• 한국분말재료학회지
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• 제16권5호
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• pp.342-350
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• 2009

Development of nanoparticulate materials technology is essential to processing of highly functional nanoparticulate materials and components with small and complex shape. In this paper, the effect of particle size on surface roughness and shrinkage of sintered Fe-8 wt%Ni nanopowder components fabricated by PIM were investigated. The Fe-8 wt%Ni nanopowder was prepared by hydrogen reduction of ball-milled Fe$_2$O$_3$-NiO powder. Feedstock of nanopowder prepared with the wet-milled powder was injection molded into double gear shaped part at 120$^{\circ}C$. After sintering, the sintered part showed near full densified microstructure having apparently no porosity (98%T.D.). Surface roughness of sintered bulk using nanopowder was less than 815 nm and it was about seven times lower than 7 $\mu$m that is typically obtainable from a sintered part produced from PIM.

• 유변학
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• 제8권1호
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• pp.58-68
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• 1996

고분자 가공에서 가장널리 사용되고 있는 사출공정은 비등온의 싸이클 공정이므로 사출조건에 따라 성형품은 다양한 형태의 열이력과 변형이력을 받게 되고 그 결과 최종성형 품의 기계적 물성이 현저히 달라지게 된다. 그러므로 우수한 물성을 갖는 성형품을 얻기위 해서는 열이력과 변형이력에 연관되어 나타나는 미세구조의 변화와 잔류응력을 최소화할수 있는 최적 성형조건의 선정이 대단히 중요하게 된다. 본 연구에서는 수치모사실험을 기초로 설정한 성형조건의 범위에서 다양한 사출성형실험을 수행하여 얻은 시편을 대상으로 미세구 조의 변화와 잔류응력에 미치는 성형조건의 영향을 조사함으로써 최적성형조건을 선정하기 위한 방안을 찾고자 하였다. 편광현미경을 사용하여 관찰한 결정성 고분자수지 시편의 내부 구조는 전형적인 skin-core 구조를 보일뿐만아니라 충전속도, 사출온도, 금형온도, 및 gate로 부터의 위치 변화에 따라 미세구조가 현저히 변함을 알수 있었으며 광탄성법과 layer removal method를 이용하여 조사한 무정형 고분지수 시편의 잔류응력은 금형온도와 사출압 에 가장 영향을 많이 받으며 두께 방향으로 parabola한 분포를 가짐을 알수 있었다. 이상의 결과로부터 사출조건의 변화에 따라 잔류응력과 내부구조가 현저히 변하게 되며 이는 성형 품의 물성에 직접적인 영향을 미치고 있음을 알수 있었다.

• 한국분말재료학회지
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• 제11권6호
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• pp.528-534
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• 2004

Using the nano Fe powders having 50 nm in diameter, Fe compact bodies were fabricated by injec-tion molding process. The relationship between microstructure and material properties depending on the volume ratio of powder/binder and sintering temperature were characterized by SEM, TEM techniques. In the compact body with the volume percentage ratio of 45(Fe powder) : 55(binder), which was sintered at $700^{\circ}C,$ the relative density was about $97{\%},$ and the values of volume shrinkage and hardness were about $66.3{\%}$ and 242.0 Hv, respec-tively. Using the composition of 50(Fe powder) : 50(binder) and sintered at $700^{\circ}C,$ the values of relative density, volume shrinkage and hardness of Fe sintered bodies were $73.3{\%},\;47.6{\%}$ and 152.8 Hv, respectively. They showed brittle fracture mode due to the porous and fine microstructure.

• 동력기계공학회지
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• 제3권3호
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• pp.70-75
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• 1999

This study is for the development of tie rod end, a parts of steering system, that would be changed with plastic material. The position of weld line is founded by the analysis of Mold Flow, computer software with FEM(Finite Element Method). Then new mold is designed by consideration with the locations of weld line. PA66(G/F 35%), PA6(G/F 45%), PET(G/F 45%) and PET(G/F 55%) are tested two types loading conditions for selecting suitable material, the requirement tensile load(more 19600N). PA6(G/F 45%) showed high mechanical properties in this study. And then, tensile strength was compared between conventional metal products and the injection molded products which were reinforced with 33%, 34%, 45%. 60% of glass fiber in matrix material. In the case of, the measured two types of tensile load values are 24500N (Method-1), 21560N (Method-2) and weight is decreased by 50% of conventional one.

