Rotational Speed Rpm Research Articles

냉각수 유량에 따른 양면 랩그라인딩 정반의 전열특성

Dept. of Mechanical Engineering, Tongmyong University(Received January 29, 2016; Revised March 17, 2016; Accepted March 17, 2016)Abstract − Recently, a double-side machining process has been adopted in fabricating a sapphire glass toenhance the manufacturability. Double-side lap grinding (DLG) is one of the emerging processes that can reduceprocess steps in the fabrication of sapphire glasses. The DLG process uses two-body abrasion with fixed abra-sives including pallet. This process is designed to have a low pressure and high rotational speed in order to obtainthe required material removal rate. Thus, the temperature is distributed on the DLG platen during the process.This distribution affects the shape of the substrate after the DLG process. The coolant that is supplied into thecooling channel carved in the base platen can help to control the temperature distribution of the DLG platen. Thispaper presents the results of computational fluid dynamics with regard to the heat transfer in a DLG platen, whichcan be used for fabricating a sapphire glass. The simulation conditions were 200 rpm of rotational speed, 50°Cof frictional temperature on the pallet, and 20°C of coolant temperature. The five cases of the coolant flow rate(20~36 l/min) were simulated with a tetrahedral mesh and prism mesh. The simulation results show that thecapacity of the generated cooling system can be used for newly developed DLG machines. Moreover, the sim-ulation results may provide a process parameter influencing the uniformity of the sapphire glass in the DLG pro-cess.Keywords − double-side lap grinding (양면 랩그라인딩), sapphire glass (사파이어 글라스), heat transfer(열전달), temperature distribution (온도분포)

Mechanical and microstructural characterization of single and double pass Aluminum AA6061 friction stir weld joints

This study focuses on the effect of single pass (SP), double sided pass (DSP) and normal double pass (NDP) method on friction stir welding of aluminum AA6061. Two pieces of AA6061 alloy with thickness of 6 mm were friction stir welded by using conventional milling machine. The rotational speeds that were used in this study were 800 rpm, 1000 rpm and 1200 rpm, respectively. The welding speed is fixed to 100 mm/min. Microstructure observation of welded area was studied by using optical microscope. Tensile test and Vickers hardness test were used to evaluate the mechanical properties of this specimen. Mechanical property analysis results indicate that at low rotational speeds, defects such as surface lack of fill and tunneling in the welded area can be observed. Vickers hardness of specimens however did not vary much when rotational speed is varied. Welded specimens using single pass method shows higher tensile strength and hardness value compared to both double pass methods up to 180.61 MPa. Moreover, DSP showed better tensile test and hardness test compared to NDP method. The optimum parameters were found to be single pass method with 1200 rpm of rotational speed. Therefore economically sound to only perform SP method to obtain maximum tensile strength for AA6061 FSW with thickness of 6 mm.

초소형 유기랭킨사이클 적용 프로토 타입 베인 팽창기에 관한 실험적 연구

In this study, performances of the vane expander protype for micro organic Rankine cycle with refrigerant R134a as a working fluid have been analyzed. While operating organic Rankine cycle for analysing expander efficiencies such as overall efficiencies, volumetric efficiencies and mechanical efficiencies under of expander inlet temperature, the power of the expander, inlet temperature of expander, inlet pressure of expander and the flow rate of the working fluid(refrigerant R134a) have been measured while varying the rotational speed of the expander. It was found that the more the expander revolution speed is high, the more the expander power, overall efficiencies and volumetric efficiencies are higher. In case of 500 rpm of rotational speed, overall efficiencies are 6~7% and in case of 1000 rpm, overall efficiencies are 11~12%. We have found that low volumetric efficiencies result in poor overall efficiencies.

