• Title/Summary/Keyword: Compaction energy

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Compaction of Ultra-fine WC Powder by High-Speed Centrifugal Compaction Process

  • Suzuki, Hiroyuki Y.;Kadono, Yuichi;Kuroki, Hidenori
    • Proceedings of the Korean Powder Metallurgy Institute Conference
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    • 2006.09a
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    • pp.24-25
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    • 2006
  • High-Speed Centrifugal Compaction Process is one of slip-using compacting method originally developed for processing of oxide ceramics. In this study, we apply the HCP to ultra-fine (0.1 micron) WC powder. Organic liquid of heptane was chosen as dispersing media to avoid possible oxidation of WC. The mixing apparatus was a key to obtain dense compacts. Only the slips mixed by high energy planetary ball mill were packed up to 55% by the HCP, and sintered to almost full density at 1673 K without any sintering aids. This sintered compact marked Vickers hardness of Hv 2750 at maximum.

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Manufacturing and Evaluation of Properties of Nanocrystalline Ni bulk by Dynamic Compaction of Nano Ni powders using a Gas-gun System (나노 니켈 분말의 가스건 고속압축을 통한 나노결정립 니켈 벌크재의 제조 및 물성)

  • Kim, Wooyeol;Ahn, Dong-Hyun;Park, Lee Ju;Park, Jong-Il;Kim, Hyoung Seop
    • Journal of Powder Materials
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    • v.21 no.1
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    • pp.44-49
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    • 2014
  • In this study, nanocrystalline nickel powders were cold compacted by a dynamic compaction method using a single-stage gas gun system. A bending test was conducted to measure the bonding strengths of the compacted regions and microstructures of the specimen were analyzed using a scanning electron microscopy. The specimen was separated into two parts by a horizontal crack after compaction. Density test shows that the powder compaction occurred only in the upper part of the specimen. Brittle fracture was occurred during the bending test of the compact sample. Dispersion of shock energy due to spalling highly affected the bonding status of the nanocrystalline nickel powder.

Numerical modeling of dynamic compaction process in dry sands considering critical distance from adjacent structures

  • Pourjenabia, Majid;Hamidi, Amir
    • Structural Engineering and Mechanics
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    • v.56 no.1
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    • pp.49-56
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    • 2015
  • Dynamic compaction (DC) is a useful method for improvement of granular soils. The method is based on falling a tamper (weighting 5 to 40 ton) from the height of 15 to 30 meters on loose soil that results in stress distribution, vibration of soil particles and desirable compaction of the soil. Propagation of the waves during tamping affects adjacent structures and causes structural damage or loss of performance. Therefore, determination of the safe or critical distance from tamping point to prevent structural hazards is necessary. According to FHWA, the critical distance is defined as the limit of a particle velocity of 76 mm/s. In present study, the ABAQUS software was used for numerical modeling of DC process and determination of the safe distance based on particle velocity criterion. Different variables like alluvium depth, relative density, and impact energy were considered in finite element modeling. It was concluded that for alluvium depths less than 10 m, reflection of the body waves from lower boundaries back to the soil and resonance phenomenon increases the critical distance. However, the critical distance decreases for alluvium depths more than 10 m. Moreover, it was observed that relative density of the alluvium does not significantly influence the critical distance value.

A Study on the Safety Prediction of Embankment Using Simple Parameter Estimation Method (물성치 추정을 통한 성토안정성 예측)

  • Park, Jong-Sung;Hong, Chang-Soo;Hwang, Dae-Jin;Seok, Jeong-Woo
    • Proceedings of the Korean Geotechical Society Conference
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    • 2009.03a
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    • pp.888-895
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    • 2009
  • Compaction is a process of increasing soil density using physical energy. It is intended to improve the strength and stiffness of soil. In embankment, degree of compaction affects the construction time, money, also method of soil improvement. In large scale embankment project, difficulties of embankment should change due to uncertainty of settlement. So it is very important to predict the final settlement and factor of safety induced by embankment. In many construction site, there are primarily design of high embankment using in-situ soil. Therefore numerical analyses are necessary for valid evaluation of the settlement prediction. But due to the construction cost and schedule, there were lacking in properties of soil and also limited number of in-situ test were performed. So we proposed the method that can easily estimate the proper soil parameters and suggest the proper method of numerical analysis. From this, two-dimensional finite-difference numerical analysis was conducted to investigate the settlement and factor of safety induced by embankment with various case of compaction rate and embankment height.

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Analysis of the Demage of Structures by Dynamic Compaction (동다짐에 의한 인접구조물 피해 분석)

  • Song, Jeong-Rak;Han, Wan-Gyun;Sin, Seung-Cheol
    • Proceedings of the Korean Geotechical Society Conference
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    • 1993.06a
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    • pp.55-72
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    • 1993
  • Dynamic compaction may cause some demages to structures becasue it uses the impact energy of heavy weight with high drop height. This study measured and analyzed the vibrations at the (bnamic compaction site which was composed of man-made land fill. From the vibration analysis, it was found that the particle velocity and attenuation was greatest in longitudinal direction and smallest in transversal direction, the dominant frequency ranged from 7 Hz to 9 Hz and the structural damage could be prevented by reducing the drop height at the vicinity of the vibration sentialive structures. Also, the damage to the office equipment could be prevented by doing the dynamic compaction work curing closed-office hours.

