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  • Title/Summary/Keyword: Microstructure development

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Impact damage model of projectile penetration into concrete target (발사체 관통 콘크리트 충격손상 모델)

  • Park, Tae-Hyo;Noh, Myung-Hyun
    • Proceedings of the Korea Concrete Institute Conference
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    • 2006.05b
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    • pp.633-636
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    • 2006
  • Impact damage modeling of concrete under high strain rate loading conditions is investigated. A phenomenological penetration model that can account for complicated impact and penetration process such as the rate and loading history response of concrete, the microstructure-penetration interaction etc. is discussed. Constitutive law compatible with Second Law of thermodynamics and coupled damage and plasticity modelling based on continuum damage mechanics are also examined. The purpose of this paper is preliminarily to study with respect to impact and penetration models for concrete before the development of that model.

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Fabrication of Nanocomposite Powders by Sonochemical Method

  • Hayashi, Yamato;Sekino, Tohru;Niihara, Koichi
    • Journal of Powder Materials
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    • v.8 no.3
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    • pp.207-209
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    • 2001
  • Nano particles have recently been a major research interest, motivated by their unusual physical and chemical properties. Such particles can be synthesized using physical and chemical methods. The physical methods need expensive installation like vacuum induction furnace, whereas in chemical methods the process in generally very simple and low cost. In this study, simple and new fabrication process by using ultrasound was investigated to prepare the nano-sized metal particles on various powders at room temperature.

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Rubber Toughened Epoxy

  • Ratna, D.;Banthia, Ajit K.
    • Macromolecular Research
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    • v.12 no.1
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    • pp.11-21
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    • 2004
  • Toughening of epoxy resins for improvement of crack resistance has been the subject of intense research interest during the last two decades. Epoxy resins are successfully toughened by blending with a suitable liquid rubber, which initially remains miscible with epoxy and undergoes a phase separation in the course of curing that leads to the formation of a two-phase microstructure, or by directly blending preformed rubbery particle. Unlike the situation for thermoplastics, physical blending is not successful for toughening epoxy resins. Recent advances in the development of various functionalized liquid rubber-based toughening agents and core-shell particles are discussed critically in this review.

Relationship between Bone Morphological Microstructure and Inflammatory Markers in Growing Mice Fed a High Fat Diet (고지방식이 공급에 따른 성장기 마우스의 골의 형태학적 미세구조와 염증지표 변화)

  • Kim, Mi-Sung;Lee, Hyun-A;Kim, Ok-Jin;Sohn, Cheong-Min
    • Journal of Nutrition and Health
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    • v.44 no.6
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    • pp.481-487
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    • 2011
  • Obesity not only reduces bone mineral density but also increases inflammatory markers. Therefore, we examined the change in inflammatory markers and morphological microstructure of the bones using a mouse model fed a high-fat diet. C57BL/6J 4-week-old male mice were divided into a control group (n = 6) and a experimental group (n = 6); the control group was provided with 10% Kcal fat diet, and the high-fat diet group was provided with 45% Kcal fat diet for 12 weeks using the free provision method. Blood was analyzed for inflammatory markers, and micro-computed tomography was used to measure the morphological microstructure of the femoral bone. The weight increases in the control group and high-fat diet group were 5.85±1.84g and 16.06±5.64g, respectively (p < 0.01), glucose was 115.00±16.88mg/dL and 188.33±13.29mg/dL (p < 0.01), and triglycerides were 65.00±6.19mg/dL and 103.33±8.02mg/dL (p < 0.05) respectively. Leptin and interleukin (IL)-6 were significantly higher in the high-fat diet group than that in the control group (p < 0.01). As a result of a biochemical index analysis of bone metabolism, osteocalcin tended to be lower in the high-fat diet group, whereas CTx was significantly higher in the high-fat diet group compared to that in the control group (p < 0.01). The thickness of the bony trabecula was significantly narrower in the high-fat diet group than that in the control group (p < 0.05), and the gap in the bony trabecula was significantly wider in the high-fat diet group than that in the control group (p < 0.05). IL-6 and the gap in the bone trabecula, which was a morphological microstructure of the bones, showed a positive correlation (p < 0.05). Taken together, inducing obesity through a high-fat diet in mice during the growth phase caused a change in bone microstructure and was correlated with the inflammation index. Accordingly, restriction of excessive fat intake may be needed to suppress the inflammatory reactions and promote normal bone formation.

