• 제목/요약/키워드: Relative compaction

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분말 가압 성형 공정 변수 최적화에 관한 연구 (Study on the Optimization of Powder Compaction Process Parameters)

  • 김정래;금영탁
    • 한국소성가공학회:학술대회논문집
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    • 한국소성가공학회 2005년도 추계학술대회 논문집
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    • pp.476-479
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    • 2005
  • In this study, the process parameters in powder compaction are optimized for getting high relative densities. To find optimized parameters, the analytic models of powder compaction are firstly prepared by 2-dimensional rod arrays with random green densities using a quasi-random multi-particle array. Then, using finite element method, the changes in relative densities are analyzed by varying the size of the particle, the amplitude of cyclic compaction, and the coefficient of friction, which influence the relative density in cyclic compactions. After the analytic function of relative density associated process parameters are formulated by aid of the response surface method, the optimal conditions in powder compaction process are found by the grid search method.

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분열 프랙탈을 이용한 다짐 에너지의 영향 분석 - 입도, 다짐도 및 투수특성을 중심으로 - (Analysis of Effect of Compaction Energy on Characters of Grain Size Distribution, Compaction and Permeability Using Fragmentation Fractal)

  • 노수각;손영환;장병욱;김성필
    • 한국농공학회논문집
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    • 제48권6호
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    • pp.59-67
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    • 2006
  • Particles of soil are crushed when soil is compacted in the in-situ or lab. Among many factors that affect the crush of particles, compaction energy is a major factor. Because the crush of particles can change physical properties, the analysis of effect of compaction energy is very important. In this study, the fragmentation fractals were used for determining the change in grain size distribution and the effect due to change in grain size distribution was estimated. Compaction energy was increased by 50, 100, 200 and 300% based on the energy of standard A compaction test. As a result, grain size distribution curves were changed and fine particles increased as compaction energy were increased. Relative compaction were ranged between $93.38{\sim}107.67$. Fractal dimension of each site increased as compaction energy increased. Relative compaction is proportional to the fractal dimension but coefficients of permeability were in inverse proportional to the involution of fractal dimension.

실내실험을 통한 수중 매립토의 다짐효과 분석 (Experimental Study on Compaction Effect of Hydraulic Fill Soils)

  • 이행우;장병욱;장웅희;봉태호
    • 한국지반공학회:학술대회논문집
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    • 한국지반공학회 2006년도 춘계 학술발표회 논문집
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    • pp.301-310
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    • 2006
  • A series of laboratory tests was carried out for analyzing compaction characteristics of hydraulic fill soils(or hydraulically filled soils). Hydraulic fill soils were settled down by the weight of soil particle itself in water and consolidated by the extraction of water from the soil structures. Water content and dry unit weight were observed as the depth of sedimentation and consolidation soil. It was found from the result that the optimum water content $(W_{cpt})$ of the maximum unit weight$(\gamma_{dmax})$ is higher than that of laboratory compaction test(KS F 2312 A method). It was due to difference in compaction energy and compaction effect between two methods. And the maximum dry unit of hydraulic fill soil is smaller than that of laboratory compaction test. Especially in terms of compaction effect, the maximum relative compaction degrees$(R_{cmax})$ of Seamangum dredged sand, river sand and mixed sand, half and half of dredged and river sands, were 85%, 91% and 86%, respectively. It means that the compaction effect can be $85\sim91%$ of the maximum unit weight in laboratory compaction test.

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세라믹스 분말 가압 성형 공정 변수설계(2부: 최적화) (Design of ceramics powder compaction process parameters (Part Ⅱ : Optimization))

  • 김정래;금영탁
    • 한국결정성장학회지
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    • 제15권1호
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    • pp.27-33
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    • 2005
  • 본 연구에서는 세라믹 제품의 고밀도를 얻기 위해 분말 압축 성형 공정 변수의 최적화가 수행되었다. 이를 위해 먼저 임의의 초기 밀도를 갖는 분말 성형체를 모델링하였다. 그리고 반복 가압 성형 공정시 상대밀도에 영향을 주는 Al₂O₃ 입자의 크기, 반복 가압 진폭 크기, 그리고 마찰계수에 따른 상대밀도의 변화를 유한요소법으로 해석하였다. 유한요소 해석 결과를 반응 표면법으로 수식화한 후, 격자 탐색법으로 가압 성형 공정 변수의 최적 조건을 찾았다. 입자의 크기가 22.5 ㎛, 반복 가압 진폭이 75 MPa, 마찰계수가 0.1103인 경우에 상대 밀도 값이 0.9390으로 최대가 되었다.

냉간 압축 하에서 나노 세라믹 분말의 치밀화 거동 (Densification Behavior of Nanocrystalline Ceramic Powder under Cold Compaction)

  • 이성철;김기태
    • 대한기계학회논문집A
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    • 제30권10호
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    • pp.1242-1248
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    • 2006
  • Densification behavior of nanocrystalline titania powder was investigated under cold compaction. Experimental data were obtained under triaxial compression with various loading conditions. Lee and Kim proposed the Cap model by developing the parameters involved in the yield function of general Cap model and volumetric strain evolution under cold isostatic pressing. The parameters in the Drucker/Prager Cap model and the proposed model were obtained from experimental data under triaxial compression. Finite element results from the models were compared with experimental data for densification behavior of nanocystalline ceramic powder under cold isostatic pressing and die compaction. The proposed model agreed well with experimental data under cold compaction, but the Drucker/Prager Cap model underestimated at the low density range. Finite element results, also, show the relative density distribution of nanocystalline ceramic powder compacts is severe compared to conventional micron powder compacts with the same averaged relative density.

