• Korea-Australia Rheology Journal
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• 제17권1호
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• pp.21-25
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• 2005

Rheological properties and crystallization kinetics of the polypropylene (PP) block copolymer and recycled PP block copolymer were studied by advanced rheometric expansion system (ARES), differential scanning calorimetry (DSC), and optical microscopy. In the study of the dynamic rheology, it is observed that the storage modulus and loss modulus for the PP block copolymer and recycled PP block copolymer did not change with frequency. In the study of the effect of the repeated extrusion on the crystallization rate, half crystallization time of the PP samples was increased with the number of repeated extrusion in isothermal crystallization temperature ($T_c$). From the isothermal crystallization kinetics study, the crystallization rate was decreased with the increase of the number of repeated extrusion. Also, from the result of Avrami plot, the overall crystallization rate constant (K) was decreased with the increase of the number of the repeated extrusion. From the study of the optical microscopy, the size of the spherulite of the PP samples did not change significantly with the number of repeated extrusion. However, it was clearly observed that the number of the spherulite growth sites was decreased with the number of repeated extrusion. From the results of the crystallization rate, isothermal crystallization kinetics, Avrami plots, and optical microscopy, it is suggested that the crystallization rate of the PP block copolymer is decreased with the increase of the number of repeated extrusion.

• 폴리머
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• 제39권3호
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• pp.475-479
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• 2015

모폴로지 분석을 통하여 반복압출에 의한 LCP(Vectra A950)와 PET 블렌드의 droplet 분산 상태를 확인하였다. 반복압출은 블렌드 조건별로 각각 2회, 3회 진행하였으며, 1회 압출 시료의 droplet 분산은 균일한 형태를 보였다. 하지만, 2회 및 3회 반복 압출 시료의 droplet 크기는 증가하였고 droplet이 시료의 중앙에 집중되는 현상을 확인할 수 있었다. 이러한 현상은 LCP/PET 블렌드의 상용성과 점탄성 거동에 기인한 것으로 생각된다. 끝으로 동일 방사조건에서 반복압출 LCP/PET 블렌드 chip을 방사하면 직경이 다른 섬유 제조가 가능할 것으로 생각된다.

• 한국분말재료학회지
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• 제16권6호
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• pp.438-441
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• 2009

Mg-Cu composites were successively fabricated using a combination of rapid solidification and extrusion processes. In addition, the microstructural variation of the composite was investigated by performing the extrusion repeatedly. It resulted that the composite formed an uniform and dense structure by the extrusion, and the microstructure became fine as the extrusion conducted repeatedly. The microstructural variation was known to be dependent on the number of extrusion and the area reduction ratio. The tensile strength was also measured as a function of the microstructural variation.

• 한국지진공학회:학술대회논문집
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• 한국지진공학회 2000년도 추계 학술발표회 논문집 Proceedings of EESK Conference-Fall 2000
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• pp.482-489
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• 2000

The cyclic extrusion damper, Lead Extrusion Damper, was invented by the W H Robinson in order to produce the isolated buildings and bridges the damping force. Recently, LED was applied to reduce the vibration of the tall building. In this study, to verify the dynamic characteristics of LED, the tests to find out the dependences on the velocity, displacement, repeated cycle, and temperature were performed at structural lab of Unison Industrial Co. Ltd. Through the result of the dynamic characteristics. we`ll define the design parameters and apply the appropriate parts.

• 동력기계공학회지
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• 제3권1호
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• pp.45-49
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• 1999

Lots of products are made in various working conditions, depending on the size and the shape of them. Usually, at first, the die for new items had been designed on the basis of experience and know-how, and then modified through trial and error. At a die design stage most of drawings have been drawn manually. Recently some forging companies save design time by repeated utilization of standardized parts with registered data base. In this study the automated die design technique for forward extrusion of axisymmetric products is developed. A standardized die system is proposed from the investigation of ones employed frequently in the metal forming field and the design rules for cold extrusion die. A design example of forward extrusion die is given and discussed.

