• 한국금형공학회:학술대회논문집
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• 한국금형공학회 2008년도 하계 학술대회
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• pp.135-139
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• 2008

Development of surface heating technology using hot jet impingement onto mold inner surface for improvement of pattern transcription. This study is focused on how to control the parameters related to hot jet impingement. The mass flow rate, the jet temperature and the duration of the impingement are major parameters. The nozzle design and other geometric configurations also affect the heat transfer to the surface. In terms of heat transfer analysis, the most important number is the heat transfer coefficient, which is influenced by the mass flow rate, nozzle design, distance between the nozzle tip and the surface. In summary, several parametric studies using the developed model are conducted to investigate the effects of mass flow rate, jet temperature and Heating Time in Surface heating technology using hot jet impingement onto mold.

• 한국산업보건학회지
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• 제23권2호
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• pp.75-83
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• 2013

Objectives: This study was conducted to estimate quartz concentrations in the airborne respirable dust from concrete manufacturing industries and to compare performance of two analytical methods, direct on filter(DOF) and the transfer methods in the Fourier Transform Infrared Spectroscopy(FTIR). Methods: Total 36 area samples were collected from 8 concrete manufacturing industries. Each respirable dust sample was collected by a 25 mm cassette attached to a 10 mm Dorr-Oliver nylon cyclone. The quartz content was estimated using the intensity of the absorption peak of quartz at $799cm^{-1}$ by FTIR. Results: By the comparison of quartz content in respirable dust between the two methods, the results of using DOF method were higher than that of transfer method. And the result of quartz concentrations in respirable dust estimated by DOF method were mostly higher than those by transfer method. Statistically significant difference of quartz concentrations in respirable dust were not found in shakeout, input, loading and transporting processes by two methods. But quartz concentrations in the molding process had the statistically significant difference between DOF and transfer method. Conclusions: The results of the study is suggested that, it be needed to correct the influence of the interferences in order to establish the DOF method when interfering minerals have an effect on quantitative analysis of quartz in respirable dust by the direct on filter method with FTIR.

• 한국산학기술학회논문지
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• 제18권7호
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• pp.310-315
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• 2017

자동차용 방수커넥터는 외부로부터 방수가 필요한 전장부품인 와이어 하네스(Wire Harness)에 연결되어 있는 핵심기능부품이며 특히 와이어씰(Wire Seal) 부품은 고온, 다습, 저온, 먼지, 약품 등의 복합적 환경에서도 체결부 기밀성이 확보되어야 한다. 이러한 와이어씰은 최근 기존의 고상실리콘고무(Heat Cure Rubber)대신 친환경 소재이며 기계적 특성이 우수한 액상실리콘고무(LSR)를 적용하고 있다. 그리고 LSR용 와이어씰을 액상사출성형(Liquid Injection Molding)공정으로 제조할 경우 고상실리콘고무를 제조 하긴 위한 압축성형방식에 비해 사이클타임이 10배이상 빠르고 스크랩이 발생하지 않아 재료의 손실이 없으며 가류 및 생산을 위한 전후처리 과정이 필요 없기 때문에 원가 절감효과가 큰 이점이 있다. 하지만, 방수커넥터를 제조하기 위한 LSR 다캐비티 사출성형공정에서는 일정한 품질의 제품을 확보하기 위하여 캐비티간 균일한 경화온도를 유지하는 것이 중요하다. 본 연구에서는 캐비티간 온도 편차를 최소화 하기 위하여 카트리지 히터의 용량을 위치마다 다르게 설계한 후 열전달 해석과 최적화 모듈을 연계하여 최적의 카트리지 히터 용량을 빠르고 효율적으로 도출하였다. 최적화 해석결과 일정한 히터 용량을 적용한 경우에 비하여 캐비티간 온도 편차는 $13.1^{\circ}C$에서 $8.1^{\circ}C$로 감소 시켜 균일 경화를 위한 온도 편차 $10^{\circ}C$ 이내인 설계 기준을 만족시킬 수 있었다.

• 한국가스학회지
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• 제15권2호
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• pp.82-87
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• 2011

열매체유는 화학공장의 가열시스템, 열교환 시스템, 가스플랜트 공정, 사출성형 시스템 및 펄프제지 공정 등에 사용된다. 열매체유는 고열이나 산화분해에 아주 안정하고 저항성이 있으며, 누출이나 방출의 경우 점화원을 만나면 쉽게 발화한다. 본 논문은 열메체유의 신유와 사용유에 대해 인화성과 열적 안정성을 고찰하였다. 열매체유의 인화성은 인화점과 자연발화점을 측정하여 평가하였고, 열적안정성은 열안정성시험기와 시차주사열량기를 사용하여 평가하였다. 실험결과로부터 열매체유의 적절한 사용과 취급과 관련된 안전대책 수립을 위해 화재 위험 특성을 제시하였다.