Monitoring Initial Glucose Concentration for Optimum pH Control during Fermentation of Microbial Cellulose in Rotary Discs Reactor

The study aimed to investigate the effect of initial glucose concentration on the microbial cellulose production using Acetobacter xylinum in a Rotary Discs Reactor (RDR-2 liter volume). The fermentations were carried out for four days at temperature 28°C, initial pH 6.5, and 9 rpm of rotation speed; meanwhile, the initial glucose concentration was manipulated in the range of 0.5-5.0 % (w/v). The cell growth was stimulated using 1.4% (v/v) ethanol in the fermentation medium. The result indicated that 1% (w/v) of initial glucose concentration provided the highest microbial cellulose yield with total wet weight of 296.1657g/l. The increase of initial glucose concentration resulted to the decrease of microbial cellulose yield and greater pH drop after fermentation. It can be conclude that production of microbial cellulose using RDR could produce relatively much higher microbial cellulose with less amounts of glucose in a shorter fermentation period compared to static fermentation due to more efficient oxygen uptake during rotary movements and homogenous environment for microbial growth.

밀링조건이 사용 후 PDP패널의 유가금속 용출효율에 미치는 영향

In this study, the microstructure and valuable metals dissolution properties of PDP waste panel powders were investigated as a function of milling parameters such as ball diameter size, milling time, and rotational speed during high-energy milling process. The complete refinement of powder could achieved at the ball diameter size of 5 mm due to sufficient impact energy and the number of collisions. With increasing milling time, the average particle size was rapidly decreased until the first 30 seconds, then decreased gradually about <TEX>$3{\mu}m$</TEX> at 3 minutes and finally, increased with presence of agglomerated particles of <TEX>$35{\mu}m$</TEX> at 5 minutes. Although there was no significant difference on the size of the particle according to the rotational speed from 900 to 1,100 rpm, the total valuable metals dissolution amount was most excellent at 1,100 rpm. As a result, the best milling conditions for maximum dissolving amount of valuable metals (Mg: 375 ppm, Ag 135 ppm, In: 17 ppm) in this research were achieved with 5 mm of ball diameter size, 3min of milling time, and 1,100 rpm of rotational speed.

두부응고제로서 Homomixer 회전속도를 달리한 염화마그네슘유화물의 제조특성

본 연구는 Homomixer의 회전속도에 따른 염화마그네슘 유화물의 제조특성을 비교하여 두부응고제로서 염화마그네슘유화물의 제조상 최적조건을 확립하기로 하였다. 염화마그네슘유화물의 입자는 Homomixer의 회전속도가 증가할수록 미세화 되었다. 입자크기는 <TEX>$1{\sim}5{\mu}m$</TEX>로 분포하고 있었다. 분산상의 입자크기가 미세화 할수록 점도의 증가와 보관 중 유상분리의 지연으로 상관관계가 있음을 나타내었다. 따라서 염화마그네슘유화물을 제조하는데 있어서 Homomixer의 회전속도는 10,000rpm 이상에서 제조하는 것이 두부응고제로서 두부의 조직 상태와 이수율 등이 가장 좋은 결과를 나타내었다. This study was used homomixer as one of the manufacturing method to establish optimal manufacturing condition with magnesium chloride emulsion as coagulant. The more rotational speed of homomixer was fast, the more particle size of magnesium chloride emulsion was minute. The particle size was distributed between 1 and <TEX>$5{\mu}m$</TEX>. The more minute particle size of emulsion had an effect on increasing viscosity of emulsion and delay of oil phase separation during storage period, so the quality of magnesium chloride emulsion had correlation with dispersed phase particle size. After all the experiments, when manufacturing magnesium chloride emulsion, it used more than 10,000 rpm of rotational speed of homomixer, it showed the best result as coagulant according to the state of texture and the water separation ratio of soybean curd.

무인헬기 부착용 원심식 볍씨 살포 장치에 관한 연구

Purpose: While an unmanned helicopter has been extensively used for spraying chemicals on agricultural crops, its low utilization (two months per year from July to August) has recently become an issue. This study aimed to increase the utilization of the unmanned helicopter. The centrifugal rice seeder, a mounting device for rice seeding for unmanned helicopter was developed and assessed its performance. Methods: The concept of the centrifugal spraying device was to obtain design criteria for centrifugal distribution. Four types of blade shapes namely straight, curved, straight wing and curved wing were developed and used. The rotational speed of the blades was tested at 1,000, 1,200 and 1,400 rpm. Results: The blade shapes, rotational blade speed and angle of trajectory were theoretically analyzed and results were validated with a series of laboratory experiments. Conclusions: The curved wing blades provided the distribution uniformity (DU) at 1,200rpm of rotational speed and 60 degree of seed drop point. The spray uniformity of 4.2% was also achieved.

