• Journal of the Korean Society for Precision Engineering
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• v.3 no.3
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• pp.40-71
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• 1986

By developing a computer program for the systematic design of worm gears, the design formulae and tables of AGMA, JGMA, BS and DIN are analized and compared. The computer program can be used on micro-computers. According to the input data of the reduction ratio, the center distance. the driving torque and the material as design parameters, the program calculate the most efficient worm gear dimension. The variation of the design parameters and other empirical coefficients in case of resulting an inadequate design gear dimension can be easily modified throuth the way of interactive method between the user and the monitoring system of computer. A proposal of the standardization of worm gears was made in which a standard module according to the DIN 323 standard series number was applied. For the more exact and effective calculation of the stress concentration and the deformation of gear teeth, a computer program using the boundary element method is also developed. Even the strength of the special gear shape such as Niemann's "Cavex" gear can be calculated in a short CPU-time. The most effort of this study has been layed on the developing a computer program for the correction of a tooth profile and face width which is most important design factor for an exact and wide teeth contacts under loads, especially by great and wide gears. For this purpose were investigated the tooth stiffness, the mesh interferences and the kinematics and the dynamics of gear mesh. The deflection and the deformation of the gear shaft due to the loads acting on gear and shaft were aslo considered. Some examples have shown the sufficient good status of teeth contact in which the correction of the tooth profile and face width were accomplished due to the calculated results.d results.

• Journal of the Korean Society of Manufacturing Process Engineers
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• v.13 no.5
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• pp.15-20
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• 2014

The wind industry grew in the first decade of the 21st century at rates consistently above 20% a year. For wind turbine, gearbox failure can be extremely costly in terms of repair costs, replacement parts, and in lost power production due to downtime. In this paper, gear tooth micro-modification for the high speed stage was used to compensate for the deformation of the teeth due to load and to ensure a proper meshing to achieve an optimized tooth contact pattern. The gearbox was firstly modeled in a software, and then the various combined tooth modification were presented, and the prediction of transmission under the loaded torque for the helical gear pair was investigated, the normal load distribution and root stress were also obtained and compared before and after tooth modification under one torque. The simulation results showed that the transmission error and normal load distribution under the load can be minimized by the appropriate tooth modification. It is a good approach where the simulated result is used to improve the design before the prototype is available for the test.

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 2009.10a
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• pp.387-390
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• 2009

This study was designed to fabricate the micro-electro-mechanical systems (MEMS) parts such as micro spur gears using hot extrusion of gas atomized Al-78Zn powders. For this purpose, it is important to develop new methods to fabricate micro-dies and choose suitable extrusion conditions for a micro-forming. Micro-dies with Ni were fabricated by LIGA technology. LIGA technology was capable to produce micro-extrusion dies with close tolerances, thick bearing length and adequate surface quality. Superplastic Al-78Zn powders have the great advantage in achieving deformation under low stresses and exhibiting good micro formability with average strain rates ranging from $10^{-3}$ to $10^{-2}\;s^{-1}$ and constant temperatures ranging from 503 to 563K. Al-78Zn powders were compacted into a cylindrical shape (${\Phi}3{\times}h10$) under compressive force of 10kN and, subsequently, the compacted powders were extruded at 563k in a hot furnace. Micro-extrusion has succeeded in forming micro-gear shafts.

• Journal of the Korean Society of Manufacturing Process Engineers
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• v.4 no.4
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• pp.7-13
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• 2005

In the case of fabricating micro pole structures such as column, square-pole and gear shaft by the micro end-milling process, it can be useful in the fields of industry, for example, micro parts, electrode for electrical discharge machining and micro mold for injection molding. In this study, machining factors and the process were analyzed. Machining experiments of various micro pole configurations were performed. Analysis of the change and effect of the cutting force according to the machining conditions was carried out. An analytical study of the deformation of the micro pole caused cutting conditions and cutting force through the finite element method and ANSYS program was carried out. As a result, this research presented a method of fabricating the column pole of below $100{\mu}m$ diameter with high aspect ratio by using micro end-milling process, and based on that, a method of fabricating a variety of applicable structures. Also the minimum size of the pole capable of fabricating through theory and experiment were demonstrated.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2003.06a
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• pp.589-592
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• 2003

In the machining process of micros shape by using high-precision machining system and micro end-mill, it is important for machining characters of tools to be grasped in order to stably use tools of micro end-mill. In this study. we carried out an analytical experiment of basic machining features by using end-mill tools for the purpose of damage prevention and manufacture of high quality when the tools of micro end-mill are used. This experiment used a micro machining system with high precision and a variety of end-mill tools commercialized from tens to hundreds microns in diameter. To establish an optimal machining condition without tool damage, cutting force was analyzed according to the changes of tool diameter and cutting conditions such as cutting speed. feed rate, depth of cut. And an examination was performed for the shape and surface illumination of machining surface according to the changes of machining conditions. Based on these micro machining conditions, micro square pillar, cylinder shaft. thin wall with high aspect ratio, and micro 3-D structures such as micro gear and fan were manufactured.

