• Design & Manufacturing
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• 제14권1호
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• pp.42-48
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• 2020

Titanium alloy has been in the spotlight as a core material in high-tech industries that require high strength and light weight because it has excellent strength and corrosion resistance and strength is higher than that of steel. Therefore, in various industries, existing steel products are intended to be replaced with titanium alloys. Titanium alloys can cause cutting tool breakage during cutting, and heat generated during cutting does not dissipate, accumulates in tools and workpieces, resulting in large wear and tear on thin workpieces. In addition, since titanium alloy is a metal with high chemical activity, the wear of the tool becomes more severe when the cutting speed is high, so machining of titanium bolt through cutting is very disadvantageous in terms of productivity. Therefore, the production of bolts using titanium alloys is being produced through a forging process to improve productivity and product quality. In this paper, hot forging molding analysis was performed on bolts used for fastening automobile parts using Ti-6Al-4V alloy, which is the most commonly used titanium alloy.

• Design & Manufacturing
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• 제17권3호
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• pp.8-14
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• 2023

In this study, basic research was conducted on manufacturing technology of thick-walled light guide a component that controls the light source of automobile lamps. As a preliminary study for manufacturing the final injection molded parts, a model for analyzing the influence of micro patterns on light guides is presented. The optical characteristics of the light guide were analyzed according to the change of the curvature radius of the micro-optical pattern, and the injection molding characteristics of the light guide according to the change of injection molding conditions were analytically evaluated. It was confirmed that the luminance uniformity improves as the R value decreases for changes in the micro-pattern R value, but it was confirmed that there are technical limitations in actual injection mold core processing and high-replication injection molding. Injection molding analysis showed that cooling channel design is very important compared to general injection molding due to thick-wall characteristics and thickness variation. It was also confirmed that the cooling channel has a great influence on the cycle time and birefringence result due to residual stress. As a result of analyzing the influence of filling time, holding condition, and cooling on shrinkage, it was found that the cooling water temperature has a significant effect on the shrinkage of ultra-fine light guide parts, and the holding condition also has a significant effect.

• 대한치과보철학회지
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• 제35권1호
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• pp.221-243
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• 1997

The objective of this study was to characterize the mechanical properties of $Y_{2}O_{3}$-containing glass infiltrated ceramic core material, which was made by pressureless powder packing method. A pure alumina powder with a grain size of about $4{\mu}m$ was packed without pressure is silicon mold to form a bar shaped sample, and applied PVA solution as a binder. Samples were sinterd at $1350^{\circ}C$ for 1 hour. After cooling, $Y_{2}O_{3}$-containing glass($SiO_{2},\;Y_{2}O_{3},\;B_{2}O_{3},\;Al_{2}O_{3}$, ect) was infiltrated to the sinterd samples at $1300^{\circ}C$ for 2 hours and cooled. Six different proportions $Y_{2}O_{3}$ of were used to know the effect of the mismatch of the thermal expansion coefficient between alumina powder and glass. The samples were ground to $3{\times}3{\times}30$ mm size and polished with $1{\mu}m$ diamond paste. Flexural strength, fracture toughness, hardness and other physical properties were obtained, and the fractured surface was examined with SEM and EPMA. Ten samples of each group were tested and compared with In-Ceram(tm) core materials of same size made in dental laboratory. The results were as follows : 1. The flexural strengths of group 1 and 3 were significantly not different with that of In-Ceram, but other experimental groups were lower than In-Ceram. 2. The shrinkage rate of samples was 0.42% after first firing, and 0.45% after glass infiltration. Total shrinkage rate was 0.87%. 3. After first firing, porosity rate of experimental groups was 50%, compared with 22.25% of In-Ceram. After glass infiltration, porosity rate of experimental groups was 2%, and 1% in In-Ceram. 4. There was no statistical difference in hardness between two materials tested, but in fracture toughness, group 2 and 3 were higher than In-Ceram. 5. The thermal expansion coefficients of experimental groups were varied to $4.51-5.35{\times}10^{-6}/^{\circ}C$ according to glass composition, also the flexural strengths of samples were varied. 6. In a view of SEM, many microparticles about $0.5{\mu}m$ diameter and $4{\mu}m$ diameter were observed in In-Ceram. But in experimental group, the size of most particles was about $4{\mu}m$, and a little microparticles was observed. The results obtained in this study showed that the mismatch of the thermal expansion coefficients between alumina powder and infiltrated glass affect the flexural strength of alumin/glass composite. The $Y_{2}O_{3}$-containing glass infiltrated ceramic core made by powder packing method will takes less time and cost with sufficient flexural strength similar to all ceramic crown made with slip casting technique.