• 전기학회논문지P
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• 제63권4호
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• pp.283-289
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• 2014

A Fresnel lens is an optical component which can be used as a cost-effective, lightweight alternative to conventional continuous surface optics. Fresnel lens solar concentrators continue to fulfill a market requirement as a system component in high volume cost effective Concentrating Photovoltaic (CPV) electricity generation. The basic principles of the fresnel lens are reviewed and some practical examples are described. To investigate the performance space of the Fresnel lens, a fast simulation method which is a hybrid between raytracing and analytical computation is employed to generate a cache of simulation data. Injection molders are warming up to the idea of cycling their tool surface temperature during the molding cycle rather than keeping it constant. Heat and cool process are now also finding that raising the mold wall temperature above the resin's glass-transition or crystalline melting temperature during the filling stage and product performance in applications from automotive to packaging to optics. This paper deals with the suitability of Fresnel lenses of imaging and non-imaging designs for solar energy concentration. The concentration fresnel lens confirmed machinability and optical transmittance and roughness measure through manufactured the prototype.

• 소성∙가공
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• 제25권6호
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• pp.402-408
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• 2016

A manufacturing technology of carbon fiber composites with thermoplastic polymer pellets and continuous woven fiber was investigated using a compression molding process. To secure the impregnation of resin into the porosity of fabric the composite specimens were prepared with general injection-molding grade polypropylene pellets and low viscosity polycarbonate pellets. Tensile tests of polypropylene and polycarbonate composites were performed. Polycarbonate composites showed higher fracture strength than that of polypropylene composites because of the difference of matrix properties. However, the increase rate of strength was lower than that of polypropylene composites due to the difference of coherence between matrix and reinforcement. To investigate the effect of carbon fiber volume fraction on the fracture strength variation polypropylene composites with different volume fraction were compression molded and tensile tests were performed together. It was shown that the fracture strength of the polypropylene composites increased by 3.2, 5.4 and 6.9 times with the increase of carbon fabric volume fraction of 0.256, 0.367, and 0.480, respectively.

• Current Optics and Photonics
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• 제2권2호
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• pp.140-146
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• 2018

In this paper, mesoscale optical surface structures are found to possess both geometric and wave optics features. The study reveals that geometric optic analysis cannot correctly predict the experimental results of light transmission or reflection by mesoscale optical structures, and that, for reliable analyses, a hybrid approach incorporating both geometric and wave optic theories should be employed. By analyzing the transmission patterns generated by the mesoscale periodic pyramid prism plates, we show that the wave optic feature is mainly ascribed to the edge diffraction effect and we estimate the relative contributions of the wave optic diffraction effect and the geometric refraction effect to the total scattering field distribution with respect to the relative dimension of the structures.

• 정보저장시스템학회논문집
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• 제3권3호
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• pp.149-153
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• 2007

Perpendicular patterned magnetic media have been regarded as a prime candidate to achieve an ultra-high magnetic recording density of over 1 Tera-bits/$inch^2$. Patterned magnetic media with nanoscale patterns have been fabricated using various nanopatterning technologies. We focused on the two technical issues of nanoinjection molding technology. Firstly, we have investigated a cost-effective method to fabricate metallic stamps. Secondly, we focused on the analysis of nanoinjection molding with passive heating, where the replication of 50 nm nanopillar arrays was successful. The effect of the thermal insulation layer on the replication quality was examined by analytical and experimental methods. Finally, we deposited a magnetic layer on a injection molded nanopillars and measured. Our methodology can provide cost-effective mass-production for patterned magnetic media.

• 한국전기전자재료학회논문지
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• 제19권4호
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• pp.386-390
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• 2006

Global consumption of aspheric lens will expand rapidly due to golbal transformation of the electronics based industry to optics based mechatronics. Especially, F-Theta lens is one of important parts in Laser Scanning Unit(LSU) because it affects the optical performance of LSU dominantly. Non axisymmetric machine based processing techologies are required to obtain high accuracy in utlra-precision aspheric core, the most important component in plastic injection molded F-Theta lens assembly. In this study, the core with non-axisymmetric aspheric shape which is used to emit the F-Theta lens was processed using the ultra precision processing technology and the shape accuracy of the core was measured. And the results there of were evaluated and compared with the emitted shape accuracy of F-Theta lens.

• 소성∙가공
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• 제15권1호
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• pp.34-41
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• 2006

Microlens arrays were fabricated by a modified LIGA process composed of the exposure of a PMMA (Polymethylmethacrylate) sheet to deep x-rays and subsequent thermal treatment. A successful modeling and analyses for microlens formation were presented according to the experimental procedure. A nickel mold insert was fabricated by the nickel electroforming process on the PMMA microlens arrays fabricated by the modified LIGA process. For the replication of microlens arrays having various diameters with different foci on the same substrate, both hot embossing and microinjection molding processes have been successfully utilized with the fabricated mold insert. Replicated microlenses showed very good surface roughness with the order of 1 nm. The focal lengths of the injection molded microlenses were successfully estimated theoretically and also measured experimentally.