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니들펀칭 라미네이팅 부직포의 특성화 연구(III) -유체의 침투특성-
이순근,박재기,주창환,Lee, Sun-Kun,Park, Jee-Ki,Joo, Chang-Whan 한국섬유공학회 2008 한국섬유공학회지 Vol.45 No.2
The characterization of fluid flow in fibrous assemblies is essential to apply the absorbent materials such as wipe, sanitary and geotextile, and further to expand the end-uses of nonwoven fabrics. The liquid transport in fibrous materials is largely governed by the structure of fabrics. Thus, we have studied fluid transport behavior of needle punching laminated nonwovens (NPLN) with different processing conditions such as punching density and number of layers by a newly designed apparatus. The results obtained are as follows: the penetration force of fluid showed a decreasing trend with increasing punching density of NPLN, but increasing trend above $400\;punches/cm^2$. The penetration velocity and penetration force increased due to the change of NPLN structure. The penetration velocity and penetration force in the NPLN fabrics decreased with increasing number of layers. Also, fluid penetration radius ratio in the NPLN fabrics generally decreased with increasing punching density, but increased above $400\;punches/cm^2$. Meanwhile, the penetration radius ratio decreased with increasing number of layers.
플라스틱 중공부품의 일체화 성형을 위한 인몰드 펀칭 공정기술에 관한 연구
이성희 한국금형공학회 2021 한국금형공학회지 Vol.15 No.4
A study on in-mold punching technology for hole piercing during molding of hollow plastic parts wasconducted. Considering the non-linearity of the HDPE plastic material, mechanical properties were obtained according tothe change in temperature and load speed. A standard specimen for the in-mold punching test was designed to implementthe in-mold punching process, and the specimen was obtained through injection molding. In order to analyze the influenceof process variables during in-mold punching, an in-mold punching mold capable of controlling variables such astemperature and support pressure of the specimen was designed and manufactured. Mold heating characteristics wereconfirmed through finite element analysis, and punching simulations for changes in process conditions were performed toanalyze punching characteristics and reflected in the experiment. Through simulations and experiments, it was found thatthe heating temperature, punch shape, punching speed, and pressure of the back side of the specimen were very importantduring in-mold punching of HDPE materials, and optimal conditions were acquired within a given range
세섬도 아라미드 섬유를 이용한 니들펀칭 부직포의 제조 및 저속충격특성에 관한 연구
권남희,정원영,최영옥,유의상 한국섬유공학회 2017 한국섬유공학회지 Vol.54 No.6
Needle-punched aramid nonwoven fabrics were manufactured with a focus on the fiber fineness, fiber length, and needle punching density to improve the absorption and distribution of impact energy, and their physical properties, structure, and low-velocity impact behavior were investigated. In addition, thermal-bonded aramid nonwoven fabrics were manufactured with different mixing ratios of the binder fibers (LM-PET), and their impact resistance properties were analyzed. The tensile strength of the aramid nonwoven fabrics were observed to increase with an increase in the needle punching density. In comparison with woven fabrics of the same weight, the nonwoven fabrics exhibited higher energy absorption capability. This can be attributed to the higher deformability of the nonwoven fabrics that arises from an easily disordered fiber network of the mechanically entangled structure when under impact. Most of the impact energy was dissipated by frictional sliding and deformation of the fibers without significant fiber fracture. Mixing the binder fibers improved the impact absorption due to physical entanglement caused by the needle punching and adhesion between the fibers and the web in the binder fibers.
압력용기용 강의 가스수소 취화 거동에 미치는 펀치속도의 영향
배경오(Kyung-Oh Bae),신형섭(Hyung-Seop Shin),백운봉(Un-Bong Baek),남승훈(Seung-Hoon Nahm),박종서(Jong-Seo Park),이해무(Hae-Moo Lee) 대한기계학회 2013 大韓機械學會論文集A Vol.37 No.12
수소를 친환경적 에너지원으로 사용하는 경우, 수소 압력용기용 강재의 수소취화 평가 및 안전성에 대한 신뢰성이 확보되어야 한다. 본 연구에서는, in-situ SP 시험법을 적용하여 수소 저장용기로 사용이 검토되고 있는 SA372 강재의 가스 수소취화 거동을 평가하였다. 표면가공 조건을 달리한 시험편을 사용하여 대기압, 고압 수소가스 압력하에서 펀치속도를 달리한 SP 시험을 통해 가스수소취화 거동을 조사하였다. 그 결과, SA372 강은 가스수소 압력하에서 현저한 수소취화 거동을 나타내었다. 이때 펀치속도에 따른 영향도 명확하게 나타나, 펀치속도가 낮을수록 현저한 수소취화를 나타내 낮은 SP 에너지 값을 나타내었다. 또한 SP 시험 후 파면양상 관찰결과도 펀치속도에 따른 수소취화 거동을 명확하게 나타내었다. 본 가압수소 시험조건에서는 시험편 표면조건의 영향은 명확하게 볼 수 없었다. When using hydrogen gas as an ecofriendly energy sources, it is necessary to conduct a safety assessment and ensure thereliability of the hydrogen pressure vessel against hydrogen embrittlement expected in the steel materials. In this study, by applying the in-situ SP test method, the gas hydrogen embrittlement behaviors in SA372 steel, which is commonly used as a pressurized hydrogen gas storage container, were evaluated. To investigate the hydrogen embrittlement behavior, SP tests at different punch velocities were conducted for specimens with differently fabricated surfaces at atmospheric pressure and under high-pressure hydrogen gas conditions. As a result, the SA372 steel showed significant hydrogen embrittlement under pressurized hydrogen gas conditions. The effect of punch velocity on the hydrogen embrittlement appeared clearly; the lower punch velocity case indicated significant hydrogen embrittlement resulting in lower SP energy. The fractographic morphologies observed after SP test also revealed the hydrogen embrittlement behavior corresponding to the punch velocity adopted. Under this pressurized gas hydrogen test condition, the influence of specimen surface condition on the extent of hydrogen embrittlement could not be determined clearly.
이민근(Min Geun Lee),정상원(Sang Won Chung),문바울(Pa Ul Mun) 대한기계학회 2013 대한기계학회 춘추학술대회 Vol.2013 No.12
The springback to the metal forming is one of the most important issues. The springback of high strength steel under U-bending has been studied for a material orientation in which U-bending process is presumed to have the highest forming. In the study, the effects of the variable on springback of U-bending depending on intrusion direction, forming speed and blank holding force are investigated. And numerical analyses are performed to predict the amount of springback and to analyze the results. Practical and physical meaning of the results are discussed.