• 제목/요약/키워드: Powder plasticity

검색결과 146건 처리시간 0.019초

금속분발소결체의 경도와 상대밀도 관계 (Relationship between Hardness and Relative Ddensity in Sintered Metal Powder Compacts)

  • 박종진
    • 한국소성가공학회:학술대회논문집
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    • 한국소성가공학회 1998년도 춘계학술대회논문집
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    • pp.168-174
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    • 1998
  • In the present study, a method for measuring the relative density by the hardness measurement was proposed for sintered metal powder compacts. It is based on the indentation force equation, by which the relative density is related with the hardness, that was obtained by the finite element analysis of rigid-ball indentation on sintered metal powder compacts. For verifying the method, it was applied to prediction of density distributions in sintered and sintered-and-forged Fe-0.5%C-2%Cu powder compacts.

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냉간압축하에서 혼합금속분말의 치밀화 모델 (A Densification Model for Mixed Metal Powder under Cold Coompaction)

  • 조진호
    • 한국소성가공학회:학술대회논문집
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    • 한국소성가공학회 2000년도 춘계학술대회논문집
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    • pp.112-118
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    • 2000
  • Densification behavior of mixed copper and tool steel powder under cold compaction was investigated. By mixing the yield functions proposed by Fleck et al. and by Gurson for pure powder in terms of volume fractions and contact numbers of Cu powder new mixed yield functions were employed for densification of powder composites under cold compaction. The constitutive equations were implemented into a finite element program (ABAQUS) to compare with experimental data for densificatiojn of mixed powder under cold isostatic pressing and cold die compaction. finite element calculations by using the yield functions mixed by contact numbers of Cu powder agreed better with experimental data than those by volume fractions of Cu powder.

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나노 구리 분말의 냉간정수압 공정에 대한 치밀화 거동 해석 (Analysis of Densification Behavior of Nano Cu Powders during Cold Isostatic Pressing)

  • 윤승채;김형섭;이창규
    • 한국분말재료학회지
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    • 제11권4호
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    • pp.341-347
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    • 2004
  • In the study, a hybrid constitutive model for densification of metallic powders was applied to cold isostatic pressing. The model is based on a pressure-dependent plasticity model for porous materials combined with a dislocation density-based viscoplastic constitutive model considering microstructural features such as grain size and inter-particle spacing. Comparison of experiment and calculated results of microscale and nanoscale Cu powders was made. This theoretical approach is useful for powder densification analysis of various powder sizes, deformation routes and powder processing methods.

설계민감도를 이용한 분말단조 공정에서의 최적 예비성형체 설계 (Optimal Preform Design in Powder Forging by the Design Sensitivity)

  • 정석환;황상무
    • 한국소성가공학회:학술대회논문집
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    • 한국소성가공학회 1998년도 춘계학술대회논문집
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    • pp.113-116
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    • 1998
  • A derivative based approach to process optimal design in powder forging is presented. The process model, the formulation for process optimal design, and the schemes for the evaluation of the design sensitivity, and an iterative procedure for the optimization are described in detail. The validity of the schemes for the evaluation of the design sensitivity is examined by performing numerical tests. The capability of the proposed approach to deal with diverse process parameters and objective functions is demonstrated through applications to some selected process design problems.

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금속 분말의 항복조건에 관한 연구 (A Study on the Yield Criterion of Metal Powders)

  • 박성준;한흥남;오규환;이동녕
    • 한국소성가공학회:학술대회논문집
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    • 한국소성가공학회 1996년도 추계학술대회논문집
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    • pp.131-138
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    • 1996
  • A new yield criterion for metal powder compaction based on continuum mechanics has been proposed. It includes three parameters to characterize the geometrical hardening of powder compact and strain hardening of incompressible metal matrix. The elasto-plastic finite element method to describe compaction of metal powders has been formulated using the new yield criterion. The values of parameters in the yield criterion can be determined using cold isostatic pressing(CIP). The finite element method can simulate compaction behavior of various copper powders.