• Journal of Aerospace System Engineering
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• v.12 no.2
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• pp.46-58
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• 2018

A two-axis gimbal-type X-band antenna is widely used to transmit bulk image data from high-resolution observation satellites. However, undesirable microvibrations induced by driving the antenna should be attenuated, because they are a main cause of image-quality degradation of the observation satellite. In this study, a pseudoelastic memory alloy (SMA) gear was proposed to attenuate the microvibrations by driving the antenna in an azimuth angle. In addition, the proposed gear can overcome the limitations of the conventional titanium blade gear, which is not still enough and is vulnerable to plastic deformations under excessive torque. To investigate the basic characteristics of the proposed SMA mesh washer gear, a static load test was performed on the thickness of the SMA mesh washer and the rotation of the gear. Moreover, The microvibration measurement test demonstrated that the SMA mesh washer gear proposed in this study is effective for microvibration attenuation.

• Korean Journal of Agricultural Science
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• v.47 no.2
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• pp.327-335
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• 2020

The purpose of this study was to analyze the load distribution and contact safety factor for the power take off (PTO) gear of a 71 kW class agricultural tractor. In this study, a simulation model of the PTO gear-train was developed using Romax DESGINER. The face load factor and contact safety factor were calculated using ISO 6336:2006. The simulation time was set at 2,736 hours considering the lifetime of the tractor, and the simulation was performed for each PTO gear stage at the engine rated power conditions. As a result of the simulation, the face load factors for the driving gear at the PTO 1^st, 2^nd and 3^rd stages were 1.644, 1.632, and 1.341, respectively. The contact safety factors for the driving gear at the PTO 1^st, 2^nd and 3^rd stages were 1.185, 1.216, and 1.458, respectively. As the PTO gear stage was increased, the face load factor decreased, and the contact safety factor increased. The load distributions for all the PTO gears were concentrated to the right of the tooth width. This causes stress concentrations and shortens the lifespan of the gears. Therefore, it is necessary to improve the face load factor and the contact safety factor with macro-geometry and micro-geometry.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.29 no.12
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• pp.796-802
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• 2016

In order to develop an electrical insulation material for gas GIS (insulation switch gear) spacer, 4 types of epoxy/micro-alumina (40, 50, 60, 70 wt%) composites and 9 types of epoxy/nano-alumina (1, 3, 5 g)/micro-alumina (40, 50, 60, 70 wt%) composites were prepared and tensile test was carried out. In here, nano-alumina was previously surface-treated with GDE (glycerol diglycidyl ether). As micro-alumina and GDE-treated nano-alumina contents increased, tensile strength increased and the highest value was shown in the system with 3 g GDE-treated nano-alumina.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2010.05a
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• pp.687-688
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• 2010

• Transactions of the Korean Society of Mechanical Engineers B
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• v.39 no.4
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• pp.371-378
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• 2015

Range extenders, which are power generation systems driven by small engines, extend the driving distance and time of electric vehicles (EVs) through continuous charging of batteries. The currently used range extenders with gasoline engines pose limitations with regard to the realization of high-power compact systems, owing to their complex structure and low energy density. In contrast, micro gas turbine (MGT) range extenders (MGT power packs) possess high power and low weight, and can therefore be significantly reduced in size despite increase in speed. In this study, an MGT power pack for the range extenders of EVs was developed using a turbo-prop micro turbine, an alternator for passenger vehicles and electric batteries. The operating characteristics of the MGT power pack were measured through a series of experiments conducted under electrical no-load and load conditions. Their power generation performance and efficiency were measured under various electrical loads and power transmission gear ratios. From the results, electrical load was found to have no influence on power generation performance. The maximum electrical power output was 0.8 kW at a core turbine speed of 150 krpm, and the application of 3:1 reduction gear to the turbine output shaft increased the power to 1.5 kW by 88%. This implies that the test results demonstrated stable power generation performance of the MGT power pack regardless of vehicle load changes, thus revealing its feasibility for use with the range extenders of EVs.