• Proceedings of the Korean Institute of Surface Engineering Conference
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• 2018.06a
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• pp.139-139
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• 2018

최근 자동차 산업을 중심으로 한 수송용 기기의 경량화 추세에 따라 대표적인 경량금속 소재인 알루미늄 합금에 대한 수요가 증가하고 있으며 이에 따라 알루미늄 합금 표면에 다양한 특성을 부여할 수 있는 표면개질 기술에 대한 필요성이 부각되고 있다. 알루미늄 합금의 대표적인 표면처리기술인 아노다이징과 유사한 원리로 표면에 세라믹 코팅층을 형성할 수 있는 기술인 플라즈마 전해 산화(Plasma electrolytic oxidation, PEO)가 주목을 받고 있다. PEO 코팅법은 전해액 내에 소재를 침지시키고 400 ~ 600V에 이르는 고전압을 인가시켜 마이크로 방전을 유도하여 표면에 치밀한 세라믹 층을 형성시키는 기술이다. 본 연구에서는 PEO법으로 표면 개질된 Al 합금 표면의 표면 조직 특성과 전기화학 특성을 평가하고, 코팅층 특성에 미치는 공정 변수의 영향을 분석하고자 하였다. PEO 처리를 위해 사용된 소재는 상용 Al 합금 판재(Al 5083-O)로서 $2cm{\times}2cm$로 절단하여, 에머리페이퍼로 1000번까지 연마하여 사용하였다. 시험을 위한 PEO 처리 시스템은 전해액 수조, 일정 온도 유지를 위한 열교환기와 칠러, 전원 발생을 위한 전원공급기(power supply)로 구성되었다. 전해액은 약 알칼리 수용액을 이용하였으며, 전원 공급기를 통해 시험편에 펄스 전류를 인가하였다. PEO 처리 후 시편에 대하여 SEM, EDS, XRD 등을 이용한 표면 특성 평가를 실시하였다. 또한 코팅층의 전기화학적 부식 특성 평가를 위해 해수용액에서 동전위분극실험을 실시하였다. 시험 결과, Al 합금의 PEO 처리 시 내식성은 개선되는 것으로 확인되었으며, 공정변수는 표면의 미세조직 및 전기화학적 특성에 큰 영향을 미치는 것으로 나타났다.

• Proceedings of the Korean Society of Dyers and Finishers Conference
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• 2012.03a
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• pp.64-64
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• 2012

아라미드는 일반적인 유기섬유와는 다른 우수한 역학적 성질을 바탕으로 보호의류 중에서 방탄방호 및 방검보호 의류에 사용되는 고부가 소재이다. 현재까지 ATY기계에서 사의 구조와 물성에 큰 영향을 미치는 Nozzle의 구조에 대한 연구결과는 많이 발표되어왔다. 그러나 최근 들어 소방방화방 검용 보호의류에 많이 사용되는 아라미드사에 ATY 공정 중에서 Nozzle의 직경이 ATY사의 물성에 어떤 영향을 미치는가에 대한 연구는 발표된 바가 없다. 따라서 본 연구에서는 Para-aramid/Nylon hybrid사를 이용하여 ATY로 제조할 경우, 표면에 생기는 loop로 인하여 타 소재와 접착시, 접착제 담지 성능이 향상되어 접착력이 상승되는 반면 아라미드 Hybrid사의 역학물성은 ATY가 가공되기 전의 물성보다 저하되는 약점을 가지고 있다. 따라서 본 연구에서는 ATY 제조공정에서 Nozzle의 직경을 달리할 때 Aramid/Nylon Hybrid ATY사의 물성변화를 분석함으로서 방화복과 방검용 보호의류에 적합한 아라미드 ATY사를 개발하고자 한다. 본 연구에서는 ATY 제조공정 중 다른 공정조건은 동일하게 하고 Nozzle의 직경을 0.6, 0.75, 1, 1.2mm로 변경하여 4가지 시료를 준비하고 물성분석을 위하여 제조된 시료의 강신도, 초기탄성률을 각각 측정하여 인장특성을 확인하였으며, 건열수축률과 습열수축률을 측정하여 시료의 열 수축률을 측정 분석하였다. 표면의 루프 발현 정도를 보기위하여 형태 불안정성을 측정 평가하였으며 영상현미경시스템을 사용하여 표면특성을 측정 평가하여 다음과 같은 결론을 얻었다. Nozzle의 직경이 증가함에 따라 절단강도는 30% 감소하였고 초기탄성률은 3배 가까이 감소하였다. 그리고 절단신도는 2배정도 증가하는 경향을 나타내었다. 또한 Nozzle의 직경이 증가함에 따라 ATY hybrid사의 건 습열수축률이 증가하다가 직경이 1.2mm일 때 감소하는 경향을 나타내었고 직경 변화에 따라 4~6%의 열 수축률의 분포를 보였다. Para-aramid/Nylon hybrid사의 형태불안정성은 0.3~0.5%를 분포를 나타내었고 Nozzle의 직경이 0.6, 1mm일 때 상대적으로 낮은 ATY의 불안정성이 확인되었다. Nozzle의 직경이 감소할수록 loop의 엉킴이 적으며 flat하였으며 직경이 1.2mm일 때 가장 조밀하고 표면에 loop가 많이 형성된 것을 확인하였다.