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High-pressure Compaction of Sawdust of Hyunsasi-poplar (Populus alba ${\times}$ P. glandulosa) for Densified Fuel (고밀화에 의한 현사시 톱밥의 고형연료화)

  • 한규성;여진기
    • Journal of Korea Foresty Energy
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    • v.22 no.2
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    • pp.54-59
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    • 2003
  • Recently, densified pellet fuel from wood biomass is widely used at North America and Europe as a regenerable and clean carbon neutral bioenergy. High-pressure compaction of sawdust of Hyunsasi-poplar (Populus alba ${\times}$ P. glandulosa) to form a densified fuel was studied. Calorific and elemental analysis were carried out to assess Hyunsasi-poplar clones as fuels. Hot-press process was adopted for compaction of sawdust and compaction was performed under temperature from 100 to 180$^{\circ}C$, at pressure of 250 to 1000 kgf/$\textrm{cm}^2$, and for 2.5 to 10 minutes. Densified fuels were evaluated by its oven-dry density and fines after 5-minute shaking test. The target density and fines of densified fuels were over 1.2 g/$\textrm{cm}^2$ and below 0.5%, respectively. When the press-temperature is over 160$^{\circ}C$, densified fuels with density eve. 1.2 g/$\textrm{cm}^2$ and with fines below 0.5% can be produced. And the pressure over 750 kgf/$\textrm{cm}^2$ was effective for this production. It was found that the optimum press condition for preparation of densified fuel was 180$^{\circ}C$ -1000 kgf/$\textrm{cm}^2$ minutes.

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Rubber Isostatic Pressing and Cold Isostatic Pressing of Metal Powder (금속 분말의 고무 등가압 성형과 냉간 정수압 성형)

  • Kim, Jong-Kwang;Yang, Hoon-Chul;Kim, Ki-Tae
    • Transactions of the Korean Society of Mechanical Engineers A
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    • v.27 no.7
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    • pp.1076-1086
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    • 2003
  • The effect of a rubber mould on densification behavior of aluminum alloy powder was investigated under cold isostatic compaction. A thickness of rubber mould and friction effect between die wall and rubber mould were also studied. The hyperelastic constitutive equation based on the Ogden strain energy potential was employed to analyze deformation of rubber. The elastoplastic constitutive equation of Shima and Oyane and that of Lee on densification were implemented into a finite element program (ABAQUS) to simulate densification of metal powder for cold isostatic pressing and rubber isostatic pressing. Finite element results were compared with experimental data for densification and deformation of aluminum alloy powder under isostatic compaction.

Strength Characteristics of Soil Concrete Using Jeju Volcaniclastic and Construction Techniques (제주도 석산 부산물인 화산토를 사용한 흙포장의 강도 및 시공 특성)

  • Hong, Chong-Hyun
    • Journal of Environmental Science International
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    • v.20 no.1
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    • pp.71-79
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    • 2011
  • In this study, a series of soil concrete mixtures were tested for the compressive strength according to ratio of aggregate to binder, compaction energy, maximum aggregate size, ratio of silica fume to cement, and ratio of water to binder. The optimum mixing ratio of soil concrete mixtures composed of volcaniclastic, cement, silica fume, concrete polymer and water were analysed. The test results for optimum proportion were as follows ; (1)ratio of aggregate to binder was 4 : 1, (2)compaction energy level was level 2, (3)maximum aggregate size was 13 mm, (4)ratio of silica fume to cement was 10%, (5)ratio of water to binder was 25%. Also, dry type construction techniques were applied using the optimum soil concrete mixture. From the results of this study, the compressive strength of soil concrete and construction techniques were suitable for making eco-friendly soil pavement.

Design and performance analysis of the linear phase para-unitary M bandfilter bank with application to image coding (영상 부호화를 위한 LPPU M 대역 필터군의 설계와 성능 분석)

  • 이창우;김종원;이상욱
    • The Journal of Korean Institute of Communications and Information Sciences
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    • v.21 no.5
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    • pp.1141-1154
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    • 1996
  • The para-unitary (PU) M band filter bank, which can beused for M band decomposition, has many useful properties. In this ppaer, attempts have been made to design and and analyze the linear phase para-unitary (LPPU) M band filter bank, which is appropriate to the image coding application. First, we derive a unified coding gain in terms of the correlation in the band, as well as the energy compaction. And M band filter bank has been designed, maximizing the new coding gain. Then, we analyze the image coding performance of the LPPU M band filter bank, such as the energy compaction, the correlation in the band and the entropy. From the analysis, it is shown that the coding gain for LPPU M band filter bank improves, and the coding gain for the LPPU 4 band filter bank approaches very closely to that for LPPU 8 band filter bank, as the length of the filter increases. This fact is also verified by the coding results on the real images.

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Characterization of Compacted and Pressureless Sintered Parts for Molybdenum Oxide Powder according to Hydrogen Reduction Temperature (수소 환원 온도에 따른 몰리브덴 산화물의 성형 및 상압소결특성 평가)

  • Jong Hoon Lee;Kun-Jae Lee
    • Journal of Powder Materials
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    • v.31 no.4
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    • pp.336-341
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    • 2024
  • Molybdenum, valued for its high melting point and exceptional physical and chemical properties, is studied in diverse fields such as electronics, petrochemicals, and aviation. Among molybdenum oxides, molybdenum dioxide stands out for its higher electrical conductivity than other transition metal oxides due to its structural characteristics, exhibiting metallic properties. It is applied as pellets to gas sensors, semiconductors, and secondary batteries for its properties. Thus, research on molybdenum dioxide compaction and pressureless sintering is necessary, yet research on pressureless sintering is currently insufficient. This study synthesized MoO3 powder via solution combustion synthesis and reduced it using the 3% hydrogen/argon gas mixture to investigate the effect of reduction temperature on the powder. Additionally, the reduced powder was compacted and subjected to pressureless sintering with temperature as a variable. The density and the microstructure of brown parts were analyzed and discussed.