• Journal of the Korean Society for Precision Engineering
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• v.18 no.1
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• pp.44-55
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• 2001

The flow behavior of semi-solid materials (SSM) is required to assist the industrial application of thixoforming technology. Particularly, to reduce many lead times, many numerical analysis packages have been developed to simulate required metal forming processes. The objectives of the development of SEMI-FORM for thixoforming process design are to predict the effect of various process variables such as pressing force, die temperature, and die velocity. However, there have not been any reports which adapt these packages to the specific characteristics of SSM. SO, this paper presents an overview of the development of thixoforming simulator of SEMI-FORM. The solver and post-processor of SEMI-FORM S/W for an automated thixoforming process design with arbitrarily shaped die are composed of FORTRAN Power Station 4.0 and Visual Basic 5.0, respectively. This developing SEMI-FORM S/W would be very useful for thixoforming practitioners and engineers to select the optimal process conditions to produce automotive parts with high quality.

• Resources Recycling
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• v.28 no.2
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• pp.3-13
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• 2019

Aluminum is the most abundant metal and the second most plentiful metallic element in the earth's crust, after silicon. Aluminum is a light, conductive, and corrosion resistant metal with strong affinity for oxygen. However, the primary aluminum production process is highly energy intensive. The recycling of aluminum scrap reduces the energy consumption and environmental burden, comparing to the primary metal production. However, the amount of the recovered metal from scrap is limited because of the difficulties to remove the impurities in the scrap. This work provides an overview of the aluminum production and recycling process, from the preparation of alumina to the scrap upgrading and the melting process.

• Journal of the Korean Society for Heat Treatment
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• v.35 no.1
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• pp.1-7
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• 2022

In this study, dissolution and melting phenomenon of the Al₂Cu was studied for the high-strength Al-Si-Cu aluminum alloy in automobile component. The Solution heat treatment was performed at 480℃ and 510℃ for 4hours. Microstructure analysis of the specimen was performed using the optical micrograph and scanning electron microscope for qualitative and quantitative analysis of various phases, the chemical composition of secondary phases was achieved by energy dispersive spectroscopy (EDS) and electron probe micro analysis (EPMA). As a result of the electron probe micro analysis, a plate like Al₂Cu phase was observed, and eutectic Si phase was observed of a coarsen plate shape. At a temperature of 510, necking phenomenon occurs in a specific part of plate like Al₂Cu, and it is segmented and dissolved in the Al matrix. When the temperature of the alloy exceeds the melting point of Al₂Cu, incipient melting occurs at the grain boundary of undissolved Cu particles

• Transactions of the Korean Society of Mechanical Engineers A
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• v.36 no.6
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• pp.609-615
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• 2012

In LSP (laser shock peening) treatment, the laser source geometries when the laser beam strikes the metal target area are diverse. The laser spot geometry affects the residual stress field beneath the treated surface of the metallic materials, which determines the characteristics of the pressure pulse. In this paper, detailed finite-element (FE) simulations on laser shock peening have been conducted in order to predict the magnitude and of the residual stresses and the depth affected in Inconel alloy 600 steel. The residual stress results are compared for circular, rectangular, and elliptical laser spot geometries. It is found that a circular spot can produce the maximum compressive residual stresses near the surface but generates tensile residual stresses at the center of the laser spot. In the depth direction, an elliptical laser spot produces the maximum compressive residual stresses. Circular and elliptical spots plastically affect the alloy to higher depths than a rectangular spot.

• 한국신재생에너지학회:학술대회논문집
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• 2008.05a
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• pp.361-363
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• 2008

