensions which are less sensitive to the product performance, and selection of manufacturing processes or machines from the alternatives have also been taken into account simultaneously. Immune genetic algorithm is used to solve the model and obtain the global optimal solution. The overrunning clutch assemble is illustrated as an example.

Abstract: Abstract. In this paper, high oil-absorbing resin is prepared, using microcrystalline cellulose as base material, and acrylate as grafting monomer. Effect of mass ratio of microcrystalline cellulose/monomer, the amount of cross-linking agent, initiator dosage, reaction temperature, and reaction time on oil-absorbing properties of the products is investigated. The optimized conditions are as followed: reaction time 6 hours, reaction temperature 70 °C, mass ratio of microcrystalline cellulose to monomer 1:1.5. The oil absorbing ratio of the product prepared under these conditions is up to 12.9 g/g for toluene, and 14.6 g/g for kerosene oil.

Abstract: With the development of lightweight vehicles, lightweight alloy materials has been increasingly used in automotive industry, automobile manufacturers are therefore looking for thinner and stronger materials so that the higher requirements has became a challenge to lightweight alloy die-casting technology. The paper summarized the applications of lightweight alloys in the automotive industry, and the new advances of lightweight alloys die-casting technology, such as low pressure die-casting, semi-solid die casting, oxygenation die-casting and the combination of different die-casting technologies, and discussed the development trend of the lightweight alloy die-casting technology.

Abstract: The passivator of potassium dichromate is one of the main electrolysis manganese passivation technologies in China. The biggest problem of hexavalent chromium passivation is chromium emission. The end-pipe treatment of Cr-containing effluents can be understood as detoxification and precipitation. Here the highly toxicity Cr(Ⅵ) is reduced to low toxicity Cr(Ⅲ) . In alkaline conditions, Cr (Ⅲ)is precipitated in the type of chromium hydroxide and produce chromium residue. The landfill of Chromium residue is a big problem to environment safety. The measures of clean process were reviewed around with emission reduction of Cr.

Abstract: Ti-43Al-5V-4Nb (at.%) intermetallic compounds with fully lamellar structure were fabricated by forging method without canning using the blended elemental powders. The process route consisted of powder blending, compacting, sintering and final fabrication by hot forging. During sintering, there existed expansion, which is detrimental to forging process. In order to overcome the difficulty, two-step forging was introduced. The total reduction of two-step forging was up to 65%. Nearly fully lamellar structure of TiAl alloy was obtained. Overall, an optimized and potentially lower cost processing route could be identified.

Abstract: In the present investigation, AZ91 magnesium alloy was vacuum diffusion bonded to a 7075 aluminum alloy. The effects of the welding temperature and holding time on the joint shear strength are investigated with the help of electron microscopy, micro-hardness and electronic universal testing machine. It is shown that in certain extent, the welding temperature and holding time have great effect on the joint shear strength. The maximum of joint shear strength is obtained and the width of diffusion layer is 34.36μm with the bonding temperature being 470°C and the holding time reaching 60min.

Abstract: Silica/epoxy resin hybrid materials are prepared with tetraethylorthosilicate (Si(OC₂H₅)₄, TEOS) and γ-aminoproplytriethyoxysiliane (H₂N(CH₂)₃Si(OC₂H₅)₃, APTES) as the silica sources, epoxy resin as the polymer matrix, by the means of in-suit sol-gel method. The dosages of TEOS and APTES in preparation of hybrid materials, and the sol-gel temperature for silica resources are discussed to make sure of the influence of the structure and properties on hybrid materials. The dispersion of Silica in the epoxy resin are examined by transmission electron microscopy (TEM).The image of fracture surfaces of hybrid materials are examined by scanning electron microscopy (SEM). The glass transmission temperatures (Tg) are tested by differential scanning calorimeter (DSC) to characterize the heat resistance of hybrid materials. The optimum mechanical performance and heat resistance for silica/epoxy resin hybrid materials are achieved with 3wt% TEOS and APTES 2wt% employed in this materials when sol-gel temperature is 60°C. In general, the mechanical and thermal properties of the hybrid materials were improved greatly as compared with the pure epoxy resin.

Abstract: This study uses the embedded browser in the most widely used CAD (Computer Aided Design) , with the mold-design navigating process of the secondarily developed component as the core, to construct a networked knowledge management platform with the interaction between the relational database management and mold-design navigating process. It then integrated the component knowledge database, historical cases and technical files, and gave the overall consideration of mold manufacture and injection molding to assist the mold design. The component knowledge database provides related components and shortens the time of mold design. The historical knowledge database offers related issue points for reference, reducing the repeated occurrence of design errors. The technical knowledge database furnishes the related knowledge in the process of mold development, accelerates the new employee training and cuts the labor cost. For the knowledge database in use, the data will automatically increase and grow, gradually becoming know-why and know-how of strong enterprises, know-what of handling problems and important core assets of the enterprise. The unified integration and utilization of the component, historical and technical knowledge databases make the mold-design navigating process more complete and accelerate the mold design. By data classification and grouping, a consistent GUI (Graphic User Interface) is established, replacing the words by icons, easier for developers to use. The accumulation and feedback of the knowledge databases provide more complete data, information and knowledge and thus considerably reducing the time for the mold development.

Abstract: A feature-based process planning approach for fineblanking-forming-stamping parts is discussed in this paper. To reduce the dependence of experience designers and improve the design efficiency and quality, a prototype of feature-based process planning system has been established. The system consists of four major modules: forming process recognition, feature representation, operation sequence design and parametric feature modeling. The graph-based process recognition and feature representation methods are introduced. The knowledge-based methods are also used for process planning. An application example is illustrated.