• Proceedings of the Korean Vacuum Society Conference
• /
• 2010.02a
• /
• pp.263-263
• /
• 2010

투명도전막(indium tin oxide; ITO)은 투명하면서도 전기 전도도가 높기 때문에, 액정표시소자(LCD; Liquid Crystal Display), 전자발광소자(ELD; Electroluminescent Display) 및 전자 크로믹 소자(Electrochromic Display)를 포함하는 평판형 표시 소자(FPD; Flat Panel Display)와 태양전지 등에 이용되고 있다. 낮은 비저항과 높은 투과율의 ITO 박막은 $300^{\circ}C$ 이상의 고온에서 코팅해야 하는 것으로 알려져 있다. 그러나 최근 플라스틱과 같은 연성 소자가 전자부품에 널리 이용되면서 ITO를 저온에서 증착해야할 필요성이 대두되고 있다. 본 연구에서는 ITO를 플라스틱에 적용하기 위한 저온 코팅 공정 및 시편의 전 후처리공정을 개발하여 박막의 특성을 알아보고자 한다. 실험에 사용된 기판은 고투과율의 고분자(polyethylene terephthalate; PET) 필름이며 $5\;{\times}\;10\;cm^2$의 크기로 절단하여 알코올로 초음파 세척을 실시하였고, 진공 용기에 장입한 후 펄스전원을 이용하여 3분간 in-situ 청정을 실시하였다. ITO 코팅은 마그네트론 스퍼터링을 이용하였으며, 코팅시간, 전처리, 후처리, 기판온도, 산소유량 등 코팅 조건에 따른 박막의 특성을 조사하였다. ITO 박막의 코팅 조건에 따른 박막의 결정구조 분석은 x-선 회절(x-ray diffraction; XRD)을 이용하였고, 박막의 표면형상과 두께 보정 및 단면의 미세조직과 결정 성장 여부 등은 투과전자 현미경(transmission electron microscope; TEM)을 이용하여 분석하였다. 또한 ITO 박막의 면저항과 분광특성은 four-point Probe (CMP-100MP, Advanced Instrument Technology), spectrophotometer (UV-1601, SHIMADZU)를 이용하여 측정하였다. ITO 박막의 광학특성 분석 결과 전광선 투과율은 두께에 따라 변화 하였지만, 색차와 Haze 값은 증착 조건에 따라 큰 차이는 보이지 않았다. 그리고 박막의 결정화에 영향을 주는 가장 중요한 인자는 기판온도이지만, 기판온도를 높이지 못할 경우 비평형 마그네트론(unbalanced-magnetron; UBM)에 의해서 플라즈마 밀도를 높이는 방법으로 유사한 효과를 얻을 수 있음을 확인하였다.

• Journal of the Korean Society of Propulsion Engineers
• /
• v.2 no.1
• /
• pp.31-40
• /
• 1998

To predict residual stresses of aluminum ring rolls after quenching and element removal, 2-D and 3-D thermal elasto-plastic analyses were performed. Strains measured by three step sectioning method were directly compared to those analysed using ABAQUS's element removal. Numerical residual stresses after quenching had similar tendency to measured ones after 2 step aging, but the difference between numerical and measured ones was large. The difference is the reason why there are nonuniform residual stress distributions to ring height direction due to small height of ring, It is judged that the increase of ring height will improve the accuracy of measured ones and decrease the difference. By direct comparison between 3-D numerical strains to simulate three step sectioning method and measured ones, the accuracy of measurement and analysis can be improved. It is concluded that there can be predicted the deformation behavior on machining complex shaped large structures with residual stresses.

• Journal of the Korean Institute of Gas
• /
• v.23 no.4
• /
• pp.74-79
• /
• 2019

Specially designed test material was used for workpiece temperature measurement in the commercial reheating furnace and a linearized thermal model was applied for real time temperature prediction. The applied furnace is a walking beam type and specification of the workpiece is a STS302 which is 160mm in width, 160mm in height and 8100mm in length. Also six thermocouples were installed in width, height and length direction for temperature measurement. Ambient temperature in the furnace was raised to 1265 Celsius degrees and it took about 2.5 hours from loading to discharging of the workpiece. As a result of the experiment, temperature of the workpiece at discharge was 1257 Celsius degrees on the average in the range of 1256 to 1259 Celsius degrees, and predicted average temperature through the thermal model was 1251 Celsius degrees. Therefore, the deviation of the analysis and test results is about 6 degrees, which is within the range of 10 degrees required by the industry.

• Composites Research
• /
• v.31 no.6
• /
• pp.392-397
• /
• 2018

In this study, the development purpose is to replace steel Tie Rod of commercial vehicle to the carbon composite by a braiding process. CFRP tie rod was designed to meet the performance requirements of existing products by designing the cross section of the core for braiding weaving and the structural design of the joint between the core and the carbon fiber. The specimens were fabricated by braiding method and applied to structural analysis through test evaluation. The manufacturing process proceeded from braiding to infusion through post-curing process. The test evaluation of the final product was satisfactorily carried out by sequentially performing tensile test, torsion test, compression test and fatigue test. In addition, the weight of CFRP tie rod could be reduced by about 37% compared to existing products.