탄소 개질반응은 $1200^{\circ}C$(도1) 이상에서 모든 탄화물질과 수분 또는 $CO_2$ 사이에서 흡열/환원반응이 일어나서 합성가스를 생성한다. 개질반응로는 산화반응로와 연결되어, 수소가스와 CO 가스의 혼합인,합성가스가 산화반응로 내에서 산소가스와 연소하여 열과 $H_2O+CO_2$를 생성하여 환원 반응로 내로 유입되어, 환원 반응로를 $1200^{\circ}C$ 이상으로 유지하고, $H_2O$와 $CO_2$는 석탄 속의 모든 탄소를 CO로 개질한다(도2). 동시에 수소가스가 생성되어 합성가스를 생성하게 된다. 석탄 속의 비탄소 물질인 슬래그(Slag)는 개질로 내에 남게 되는데, 개질로를 슬래그 융점(non-fluid point) 이하에서 고체상태로 포집함으로서 Fly-ash로 처리된다. 개질로 내의 온도를 $1200{\sim}1300^{\circ}C$(석탄 슬래그 융점)로 유지함으로서 개질반응이 지속되어 합성가스가 생성된다. IGCC 시스템에서는 합성가스를 가스터빈 속에서 $O_2E가스와 연소하여 고온의 가스를 생성하여 터빈을 가동해 발전을 하고 배출가스를 $1500{\sim}1700^{\circ}C$에서 배출한다. 재래식 IGCC(도4)에서는 ${\sim}1500^{\circ}C$의 배출가스를 열교환 시스템에 의해 증기를 생성하여 Steam turbine(증기터빈)을 가동하여 추가 전력을 생산했다. 그러나 본 시스템에서는 배출가스(증기와 $CO_2E 가스)를 위의 개질로에 유입하여 개질로 온도를 $1200{\sim}1300^{\circ}C$로 유지함으로서 더 많은 합성가스를 생성 하게 된다(도3). 이렇게 하여 Oxidation-reduction cycle을 형성하게 된다. 새로운 IGCC 시스템에서 가스 터빈의 배출가스가 석탄 개질로에 연결되고 석탄개질로의 합성가스 출구가 가스터빈의 가스 입구에 연결됨으로서,외부에너지 주입 없이 지속 가능한 가스화 반응과 터빈 사이클(Cycle)을 완성하여 IGCC 시스템의 석탄 열효율을 1단계 상승시켰다. 이렇게 설계된 석탄가스화기는 Lurgi형 석탄가스화 기와 달리 석탄개질반응의 효율을 높일 수 있고, 슬래그 처리가 간단하기 때문에 석탄가스화기가 소형화 될 수 있으며 슬래그(Slag)용융에 따른 석탄가스화기의 외벽손상을 피할 수 있다.

• Journal of Nuclear Fuel Cycle and Waste Technology(JNFCWT)
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• v.16 no.3
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• pp.377-387
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• 2018

Korea's first commercial nuclear power plant, Kori Unit 1, was permanently shut down on June 18, 2017, after 40 years of successful operation. Kori Unit 1 plans to construct a waste treatment facility in the turbine building prior to commencement of dismantling in earnest. Various radioactive wastes are decontaminated, disassembled, cut and melted in the waste treatment facility and sent to the radioactive waste repository. The proportion of metal radioactive waste in dismantled waste is about 70%, of which large metal radioactive waste is mainly generated in the primary circuit and has high radioactivity, so radiation exposure must be managed during disassembly. In this study, the steam generators are selected as large metal radioactive waste, the exposure doses of the dismantling workers are calculated using RESRAD-RECYCLE code and the methods for reducing the exposure doses are suggested.

• Applied Chemistry for Engineering
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• v.21 no.5
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• pp.581-585
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• 2010

The surface of Alnico, one of the industrial dust waste, was treated with 1,3,5-trivinyl-1,3,5-trimethylcyclotrisilazane (VMS) as a surface treating agent and used as the filler for vibration isolator rubber. Maleated EPDM prepared from bulk polymerization of EPDM with maleic anhydride was copolymerized with ${\alpha},{\omega}$-bis(3-aminopropyl)polydimethylsiloxane to obtain maleated EPDM-polydimethylsiloxane copolymer (MEPDM-PDMS). EPDM/Alnico/MEPDM-PDMS vibration isolator rubber was prepared from compounding with Alnico treated with surface treating agent, 25 and 50 phrs to EPDM, respectvely based on 1 to 10 wt% of MEPDM-PDMS to EPDM. From the measurement of the thermal properties to the rubber, the glass transition temperatures (Tg) for the rubber containing maleated EPDM-PDMS copolymer was slightly lower temperature, $33^{\circ}C$ than EPDM rubber, and also DMA results showed higher tan ${\delta}$ peak to the rubber prepared from compounding with EPDM-PDMS copolymer. From the results, rubber prepared using EPDM-PDMS copolymer had better vibration isolator property.

