• Transactions of the Korean Society of Mechanical Engineers A
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• v.41 no.6
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• pp.553-560
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• 2017

3D printing technology has been a great interest in human bio-interfaces and human-like robotics since they require arbitrary and adaptive manufacturing. This research mainly concerns the 3D fabrication of a packed biosensor using elastomeric sheets made of PDMS. It is essential to design the PDMS molding with 3D printing since, in the case of biosensors, it should not only produce a conformal shape depending on an arbitrary skin surface but also guarantee a uniform thickness distribution during solidification in the PDMS prepolymer solution. To satisfy the characteristics of the PDMS molding, such as flexibility in the de-molding and stiffness in the solidification processes, multi-materials have been selectively applied to the PDMS molding design, which has been validated with finite element analyses and compared with the 3D printed molding.

• Composites Research
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• v.12 no.2
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• pp.70-81
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• 1999

Resin transfer molding(RTM) as a composite manufacturing process is currently of great interest in the aerospace industry requiring high performance composite parts. In this study, an analysis of mold filling in the RTM process was carried out by numerical simulation using finite element/control volume technique. Experimental work for the visualization of resin flow through fibrous preform was also conducted in order to quantitatively measure the permeabilities of the fiber mats and to evaluate the validity of the developed numerical code. The different types of fiber mats and silicon oils were selected as reinforcements and resin materials, respectively. The effects of fibrous preform structure, mold geometry, and preplaced insert on the flow front patterns during mold filling were examined by integrating the model predictions and experimental results. The flow fronts predicted by numerical simulation were in good agreement with those observed experimentally. However, according to the regions of the mold, some deviations between predicted and observed flow fronts could be found because of non-uniform fiber volume fraction. Weldline locations for the resin flow through round insert preplaced in the mold could be qualitatively deduced based on predicted flow fronts.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.37 no.8
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• pp.751-758
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• 2009

Failure strengths of composite single-lap adhesive joints were investigated with various parameters such as manufacturing method, overlap length and adherend thickness. A total of 335 single-lap joint specimens were tested under tension. Specimens were fabricated with 4 different manufacturing processes; cocuring without and with adhesive, secondary bonding and co-bonding. Each manufacturing process has 5 different overlap lengths and 4 different thicknesses, respectively. As expected, failure strength is higher in thicker adherend joints and lower in larger overlap length specimens. Interesting result is that the secondary bonded joints show the higher strength than the cobonded and cocured joints with adhesive, and give close or even higher strength compared with non-adhesive cocured case.

• Proceedings of the Korea Society for Industrial Systems Conference
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• 1999.05a
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• pp.176-181
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• 1999

가교 발포 공정을 거치는 대부분의 단열재의 생산 제조 공정은 혼합$\longrightarrow$압출$\longrightarrow$성형$\longrightarrow$발포$\longrightarrow$권취$\longrightarrow$포장 과 같은 공정을 거치게 된다. 생산방식에 있어서는 크게 두가치 공정에 따라 대별된다. 하나는 "인-라인" 방식의 제조공정이며 다른 하나는 "오프-라인" 방식의 제조공정이다. "인-라인"의 생산방식은 공정불량의 감지가 용이하고 재공품의 재고가 적은 장점이 있는 반면에 생산수율은 높지 못한편이다. 반면에 "오프-라인"의 생산방식은 생산수율은 상대적으로 매우 높지만 공정불량에 대한 위험이 크며 재공품의 재고가 증가하는 경향이 있다. 본 연구에서는 "인-라인" 생산방식과 "오프-라인" 생산방식의 장\ulcorner단점을 분석하여 생산되는 제품에 따라서 적절한 생산방식을 채택하여 줌으로써 회사 전체의 생산성 향상을 제고 할 수 있는 방법론을 개발하고자 한다. 이러한 문제를 해결하기 위해서 먼저 공정의 분석을 통한 수학적 모델을 제시하고 그 해법을 연구하며, 사례를 들어 설명한다.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2010.11a
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• pp.271-275
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• 2010

Forming tool design is carried out for a manufacturing a outer shell structure of the nozzle extension of regenerative cooling thrust chamber. The method which manufactures outer shell structure of nozzle extension is a metal forming process using thin plate. Because the configuration of outer shell structure is changed after forming process by springback effect, the outer shell structure can't be exactly formed with the same forming tool as configuration of the nozzle extension. Therefore forming tool design considering springback effect is necessary for manufacturing the outer shell structure of the nozzle extension. In this study, new designed forming tool configuration was generated to decrease the errors between nozzle contour and formed structure. The analysis results show that the errors between nozzle contour and formed structure is significantly decreased using the new designed forming tool.

