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이선곤 ( Sun Kon Lee ),강세호 ( Sae Ho Kaong ),양철수 ( Cheol Soo Yang ),우창기 ( Chang Ki Woo ) 한국안전학회(구 한국산업안전학회) 2014 한국안전학회지 Vol.29 No.5
When the fluid energy convert into kinetic energy due to water hammer, the propagation velocity of pressure wave appear. The propagation velocity of pressure wave(1050 m/s) of very fast could be damage to the pipeline system. If the occurrence of water hammer is due to down-pressure, the faster the air exhaust or supply device is needed. it is high Speed Air Valve. In this paper, Each3.12, 3.13, 3.72, 3.74 kg/㎠ pipeline pressure were setting, and then executed pressure rapid drop for obtaining a high Speed Air Valve Operating time and pressure change data. the result was that pipe line pressure stabilization time were each 0.98, 1, 1.22, 1.25 sec. In other words, that pressure drop experimental results pipe line pressure was equal to atmospheric pressure without negative pressure After about one second. The study result would be useful to pipe line system stability design because this data could be foresee pressure stabilization time.
Fused Deposition Modeling 3D Printing-based Flexible Bending Sensor
Sun Kon Lee(이선곤),Young Chan Oh(오영찬),Joo Hyung Kim(김주형) 한국기계가공학회 2020 한국기계가공학회지 Vol.19 No.1
Recently, to improve convenience, flexible electronics are quickly being developed for a number of application areas. Flexible electronic devices comprise characters such as being bendable, stretchable, foldable, and wearable. Effectively manufacturing flexible electronic devices requires high efficiency, low costs, and simple processes for manufacturing technology. Through this study, we enabled the rapid production of multifunctional flexible bending sensors using a simple, low-cost Fused Deposition Modeling (FDM) 3D printer. Furthermore, we demonstrated the possibility of the rapid production of a range of functional flexible bending sensors using a simple, low-cost FDM 3D printer. Accurate and reproducible functional materials made by FDM 3D printers are an effective tool for the fabrication of flexible sensor electronic devices. The 3D-printed flexible bending sensor consisted of polyurethane and a conductive filament. Two patterns of electrodes (straight and Hilbert curve) for the 3D printing flexible sensor were fabricated and analyzed for the characteristics of bending displacement. The experimental results showed that the straight curve electrode sensor sensing ability was superior to the Hilbert curve electrode sensor, and the electrical conductivity of the Hilbert curve electrode sensor is better than the straight curve electrode sensor. The results of this study will be very useful for the fabrication of various 3D-printed flexible sensor devices with multiple degrees of freedom that are not limited by size and shape.
Study on Electrical Characteristics of FDM Conductive 3D Printing According to Annealing Conditions
Sun Kon Lee(이선곤),Yong Rae Kim(김용래),Tae Jung Yoo(유태정),Ji Hye Park(박지혜),Joo Hyung Kim(김주형) 한국기계가공학회 2018 한국기계가공학회지 Vol.17 No.6
In this paper, the effect of different 3D printing parameters including laminated angle and annealing temperature is observed their effect on FDM conductive 3D printing. In FDM 3D printing, a conductive filament is heated quickly, extruded, and then cooled rapidly. FDM 3D Print conductive filament is a poor heat conductor, it heats and cools unevenly causing the rapid heating and cooling to create internal stress. when the printed conductive specimens this internal stress can be increase electrical resistance and decrease electrical conductivity. Therefore, This experiment would like to use annealing to remove internal stress and increase electrical conductivity. The result of experiment when 3D printing conductive specimen be oven cooling of annealing temperature 120℃ electrical resistance appeared decrease than before annealing. So We have found that 3D printing annealing removes internal stresses and increases the electrical conductivity of printed specimens. These results are very useful for making conductive 3D printing electronic circuit, sensor ect...with electrical conductance suitable for the application.
이선곤 ( Sun Kon Lee ),양철수 ( Cheol Soo Yang ) 한국안전학회(구 한국산업안전학회) 2011 한국안전학회지 Vol.26 No.1
When the pumps stopped in the operation by the power failure, the hydraulic transients take place in the sudden change of a velocity of pipe line. Each and every water hammer problem shows the critical stage to be greatly affected the facts of safety and reliability in case of power failure. The field tests of the water hammer executed at Cheong-Yang booster pump station having an air chamber. The effects were studied by both the practical experiments and the CFD(Computational Fluid Dynamics : Surge 2008). The result states that the system with water hammering protection equipment was much safer when power failure happens. The following data by a computational fluid dynamic analysis are to be shown below, securing the system stability and integrity. (1) With water hammering protection equipment. ① Change of pressure : Up to 15.5 kg/cm2 in contrary to estimating 16.88 kg/cm2. ② Change rate of water level : 52~33% in contrary to estimating 55~27%. ③ Note that the operational pressure of pump runs approx. 145 m, lowering 155 m of the regularity head of pump. ④ Note that the cycle of water hammering delays from 80 second to 100 second, together with easing the function of air value at the pneumatic lines. (2) Change of pressure without water hammering protection equipment : Approximate 22.86 kg/cm2. The comprehensive result says that the computational fluid dynamics analysis would match well with the practical field-test. It was able to predict Max. or Min. water hammering time in a piping system. This study aims effectively to alleviate water hammering in a pipe line to be installed with air chamber at the pumping station and results in making the stability of pump system in the end.