• 박물관보존과학
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• 제26권
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• pp.161-182
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• 2021

완구(碗口)란 유통식 화기로 발사체 장전 부분이 사발(碗) 형태인 화포이다. 발사체로는 비격진천뢰(飛擊震天雷)나 단석(團石) 등을 사용하였다. 『화포식언해(火砲式諺解)』(이서(李曙), 1635)에 의하면, 대·중·소·소소완구 등 총 4종으로 구분되며, 실물은 대완구 1점(보물 제857호), 중완구 2점(보물 제858호, 제859호) 등 총 3점이 전한다. 본 연구에서는 임진왜란기에 제작된 국립진주박물관 소장 중완구(보물 제858호)와 해군사관학교 박물관 소장 중완구(보물 제859호)의 과학적 조사를 토대로 제작 기술을 확인하였다. 첫 번째로 국내 현전하는 중완구가 단 두점인 만큼 정밀 3D 스캐닝 정보를 바탕으로 세부 제원을 서로 비교하고, 동 시기의 문헌 기록 수치와 함께 검토하였다. 전체 크기차는 근소하나 중량에서 5,507g의 차이를 보이고, 세부적으로 심지구멍 위치와 손잡이 길이가 상이하다. 한편 현전 중완구는 『화포식언해』의 중완구 제원과 가장 유사하다. 두 번째로는 중완구의 성분을 분석하고 기존 청동제 화약 무기와 함께 검토하였다. 표면 성분 분석결과, 중완구는 Cu-Sn-Pb의 삼원계 합금이며, 평균 함량(wt%)은 Cu 85.24 : Sn 10.16 : Pb 2.98이다. 중완구의 재료 성분은 기존에 조사된 조선 청동 화약 무기의 평균 성분과 매우 유사하며, 중세 유럽의 청동제 화포 재료(Gun-metal)와도 유사한 경향임을 확인하였다. 마지막으로 중완구 표면의 주조 결함(casting defect)과 CT 상을 토대로 주조 기법을 추정하였다. 측면의 주조분할선으로 보아 주형을 반으로 나눈 분할 제작(piece mold)이며, 용탕의 주입은 약실끝 부분으로 포구가 바닥에 오는 수직 주형 설계로 추정한다. 특히 포신 기벽에서 주형과 코어를 고정하는 보조 장치인 채플릿(chaplets)이 확인되므로 이는 기벽을 일정하게 형성하는 역할을 했을 것이다. 한편 보물 제858호와 제859호 중완구 두 점은 외형이 매우 유사하지만, 채플릿의 수량과 배치가 상이하여 주형 설계 일부가 달랐을 것으로 예상한다.

• 한국산학기술학회논문지
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• 제18권6호
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• pp.395-399
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• 2017

자동차에 사용되는 LPI 연료필터 하우징 제품은 기존 다이캐스팅 공정에서 냉간 단조 공정으로 개발하여 경량화 및 내구성을 향상하였다. 하지만 T자형 단조 형상이기 때문에 제품을 생산하였을 경우 제품의 싱크 문제가 발생하게 된다. 이로 인해 제품의 후처리 가공 문제가 발생한다. 본 연구에서는 이러한 문제를 개선하기 위해 성형 해석 시뮬레이션을 이용해 문제를 예측하고 개선방안에 대해 연구했다. 성형 해석 시뮬레이션을 이용하여 문제를 개선하기 위해 완전 성형이 가능한 최적 블랭크의 부피를 결정하였다. 그리고 최적의 블랭크 부피에 맞춰 성형 해석 시뮬레이션을 수행하였고 싱크 현상을 가시화했다. 싱크 현상을 개선하기 위해 냉간 단조 공정 진행 시 싱크 부 밑 부분에 패드를 받침으로 싱크 현상을 개선하였다. 적정한 패드력을 구하기 위해 파라미터 스터디를 진행하였고, 적정한 패드력으로 공정 진행 시 싱크 문제를 개선하였다. 그리고 실제 산업 현장에 적용하여 싱크 문제 개선에 대한 검증을 수행했다.

