Advanced Materials Research Vols. 476-478

Abstract: Experimental study on ultrasonic and electromagnetic roll-casting of magnesium alloy was carried out using a self designed and installed twin roll continuous horizontal caster . 2.5mmthickness and 200mmbreadth of AZ31B magnesium alloy casting strips were produced successfully. The results show that the ultrasonic and electromagnetic field is transferred into roll-casting zone and result in a great decrease of the grain size,the average grain size has decreased to 10～15μm from 60～70μm; and also improved the mechanic properties of the AZ31B magnesium alloy sheet, the tensile strength and yield strength and elongation and hardness are improved by 25%and 44.4% and 120.7% and 12%respectively. On this basis, the mechanism of grain refinement during cast-rolling process with ultrasonic cavitation and electromagnetic field effect are discussed.

Abstract: Compositions and hardness of four prehardened steels for plastic mould blocks with more than 1 m thick, named QTPA, QTPB, QTPC and QTPD were tested, and microstructures at center and surface of blocks were observed. The results show that hardness uniformity of the QTPC steel block is less than ± 4 HRC, its center appears pearlite, while microstructures at center of the other three steel blocks are martensite and bainite, hardness uniformity of the QTPA steel is less than ±1 HRC, hardness uniformity of the QTPB and QTPD steels are less than ±2 HRC. Combined with the compositions analysis, molybdenum has bigger effect on the hardenablity and hardness uniformity of the large section prehardened steels for plastic mould block, and QTPC steel with higher carbon and lower Molybdenum content makes the hardness uniformity be less than the others.

Abstract: Great prospect in ultra precision leads to the urgent requirement for the research on the nanometric machining of metallic glass (MG). Molecular dynamics simulation is carried out to find out the nanometric cutting mechanisms of MG. The MG workpiece, Cu50Zr50, is prepared using fast cooling simulation in isothermal-isobaric ensemble. Interactions of Cu and Zr atoms are described by Finnis-Sinclair potential. Morse potential is adopted for the interaction between the carbon atom in the diamond tool and the metal atom in the workpiece. Simulation results show that, different from cutting crystal material, there is not visible shear zone ahead of the tool. That is to say the mechanism in nanometric cutting MG may be plastic cutting.

Abstract: The Drum Solid-state Fermentation Equipment was developed, the equipment included the parts of the feed, mixing, disinfection, cooling, inoculation and fermentation, and it could undertake sterile operation and control temperature automatically. The three-dimensional model of the equipment was built using the solidworks software. The selection of the material and structure of the key parts were optimized by using Simulation, and the stress was analysed by the software in solidworks. The running animation of the equipment was produced by using the plug-in module COSMOSMotion, which showed the real state of the equipment movement, such overall design improved the efficiency and accuracy.

Abstract: Cell assembly technology adopting the gelatin-based composite materials has found broad application in the field of disease mechanism research, drug development and organ reconstruction etc. But there are still several troublesome problems, such as the necessaries of high forming concentration of gelatin-based materials and the cell damage produced during extrusion. In view of existing situation, a modified gelatin-based cell assembling process using glycerin was brought forward. The results showed that adding 10% (v/v) glycerin to the existing gelatin-based composite materials, the cells inactivation effect under 4 °C or lower temperature environment can be reduced obviously, meanwhile, the glycerin has a compensatory effect of gelatin. It can significantly improve the forming temperature and the cell survival rate, get high cell survival rate even when the scanning speed is on 40 mm/s. In addition, the glycerin is easier to dissolve in culture medium in the tissue analog training process; it is more conducive to the rapid materials degradation, as well as cell proliferation and tissue regeneration. Therefore, modified gelatin-based cell assembly process with glycerin will be more widely used in tissue or organ in vitro assembly process.

Abstract: Diesel spray characteristics are closely related to the combustion of the engine where the spray tip penetration and the fuel atomization play a key role especially for direct injection (DI) diesel engine. With different nozzles, the fuel atomization and evaporation will be different thereby affecting the combustion and emission characteristics. A three-dimensional model is built based on the parameters of a DI diesel engine, and its validation is also validated. Three nozzle-hole layouts are designed in this research, including the conventional hole, multi-hole, and group-hole. The spray characteristics and combustion process are studied with three different nozzle-hole layouts by the way of numerical simulation. Further more, the effect of inter-hole spacing of group-hole nozzle on the evaporation rate and combustion process is researched here.

Abstract: Three inclusion detection methods: image analysis, colorimetry and flux rinsing were compared aiming at the removal of solid oxide inclusions in molen aluminum in this paper. The testing results obtained from the comparative experiments indicate that the content of inclusions in aluminum can be detected quantitatively and quickly using the three methods. Image analysis is more intuitionistic, but testing value is a little larger; colorimetriy and flux rinsing method are of high accuracy, but testing values are estimated to be a little lower.

Abstract: In this study, biomimetic synthesis of hydroxyapatite (HAp) nanocomposites based on bacterial cellulose (BC) with sodium alginate (SA) surface modification was studied. The results showed that SA treatment promoted the apatite nucleation ability of BC in SBF solution. The FE-SEM images demonstrated that HAp nanoparticles were successfully formed in the three dimensional nanofiber network of BC. FTIR spectra indicated that the obtained HAp crystals were partially substituted with carbonate, which were very similar with natural bones. It was also found that both of crystallite size and crystallinity of HAp crystals observed from XRD pattern were very low. The resultant nanocomposites consisted of nano-scale HAp crystals and SA treated BC nanofibrous have great potential application in bone tissue engineering.

Abstract: By fine earth freeze-thaw simulated experiment and cut experiment in the room, this paper studied the sheer strength characteristic parameter before and after the freezing-thaw cycling, and got the change discipline of the internal cohesive force c, internal friction angle Ф in the different temperature range and the number of the freezing-thaw cycling, deduced the calculation formula of c, Ф and T(soil nail counteract evulsion force) according to the experiment data, and compared the effect of the firmness.

Abstract: The effects of varying the additions of magnesium aluminate spinel (0, 3, 6, 9, 12 wt. %) on the physical properties and slag resistance of Al2O3-SiC-C based castables were investigated. The composition of the specimens was determined by X-Ray diffraction (XRD). The results revealed that the incorporation of appropriate amount of MgAl2O4 in Al2O3-SiC-C based castables could promote the sintering of the specimens, decrease apparent porosity, and improve bulk density and strength. The slag resistance of the castables was improved due to an increase in the viscosity of molten slag, caused by the solid solution of Fe2+ or Fe3+ ions from the molten slag in MgAl2O4. However, further addition would led to a decrease in slag resistance because much Mg2SiO4 was produced.