• Title/Summary/Keyword: near-net shape

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Finite Element Analysis of Compression Holding step Considering Solidification for Semi-Solid Forging (반용융 단조에서 응고 현상을 고려한 가압유지 단계의 유한요소해석)

  • Park, J.C.;Park, H.J.;Cho, H.Y.
    • Journal of the Korean Society for Precision Engineering
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    • v.14 no.10
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    • pp.102-108
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    • 1997
  • The technology of Semi-Solid Forging (SSF) has been actively developed to fabricate near-net- shape products using light and hardly formable materials. Generally, the SSF process is composed of slug heating, forming, compression holding and ejecting step. After forming step in SSF, the slug is compressed during a certain holding time in order to be completely filled in the die cavity and be accelerated in solidification rate. This paper presents the analysis of temperature, solid fraction and shrinkage at compression holding step for a cylindrical slug, then predicts the solidification time to obtain the final shaped part. Enthalpy-based finite element analysis is performed to solve the heat transfer problem considering phase change in solidification.

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Preform Design for the Sinter-forging Process of Arc-shaped Powdered Magnets (원호 형상을 가지는 분말자석 단조성형공정에서의 예비성형체 설계)

  • Kim, Seung-Ho;Lee, Choong-Ho;Huh, Hoon
    • Transactions of Materials Processing
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    • v.8 no.2
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    • pp.135-142
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    • 1999
  • Tube Process(TP) is one of the processes to produce permanent magnets. Advantage claimed for this process is that it can accmplish both densification and anisotropication in one step forming. This process is distinguished from other processes since it uses deformable tube for densification of powder magnets. TP has, however, difficulties in manufacturing permanent magnets from Nd-Fe-B green powder due to folding resulted from large height reduction and localized densification. Therefore, an adequate preform is necessary to reduce folding resulted from large height reduction and localized densification. Therefore, an adequate preform is necessary to reduce folding, lead magnets into almost desired final shape and get uniform densification. In this paper, preform design for TP is carried out without a deformable tube to investigate the behaviour of magnet sinter-forging. Preform design is accomplished to increase the effective magnet area with a near net shape and uniform densification.

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FEM Analysis for Optimization of Hot Forging Process of Piston Crown (피스톤크라운의 열간단조공정 최적화를 위한 유한요소해석)

  • Min, K.Y.;Lim, S.J.;Choi, H.J.;Choi, S.O.;Park, Y.B.
    • Transactions of Materials Processing
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    • v.18 no.6
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    • pp.444-447
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    • 2009
  • Piston crown to the hot forge a unified nature of the product has a shape with multi-level step forging process, so if you are not a mechanical professional, this process could lead to a significant loss to the material. Therefore, material technology in minor terms; continue to improve the collection rate that undamaged the product material. The piston crown and the manufacturing products such as marine diesel engines are being forged to reduce costs and to improve mechanical properties. Piston crown molding is a hot forging process that works in large volume forging products. Because of the size of the hard plastic material flow process for improving the design and actual field experience through advanced plastic technology, it is important to interpret the results. Also for many experimental plastic procedures, the accumulation of results is very important.

엔드밀 가공시 표면형성 예측 시뮬레이터 개발

  • 이영구;고성림
    • Proceedings of the Korean Society of Precision Engineering Conference
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    • pp.263-263
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    • 2004
  • 엔드밀 가공 공정은 항공산업과 자동차 부품 및 금형 가공 산업에서 널리 사용되고 있다. 정형가공 (near net shape) 기술의 발달에 따라 금형 가공시 허용공차 이내로 표면 오차를 유지하면서 가공시간을 감소시킬 필요성이 증대되었고 이에 따라, 절삭과정을 정확히 나타냄으로써 최종표면 형상을 정확히 예측할 수 있는 절삭모델을 통해 표면형성 예측 시뮬레이터의 개발 필요성이 있어왔다. 본 논문에서는 주어진 절삭조건에서 공구의 처짐과 런아웃을 고려한 절삭력 모델에 대하여 절삭력과 표면형성 데이터를 코딩된 포트란 프로그램에서 얻고 이것을 MFC와 연동시켜 예측 결과를 쉽게 확인할 수 있는 초보단계의 시뮬레이터 개발에 대하여 연구하였다.(중략)

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Yield and Compression Behavior of Semi-Solid Materials by Upper-Bound Method (상계법에 의한 반용융 재료의 항복과 압축거동)

  • 최재찬;박형진;박준홍
    • Journal of the Korean Society for Precision Engineering
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    • v.15 no.6
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    • pp.139-144
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    • 1998
  • In Semi-Solid Forging, it is necessary to control the forming variables accurately in order to make near-net-shape products. Generally, the defects of products may occur due to liquid segregation which can be caused by the degree of deformation and strain rate, and condition of friction in Semi-Solid Forging, where the segregation is to be predicted by flow analysis. This paper presents the feasibility of theoretical analysis model using the new yield function for compressible P/M materials which is proposed by Doraivelu et at. to the flow analysis of the semi-solid dendritic Sn-15%Pb alloys instead of adopting the yield criterion of Shima and Oyane which is used by Charreyron and Flemings. The simple compression process is taken into consideration as the model to confirm the usefulness of the adopted yield function. The distribution of the liquid fraction at various strains and strain rates in radial direction, and the influence of friction are estimated by upper-bound method.