• Resources Recycling
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• v.29 no.4
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• pp.67-72
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• 2020

Recycling processes of spent copper wires cosisnt of several steps of cutting and chopping processes for peeling covering materials followed by gravity separation processes, where copper is recovered. Because copper thin wires could be lost during further recycling processes, the wire may need to be further treated. In the present study, the copper thin wire was treated with ball milling to prevent the loss. Since the aggregation of the copper wire could be formed by bending and entangling the copper wire each other, the degree of flexion of the copper wire was measured after ball milling. When the 0.5 cm and 3 cm copper wires were used, the 0.5 cm copper wire was not bent and the 3 cm copper wires were aggregated regardless of the ball addition. When the 1 cm and 2 cm copper wires were used, the degree of flexion was remarkable when the balls were added. In the tests using 2 cm copper wires, the aggregation ratio of the copper wire gradually increased with the amount of the 20 mm alumina ball, and when 200 ml of 30 mm alumina ball was used, the aggregation ratio increased to 89.29 %, but after increasing the ball amount further, the aggregation ratio decreased. Thus, it is expected that the loss of the copper wire could be reducedif when the copper thin wire is treated with ball milling by the aggregation of copper thin wires.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.35 no.12
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• pp.1663-1668
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• 2011

Surface hardening treatment is required to improve the wear-resistance of press die because severe abrasion of die occurs during the drawing process in which the forming of the automotive body is completed and during the trimming process in which the unnecessary parts are cut. In this study, experiments on the laser surface treatment of press die are performed. Specimens are heat-treated separately at certain plate and edge position by using a diode laser to carry out suitable surface hardening treatment to reduce the wear during the drawing and the trimming processes, and the proper conditions for heat treatment are found. Spheroidal and flake graphite cast iron specimens are used, and the heat treatment characteristics of the two materials are compared. From the results of the study, it is confirmed that the heat treatment characteristics differed depending on the materials.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.15 no.7
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• pp.4310-4317
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• 2014

The HACCP (Hazard Analysis Critical Control Point) system was applied to Handmade Rice Cakes. The main ingredients of rice cakes, work facilities and workers were provided from the KB company located in Seogye-dong Yongsan-gu, Seoul between September 12, 2012 and February 13, 2013. The manufacturing process chart was prepared by referring to the manufacturing process of rice cake manufacturers in general. Microbiological hazard analysis of the raw materials and after the steaming process of rice-cakes showed a safe result. On the other hand, the microorganism test on the manufacturing environment and workers suggested that the microbiological hazard can be reduced through systematic cleaning and disinfection, accompanied by improved personal hygiene based on hygienic education for workers on the management of microorganisms in the working area.

