• Title/Summary/Keyword: near-net shape

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Mechanical Strength Values of Reaction-Bonded-Silicon-Carbide Tubes with Different Sample Size (튜브형상 반응소결 탄화규소 부품의 시편크기에 따른 강도평가 유용성 고찰)

  • Kim, Seongwon;Lee, Soyul;Oh, Yoon-Suk;Lee, Sung-Min;Han, Yoonsoo;Shin, Hyun-Ick;Kim, Youngseok
    • Journal of Korean Powder Metallurgy Institute
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    • v.24 no.6
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    • pp.450-456
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    • 2017
  • Reaction-bonded silicon carbide (RBSC) is a SiC-based composite ceramic fabricated by the infiltration of molten silicon into a skeleton of SiC particles and carbon, in order to manufacture a ceramic body with full density. RBSC has been widely used and studied for many years in the SiC field, because of its relatively low processing temperature for fabrication, easy use in forming components with a near-net shape, and high density, compared with other sintering methods for SiC. A radiant tube is one of the most commonly employed ceramics components when using RBSC materials in industrial fields. In this study, the mechanical strengths of commercial RBSC tubes with different sizes are evaluated using 3-point flexural and C-ring tests. The size scaling law is applied to the obtained mechanical strength values for specimens with different sizes. The discrepancy between the flexural and C-ring strengths is also discussed.

Heat and Wear Resistance Characterization of SiCp Reinforced Al Matrix Composites (SiCp입자강화 Al 복합재료의 내열 및 마모특성)

  • Kim, Sug-Won;Kim, Wan-Ki;Woo, Kee-Do;Ahn, Haeng-Keun
    • Journal of Korea Foundry Society
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    • v.20 no.6
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    • pp.377-385
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    • 2000
  • Al matrix composites as the most promising MMCs can be expected to be excellent engineering materials in the nearest future. So as to improve material properties of composite, many manufacturing processes have been developed. Among them, squeeze casting process which offers fine microstructure and near-net-shape is one of the most successful MMCs manufacturing processes. But, in case of with subsieve size particles (under 44 ${\mu}m$), it is very difficult to homogeneously distribute particles in matrix of Al matrix composite by various casting processes, including squeeze casting used so far. Duplex process which was developed in previous study was used to distribute the particle of subsieve size more homogeneously in matrix of Al matrix composite. Microstructures, wear and heat resistance characterization of Al-Si-Cu-Mg-(Ni)/SiCp manufactured by duplex process were examined to clarify the effect of manufacturing conditions, particle size of reinforcement and alloying elements. Al matrix composites reinforced with SiCp(10 ${\mu}m$) have the lowest wear amount among composites reinforced with 3 ${\mu}m$, 5 ${\mu}m$ and 10 ${\mu}m$ SiCp. The wear amount of Al matrix composites with 10 wt.% SiCp(3, 5, 10 ${\mu}m$) was decreased according to the increase of the sliding speed because abrasive wear takes place at high sliding speed of 4m/s and worn debris with block type occurs at low sliding speed of 1m/s. As for heat resistance, it is made clear that remarkable heat resistance property can be obtained by addition of Ni element in Al matrix composites.

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Development of Combined Sheet Metal Forming and Plate Forging of a Metal Seal Part of Hub Bearing for an Automobile (자동차 허브 베어링용 씰 금속부품의 판재성형 및 판단조의 복합성형 공정 개발)

  • Park, K.G.;Moon, H.K.;Oh, S.K.;Joun, M.S.
    • Transactions of Materials Processing
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    • v.29 no.4
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    • pp.194-202
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    • 2020
  • In this paper, experimental and numerical study on a combined sheet metal forming and plate forging of a seal part of a passenger car's hub bearing is conducted to develop the new process of which target is to remove machining process by plate forging and to achieve near-net shape manufacturing. The previous process of a sheet metal forming inevitably needed a machining process for making stepped sheet after conventional sheet metal forming in a progressive way. The stepped sheet is intended to be formed by plate forging in this study. Through the systematic way of developing the combined forming process using solid elements based-elastoplastic finite element method (FEM), several conceptual designs are made and an optimized process design in terms of geometric dimensioning and tolerance of straightness of the thin part is found, which is exposed to bending in metal forming of axisymmetric part. The predicted straightness measured by the slope angle of the tilted thin region is compared with the experimental straightness, showing that they are in a good agreement with each other. Through this study, a systematic approach to optimal process design, based on elastoplastic FEM with solid elements, is established, which will contribute to innovating the conventional small-scaled sheet metal forming processes which can be dealt with by solid elements.

Fabrication of SiCf/SiC Composite by Chemical Vapor Infiltration (화학기상침착법에 의한 SiCf/SiC 복합체의 제조)

  • Park, Ji Yeon;Kim, Daejong;Kim, Weon-Ju
    • Composites Research
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    • v.30 no.2
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    • pp.108-115
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    • 2017
  • Among several fabrication processes of $SiC_f/SiC$ composites, the chemical vapor infiltration (CVI) process has attractive advantages in manufacturing complex net-or near-net-shape components at relatively low temperatures, easily controlling the microstructure of the matrix and obtaining the highest SiC purity level. However, it has disadvantages in that the ratio of residual pores in matrix is higher than other processes and processing time is relatively long. To reduce the residual porosity, the whisker-growing-assisted CVI process, which is composed of whisker growth and matrix filling steps has been developed. The whiskers grown before matrix filling may serve to divide the large natural pores between the fibers or bundles so that the matrix can be effectively filled into the finely divided pores. In this paper, the fundamentals of the CVI process for preparation of $SiC_f/SiC$ composites and some experimental results prepared by CVI and whisker-growing-assisted CVI processes are briefly introduced.