Microstructure and Mechanical Properties on Solid Solution Heat Treatment of Al-6Si-2Cu Alloy for Lightweight Automotive (자동차용 Al-6Si-2Cu 합금의 용체화처리에 따른 미세조직 및 기계적 특성 변화)

  • Hong, Seung-Pyo;Kim, Chung-Seok
    • Korean Journal of Materials Research
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    • v.24 no.10
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    • pp.538-542
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    • 2014
  • Microstructural and mechanical characteristics of Al-6Si-2Cu alloy for lightweight automotive parts were investigated. The test specimens were prepared by gravity casting process. Solution heat treatments were applied to as-cast alloys to improve mechanical properties. The microstructure of the gravity casting specimen presents a typical dendrite structure, having a secondary dendrite arm spacing (SDAS) of 37μm. In addition to the Al matrix, a large amount of coarsened eutectic Si, Al2Cu intermetallic phase, and Fe-rich phases were identified. After solution heat treatment, single-step solution heat treatments were found to considerably improve the spheroidization of the eutectic Si phase. Two-step solution treatments gave rise to a much improved spheroidization. The mechanical properties of the two-step solution heat treated alloy have been shown to lead to higher values of properties such as tensile strength and microhardness. Consequentially, the microstructural and mechanical characteristics of Al alloy have been successfully characterized and are available for use with other basic data for the development of lightweight automotive parts.

Performance of self-curing concrete as affected by different curing regimes

  • El-Dieb, A.S.;El-Maaddawy, T.A.
    • Advances in concrete construction
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    • v.9 no.1
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    • pp.33-41
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    • 2020
  • In this study, polyethylene glycol (PEG) and polyacrylamide (PAM) have been used as self-curing agents to produce self-curing concrete (SC). Compressive strength, ultrasonic pulse velocity (UPV), bulk electrical resistivity, chloride ion penetrability, water permeability, and main microstructural characteristics were examined under different curing regimes, and compared to those of the control concrete mixture with no self-curing agents. One batch of a control mixture and one batch of a SC mixture were air-cured in the lab to act as non-water-cured samples. The water curing regimes for the control mixture included continuous water curing for 3, 7, and 28 days and periodical moist curing using wetted burlap for 3 and 7 days. Curing regimes for the SC mixtures included 3 days of water curing and periodical moist curing for 3 and 7 days. SC mixtures showed better microstructure development and durability performance than those of the air-cured control mixture. A short water curing period of 3 days significantly improved the performance of the SC mixtures similar to that of the control mixture that was water cured for 28 days. SC concrete represents a step towards sustainable construction due to its lower water demand needed for curing and hence can preserve the limited water resources in many parts of the world.

Development of a Cast Tool Steel with Excellent Performance for Application to Cold-Work Press Dies (냉간프레스금형용 고성능 주강 개발)

  • Kang, Jun-Yun;Park, Jun-Young;Kim, Byunghwan;Kim, Hoyoung
    • Journal of the Korean Society for Heat Treatment
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    • v.31 no.6
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    • pp.290-299
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    • 2018
  • The microstructure of a newly developed alloy tool steel (KV1) for casting cold-work press dies was analyzed using advanced scanning electron microscopy. Its mechanical properties and durability in use as piercing inserts were tested. It contained a continuous network structure which originated from the micro-segregation during solidification and was composed of retained austenite and primary carbides. However, after quenching and tempering, its continuity was destroyed due to the decomposition of austenite. The discontinuous spatial distribution and the smaller amount of primary carbide in the network presented KV1 enhanced ductility compared to the common alloy (HK700). The reduced C and Cr, the addition of V resulted in a small amount of primary carbides which primarily consisted of MC, as well as fine and uniform dispersion of precipitates. Owing to these features, KV1 exhibited delayed initiation of chipping when used for piercing inserts.