Appropriate Conditions for Preparation of Nanosized WO&lt;sub&gt;3&lt;/sub&gt; through High-Energy-Milling

In order to synthesize WC-Co nanopowders through an integrated mechanical and thermal activation process, WO3-Co2O3-C nanopowders need to be obtained first. It is critical how to obtain the WO3-Co2O3-C nanopowders efficiently. The effect of processing parameters on the grain size during high-energy-milling of WO3-Co2O3-C mixed powders was studied via X-ray diffraction (XRD) and transmission electron microscopy (TEM). The results show that the grain size of reactants can be effectively decreased with increasing the milling time, rotation speed, and charge ratio. After a certain time milling, both WO3 and C powders achieve nano-level in grain size and mixed homogeneously. The appropriate milling parameters for fabricating nanosized WO3+C+Co2O3 powders are suggested to be 4 to 8 hours of milling time, 400 RPM of rotation speed, and 40:1 to 60:1 of charge ratio.

Isothermal corrosion testing of frit furnace refractories

In this paper, the corrosion behaviour of aluminosilicate type refractories in frit melts is studied in an isothermal corrosion test setup. A refractory brick of largely andalusite and sillimanite composition was compared to another refractory brick of mullite and sillimanite composition, both of which were made by different manufacturers for use in different frit furnaces. The industrial frit used for corrosion tests was a commercial product used in a wall tile glaze formulation. Corrosion tests conducted under isothermal conditions provide quantitative and reproducible data about the corrosion performance of refractories. In this study, tests were performed by partially immersing a 15 mm × 15 mm × 115 mm refractory specimen into a frit melt at temperatures between 1404 and 1504 °C. The effects of temperature, duration of exposure and the refractory brick type were investigated using a statistically designed set of experiments. The ANOVA (analysis of variance) table indicated that temperature and test duration were the most important factor effects, as expected. Increasing both temperature and exposure duration led to an increased amount of corrosion as measured by the cross-sectional area loss of the corroded refractory specimen. Postmortem microstructural analysis was also done on the specimens, with extensive amount of ZnO·Al 2O 3 precipitation observed along the frit–refractory interface, where crystals of mullite and alumina were also found to precipitate. Increasing the amount of exposure time and temperature produced more ZnO·Al 2O 3 precipitation. As identified by SEM-EDS analysis, mullite crystals were in the needle-like morphology, while alumina crystals were generally cubic. Additional experiments were conducted by rotating the specimens in the melt at 50 rpm of rotational speed. Due to the reduction of boundary layer thickness, more dissolution was observed from the rotated specimens. In all specimens, corrosion was more pronounced in the bond phase than through the large filler grains of mullite and andalusite.

Lipase-catalyzed acylation of l-carnitine with conjugated linoleic acid in [Bmim]PF6 ionic liquid

Improving significantly the acylation reaction of l-carnitine with conjugated linoleic acid catalyzed by lipase needs to select an efficient and suitable reaction medium that is not only polar but also hydrophobic. [Bmim]PF6 which is satisfied with the above two requirements was applied as the reaction medium. The optimal reaction conditions were: Novozyme 435 as the catalyst, 5:1 of molar ratio of fatty acid to l-carnitine, 40 g L−1 lipase, 0.22 aW of initial water activity, 125 g L−1 molecular sieves (they were added within 0–3 h of reaction time), 60 °C of reaction temperature, 200 rpm of rotation speed, 32 h of reaction time. The overall conversion could reach 98.27%. The conversion in [Bmim]PF6 was 2.13 and 1.56 times higher than that in acetonitrile and in solvent-free system, respectively. The lipase in the present work could be used eight times. [Bmim]PF6 as the reaction medium was better than acetonitrile and solvent-free system.

