Gas carburizing 에 의한 steel 의 표면경화

임정호,이창희,윤전박 ( Jeong Ho Lim,Chang Hee Lee,Eui Pak Yoon ) 대한금속재료학회 1997 大韓金屬學會會報 Vol.10 No.1

연조 슬라이버의 선밀도 거동 해석. I. 스테이플 길이 분포와 슬라이버 점도 효과

임정호,김종성,허유,Lim, Jung Ho,Kim, Jong S.,Huh, You 한국섬유공학회 2017 한국섬유공학회지 Vol.54 No.5

This study deals with the thickness irregularity of the sliver delivered from a drawing process based on a theoretical model. The thickness variation was expressed as CV(%) of the linear density of the drawn sliver in a steady state. Under the given simulation conditions the simulation results illustrate that the sliver linear density shows two types of behavior: a constant linear density and a periodically changing linear density with traveling peaks. For uniform staple-length slivers the linear density has multi-modal fluctuations, whereas the slivers with a distributed staple length show no fluctuation in the linear density at low sliver viscosity. The irregularity of uniform staple-length slivers is higher than that of the staple length distributed one. As the sliver viscosity increases, the irregularity of the drawn slivers increases.

마찰 정방에서 굵기 동역학의 실험적 확인

임정호,김종성,허유,Lim, Jung-H.,Kim, Jong-S.,Huh, You 한국섬유공학회 2011 한국섬유공학회지 Vol.48 No.5

Dynamics of the bundle thickness in a friction yarn formation process was ascertained experimentally from the view point of the thickness of in-process bundle and output bundle. By changing the thickness of input fleece the thickness distribution of the in-process bundle on the friction drum and the irregularity of the output bundle in a steady state were measured. The experimental results were then compared with the simulation results derived on the basis of the dynamic model, while a step signal and a sinusoidal signal were applied. Experimental results turned out to be in a good agreement with the simulation result, which indicates that the theoretical model describes the dynamics of the frictional bundling process very good. The cross-sectional area of the in-process bundle increased linearly to the drum position in response to a step change in the input fleece thickness, which indicates that the friction bundling process can be though of as an integrating system with an interval. The periodic change in the input fleece thickness yielded also a good correspondence of the experimental results with those from the simulation. However, the thickness behavior of the output friction yarn for the periodic change in input fleece thickness demonstrated the dependency on the take-up speed of the output bundle.

집속 유동에서 속도분산모형과 집속체 불균제 예측성

임정호,김종성,허유,Lim, Jung-H.,Kim, Jong-S.,Huh, You 한국섬유공학회 2011 한국섬유공학회지 Vol.48 No.6

This study reports on the output linear density that was attained by simulation for various levels of draft roller gauge and draft ratio, based on the dynamic model with approximated sinusoidal velocity variance model to specific fiber length distributions to test the model feasibility, while a random variation for the input bundle linear density was provided. Results from model simulation showed that a process resonance could take place, when the draft roller gauge or draft ratio reached the critical values, because there were fundamental frequencies which spread in the irregularity of the bundle linear density, giving rise to some resonance. Thus, the irregularity of the output linear density began increasing steeply. From the view point of the output linear density as a whole, the irregularity decreased, as the draft roller gauge increased. A process resonance occurred in the range of draft roller gauge between 1.25 and 1.5 multitudes of the (maximal) fiber length. Length distribution led to a lower fundamental frequency (longer fundamental wavelength) than the uniform fiber length. High draft ratio yielded high irregularity in the output bundle. Especially, the process resonance occurred between the draft ratio 20 and 30. In the draft ratio range higher than 30, the output included wide-ranged regularly oscillatory components of irregularity that corresponded to the integer-multiple of the fundamental frequency, which shifted to a higher value, when the fiber length was distributed. In addition, the approximated sinusoidal velocity variance model turned out to be adequate to estimate the irregularity of the bundle linear density with both the uniform and the quadratic fiber length distribution.

마찰에 의한 토크 꼬임 발생 기구의 이론적 고찰

임정호,간바트,허유,Lim, Jung Ho,T., Ganbat,Huh, You 한국섬유공학회 2014 한국섬유공학회지 Vol.51 No.5

This research comprises a theoretical investigation of the bundle twists created by the bundle thickness distribution while a bundle rotates by frictional force. The torque from the thickness differentials generates the twists of interest (i.e., the resulting rotation bundle differentials found in the friction area). Therefore, a theoretical model describing the dynamics of the twists per length was derived by applying continuous torque. The temporal bundle thickness is also considered. Using the model, the temporal profiles and spatial distributions of the torque twists are characterized. Under an arbitrarily chosen condition that allows simple interpretation of the torque twist characteristics, the governing equation system consisting of the model for the temporal distributions of the bundle radius on the friction drum surface and the model for the dynamic torque twists is solved, and the generation mechanisms of the torque twists are characterized. Results show that the torque twists propagate along the bundle axis in the form of a moving wave during the short time when the bundle first passes through the friction zone. After the bundle reaches a steady state, the torque twists increase very fast and then slow down as the bundle is moved by the take-up operation. Thus, the central area around the bundle axis becomes highly twisted by the superposition of the torque twists. This is because the input fleece fibers at the center accumulate for a longer distance than for the area near the bundle surface. However, at the exit of the friction area, the number of torque twists is almost zero because there is no accumulation distance for the torque twists to occur. This indicates that the torque twists are distributed with respect to the radial direction. This arc of torque-twist distribution can be described by a reciprocal relationship with respect to the radial position of the bundle cross-section.

