• Proceedings of the Korean Fiber Society Conference
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• 1999.04a
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• pp.310-313
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• 1999

• Transactions of the Korean Society of Mechanical Engineers
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• v.15 no.1
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• pp.127-138
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• 1991

A gear forming method by cold extrusion and an analytical method with its numerical solution program based on the upper bound method were developed. In the analysis the involute curve was as a shape of die and the upper bound method was used to calculate energy dissipation rate. By this method the power requirement and optimum conditions necessary for extruding helical(spur) gear were successfully calculated. These numerical solutions are in good agreement with experimental data. In the experiment, 4-6 class helical gear of KS standard for automobile transmission was successfully manufactured.

• Proceedings of the Korean Powder Metallurgy Institute Conference
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• 2001.11a
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• pp.29-29
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• 2001

열전재료는 열전현상을 가지고 있어 열전발전과 열선냉각이 가능하기 때분에 해저용, 우주용, 군사용의 특수 전원으로 이미 실용화되어있고, 반도체, 레이저 다이오드, 적외선 검출소자 등의 냉각기로 쓰여지고 있어 많은 연구자들이 이들 재료에 대한 연구에 관을 갖고 열전특성을 향상시키기 위하여 많은 연구를 진행하고 있다 이들 열전재료는 사용 온도구역에 따라 3종류로 구분하고 있으며, 실온부근의 저온 영역(20$0^{\circ}C$)이하에서는 $Bi_2Te_3$계 재료, 중온영역(20$0^{\circ}C$~50$0^{\circ}C$)에서sms (Pb,Ge) Te계 재료, 고온영역(50$0^{\circ}C$~lOoo$^{\circ}C$)에서는 Si-Ge계 Fe Si계 재료가 이용되고 있다. 본 연구에서는 실온에서 성능지수가 높은 Bi_2(Te,Se)_3$에 대한 연구를 진행하였다. Bi_2(Te,Se)_3$계 열전재료는 기존의 공법인 Zone melting법을 이용하는 경우 성능지수가 높으나, 단위정이 Rhombohedral 구조파 기저면(basal plane)에 벽개성이 있는 관계로 재료의 적지 않은 손실과 가공상의 어려움이 있다. 또한 사료전체에 걸쳐 화학적으로 균질한 고용체를 얻는 것도 어려운 문제점으보 부각되고 있디 따라서 이와같은 문제점을 보완하기 위하여 용질원자의 편석감소, 고용도의 증가, 균일 고용체 형성, 결정립의 미세화등의 장점이 있는 급속응고법을 본 연구에 응용하였다. 본 연구에서는 위에서와 같은 급속응고의 장점과 대량 가공이 능늪한 연간압출공정을 이용하여 제조된 분말을 성형화 하였다. 특히 열간압출 가공에 있어서 압축다이 각 변화는 재료의 소성유동에 매우 중요한 역하을 하게되며, 이와 갇은 소성유동은 본 재료의 열전특성에 중요한 영향을 미치는 C 면 배양에 중요한 역할을 한 것으 로 기대된다. 이에 본 연구에서는 압출다이 각도 변화에 따른 미세조직변화와 이들 조직이 강도와 열전특성에 미치는 영향을 석하고자 한다. 압출재의 미세조직은 XRD(X Ray Diffraction), SEM(Scanning Electron Microscopy)으로 분석하였으며, 열전특성인 Seebeck계수($\alpha$)와 전기비저항( $\rho$ )은 열전측정장치로, 기계적 강도는 MTS장비를 이용하여 이루어졌다. 또한 압축다이각도 변화에 따른 결정방위 해석은 모노크로미터가 장착된 X RD장비감 이용하여 분석되었다.

• Proceedings of the Computational Structural Engineering Institute Conference
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• 2011.04a
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• pp.450-453
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• 2011

압출공법(incremental launching method)은 교대 배후에 거더 제작장소를 설치하고, 콘크리트를 이어쳐서 교량거더를 제작하고, 이것을 잭(jack)으로 밀어내는 가설방법이다. 이 공법에 의해 시공되는 교량의 상부단면은 시공 중에 지간의 중앙부와 지점부에 일시적이나마 모두 위치하게 된다. 따라서 단면들은 자중에 의해 발생되는 최대 정모멘트와 최대 부모멘트, 그리고 최대 전단력을 모두 경험하게 되는 구조적 특성을 가지고 있다. 한편 거더의 캔틸레버 작용을 감소시키기 위하여 거더의 선단에 압출추진코(launching nose)를 부착시킨다. 상부단면에 발생하는 이 일시적인 응력의 크기는 압출추진코의 단면특성에 따라 달라진다. 본 논문에서는 압출추진코와 상부단면의 상호작용에 관한 해석식의 정확성을 유지하고, 활용도를 높이기 위해서 압출추진코를 유사등단면(강성;등단면, 중량;변단면)으로 가정하여 단순화된 해석식을 제안하였고, 압출추진코의 단면이 등단면으로 가정한 기존 해석식의 정확성을 향상시키기 위해서 다이아프램의 중량을 집중하중으로 치환시켜 변형된 등단면 해석식을 제안하였다. 그리고 제안된 2개의 해석식의 정확성과 활용성을 판단하기 위해 실제 ILM교량 설계자료들을 통해 전산구조해석 프로그램과, 기존 해석식들과 비교 분석 하였다.

