• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 1997.11a
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• pp.28-28
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• 1997

복합재료 부품을 설계할 때 필연적으로 한 부품이 두 가지 역할을 해야 하는 경우, 적용할 소재의 특성이 두 가지 필요조건을 만족하는 경우는 문제없으나 그렇지 않으면 단일 부품을 두 가지 소재로 설계/제조하여야 한다. 이때 계면의 강도를 최대로 할 수 있는 방법중의 하나가 involute construction 공정이며, 이 공정을 적용하는데 필요한 패턴설계와 적층 공정 및 두 소재사이의 계면 위치 등에 관하여 연구하였다. 계면의 형상을 톱니형으로 하기 위하여 패턴 설계는 1부품에 4가지 설계가 필요하고 적층 공정은 적층 치구를 이용하여야 한다. 계면의 위치는 적층 오차, 성형 중 수축 등을 고려하여 설계하여야 원하는 치수로 부품을 제작할 수 있다는 결론을 얻을 수 있었다. 적층 오차와 성형 중 수축에 의한 양을 분석하여 재 설계하였으며 그 결과 원하는 부분에 정확히 계면을 위치하게 할 수 있는 방법을 개발하였다. 2질 일체형 부품을 이러한 방법으로 제작하면 fabric prepreg를 이용하는 어떤 방법 보다도 정확한 부품을 제작할 수 있을 것으로 생각된다.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 1997.10a
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• pp.1047-1050
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• 1997

Rapid Prototyping(RP) is an efficient method for rapid design verification and trial manufacturing. In order to improve their unique characteristics according to the working principles. Variable Lamination Manufacturing process and corresponding CAD/CAM system is developed. The objective of this study is to improve dimensional accuracy of VLM-ST process, and it can be done by offset for cutting error correction, cutting path correction for sharp edge and reference shape generation. To verify the proposed algorithms, they applied to three-dimensional shapes, such as spanner and mechanical part.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.35 no.12
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• pp.1647-1653
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• 2011

The cycle time in injection moulding greatly depends on the cooling time of the plastic part that is controlled by cooling channels. Cooling channels are required to facilitate the heat transfer rate from the die to the coolant without reducing the strength of the die. Employing layered manufacturing techniques (LMT), a die embedding conformal cooling channels can be fabricated directly while conventional cooling channels are usually made of straight drilled hole. Meanwhile, H13 tool steel is widely used as the die material because of its high thermal resistance and dimensional stability. However, H13 with a low thermal conductivity is not efficient for certain part geometries. In this context, the use of functionally graded materials (FGMs) between H13 and copper may circumvent a tradeoff between the strength and the heat transfer rate. This paper presents a method for modeling of conformal cooling channels made of FGMs.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.28 no.5
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• pp.217-221
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• 2018

Selective laser melting (SLM) technique is one of the additive manufacturing processes, in which functional, complex parts can be directly manufactured by selective melting layers of powder. SLM technique has received great attention due to offering a facile part-manufacturing route and utilizing a hard-to-manufacturing material (e.g. Ti6Al4V). The SLM process allows the accurate fabrication of near-net shaped parts and the significant reduction in the consumption of raw materials when compared to the traditional manufacturing processes such as casting and/or forging. In this study, we focus the high-speed additive manufacturing of Ti6Al4V parts in the aspect of manufacturing time, controlling various process parameters.

• Journal of Korean Society of Steel Construction
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• v.24 no.4
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• pp.399-410
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• 2012

In this study, vibration tests are performed on cantilevered and clamped-clamped laminated composite rectangular plates using experimental modal analysis technique. The damages are simulated by applying progressive line cracks to the laminated composite plates for damage evaluations due to crack growth. The changes of frequency response functions(FRFs), MAC values, and modal parameters (frequency, mode shape and damping ratio) of the damaged composite plates, which are obtained by the modal testing of impact hammer, are investigated. Each experimental modal parameter of the progressively damaged composite plates is compared with natural frequencies and mode shapes obtained by finite element analysis. It is seen that the damage can be evaluated from the changes in the geometric properties and structural behaviors of the laminated composite plates resulting from the model updating process of the finite element model as a benchmark.

• Journal of Korean Society of Steel Construction
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• v.10 no.2 s.35
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• pp.201-209
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• 1998

The presence of elevated temperature can alter significantly the structural response of fibre-reinforced laminated composites. A thermal environment causes degradation in both strength and constitutive properties, particularly in the case of fibre-reinforced polymeric composites. Furthermore, associated thermal expansion, either alone or in combination with mechanically induced deformation, can result in buckling, large deflections, and excessively high stress levels. Consequently, it is often imperative to consider environmental effects in the analysis and design of laminated systems. Exact analytical solutions of higher-order shear deformation theory is developed to study the thermal buckling of cross-ply and antisymmetric angle-ply rectangular plates. The buckling behavior of moderately thick cross-ply and antisymmetric angle-ply laminates that are simply supported and subject to a uniform temperature rise is analyzed. Numerical results are presented for fiber-reinforced laminates and show the effects of ply orientation, number of layers, plate thickness, and aspects ratio on the critical buckling temperature and compared with those obtained using the classical and first-order shear deformation theory.

• Journal of the Korean Society for Advanced Composite Structures
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• v.1 no.2
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• pp.14-19
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• 2010

Theories for advanced composite structures are too difficult for such design engineers for construction and some simple but accurate enough methods are necessary. The senior author has reported that some laminate orientations have decreasing values of $D_{16}$, $B_{16}$, $D_{26}$ and $B_{26}$ stiffnesses as the ply number increases. For such plates, the fiber orientations given above behave as specially orthotropic plates and simple formulas developed by the senior author. Most of the bridge and building slabs on girders have large aspect ratios. For such cases further simplification is possible by neglecting the effect of the longitudinal moment terms(Mx) on the relevant partial differential equations of equilibrium. In this paper. the influence of the aspect ratio on the natural frequency of the composite laminated plates is studied and it is concluded that the method used is sufficiently accurate for engineering purposes.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2004.05a
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• pp.305-305
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• 2004

쾌속조형 기술은 3차원 CAD 데이터를 일정한 두께 간격으로 슬라이싱한 각 층을 다양한 방법으로 만들고, 이러한 층을 한층씩 적층하여 원하는 3차원 형상을 신속하게 제작하는 기술이다. 쾌속 조형법은 초기에는 광(beam)에 의해 형상이 만들어진다고 하여 광조형법이라고 불렸다. 그 후 시작품(Prototype)을 신속(Rapid)하게 제작할 수 있다는 사실로부터 'Rapid Prototyping' 또는 '쾌속 조형법' 이라고 불려지게 되었다.(중략)

• Proceedings of the Korean Society of Laser Processing Conference
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• 2000.06a
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• pp.24-30
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• 2000

• Composites Research
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• v.19 no.2
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• pp.13-19
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• 2006

In this paper, parametric study was carried out to design sandwich structures for EDM machines controlling stacking sequence, stacking thickness of composites and rib configuration. Sandwich structures which are dealt with in this paper are composed of fibre reinforced composite for skin material and foam or resin concrete for core materials. The sandwich column has cruciform rib to enhance bending stiffness of the structure and the bed has several vertical ribs to resist the normal forces and vibration. The design parameters such as rib thickness and stacking sequence were controlled to enhance the system robustness. Finite element analysis was also carried out to verify the variation of static and dynamic stiffness of the structures according to the variation of the parameters. Vibration tests were performed to verify the natural frequencies and damping ratios of the manufactured composite structures. The appropriate shape and configuration conditions for micro-EDM machine structures are proposed.