• International Journal of Aerospace System Engineering
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• 제4권1호
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• pp.9-12
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• 2017

In this study, an investigation on mechanical properties of flax natural fiber composite is performed as a precedent study on the design of eco-friendly structure using flax natural fiber composite. The Vacuum Assisted Resin Transfer Molding-Light (VARTML) manufacturing method is adopted for manufacturing the flax fiber composite panel. The VARTML is a manufacturing process that the resin is injected into the dry layered-up fibers enclosed by a rigid mold tool under vacuum. In this work, the resin flow analysis of VARTM manufacturing method is performed. A series of flax composite panels are manufactured, and several kinds of specimens cut out from the panels are tested to obtain mechanical performance data. Based on this, structural design of chemical storage tank for agricultural vehicle was performed using flax/vinyl ester. After structural design and analysis, the resin flow analysis of VARTM manufacturing method was performed.

• International Journal of Aerospace System Engineering
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• 제1권1호
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• pp.21-28
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• 2014

In this study, an investigation on mechanical properties of flax natural fiber composite is performed as a precedent study on the design of eco-friendly structure using flax natural fiber composite. The Vacuum Assisted Resin Transfer Molding-Light (VARTML) manufacturing method is adopted for manufacturing the flax fiber composite panel. The VARTML is a manufacturing process that the resin is injected into the dry layered -up fibers enclosed by a rigid mold tool under vacuum. In this work, the resin flow analysis of VARTM manufacturing method is performed. A series of flax composite panels are manufactured, and several kinds of specimens cut out from the panels are tested to obtain mechanical performance data. Based on this, structural design of chemical storage tank for agricultural vehicle was performed using flax/vinyl ester. After structural design and analysis, the resin flow analysis of VARTM manufacturing method was performed.

• 한국섬유공학회:학술대회논문집
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• 한국섬유공학회 2002년도 봄 학술발표회 논문집
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• pp.384-387
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• 2002

In the resin transfer molding, there are many advantages such as high volume, high performance, and low cost, The permeability is essential in the design and operation of the process, Traditionally, the determination of permeability can be divided as three methods, which are experimental measurement, analytical, and numerical prediction using the Darcy's law. In this study, the permeability in the microscopic level is first computed on the square-packing and hexagonal packing structures of the filaments inside the yarn by using CVFEM. (omitted)

• 한국복합재료학회:학술대회논문집
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• 한국복합재료학회 2001년도 추계학술발표대회 논문집
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• pp.43-48
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• 2001

To overcome the disadvantages of conventional excavation technology, various trenchless (or excavation free, or no-dig) repair-reinforcement technologies have been developed and tried. But trenchless technologies so fat developed have some brawbacks such as high cost and inconvenience of operation. In this study, a repairing-reinforcing process for underground pipes with glass fiber fabric polymer composites using VARTM(Vacuum Assisted Resin Transfer Molding) has been developed. The developed process requires shorter operation time and lower cost with smaller and simpler operating equipments than those of the conventional trenchless technologies. For the reliable operation of the developed method, a simple method to apply pressure and vacuum to the reinforcement was devised and flexible mold technology was tried. Also, resin filling and cure status during RTM process were monitored with a commercial dielectrometry cure monitoring system, LACOMCURE. From the investigation, it has been found that the developed repairing-reinforcing technology with appropriate process variables and on-line cure monitoring has many advantages over conventional methods.

• 한국복합재료학회:학술대회논문집
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• 한국복합재료학회 2005년도 춘계학술발표대회 논문집
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• pp.71-75
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• 2005

For the damage tolerance improvement of conventional laminated composites, stitching process have been utilized for providing through-thickness reinforcements. 2D preforms were stacked with S-2 glass plain weave and S-2 glass MWK (Multi-axial Warp Knit) L type. 3D preforms were fabricated using the stitching process. All composite samples were fabricated by RTM (Resin Transfer Molding) process. To examine the damage resistance performance the low speed drop weight impact test has been carried out. For the assessment of damage after the impact loading, specimens were examined by scanning image. CAI (Compressive After Impact) tests were also conducted to evaluate residual compressive strength. Compared with 2D composites, the damage area of 3D composites was reduced by 20-30% and the CAI strength showed 5-10% improvement.

• Nuclear Engineering and Technology
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• 제38권5호
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• pp.423-426
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• 2006

A developed neutron activation analysis(NAA) and gamma-spectrometry were applied to improve the analytical sensitivity and precision of impurities in electronic-circuit raw materials. It is well known that soft errors in high precision electronic circuits can be induced by alpha particles emitted from naturally occurring radioactive impurities such as U and Th. As electronic circuits have recently become smaller in dimension and higher in density, these alpha-particle emitting radioactive impurities must be strictly controlled. Therefore, new NAA methods have been established using a HTS(Hydraulic Transfer System) irradiation facility and a background reduction method. For eliminating or stabilizing fluctuated background caused by Rn-222 and its progeny nuclides in air, a nitrogen purging system is used. Using the developed NAA and gamma-spectrometry, ultra trace amounts of U(0.1ng/g) and Th(0.01ng/g) in an alumina ball and high purity silica used for an epoxy molding compound (EMC) could be determined.