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 2005.05a
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• pp.144-147
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• 2005

In hydrostatic extrusion the billet in the container is extruded through a die with a liquid acting as a pressure medium, instead of by the direct application of the load by a ram. And the extrusion pressure can be affected by the flow stress and they are affected by the temperature. So in this study the temperature is the main issue with a extrusion ratio and a half die angle. As extrusion temperature goes down from $300^{\circ}C$ to $200^{\circ}C$, tensile strength goes up to 310MPa. Because velocity of extrusion is higher than the conventional extrusion, there is another characteristic in the sense of microstrure. The temperature was sotted to $300^{\circ}C,\;250^{\circ}C,\;200^{\circ}C$, respectively. There is a increase of extrusion pressure abot $15\%$.

• Journal of the Korean Society of Manufacturing Process Engineers
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• v.20 no.1
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• pp.34-41
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• 2021

Interventional radiology and minimally invasive surgery both require a precisely shaped microcatheter. Microcatheters are manufactured using polymer extrusion processes with a die and puller. The manufacturing parameters and die geometry greatly influence the profile of the extrudate and designing dies using a trial-and-error process is expensive and requires a lot of time. Therefore, predicting the profile of the extrudate is important for manufacturing microcatheters. This study investigates the effects of die design and geometry on the profile of the extrudate. The profiles of the extrudate are predicted using ANSYS Polyflow with respect to the different die geometries. The outer and inner diameters and wall thickness of the predicted extrudate are compared to those of a target extrudate. The die swell of melt polymer and the effect of the pulling are both examined. Optimized die designs are suggested for manufacturing the target extrudate.

• Proceedings of the KSME Conference
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• 2001.06d
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• pp.311-318
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• 2001

A three-dimensional numerical analysis of the flow and heat transfer characteristic of wood-flour-filled polypropylene melt in an extrusion die was carried out Used for this analysis were Finite Concept Method based on FVM, unstructured grid and non-Newtonian fluid viscosity model. Temperature and flow fields are closely coupled through temperature dependent viscosity and viscous dissipation. With large Peclet, Nahme, Brinkman numbers, viscous heating caused high temperature belt near die housing, Changing taper plate thickness and examining some predefined parameters at die exit investigated the effect of taper plate on velocity and temperature uniformities. In the presence of taper plate, uniformity at die exit could be improved and there existed an optimum thickness to maximize it.

• Transactions of Materials Processing
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• v.7 no.2
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• pp.177-185
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• 1998

The kinematically admissible veolcity field is developed for the shapes of dead metal zone and the curving velocity distribution in the eccentric plane dies extrusion. The shape of dead metal zone is defined as the boundary surface with the maximum friction constant between the deformable zone and the rigid zone. The curving phenomenon in the eccentric lane dies is caused by the eccentricity of plane dies. The axial velocity distribution in the plane dies is divided in to the uniform velocity and the deviated velocity. The deviated velocity is linearly changed with the distance from the center of cross-section of the workpiece. The results show that the curvature of products and the shapes of the dead metal one are determined by the minimization of the plastic work and that the curvature of the extruded products increase with the eccentricity.

• Proceedings of the Korean Society of Machine Tool Engineers Conference
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• 2003.04a
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• pp.161-166
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• 2003

The micro-extruding die is a die for manufacturing of fine-wire by extruding process. The fine-wire made from the micro-extruding can be effectively applied to fields of semiconductor parts and medical parts etc. It is predicted that the demand of fine-wire in industry is more and more increasing. In this study $\phi50\mu m$ micro-drill which is coated with diamond is used for drilling of super micro-hole sizes. For the machining of taper parts of entrance and exit, drill having $\phi50\mu\textrm{mm}$ inclination angle $20^{\circ}$and angle $30^{\circ}$ is used. This is useful for anti tool-breakage and excessive too-wear in drilling process. After micro-drilling, the polishing process by diamond abrasive and polishing wood s carried out for increasing surface roughness.

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 2002.11a
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• pp.23-32
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• 2002

The torsional forward extrusion is the process that is executed by punch travel and die rotation. The advantages of having the die rotation on this process are that forming load can be reduced and optimal die angle can be increased. This provides a possibility to extrude cold-worded material where a large extrusion force and die angle are required. Also, this process can improve the material properties owing to the high deformation and uniform strain distribution. The forming load and optimal die angle of this process are determined by the upper bound analysis using stream function and the optimization technique. To verify the theoretical result, we have carried out experiments and FE simulations using DEFORM3D.