• Title/Summary/Keyword: 기공압착

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An Experimental Study on Void Closure Behavior with respect to Reductions in Height (압하율에 따른 기공압착 거동에 관한 실험적 연구)

  • Choi, I.J.;Choi, H.J.;Park, H.J.;Choi, S.;Jung, T.W.;Park, D.K.;Choi, S.K.;Lim, S.J.
    • Proceedings of the Korean Society for Technology of Plasticity Conference
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    • 2009.05a
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    • pp.114-117
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    • 2009
  • In this work, closing behavior of the voids generated in a casting process was investigated for various parameters such as reductions in height void size and billet rotation during hot open die forging process. The reduction in height and path schedule including the number of paths and billet rotation were chosen as key process variables to express the change of geometrical void shape and void closing behavior. On the other hand, values of die overlapping and die width ratio were set to be constant. Extend of void closure was observed and evaluated using tensile test and microscope. Based on the experimental result, it is ensured that void closure do not occur at 15% and 30% reduction in height as well as one or two rotations of a billet. The useful datum obtained from this study could be utilized to establish an optimum path schedule in the open die forging process.

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Properties of High Power Flip Chip LED Package with Bonding Materials (접합 소재에 따른 고출력 플립칩 LED 패키지 특성 연구)

  • Lee, Tae-Young;Kim, Mi-Song;Ko, Eun-Soo;Choi, Jong-Hyun;Jang, Myoung-Gi;Kim, Mok-Soon;Yoo, Sehoon
    • Journal of the Microelectronics and Packaging Society
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    • v.21 no.1
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    • pp.1-6
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    • 2014
  • Flip chip bonded LED packages possess lower thermal resistance than wire bonded LED packages because of short thermal path. In this study, thermal and bonding properties of flip chip bonded high brightness LED were evaluated for Au-Sn thermo-compression bonded LEDs and Sn-Ag-Cu reflow bonded LEDs. For the Au-Sn thermo-compression bonding, bonding pressure and bonding temperature were 50 N and 300oC, respectively. For the SAC solder reflow bonding, peak temperature was $255^{\circ}C$ for 30 sec. The shear strength of the Au-Sn thermo-compression joint was $3508.5gf/mm^2$ and that of the SAC reflow joint was 5798.5 gf/mm. After the shear test, the fracture occurred at the isolation layer in the LED chip for both Au-Sn and SAC joints. Thermal resistance of Au-Sn sample was lower than that of SAC bonded sample due to the void formation in the SAC solder.

A Study on the Parameters Contributing to the Void Crushing in the Cogging Process of Large Forged Products (대형 단조품 코깅 공정의 기공 압착 인자에 대한 연구)

  • Song, M.C.;Kwon, I.K.;Park, Y.G.
    • Proceedings of the Korean Society for Technology of Plasticity Conference
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    • 2007.05a
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    • pp.127-130
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    • 2007
  • Effect of the forging process parameters on the void crushing is the cogging process has been studied in order to find the most effective factor. The Process parameters used for this study are die width ratio, reduction ratio and pre-cooling time before cogging process. Void crushing analysis about the selected process parameters was carried out using FE analysis. The results of FE analysis were evaluated by Taguchi method. It was found that the efficiency of void crushing increases with an increase in the values of all selected process parameters and the principal factor controlling the void crushing was identified as the reduction ratio.

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A Study on the Parameters Determining the Void Crushing Ratio in the Cogging Process of Large Forged Products (대형 단조품 코깅 공정의 기공 압착 인자에 대한 연구)

  • Song, M.C.;Kwon, I.K.;Park, Y.G.
    • Transactions of Materials Processing
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    • v.16 no.7
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    • pp.502-508
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    • 2007
  • Effect of the process parameters of the cogging process on the void crushing has been studied in order to identify the most effective factor. The process parameters considered in this study are die width ratio, reduction ratio and pre-cooling time before cogging process. Void crushing analysis with the selected process parameters was carried out using FE analysis. The results of FE analysis were evaluated by Taguchi method. It was found that the efficiency of void crushing increases with an increase in the values of all selected process parameters and the principal factor controlling the void crushing was identified as the reduction ratio.

Prediction of Void Crushing Behavior in Upset & Bloom Forging of Large Ingot (대형인곳의 업셋-블룸단조에서의 기공 압착 거동 예측)

  • Kwon I.K.;Kim K.H.;Youn Y.C.;Song M.C.
    • Proceedings of the Korean Society for Technology of Plasticity Conference
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    • 2004.10a
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    • pp.325-328
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    • 2004
  • This paper deals with void crushing behavior by ingot forging process which consists of sequential operations of upset forging and bloom forging. The predicted results of void crushing behavior by the simplified global-local method using F.E. analysis showed that the inherent void at the top region of the ingots remains incompletely crushed even after several forging operations. From the results of the hot upset forging test using the billets with drilled voids, it was found that the bonding efficiency of the void after forging process increases with an increase in deformation, and a decrease of initial diameter of voids.