• 소성∙가공
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• 제16권5호통권95호
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• pp.386-390
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• 2007

In order to, simultaneously, synthesize and control the size of microstructure of amorphous/crystalline composites, a repeated extrusion process was performed using the gas atomized $Cu_{54}Ni_6Zr_{22}Ti_{18}$ metallic glass powders and the crystalline brasses. The size of microstructure in the resultant composites was varied depending on the pass of extrusion as well as on the area reduction ratio. The microstructure could be estimated using an equation of $r_n=r_{n-1}/R^{1/2}$, where R is reduction ratio and $r_n$ is the resultant radius of the extruded bar after n pass. Theory of microstructural refinement as well as the relationship between the resultant microstructures and mechanical properties was discussed.

• 한국식품영양과학회지
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• 제43권2호
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• pp.258-264
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• 2014

본 실험은 사출구 온도와 반복 압출성형이 백삼압출성형물의 화학적 조성 및 항산화 활성에 미치는 영향을 분석하였다. 압출성형 조건은 수분함량과 스크루 회전속도를 고정시키고 사출구의 온도를 $100^{\circ}C$, $120^{\circ}C$, $140^{\circ}C$로 1회, 2회 반복 압출성형 실험을 하였다. 압출성형백삼의 일반성분은 백삼과 비교하여 크게 변화하지 않았지만 조지방은 감소하였다. 환원당과 총당은 백삼이 각각 $64.76{\pm}0.06$ mg/g, $187.12{\pm}2.02$ mg/g으로 측정되었으며 백삼압출성형물의 환원당은 백삼보다 감소하고 총당은 백삼보다 증가하였다. 총 페놀성 화합물은 압출성형공정에서 모두 증가하였는데 사출구 온도 $140^{\circ}C$에서 1회, 2회 그리고 사출구 온도 $120^{\circ}C$에서 2회 백삼압출성형물은 각각 $5.70{\pm}0.03$ mg/g, $8.55{\pm}0.03$ mg/g, $4.91{\pm}0.08$ mg/g으로 홍삼보다 많이 추출되었다. DPPH 라디칼 소거능도 사출구 온도 $140^{\circ}C$에서 1회, 2회 그리고 사출구 온도 $120^{\circ}C$에서 2회 압출성형물이 홍삼보다 높게 측정되었다. 환원력 또한 압출성형백삼이 백삼보다 높게 측정되었고, 사출구 온도 $140^{\circ}C$에서 1회, 2회 그리고 사출구 온도 $120^{\circ}C$, 2회 압출성형물은 각각 $0.58{\pm}0.002$, $0.59{\pm}0.003$, $0.80{\pm}0.004$로 홍삼보다 높게 측정되었다. 조사포닌은 백삼이 $38.84{\pm}0.35$ mg/g으로 나타났고, 사출구 온도 $140^{\circ}C$에서 2회 압출성형물이 $50.07{\pm}1.00$ mg/g으로 가장 높게 측정되었으며 다른 백삼압출성형물도 백삼보다 모두 증가하였다. UPLC로 측정한 진세노사이드의 조성은 압출성형과 반복 압출성형을 통하여 증가하였고, 백삼에서 추출되지 않았던 Rh1은 압출성형공정 후 추출되었다. 또한 $140^{\circ}C$에서 2회 압출성형물은 Rg3s, Rg3r이 추출되어 홍삼의 특유성분도 확인할 수 있었다.

