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김광희(Kwang-Heui Kim),윤문철(Moon-Chul Yoon),곽재섭(Jae-Seob Kwak) 한국기계가공학회 2022 한국기계가공학회지 Vol.21 No.2
In this study, we investigated whether the interference occurring in forming roll surfaces could be eliminated by increasing the radius of the variable section forming rolls. The surfaces of the rolls capable of forming products with different flange heights and bend angles with the bend line tilted at an angle of 1° from the longitudinal axis were created using the general CAD software CATIA. Roll interferences were determined for the change in the forming roll radius. The minimum gaps between the upper and lower roll surfaces were measured for the change in the forming roll radius, and the roll interferences were calculated from the difference between the measured value and the thickness of the product. It was observed that the thickness of the product had a slight effect on the roll interference when the thickness was between 0.8 and 1.2 mm. It was also observed that the roll interference could be eliminated by increasing the roll radius.
길이방향을 따라 선형 대칭적으로 변하는 좌우대칭 U형 단면을 가진 제품의 포밍 롤 설계
김광희(Kwang-Heui Kim),윤문철(Moon-Chul Yoon) 한국기계가공학회 2016 한국기계가공학회지 Vol.15 No.4
Recently, automobile industries have been developing many structural automotive parts made of thin, high-strength steel strips to produce safer and more environmentally friendly cars. The roll forming process has been considered one of the most efficient processes in manufacturing high-strength steel parts because it is a high-speed process that forms sheets in increments. However, most automotive parts vary longitudinally in their cross-sections. Therefore, it is difficult to apply the roll forming process to automotive parts made of high-strength steel. A variable section roll forming process has been proposed in recent studies. The rotational axes of the forming rolls are fixed, and the forming rolls have three-dimensional shape. As such, the cross-section of the part varies linearly along its length, and the angle between the bend line and longitudinal axis is less than 1 degree. Thus, the rate of cross-sectional variation along the length is relatively small. In this study, the rate of cross-sectional change along the length of a forming roll has been increased. Moreover, the angle between the bend line and longitudinal axis has been increased up to 15 degrees. The variable sections of the forming rolls have been designed for high strength steel parts with a symmetric u-type cross-section that varies linearly and symmetrically along the longitudinal axis.
AE 센서와 신경회로망을 이용한 NAK80 금형강의 자기연마 가공특성 모니터링
김광희(Kwang-Heui Kim),신창민(Chang-Min Shin),김태완(Tae-Wan Kim),곽재섭(Jae-Seob Kwak) 한국생산제조학회 2012 한국생산제조학회지 Vol.21 No.4
The magnetic abrasive polishing (MAP), for online monitoring with AE sensor attachment, was performed in this study. To predict the surface roughness after the magnetic abrasive polishing of NAK80, the signal data acquired from the AE sensor were analyzed. A dimensionless coefficient, which consisted of average of AErms and standard deviation of AE signal, was defined as a characteristic of the MAP and a prediction model was obtained using least square method. A neural network, which had multiple input parameters from AE signals and polishing conditions, was applied for predicting the surface roughness. As a result of this study, it was seen that there was very close correlation between the AE signal and the surface roughness in the MAP. And then on-line prediction of the surface roughness after the MAP of the NAK80 was possible by the developed prediction model.
김광희(Kwang-Heui Kim) 한국해양공학회 1999 韓國海洋工學會誌 Vol.13 No.4
Roll forming process is simulated with a commercial FEM code LS-DYNA. The rolls are treated as rigid bodies rotating with a constant angular velocity. The strip and the rolls are modeled with 4-node plate elements. It is assumed that the nodes along the front end of the strip move along paths given by sine functions. It is found that the analysis can be applied to the optimal design of forming rolls. With these analyses, it is expected that forming defects can be avoided and process development efforts can be reduced.
김광희(Kwang-Heui Kim),윤문철(Moon-Chul Yoon) 한국기계가공학회 2006 한국기계가공학회 춘추계학술대회 논문집 Vol.2006 No.-
Most of the defects found in roll formed product are due to the excessive longitudinal tensile strains. So to design the optimum flower of the roll forming process, it is necessary to predict the longitudinal strains which will takes place in the strip. In this study, strain gauges are attached on the surfaces of high strength steel strips and the longitudinal strains are measured directly during the experimental roll forming carried out in the small three-stage roll forming machine.
김광희(Kwang-Heui Kim),김병탁(Byung-Tak Kim) 한국기계가공학회 2006 한국기계가공학회 춘추계학술대회 논문집 Vol.2006 No.-
The roll forming process is simulated by the three-dimensional elastic-plastic finite element method using the solid elements. U-shaped specimen of high strength steel is analyzed and the experimental roll forming is carried out in the small roll forming machine. Strain gauges are attached on the strips and the longitudinal strains are measured during the roll forming process. The results of the analysis and the experiment show good agreements.
Lubrication Behavior of Slider Bearing with Square Pocket Surface
진도훈,김광희,윤문철,Chin, Do-Hun,Kim, Kwang-Heui,Yoon, Moon-Chul The Korean Society of Manufacturing Process Engine 2017 한국기계가공학회지 Vol.16 No.5
In this paper, the characteristics and load carrying capacity of square pocket surfaces on a slider bearing are discussed for the thin film effect by the square pocket slider bearing. To study the lubrication, a Reynolds equation is used in this paper for the analysis of the slider bearing characteristics with square pocket surfaces. For numerical analysis, the central differencing scheme finite difference method is used. In a slider bearing with square pocket surfaces, the simulation dependent parameters such as pressure and load carrying capacity of the bearing can be acquired from the independent parameters, the slope of the slider bearing and number of pockets on the upper slider. These results can be acquired by the programmed softwar,e and they can be analyzed and stored in a sequential data file for later analysis. Furthermore, their pressure and load capacity distribution can be displayed easily by using the developed program with the Matlab GUI.
노형주,김광희,Roh, Hyung-Ju,Kim, Kwang-Heui 한국금형공학회 2008 한국금형공학회지 Vol.2 No.4
Roll forming process for the bumper beam of high strength steel is developed by an experimental method. The size of the bumper beam is reduced to 1/1.8 to save development time and cost. The developed forming rolls are installed in the small three-stage roll forming machine and roll forming experiments are carried out. It is found that the experimental method using small forming machine is effective in developing roll forming process for the bumper beam of high strength steel.
윤종태,김광희,김병탁,Youn, Jong-Tae,Kim, Kwang-Heui,Kim, Byung-Tak 한국인쇄학회 2003 한국인쇄학회지 Vol.21 No.2
In gravure printing, all of the ink in the gravure cells does not leave the cell onto the substrate. The ink transfer from plate to paper in the gravure printing was simulated by computer. A few studies have dealt with cell withdrawal with simplified Newtonian flow models however, this work was performed with the non-Newtonian inks with different simulation software.