• KSCE Journal of Civil and Environmental Engineering Research
• /
• v.39 no.3
• /
• pp.369-380
• /
• 2019

When a extreme loading such as blast is applied to prestressed concrete (PSC) structures and infrastructures for an instantaneous time, serious property damages and human casualties occur. However, a existing design procedure for PSC structures such as prestressed containment vessel (PCCV) and gas storage tank do not consider a protective design for extreme internal blast scenario. Particularly, an internal blast is much more dangerous than that of external blast. Therefore, verification of the internal blast loading is required. In this paper, the internal blast resistance capacity of PSC member is evaluated by performing internal blast tests on RC and bi-directional PSC scaled down specimens. The applied internal blast loads were 22.68, 27.22, and 31.75 kg (50, 60, and 70 lbs) ANFO explosive charge at 1,000 mm standoff distance. The data acquisitions include blast pressure, deflection, strain, crack patterns, and prestressing force. The test results showed that it is possible to predict the damage area to the structure when internal blast loading occurs in PCCV structures.

• Journal of the Korea Academia-Industrial cooperation Society
• /
• v.22 no.1
• /
• pp.305-312
• /
• 2021

This study examines the damage to the submarine's escape trunk hatch spring through microstructure analysis. The cause of the escape trunk's damage during the submarine's construction and its improvement measures were reviewed. To determine the cause of breakage of the escape trunk spring, samples were taken from the damaged product and analyzed for chemical composition, hardness, and microstructure. In particular, the breakage part of the spring was analyzed in-depth by using a scanning electron microscope to determine the cause of corrosion destruction. Finally, a spring shape design method was proposed through the investigation of the cause of spring breakage. In addition, a newly improved spring was produced by applying a nylon coating with excellent corrosion resistance and abrasion resistance. Applying to an actual submarine trunk hatch revealed that the coating peeling phenomenon due to the contact between the springs is significantly improved when the hatch is opened or closed compared to the existing products.

• Journal of the Korean Society of Marine Environment & Safety
• /
• v.27 no.4
• /
• pp.521-528
• /
• 2021

In this study, to repair damaged economizer fin tubes on ships, sealing treatment was performed after applying arc thermal spray coating technology using Inconel 625. A solid particle erosion (SPE) experiment was conducted according to ASTM G76-05 to evaluate the durability of the substrate, thermal spray coating (TSC), and thermal spray coating+sealing treatment (TSC+Sealing) specimens. The surface damage shape was observed using a scanning electron microscope and 3D laser microscope, and the durability was evaluated through the weight loss and surface roughness analysis. Consequently, the durability of the substrate was superior to that of TSC and TSC+Sealing, which was believed to be owing to numerous pore defects in the TSC layer. In addition, the mechanism of solid particle erosion damage was accompanied by plastic deformation and fatigue, which were the characteristics of ductile materials in the case of the substrate, and the tendency of brittle fracture in the case of TSC and TSC+Sealing was confirmed.

• Composites Research
• /
• v.22 no.2
• /
• pp.30-36
• /
• 2009

In this paper, we propose the design method for the composite torque link of a landing gear for a helicopter. The composite torque link has to be light weighted and very stiff to keep the shock absorber in the landing gear of helicopter. The configuration and structural shape has to be designed in consideration of the RTM (Resin Transfer Molding) manufacturing process which is adopted to minimize the manufacturing cost. The mechanical properties are obtained through the coupon tests with the specimens made by the same manufacturing process for the composite structure. The optimal design process was performed through iterative modifications of the models which were verified by stress analysis using FEM. The composite torque link has lug-shaped parts and is very thick, so 3D Layered solid elements of ABAQUS were used to get the stress field including the stress components in thickness direction and non-linear static analysis using contact B.C. of rigid-deform condition was used to get the optimal design.

• Composites Research
• /
• v.19 no.4
• /
• pp.7-14
• /
• 2006

Interfacial shear strength between epoxy and carbon fiber has been analyzed utilizing the microbond specimen with an epoxy micro-droplet adhered onto single carbon fiber. The interfacial shear stress distributions along the fiber/matrix interface were calculated by finite element analysis using three kinds of finite element models such as droplet model, circular-crosssection model and pull-out model. Conclusions were obtained as follows. (1) Interfacial shear stress distribution showed that larger stresses were concentrated in the fiber/matrix interface for microbond test than for pull-out test. Thus, debonding at the fiber/matrix interface during microbond test was liable to occur at low load level. (2) Microbond test showed higher interfacial strength which was caused by various effects of micro-droplet geometry and size as well as stress concentration in the region contacting with the micro-vise tip.

• KSCE Journal of Civil and Environmental Engineering Research
• /
• v.26 no.4A
• /
• pp.775-785
• /
• 2006

This study focused on the development of surface deformations of GFRP rebars with a better bond characteristic for reinforcing concrete, and simultaneously, of GFRP rebars with more simple and economic production process. This research paper describes a development and bond performance of GFRP rebar with molded deformations, which is composed of polymer resin and milled glass fiber. To determine proper mix ration of milled fibers, material test of hardened epoxy and pullout tests of GFRP rebar with various mix ratio were conducted. The test results indicate that the new strategy of using a mixture of epoxy resin and milled fiber could be successfully applied to a surface structure of GFRP rebar to enhance bond with concrete. The bearing resistance of the ribs was further enhanced by the milled fibers at mechanical and environmental loading state.