• 한국식품영양과학회지
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• 제44권6호
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• pp.921-927
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• 2015

본 실험은 사출구 온도와 반복 압출성형이 백삼압출성형물의 물리적 특성에 미치는 영향을 분석하였다. 압출성형 조건은 수분 함량 20%와 스크루 회전속도 200 rpm을 고정시키고 독립변수로서 사출구 온도 $100^{\circ}C$, $120^{\circ}C$, $140^{\circ}C$로 1회, 2회 반복 압출성형 실험을 하였다. 비기계적 에너지 투입량은 사출구 온도 $140^{\circ}C$에서 1회 압출성형물이 295.0 kJ/kg으로 가장 낮게 측정되었다. 조직감 특성 중 탄성계수에서는 사출구 온도 $100^{\circ}C$에서 2회 압출성형물이 $7.53{\times}10^8N/m^2$로 가장 높게 측정되었으며, 사출구 온도 $120^{\circ}C$에서 1회 압출성형물이 $1.78{\times}10^8N/m^2$로 가장 낮은 결과값을 나타냈다. 또한 파괴력은 사출구 온도 $100^{\circ}C$에서 2회 압출성형물이 $7.49{\times}10^5N/m^2$로 가장 높게 측정되었으며, 사출구 온도 $140^{\circ}C$에서 2회 압출성형물이 $1.33{\times}10^5N/m^2$로 가장 낮게 측정되었다. 팽화 특성에서 $120^{\circ}C$ 1회 백삼압출성형물의 직경팽화율이 $2.283{\pm}0.011$로 가장 높게 측정되었으며, 비길이 체적밀도에서는 사출구 온도 $140^{\circ}C$에서 1회 압출성형물과 사출구 온도 $100^{\circ}C$에서 2회 백삼압출성형물이 각각 $123.790{\pm}2.802m/kg$, $0.260{\pm}0.020g/cm^3$로 가장 높게 측정되었다. 수분흡착지수(WAI)와 수분용해지수(WSI)는 백삼압출성형물 모두 백삼분말보다 증가하였다. WAI는 1회 압출성형을 하였을 때 증가하였으며, 2회 압출성형을 하였을 때는 감소하였다. 또한 사출구 온도가 증가할수록 WAI도 증가하였다. WSI의 경우 WAI와 반대로 사출구 온도가 증가하면 감소하는 경향이 나타났다. 위 연구를 통하여 백삼의 압출성형 조건을 달리하여 물리적 특성의 향상과 새로운 백삼제품 및 소재의 개발 가능성을 확인할 수 있었다.

• 한국소성가공학회:학술대회논문집
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• 한국소성가공학회 2001년도 제4회 압출 및 인발가공 심포지엄
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• pp.99-106
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• 2001

The design for cold extrusion dies is very important, because the die insert is subjected to very high radial and hoop stresses. The design of cold extrusion dies has many constrained conditions. In this paper, the used assumptions are such that the yield strength of each ring is selected according to the allowable tensile or compressive hoop stress in each ring and the maximum allowable inner pressure, when yielding occurs in one ring of the dies, is obtained by the proposed equation. In order to obtain design variables, such as diameter ratios and interferences, using the maximum inner pressure, the flexible tolerance method was used for shrink-fitted thick-walled cylinders. ANSYS APDL was used to perform the repeated analysis of deformation of the dies due to the variation of the design variables. The response surface methodology is utilized to analyze the relationship between the design variables and the maximum radial displacement of the die insert during extrusion. From the results, it is found that outer diameter of the die Insert has the largest effect on the minimization of maximum radial displacement at the inner surface of the dies.

• 한국정밀공학회지
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• 제22권1호
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• pp.167-174
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• 2005

The design for cold extrusion dies is very important, because the die insert is subjected to very high radial and hoop stresses. The design of cold extrusion dies has many constrained conditions. In this paper, the used assumptions are such that the yield strength of each ring is selected according to the allowable tensile or compressive hoop stress in each ring and the maximum allowable inner pressure, when yielding occurs in one ring of the dies, is obtained by the proposed equation. In order to obtain design variables, such as diameter ratios and interferences, using the maximum inner pressure, the flexible tolerance method was used for shrink-fitted thick-walled cylinders. ANSYS APDL was used to perform the repeated analysis of deformation of the dies due to the variation of the design variables. The response surface methodology is utilized to analyze the relationship between the design variables and the maximum radial displacement of the die insert during extrusion. From the results, it is found that outer diameter of the die insert has the largest effect on the minimization of maximum radial displacement at the inner surface of the dies.