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A Study on the characteristics of high speed precision bar cropping (환봉의 고속정밀절단 특성에 관한 연구)

  • 임성주;김소겸;나경환;정성종
    • Proceedings of the Korean Society for Technology of Plasticity Conference
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    • pp.209-217
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    • 1994
  • The present study is concerned with the characteristics of the high speed precision bar cropping. This process is a practical application of High Energy Rate Forming in which the impact energy source is given by internal combustion engine. To enhance the added value of product, the recent forging fields trend toward the near net shape processes through the cold and closed die forging. For the purpose of these processes the precedent process is to obtain the precision billet which has little weight deviation and defect. The accuracy of initial billet by bar cropping depends upon the process parameters and die design technology. Therefore, in order to investigate the effect of process parameters upon product quality, the cropping experiments are carried out according to the various parameters such as billet clearence, billet length, billet material, cropping speed and so on. From these results some criteria of the optimal die design for the product of good quality are suggested.

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Hot Forming Design of a CAM for Vessel Engine (선박엔진용 캠의 열간 성형공정설계)

  • Yeom, J.T.;Kim, J.H.;Kim, J.H.;Hong, J.K.;Lee, J.S.
    • Proceedings of the Korean Society for Technology of Plasticity Conference
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    • pp.417-420
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    • 2009
  • The hot forming process of a CAM for vessel engine was designed by finite element (FE) simulation and experimental analysis. An aim of process design was to achieve the near-net shaped CAM forgings by hot forging process. Based on the compression test results of the low alloy steel, deformation processing map was generated using the superposition approach between the dynamic materials model (DMM) and flow stability and/or instability criteria. From the processing map, the initial heating temperature was determined as $1200^{\circ}C$. FE analysis was simulated to predict the formation of rolling defects and deformed shape with different forging designs. Optimum process design suggested in this work was made by comparing with the CAM for vessel engine manufactured by actual forging process.

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FEM Analysis for Optimization of Hot Forging Process of Piston Crown (피스톤크라운의 열간단조공정 최적화를 위한 유한요소해석)

  • Min, K.Y.;Lim, S.J.;Choi, H.J.;Choi, S.O.;Park, Y.B.
    • Proceedings of the Korean Society for Technology of Plasticity Conference
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    • pp.98-101
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    • 2009
  • Piston crown to the hot forge a unified nature of the product has a shape with multi-level step forging process, so if you are not a mechanical process that can be a significant loss is material. Therefore, minor in terms of material technology; continue to improve the collection rate should be. The Piston crown and the manufacturing of products such as marine diesel engines, reducing costs and to improve mechanical properties of the method are being forged. Piston crown molding hot forging process the large volume forging products handling because of the size of the size of the hard plastic material flow process for improving the design and actual field experience through advanced plastic technology, and it is important to interpret the results and for many experimental plastic The accumulation of results is very important.

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Near Net Shape Processing of RE-Ba-Cu-O Bulk Superconductors

  • Murakami, M.;Fujishiro, M.;Miyazaki, T.;Nariki, S.;Sakai, N.;Hirabayashi, I.
    • Proceedings of the Korean Powder Metallurgy Institute Conference
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    • pp.1319-1320
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    • 2006
  • Several practical applications of melt-textured bulk superconductors require the complex-shaped products such as curved, ring-shaped, and drilled blocks rather than simple shaped pellets. However, melt-textured bulk superconductors are often damaged when they are cut, grinded, or drilled. With the aim of reducing such damages, we have investigated the preparation of the complex-shaped bulk superconductors by previously machining binder-added precursors and pre-sintered precursors. We could produce various complex-shaped bulk superconductors without cracking from these machined precursors

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Analysis of Laser Control Effects for Direct Metal Deposition Process

  • Choi Joo-Hyun;Chang Yoon-Sang
    • Journal of Mechanical Science and Technology
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    • v.20 no.10
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    • pp.1680-1690
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    • 2006
  • As a promising and novel manufacturing technology, laser aided direct metal deposition (DMD) process produces near-net-shape functional metal parts directly from 3-D CAD models by repeating laser cladding layer by layer. The key of the build-up mechanism is the effective control of powder delivery and laser power to be irradiated into the melt-pool. A feedback control system using two sets of optical height sensors is designed for monitoring the melt-pool and real-time control of deposition dimension. With the feedback height control system, the dimensions of part can be controlled within designed tolerance maintaining real time control of each layer thickness. Clad nugget shapes reveal that the feedback control can affect the nugget size and morphology of microstructure. The pore/void level can be controlled by utilizing pulsed-mode laser and proper design of deposition tool-path. With the present configuration of the control system, it is believed that more innovation of the DMD process is possible to the deposition of layers in 3-D slice.