• Proceedings of the Korean Society of Postharvest Science and Technology of Agricultural Products Conference
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• 2003.10a
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• pp.214.2-215
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• 2003

압출조리 공법에 의한 한국형 쌀 이유식 제조에서 아밀라제 첨가가 압출미분의 물성 변화에 미치는 영향을 알아보았다. 압출조리기의 스크류 회전수는 200rpm, 원료의 사입속도는 180g/min로 고정하여 작동하였다. 원료 쌀가루의 수분함량은 18, 23, 28%로 가수하였고 첨가된 아밀라제는 Bacillus licheniformis로부터 분리한 Termamyl 120LS(NOVO사), Bacillus amylolichuefaciens로부터 분리한 BAN 240L(NOVO사) 및 맥아분말이다. 아밀라제 첨가에 의해 압출미분의 수용성지수는 3배까지 증가했고, 환원당 생성량은 원료의 수분함량에 크게 영향을 받아 28% 수분함량에서 급격히 증가하여 수용성지수와는 다른 경향을 나타내었다. 겔 투과크로마토그래피에 의한 분자량적 구조 변화 측정 결과 아밀라제 첨가에 의해 고분자 획분이 상당히 감소했으며 상대적으로 저분자 획분이 증감함을 알 수 있었다. 아밀라제의 잔존환성은 아밀라제 종류에 따라 다르며 가장 내열성인 Termamyl 120LS의 경우 용융부위 온도 14$0^{\circ}C$에서 27%까지 감소하였다. 침전법에 의한 분산특성은 아밀라제 작용에 의해 수용성 물질이 증가함에 따라 침전층의 감소를 나타내었으나 처리온도가 14$0^{\circ}C$로 증가하면 침전층의 높이는 증가하였다. 겉보기 점도는 아밀라제 첨가에 의해 무처리 압출미분의 1/4~1/200로 감소하였다. 시판 이유식의 권장농도에서의 점도와 같은 점도 수준에 도달하기 위해서는 원료의 수분함량(18, 23, 28%), 아밀라제 종류 및 첨가량, 계량부위 온도에 따른 각 작동조건의 압출미분을 최고 1.8배의 양을 사용할 수 있었다. 이상에서 살펴본 바와 같이 원료 쌀가루에 첨가된 아밀라제가 압출조리기내를 통과하면서 쌀가루의 가수분해를 일으켜 환원당 등 수용성 물질이 증가하고 분산특성이 좋아지며 점도가 낮아지고 결국 이유식의 열량밀도를 증가시킬 수 있음을 확인할 수 있었다.

• Elastomers and Composites
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• v.45 no.1
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• pp.12-16
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• 2010

In this work, the effect of hydrophobic treated silica on the water absorption, thermal stabilities, and mechanical properties of the epoxy nanocomposites were investigated as a function of the silica content. As filler, fumed silica treated by dimethyldichlorosilane was used. It was found that the silica was well dispersed in the epoxy resins by the melt-mixing method with the addition of a silane coupling agent. The water absorption of the nanocomposites decreased with an increase of the silica content due to the effect of hydrophobic treated silica. The thermal properties, such as thermal degradation temperature, glass transition temperature ($T_g$), and coefficient of thermal expansion (CTE), of the nanocomposites were improved by the addition of silica. Furthermore, the mechanical properties of the nanocomposites, that is, the tensile strength and modulus, were enhanced with increasing silica content. This was attributed to the physically strong interaction between silica and epoxy resins.

• Journal of the Korean Society for Heat Treatment
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• v.4 no.2
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• pp.19-26
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• 1991

This study has been constructed to establish the formation of the VC layer on various steels by immersion in fused borax bath containing Fe-V powder. The result obtained from the experiment are as follows. (1) The carbide is supposed to grow on the front surface of the carbide layers by the reaction between carbide-forming elements dissolved in the fused borax and carbon atoms successively supplied through the layer from the matrix. (2) The growth rate of the carbide layers was controlled by the diffusion rate of C in the carbide layer and C content in the matrix. (3) Carbide layer formed on the surface of the specimen is VC layer and the hardness of this layer is above $H_v$ 3000.