사질토 지반의 상대다짐도 및 토층에 따른 연직지중응력 분포 특성 (Characteristics of Vertical Stress Distribution in Sandy Soil According to the Relative Compaction and Composition of the Soil Layer)

  • 남효석;이상호
    • 한국농공학회논문집
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    • 제52권2호
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    • pp.43-50
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    • 2010
  • This study was carried out to evaluate the vertical stress properties in sandy soil according to changes of foundation condition in soil bin compacted three layers. The following conclusions and comparisons have been made based on careful analysis from theoretical and experimental methods. : When sandy soil subjected to circular uniform load, the vertical stress increments ($\Delta\sigma_z$) was increased as load increasing, the maximum values of $\Delta\sigma_z$ was achieved at the point loading axis, and $\Delta\sigma_z$ was not shown over at a distance of three times of loading plate width (B). The vertical stress increments were achieved largely at 80 % relative compaction (Rc) compared to 95 % relative compaction due to stress concentration in sandy soil. When sandy soil subjected to circular uniform load, the $\Delta\sigma_z$ differences between theoretical and experimental values as load increased were more increased and its maximum differences were achieved at stress axis. When gravel surface macadamized over sandy soil subjected to load, the $\Delta\sigma_z$ was concentrated to load axis as load increasing, so that macadamization will be decreased load transmission.

Field study of the process of densification of loose and liquefiable coastal soils using gravel impact compaction piers (GICPs)

  • Niroumand, Bahman;Niroumand, Hamed
    • Geomechanics and Engineering
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    • 제30권5호
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    • pp.479-487
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    • 2022
  • This study evaluates the performance of gravel impact compaction piers system (GICPs) in strengthening retrofitting a very loose silty sand layer with a very high liquefaction risk with a thickness of 3.5 meters in a multilayer coastal soil located in Bushehr, Iran. The liquefiable sandy soil layer was located on clay layers with moderate to very stiff relative consistency. Implementation of gravel impact compaction piers is a new generation of aggregate piers. After technical and economic evaluation of the site plan, out of 3 experimental distances of 1.8, 2 and 2.2 meters between compaction piers, the distance of 2.2 meters was selected as a winning option and the northern ring of the site was implemented with 1250 gravel impact compaction piers. Based on the results of the standard penetration test in the matrix soil around the piers showed that the amount of (N1)60 in compacted soils was in the range of 20-27 and on average 14 times the amount of (1-3) in the initial soil. Also, the relative density of the initial soil was increased from 25% to 63% after soil improvement. Also the safety factor of the improved soil is 1.5-1.7 times the minimum required according to the two risk levels in the design.

자기펄스 성형 및 방전 플라즈마 소결 공정으로 제조한 텅스텐 소결체의 특성 (Fabrication and Properties of Densified Tungsten by Magnetic Pulse Compaction and Spark Plasma Sintering)

  • 이의선;변종민;정영근;오승탁
    • 한국재료학회지
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    • 제30권6호
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    • pp.321-325
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    • 2020
  • The present study demonstrates the effect of magnetic pulse compaction and spark plasma sintering on the microstructure and mechanical property of a sintered W body. The relative density of green specimens prepared by magnetic pulse compaction increases with increase in applied pressure, but when the applied pressure is 3.4 GPa or more, some cracks in the specimen are observed. The pressureless-sintered W shows neck growth between W particles, but there are still many pores. The sintered body fabricated by spark plasma sintering exhibits a relative density of above 90 %, and the specimen sintered at 1,600 ℃ after magnetic pulse compaction shows the highest density, with a relative density of 93.6 %. Compared to the specimen for which the W powder is directly sintered, the specimen sintered after magnetic pulse compaction shows a smaller crystal grain size, which is explained by the reduced W particle size and microstructure homogenization during the magnetic pulse compaction process. Sintering at 1,600 ℃ led to the largest Vickers hardness value, but the value is slightly lower than that of the conventional W sintered body, which is attributed mainly to the increased grain size and low sintering density.

폐 스테인레스강 단섬유로 강화한 알루미늄 복합분말의 자기펄스압 성형 및 소결 특성 (Magnetic Pulsed Compaction and Sintering Characteristics of Al Composite Powders Reinforced with Waste Stainless Steel Short Fibers)

  • 현창용;원철현;박재순
    • 한국분말재료학회지
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    • 제14권6호
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    • pp.380-385
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    • 2007
  • Characteristics of Al-based composites with waste stainless steel short fiber, fabricated by magnetic pulsed compaction and sintering were investigated. The compacts prepared by magnetic pulsed compaction showed high relative density and homogeneous microstructure compared with that by conventional press compaction. The relative density of sintered composites at $430^{\circ}C$ for 1 h exhibited the same value with compacts and decreased with increase in STS short fiber content. The reaction between Al and STS phase was confirmed by the microstructural analysis using EDS. The sintered composites, prepared by magnetic pulsed compaction, showed increased hardness value with increasing STS fiber content. Maximum yield strength of 100 MPa and tensile strength of 232 MPa were registered in the AI-based composite with 30 vol% STS short fiber.