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알루미나 분말 성형체의 고온 치밀화 성형 공정 해석을 위한 모델 (Model for High Temperature Densification)

  • 권영삼;김기태
    • 한국소성가공학회:학술대회논문집
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    • 한국소성가공학회 1994년도 춘계학술대회 논문집
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    • pp.159-166
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    • 1994
  • A constitutive model was proposed to analyze creep densification and grain growth of alumina powder compacts during high temperature processing. Theoretical results from the constitutive model were compared with various experimental data of alumina powder compacts in the literature including pressureless sintering, sinter forging and hot pressing. The proposed constitutive equations were implemented into finite element analysis program (ABAQUS) to simulate densification for more complicated geometry and loading conditions. High temperature forming processing of alumina compact with complicated shape was simulated. Processing of Alumina Powder Compacts

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커넥팅 로드의 분말단조를 위한 소결 및 단조특성의 실험적 연구 (Experimental Research of Powder Forging for Sub-Scale Connecting rods)

  • 이동원;이정환;정형식;이영선;박종진
    • 한국소성가공학회:학술대회논문집
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    • 한국소성가공학회 1994년도 춘계학술대회 논문집
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    • pp.149-158
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    • 1994
  • Powder forged Connecting Rods have become attractive for use in automotive engines. The powder forging process offers beneficial material utilization as well as the minimization of finishing operations over that of conventionally forged rods. In the present work, the sintering behavior of Fe-2Cu-0.6C, optimum preform design and forgeability of various forging variables were investigated. Our data were generated using a newly proposed sub-scale con-rod developed specifically to simulate the powder forging process. We obtain optimum condition of sintering and powder forging process.

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SLS 공정을 이용한 Fe-Cr 분말의 적층에 관한 연구 (Characterization for selective laser sintered Fe-Cr powder)

  • 손영명;장정환;주병돈;성민영;문영훈
    • 한국소성가공학회:학술대회논문집
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    • 한국소성가공학회 2009년도 춘계학술대회 논문집
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    • pp.282-285
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    • 2009
  • Selective laser sintering (SLS) is a fast growing process of rapid production fur metallic based parts. To restore damaged mold surface using SLS, single layer experiments of $20{\mu}m$ Fe-Cr powder was performed under various heat input. Process window of $20{\mu}m$ Fe-Cr powder provided feasible process parameters for the smooth regular surface. To estimate coherence between melted powder and basematal, tendency of hardness distribution has been observed. Hardness of melted zone and remelted zone was diversified from 5GPa to 6.5GPa. It is over 2 times compared of hardness of basemetal. Average surface roughness of each direction on surface of melted powder was measured. Experimental results show that the mold restoring process using SLS can be successfully applied in the mold repair industry.

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분말야금법을 이용한 유압펌프용 실린더 블록의 제조 가능성 연구 (Feasibility Study on Making a Cylinder Block of a Hydraulic Pump by Powder Metallurgy)

  • 지창운;정석환;권영삼;강민석;전만수
    • 한국소성가공학회:학술대회논문집
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    • 한국소성가공학회 2005년도 춘계학술대회 논문집
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    • pp.258-261
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    • 2005
  • In this paper, experimental and numerical attempts are made fur application of powder metallurgy forming technology to making the cylinder block of a hydraulic pump of which height reaches nearly 70 mm and is ten times larger than the wall thickness. Leak tests with several compositions are carried out in order to find allowable powder composition to prevent leak under high pressure in service and CAE techniques are applied to finding proper process conditions. Through the research, the possibility of the powder formed cylinder block that is very competitive from the point of both cost and mass production has been shown, even though its thickness exceeds the recommended limit considering heterogeneous density distribution caused by the friction between a powder compact and dies.

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분말 압출 공정에서 온도 유지시간 제어를 통한 미세기어의 내피로성 향상 연구 (Improvement of fatigue resistance of the miniature gear by controlling holding time of temperature in the hot powder extrusion process)

  • 김진우;이경훈;황대원;김병민
    • 한국소성가공학회:학술대회논문집
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    • 한국소성가공학회 2009년도 추계학술대회 논문집
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    • pp.449-452
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    • 2009
  • This paper was designed to fabricate the miniature spur gear with pitch circle of 1.8 by hot extrusion process of mechanically alloyed Zn-22wt%Al powder at various temperature. The mechanical alloying was preformed for ball milled times of 8h, 16h and 32h by the planetary ball milling. Mechanically alloyed powders were compacted cylindrical performs. Extrusions of the miniature spur gear using the alloyed powder were carried out at different extrusion temperatures. The extruded spur gear was sintered for 2h at $350^{\circ}C$ in argon atmosphere. The friction between the die and the powdered billet and the internally different density due to complex product shape cause the internal crack. To overcome the mentioned problems, high dimensional accuracy at cross section of the spur gear and uniform Vickers hardness could be obtained by graphite lubricant and controlling holding time.

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