Effects of compressive stress, feeding rate and speed of rotation on palm kernel oil yield

Compressive stress, feeding rate and rotational speed are some of the operational parameters that influence efficiency of an oil expeller. A 3 × 3 factorial experimental design was employed to determine the effects of these parameters on palm kernel oil expression using oil expeller. Obtained data were analysed statistically by regression and ANOVA to obtain relationship between independent variables; compressive stress, feeding rate and speed of operation of the oil expeller and dependent variable; oil yield. Maximum oil yield of 46.3% was recorded at 30 MPa compressive stress, 150 kg/h feed rate and 110 rpm of rotational speed while minimum oil yield of 16.3% was obtained at 10 MPa compressive stress, 50 kg/h feed rate and 110 rpm of rotational speed. The developed model equation fitted well with obtained data ( R 2 = 0.84) an indication that the model fits well with the data. The results also showed that predictor correlated positively and directly proportional to the oil yield. However, from the coefficient table, it was discovered that only the compressive stress significantly affect the oil yield at p < 0.05.

Mechanical alloying synthesis and bioactivity evaluation of nanocrystalline fluoridated hydroxyapatite

The aim of this work was preparation, characterization and bioactivity evaluation of nanocrystalline fluoridated hydroxyapatite (FHA) with different degree of fluoridation via the mechanical alloying (MA) method, and investigating the effect of MA parameters on the synthesizing process. Nanocrystalline FHA with a chemical composition of Ca 10(PO 4) 6OH 2− x F x (where x values were selected equal to 0.0, 0.5, 1.0, 1.5 and 2.0) were synthesized using different milling conditions. X-ray diffraction (XRD), Fourier transform infrared (FTIR), transmission electron microscopy (TEM), scanning electron microscopy (SEM) and ICP-OES analysis techniques were utilized to characterize the synthesized FHA. In vitro tests were performed by immersing the prepared FHA in simulated body fluid (SBF). The changes of pH of the SBF were measured at pre-determined time intervals using a pH meter. The calcium and phosphorous ion concentrations of SBF were determined using the ICP-OES analysis. Bone-like apatite formation on the surface of the immersed samples was investigated by SEM. The results showed that only the FHA nanopowders, which were synthesized after 6 h of high-energy ball milling under optimized MA parameters including; 300 rpm of rotation speed, ball-to-powder weight ratio (B/P) equal to 35, and 8 balls with 20 mm in diameter, could fulfill the requirements of ASTM F1185–88 to be used as a biomaterial. In vitro test indicated that the dissolution rate of FHA decreased as the result of increasing the fluorine content of nanocrystalline FHA. Larger quantity of tiny nucleus was observed on the surface of samples with higher fluorine content after 8 h of soaking in the SBF.

Development of Rotating-Mesh Basket Type Bioreactor for Carrot Embryo Production in Immobilized Callus System.

Mass-production of regenerated plantlets using alginate bead encapsulating carrot callus was studied. When gel beads were cultivated in a flask containing regeneration medium, somatic embryos were released at high frequency from the gel beads and developed into plantlets. When a callus less than 320 μm in size was immobilized in the beads, a larger number of embryo was released from the beads. At 0.11 ml-pcv/ml-gel of inoculum size, the maximum number of embryo was obtained. In order to develop a suitable bioreactor for the immobilized callus system, three types of bioreactors, namely air-lift, horizontally shaking vessel and rotating mesh-basket types, were tested. In the case of the rotating mesh-basket type, a larger amount of released cells was obtained. Plantlet formation from the released cells reached a level of 115% compared with that of the flask culture. To achieve continuous recovery of released cells and perform long term culture, a cyclone type cell separator was designed and used in conjunction with a rotating mesh-basket type bioreactor. When 110 ml/min of medium flow was passed through the separator, 90% of suspended cells were collected after 40 min of operation time. Long term cultures at 50, 100, and 150 rpm of rotational speed were carried out. In the experiment at 100 rpm, almost constant values of released cell volume and number of embryos were obtained during 12 d. They were 3 ml-pcv/l-medium/d and 7000 plantlets/g-released cells, respectively.