FDM 3D프린팅 윤활유에 따른 내부응력 완화에 관한 연구
이선곤(Sun Kon Lee),김용래(Yong Rae Kim),김수현(Su Hyun Kim),강선호(Sun Ho Kang),김주형(Joo Hyung Kim) 한국기계가공학회 2019 한국기계가공학회지 Vol.18 No.2
In this paper, the effects of different 3D printing conditions including oil lubrication and annealing are observed for their effects on tensile testing. In 3D printing, a press-out extrude filament is rapidly heated and cooled to create internal stress in the printed part. The 3D printing internal stress can be removed using oil-coated filament and annealing. During the oven cooling at an annealing temperature of 106℃, the stress of the specimens with laminated angle 0° tends to increase by 12.6%, and that of the oil-coated filament printing specimens is increased by 17%. At the annealing temperature of 106℃, the stress of the oil-coated filament printing specimens tends to increase by 35%. In this study, we have found that the oil lubrication and annealing remove the internal stresses and increase the strength of the printed specimens. The oil lubrication and annealing reform the crystalline structures to even out the areas of high and low stress, which creates fewer fragile areas. These results are very useful for the manufacture of 3D printing products with a suitable mechanical strength for applications.
LED TV 스피커 프레임용 사출 성형공정 구현에 관한 실험적 연구
이선곤(Sun Kon Lee),김상현(Sang Hyun Kim) 한국기계가공학회 2013 한국기계가공학회지 Vol.12 No.5
Injection molding process is one of the most important methods to produce plastic parts with high efficiency and low cost. The objective of this study is to implement the best plastic injection molding process for LED TV speaker frame. Moldflow analysis and simulation of plastic injection molding process were carried out in order to predict optimal modeling operation conditions and then injection molded part was produced various type of resin temperature, filling time and injection pressure variation. the result was that the best injection molding condition is set as 60bar pressure, 2sec filling time and 310°C degree. The study result would be useful to variety of plastic injection molding process.
FDM 3D프린팅 어닐링 조건에 따른 내부응력 완화에 관한 연구
이선곤(Sun Kon Lee),김용래(Yong Rae Kim),김수현(Su Hyun Kim),김주형(Joo Hyung Kim) 한국기계가공학회 2018 한국기계가공학회지 Vol.17 No.4
In this paper, the effects of different 3D printing parameters including laminated angle and annealing temperature, were observed for their effects on tensile testing. In 3D printing, a filament is heated quickly, extruded, and then cooled rapidly. Because plastic is a poor heat conductor, it heats and cools unevenly causing the rapid heating and cooling to create internal stress within the printed part. Therefore, internal stress can be removed using annealing and to increase tensile strength and strain. During air cooling at annealing temperature 140℃, the strain of laminated angle 45° specimens tended to increase by 46% while the tensile stress tended to increase by 7.4%. During oven cooling at annealing temperature 140℃, the strain of laminated angle 45° specimens tended to increase by 34% while the tensile stress tended to increase by 22.2%. In this study, we found "3D printing with annealing" eliminates internal stress and increases the strength and stiffness of a printed piece. On the microstructural level, annealing reforms the crystalline structures to even out the areas of high and low stress, which created fewer weak areas. These results are very useful for making 3D printed products with a mechanical strength that is suitable for applications.
Sun Kon Lee(이선곤),Young Chan Oh(오영찬),Joo Hyung Kim(김주형) 한국기계가공학회 2020 한국기계가공학회지 Vol.19 No.1
In this paper, the performances of the electrical characteristics of the Fused Deposition Modeling (FDM) 3D-printed flexible resistance sensor was evaluated. The FDM 3D printing flexible resistive sensor is composed of flexible-material thermoplastic polyurethane and a conductive PLA (carbon black conductive polylactic acid) polymer. While 3D printing, polymer filaments heat up quickly before being extruded and cooled down quickly. Polymers have poor thermal conductivity so the heating and cooling causes unevenness, which then results in internal stress on the printed parts due to the rapidity of the heating and cooling. Electrical resistance measurements show that the 3D-printed flexible sensor is unstable due to internal stress, so the 3D-printed flexible sensor resistance curve does not match the increases and decreases in the displacement curve. Therefore, annealing was performed to eliminate the mismatch between electrical resistance and displacement. Annealing eliminates residual stress on the sensor, so the electrical resistance of the sensor increases and decreases in proportion to displacement. Additionally, the resistance is lowered in comparison to before annealing. The results of this study will be very useful for the fabrication of various devices that employ 3D-printed flexible sensor that have multiple degrees of freedom and are not limited by size and shape.