• Journal of the Korea Organic Resources Recycling Association
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• v.12 no.4
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• pp.85-94
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• 2004

Waste wood-plastic composite panels are made on different hot press molding conditions, and tested for apparent density, water absorption, expansion in thickness and flexural strength. From the test results, regardless of molding temperature and molding time, the apparent density of the composite panels is increased with an increase in the molding pressure, while their water absorption is decreased with an increase in the molding pressure. The flexural strength of the composite panels is markedly increased with increasing molding pressure, molding temperature and molding time, and tends to become nearly constant at a molding temperature of $120^{\circ}C$ and a molding time of 15min.

• Proceedings of the KAIS Fall Conference
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• 2009.12a
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• pp.678-681
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• 2009

사출성형은 열가소성수지의 가공법으로써 정밀도나 고품질의 제품을 효과적으로 생산하는데 널리 이용되며 플라스틱은 현재 광범위하게 사용되고 있는 공업재료 중의 하나이다. 과거에는 플라스틱을 일회용품 및 외장재로 사용하였다. 그러나 산업기술이 발전하며 플라스틱은 금속을 대체 할 수 있는 재료로서 사용할 수 있다는 인식의 변화로 점차 기계요소용 재료로 사용되고 있으며 기계요소용 재료로 사용됨에 따라 플라스틱 제품이 정밀한 부품으로 사용되기 위해서는 금형의 가공뿐만 아니라 사출성형 시 용융수지가 금형의 각 캐비티에 균형적으로 충전되는것이 요구된다. 이러한 요구조건을 만족하기 위해서는 각 캐비티의 가공치수는 매우 높은 정밀도를 유지해야 하며, 각 캐비티에서의 충전과 냉각도 동일한 상태를 유지해야 한다. 충전 불균형은 성형품의 품질에 큰 저해 요인으로서 플라스틱 제품의 치수성, 밀도, 외관품질, 강도 등에 불균일한 결과를 가져오는 요인으로 지적되고 있다. 실제로 충전 불균형은 충전 단계에서 런너 내에서 발생하는 불균일한 전단분포에 기인하여 발생되므로 점도변화에 영향을 주는 수지의 물성, 런너의 배열과 같은 외부 요인과 사출압력, 사출속도, 수지온도, 금형온도와 같은 성형공정 조건에 의한 요인에 의한 충전 불균형의 양상이 달라지게 된다. 본 연구는 다수 캐비티 금형에서 충전 불균형 현상에 대한 원인을 검토하고 실제로 사출성형을 실시하기 전 사출성형해석 소프트웨어를 이용하여 시뮬레이션을 하여 다수 캐비티에 대한 충전 패턴을 미리 예측하여 보았다.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.17 no.5
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• pp.223-230
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• 2007

Plasticity of clay bodies containing bottom ashes(BA) and small portion of other wastes was investigated. Plasticity indices of clay bodies using Atterberg limits were measured. It was confirmed that the plasticity indices could be applicable in actual forming process by extrusion. The forming possible compositions were found by changing the contents of water, bottom ash, stone dust, and sewage sludge. The relationship between the plasticity and physical properties of the aggregate green body was also investigated. The compositions for extrusion forming can be expected by measured the plasticity indices and these results were confirmed by real extrusion process. There is also strong relationship between the plasticity indices and the property of aggregate green body.

• Composites Research
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• v.27 no.6
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• pp.231-235
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• 2014

Autoclave processing has a good quality of product, but manufacturing cost is expansive. After curing of composite, the unwanted deformation and distortion increase the manufacturing cost by redesign of tool parts. Therefore, manufacturing cost down is a big issue in processing level. For the reduction of tool costs, it is important to investigate the effects of tool materials and tool surface conditions. In this paper, we organized user subroutine in ABAQUS to consider the thermal effects of part and tool, and the results are compared with commercial code, COMPRO. And this paper suggests reference point for the selection of tool materials to reduce manufacturing costs.

• Journal of the Korean Ceramic Society
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• v.36 no.1
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• pp.97-105
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• 1999

In the binary system of SiC and carbon, porosity and pore size distribution of green body was controlled by varying pH, by the addition of polyelectrolyte dispersants, and by using different particle size of starting powders. The preforms having different green microstructure were fabricated by slip casting from suspensions having different dispersion condition. The reaction bonding process was carried out for these preforms. The condition of reaction bonding was 1600$^{\circ}C$ and 20 min. under vacuum atmosphere. The analyses of optical and SEM were studied to investigate the effect of green microstructure on that of reaction bonded silicon carbide and subsequently the mechanical properties of sintered body was investigated. Different green microstructures were obtained from suspensions having different dispersion condition. It was found that the pore size could be remarkably reduced for a fine SiC(0.5$\mu\textrm{m}$). The bimodal microstructure was not found in the present study, which is frequently observed in the typical reaction bonded silicon carbide. It is considered that the ratio between SiC and C was responsible for the formation of bimodal microstructure. For the preform fabricated from the well dispersed suspension, the 3-point bending strength of reaction-bonded silicon carbide was 310${\pm}$40 MPa compared to the specimen fabricated from relatively agglomerated particles having lower value 260${\pm}$MPa.