• Journal of Nuclear Fuel Cycle and Waste Technology(JNFCWT)
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• v.18 no.2
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• pp.157-167
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• 2020

Removing radioactive concrete is crucial in the decommissioning of nuclear power plants. However, this process generates radioactive aerosols, exposing workers to radiation. Although large amounts of radioactive concrete are generated during decommissioning, studies on the internal exposure of workers to radioactive aerosols generated from the cutting of radioactive concrete are very limited. In this study, therefore, we calculate the internal radiation doses of workers exposed to radioactive aerosols during activities such as drilling and cutting of radioactive concrete, using previous research data. The electrical-mobility-equivalent diameter measured in a previous study was converted to aerodynamic diameter using the Newton-Raphson method. Furthermore, the specific activity of each nuclide in radioactive concrete 10 years after nuclear power plants are shut down was calculated using the ORIGEN code. Eventually, we calculated the committed effective dose for each nuclide using the IMBA software. The maximum effective dose of ¹⁵²Eu constituted 83.09% of the total dose; moreover, the five highest-ranked elements (¹⁵²Eu, ¹⁵⁴Eu, ⁶⁰Co, ²³⁹Pu, ⁵⁵Fe) constituted 99.63%. Therefore, we postulate that these major elements could be measured first for rapid radiation exposure management of workers involved in decommissioning of nuclear power plants, even if all radioactive elements in concrete are not considered.

• Journal of the Korean Society of Marine Environment & Safety
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• v.23 no.4
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• pp.421-431
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• 2017

A process-centric simulation modeling method has been proposed to define a shipbuilding simulation model. Existing modeling methods have limitations for expressing various production information for a shipyard. The advanced process-centric modeling method proposed in this paper offers an improvement, effectively representing production information and constraints for a shipyard. To achieve this, a method and diagram components to define a process-centric simulation model in detail have been suggested. The modeling method can assign priorities when multiple products and facilities are assigned to the process. And layer concept was applied to express simulation model with hierarchical structure. To verify the effectiveness of the modeling method, comparative analysis has been performed and the actual shipbuilding process has been modeled using the proposed method. When a single facility was used for various purposes, we found that the proposed method was more advantageous than existing methods. As a result, it was possible to express constraints and flows that were difficult to identify with existing process-centric simulation modeling methods, and the methods were improved for use in shipyard production planning verification simulations.

• Journal of the Korean Society for Precision Engineering
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• v.21 no.4
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• pp.109-119
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• 2004

Rapid prototyping (RP) technologies have been widely used to reduce the lead-time and development cost of new products. $VLM-_{ST}$ process has been developed to overcome the currently developed RP technologies such as a large building time, a high building cost, an additional post-processing and a large apparatus cost. $VLM-_{ST}$ process requires an additional human interaction due to the manual stacking and bonding. Hence, building time, building cost and the part quality are dependent on the skill of labor. A novel RP process, fully automated $VLM-_{ST}$ process ($VLM-_{ST}$), has been developed to improve building efficiency of the process and the human dependency of the part. The objective of this work is to propose a $VLM-_{ST}$ process and to develop an apparatus for implementation of the process. $VLM-_{ST}$ process and its apparatus have various technical novelties such as two step cutting using a rotating table, an automatic stacking method using two pilot holes and two reference shapes, a concept of automatic unit shape layer (AUSL), and an automatic bonding using the bonding roller and building magazine. In order to examine the efficiency and the applicability of the proposed process, various three-dimensional shapes, such as a piston, a human head shape and a human bust shape, were fabricated on the apparatus.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.10 no.5
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• pp.929-934
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• 2009

In this work, the punchless piercing process with application of alternate high pressure has been proposed as a method to obtain pierced holes having nearly vertical wall over thin metal plates. The numerical simulation considering Lemaitre damage model has been accomplished for the proposed method. The simulated results have been compared with those by conventional one-way punch less piercing process. It has been revealed that the fractured section made by pressure alternation method shows nearly steep wall where the deviation angle from the vertical line is as small as $3.6^{\circ}$.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.11 no.5
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• pp.218-223
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• 2001

The chemical-mechanical polishing process was carried out for 2"-dia. sapphire wafer grown by horizontalBridgman method on the urethane lapping pad with the silica sol. The polished wafer shows the full-width at halfmaximum of 200~400 arcsec in double-crystal X-ray diffraction, indicating that the slicing, grinding and lapping processes before the polishing process affected the crystalline structural property of the wafer surface by the mechanical residual stress. For the inclusion of surface treatments after chemical-mechanical polishing such as the thermal annealing at the temperature of $1,200^{\circ}C$for 4 hrs. and chemical etching, the crystalline quality was sigdicantly enhanced with the reduced full-width at half maximum up to 8.3 arcsec.arcsec.