• 한국산학기술학회논문지
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• 제14권2호
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• pp.542-547
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• 2013

본 연구에서는 알루미늄 폼 코어 복합재료의 기계적 성질을 시뮬레이션 해석을 통하여 고찰하였다. 시험편 모델에는 50J, 70J, 100J의 충격에너지를 가하였다. 50J, 70J 및 100J의 충격에너지에 대해서는 각각 3.4 ms, 3.2 ms 및 3.2 ms의 시점에서 최대하중이 발생하였다. 50J의 충격에너지를 가한 경우는 스트라이커가 복합재료의 상부 면재를 뚫고, 심재까지 손상을 입혔다. 그러나 하부 면재까지는 손상이 없이 그대로이었고 52 J의 에너지가 발생하였다. 70J의 충격에너지를 가한 경우는 스트라이커가 상부 면재를 관통한 후 하부 면재까지 손상을 주었고 65 J의 에너지가 발생하였다. 100J의 충격에너지를 가한 경우는 스트라이커가 면재와 심재를 완전히 관통하여 손상을 주었다. 스트라이커가 상부 면재를 관통하는 시점에서는 최대하중이 되고 그 후로는 하중이 급격히 감소하다가 하부 면재에 도달할 때에 다시 급격히 증가하고 있다가 감소하였고 95 J의 에너지가 발생하였다.

• 대한기계학회논문집
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• 제17권6호
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• pp.1412-1422
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• 1993

본 연구는 각주형 금형부품을 절삭가공할때 부품의 설계데이터로부터 부품의 형상적인 특징을 추출하여 공정설계시스템인 MOLDCAPP과 작업설계시스템인 COPS에서 사용할 수 있는 정보를 생성함으로써 CAD/CAM의 연결을 자동화할 수 있는 특징형상 인식 시스템을 개발하는 연구로, 특징형상 인식기법의 창안보다는, 가용한 기술의 장 점을 사용하여 각주형 공작물의 기계 절삭가공으로 생성될 수 있는 형상을 특징형상으 로 정의하고 ACIS로 설계된 CAD데이터로부터 정의된 특징형상을 추출하여 각 특징형상 들의 형상 데이터를 결정함으로써 MOLDCAPP, COPS 등의 공절설계시스템의 입력데이터 를 생성할 수 있도록 Fig.1과 같이 설계하였다. 특히 PART시스템과 같이 인식대상이 포괄적이지 않으나, 금형부품상의 특징형상으로 범위를 축소하고 금형부품의 가공특징 을 고려하여 인식규칙을 단순화함으로써 금형가공공정의 CAD/CAM연결에 이용될 수 있도록 하였다.

• 구강회복응용과학지
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• 제18권3호
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• pp.217-224
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• 2002

The purpose of this study was to evaluate the influence of saliva contamination on the resin bonding of the etched metal retainers. The test samples were made of Verabond, and divided into 3 groups. Retainers in group1 had normally etched metal surfaces. Retainers in group2 had normally etched metal surfaces which were saliva-contaminated for 30 seconds and cleaned with streaming, luke-warm for 1 minute and dried thoroughly. Retainers in group3 had normally etched metal surfaces which were saliva- contaminated for 30 seconds and dried thoroughly without water-cleansing. Each 3 group specimen was watched on SEM. A resin core, 5mm in diameter and 6mm in length, was made of Panavia using Teflon mold on the each specimen. These 3 groups were tested to evaluate shear bond strength, using universal testing machine. The results were as follows : 1. The shear bond strength showed no significant difference between group1 and group2. 2. The shear bond strength showed significant difference between group1 and group3. 3. The shear bond strength significant difference between group2 and group3. 4. Scanning electron microscope photographs of group1 and group2 showed no signs of contamination but of group3 showed somewhat contaminated.

• 한국기계가공학회지
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• 제14권6호
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• pp.7-13
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• 2015

The production processes were reviewed through the injection analysis of the shift lever as a core component of an auto lever installed in the automatic transmission of cars. The injection analysis was carried out for the shift lever and rod among the components in a shift lever module. The shift lever and rod are designed for injection molding with the insertion of a tube, a pin cable plate, and a steel rod for securing the strength of the product. The charging time, failure of injection molding, weld line, air trap, and deformation were reviewed according to this insert. Analyses on various gate positions were carried out for reviewing the cultivation and deformation of fiber around major components, such as the generation section of manipulation feeling and assembly section, so that optimal gate conditions might be reviewed and reflected in the mold design. Finally, we plan to compare the analysis results with the production of trial products.

• 소성∙가공
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• 제15권4호
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• pp.326-332
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• 2006

Sandwich structures, which are composed of a thick core between two faces, are commonly used in many engineering applications because they combine high stiffness and strength with low weight. Depending on the sheets by a rolling process, which is a more efficient and economical approach compared to other types of processes, has become an increasingly important subject of study. In this paper, we made a roll forming machine which progressive forming possible and force measurement for a roll forming of the sheet metal forming. And we designed a roll molding that arrayed of embossing size 3mm in diameter fabricate micro dimple inner structure plate. We carried out forming experiment such as array change and thickness to sts304 sheet. Ultimately, this research developed inner structure plate of high stiffness.