알루미늄합금 용탕중의 산화개재물 형성

임정호,김기배,윤우영,윤의박 ( Jeong Ho Lim,Ki Bae Kim,Woo Yung Yoon,Eui Pak Yoon ) 한국주조공학회 1998 한국주조공학회지 Vol.18 No.5

N/A Formation of oxide inclusions in the molten aluminium alloys during solidification is investigated. The oxidation tendency of both Al-4.5wt%Cu and Al-7wt%Si alloys is increased with melt temperature, particularly over 700˚C. However, an Al-5wt%Mg alloy exhibits a decreasing mode over 800˚C. The oxidation behavior with holding time shows the S curve shape for all of the alloys. It is shown that the mechanism of oxidation of Al-5wt%Mg alloy has a two step process different from that of Al-4.5wt%Cu and Al-7wt%Si alloys. The species and morphology of oxide inclusions in each alloy is also shown. The microstructure was more coarsened during solidification when the melt contains a large amount of oxide inclusion than when it doesn`t. This result can be explained in terms of both the hindrance of heat extraction by oxide film formed on the aluminium melt and the difference of heat capacity between the aluminium melt and oxide inclusion during solidification. (Received March 2, 1998)

프랑스의 천일염 생산 및 운영 현황

임정호,Lim, Jeong-Ho 한국식품연구원 2011 食品技術 Vol.24 No.2

참깨를 이용하여 제조한 냉압착유의 품질 특성

임정호,Lim, Jeong-Ho 한국식품연구원 2008 食品技術 Vol.21 No.1

마찰 드럼 상에서 집속체 표면 꼬임 특성

임정호,간바트,허유,Lim, Jung H.,Ganbat, T.,Huh, You 한국섬유공학회 2013 한국섬유공학회지 Vol.50 No.3

This research determines the traits of bundle twists that appeared on the bundle surface, while the input fiber fleece is transformed to a bundle by using friction drums. A mathematical model is suggested to describe the twists generated in the friction area. Based on the bundle thickness dynamics, which is supposed to determine the geometrical array of the fibers joined layer by layer on the outer surface of an in-process bundle that rotates about the bundle axis, twists on the bundle surface are mathematically described, taking into account the bundle-drum slippage ratio, fiber fleece-feeding angle, and friction ratio. Twists are expressed in terms of the number of twists per length and the twist angle. Results show that the slippage ratio has a significant influence on the number of twists per length, but its influence on the twist angle is minimal. The fleece-feeding angle appears to be an important factor in deciding the twists. In addition, a critical fleece-feeding angle that corresponds to an angle that changes the twist direction could be determined. The friction ratio is positively related to the bundle twists, i.e., the twist number increases linearly with increasing friction ratio. However, the friction ratio is negatively related to the twist angle, i.e., at low friction ratios, the twist angle changed significantly, whereas a high friction ratio led to an almost constant twist angle.

연조 슬라이버의 선밀도 거동 해석. II. 연조비와 롤러 간격 효과

임정호,김종성,허유,Lim, Jung Ho,Kim, Jong S.,Huh, You 한국섬유공학회 2018 한국섬유공학회지 Vol.55 No.6

The behavioral characteristics of sliver linear density under roller drafting operation were investigated in this study. A theoretical model describing the dynamic behavior of the staples flowing in a single direction was applied. While the model parameters remained constant, the process parameters including draw ratio and roller distance were varied. Simulations of the dynamic behavior of the drawn sliver linear density showed that it was dependent on the process conditions, and the effects varied depending on the staple length distribution. For uniform length staples, the linear density of the drawn sliver showed periodic changes at a steady state when the drawing roller distance was long. For the short drawing zone, the drawn sliver exhibited a constant steady state linear density. Increasing the draw ratio caused the linear density to change periodically which resulted in an increase in the CV% of the drawn sliver linear density. For length distributed staples, the linear density was sensitive to the draw ratio. At a low draw ratio, for example, DR=4, the drawing zone length did not affect the sliver linear density, and a constant linear density was observed. However, at high draw ratios, for example, DR=12, the drawing zone length affected the linear density behavior of the drawn sliver, showing periodic changes in the steady state. Thus, high draw ratios and long drawing zones caused a drastic increase in the CV% of the quasi-steady state linear density. In general, the two passes of sliver in a drawing operation with low draw ratio resulted in improved properties, that is, a more even linear density of the drawn sliver than that obtained using single drawing pass with a high level draw ratio, which drastically increased the linear density.