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대형 강괴의 코깅공정 해석 및 개선에 관한 연구

  • Jo, Jong-Rae;Park, Chi-Yong;Yang, Dong-Yeol;Kim, Dong-Jin;Park, Il-Su
    • Transactions of Materials Processing
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    • v.1 no.2
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    • pp.32-39
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    • 1992
  • 대형 강괴의 자유단조 공정 중에서 코깅(cogging)작업은 강괴 단조의 초기에 단면을 줄이면서 길이 방향으로 늘리는 작업이다. 코깅 작업의 역활은 주조시 발생하는 강괴 내부의 기공을 압착시켜 제거하며 주조 조직을 파괴하여 물성치를 균질화하고 향상시키는 것이다. 그러나 대형강괴의 작업에는 제약조건이 많이 있고 작업공정에서 공정변수도 여러가지 이다. 따라서 본 논문에서는 변형해석과 온도해석을 할 수 있는 3차원 열-점소성 유한요소해석 프로그램을 개발하고, 코깅공정에서 다이의 형상과 다이폭, 다이 겹침과 엇갈리기, 강괴의 온도 구배, 압하 깊이와 패스 설계등의 여러 공정 변수의 영향을 해석하여, 단조 효과를 최대화하는 최적의 단조 공정을 예측하여 공정개선에 적용하는 것이 목적이다.

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Comparative Study on Pore Closing in Open Die Forging by Conventional Forging Press and Radial Forging Machine (일반자유단조 프레스와 방사형 단조 프레스의 기공 압착에 관한 비교 연구)

  • Kim, S.H.;Lee, M.C.;Jang, S.M.;Eom, J.G.;Joun, M.S.
    • Transactions of Materials Processing
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    • v.19 no.7
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    • pp.399-404
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    • 2010
  • We propose an analysis model for simulating the detailed procedure of pore closing in open die forging of shafts. In the analysis model, an artificial symmetric plane is used, on which initial pores are located to be traced. The analysis model is employed to carry out three-dimensional simulation of pore closing in shaft free forging by both conventional free forging press and radial forging machine. With this result, two typical types of free forging equipment for manufacture of shafts are compared in detail. It has shown that the radial forging machine is much superior to the conventional open die forging press especially in pore closing under high hydrostatic pressure with sound strain.

The Study of void Closing Behavior in Upset Forging of Large Ingot (대형 잉곳의 업셋 단조에서의 기공 압착 거동에 관한 연구)

  • Lee K. J.;Bae W. B.;Cho J. R.;Kim D. K.;Kim J. T.
    • Proceedings of the Korean Society for Technology of Plasticity Conference
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    • 2005.10a
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    • pp.406-409
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    • 2005
  • In the forging operation of large ingot two break-down process are upsetting and cogging. The first purpose of upsetting is to ensure sufficient forging ratio for subsequent cogging operations and consolidate the voids along the centerline. The second purpose is related to improve the physical properties for a final product. Voids which are generated during the casting process can be one of the decisive defects of materials. So it is necessary to know the standard of Judgment for void-closure in upsetting operation. In practical conditions, FEM analysis(DEFORM 2D 8.1) was carried out to decide how much effective strain has influence on void-closure. It is finally suggested that the function consists of the effective strain of analysis data and the area rate of void.

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Finite Element Simulation of a Pore Closing Process during Upsetting in Open Die Forging (자유단조에서 업세팅 공정 중 기공 압착 과정의 유한요소 시뮬레이션)

  • Lee, M.C.;Cho, J.H.;Choi, I.S.;Jang, S.M.;Joun, M.S.
    • Proceedings of the Korean Society for Technology of Plasticity Conference
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    • 2008.05a
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    • pp.79-83
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    • 2008
  • We carry out three-dimensional simulation of pore closing processes during upsetting in open die forging. Several pores on a plane section of a cylindrical material are traced at the same time and the results of hydrostatic pressure and effective strain are discussed to reveal the parameters affecting pore closing phenomena. Five different sizes of pores are also investigated by simulation to reveal the pore size effect in pore closing during upsetting. AFDEX 3D is employed for this study.

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Development of High-strength Polyethylene Terephthalate (PET) Sheet Through Low Melting Point Binder Compounding and Compression Process (저 융점 바인더 복합화 및 압착공정을 통한 고강도 폴리에틸렌 테레프탈레이트(PET) 시트 개발)

  • Moon, Jai Joung;Park, Ok-Kyung;Kim, Nam Hoon
    • Composites Research
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    • v.33 no.5
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    • pp.282-287
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    • 2020
  • In the present study, a high-strength polyethylene terephthalate (PET) sheet was fabricated through a densification process of low melting PET fiber (LMF) combined PET sheet. During the thermal heat treatment process of the combined LMF, individual PET fiber was connected, which in turn leads to the improvement of the interfacial bonding force between the fibers. Also, the densification of the PET sheet leads to reduce macrospore density and in return could enhance the binding force between the overlapped PET networks. Consequently, the asprepared LMF-PET sheet showed about 410% improved tensile strength and the same elongation compared to before compression. Besides, the enhanced bonding force can prevent the shrinkage of the PET fiber network and exhibited excellent dimensional stability.