• 대한기계학회:학술대회논문집
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• 대한기계학회 2001년도 추계학술대회논문집A
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• pp.349-354
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• 2001

The split Hopkinson pressure bar has been used for a high strain rate impact test. Also it has been developed and modified for compression, shear, tension, elevated temperature and subzero tests. In this paper, SHPB compression tests have been performed with pure titanium at elevated temperatures. The range of temperature is from room temperature to $1000^{\circ}C$ with interval of $200^{\circ}C$. To raise temperature of the specimen, a radiant heater which is composed of a pair of ellipsoidal cavities and halogen lamps is developed at high temperature SHPB test. There are some difficulties in a high temperature test such as temperature gradient, lubrication and prevention of oxidation of specimen. The temperature gradient of specimen is affected by the variation of temperature. Barreling occurred at not properly lubricated specimen. Stress-strain relations of pure titanium have been obtained in the range of strain rate at $1900/sec{\sim}2000/sec$ and temperature at $25^{\circ}C{\sim}1000^{\circ}C$.

• Steel and Composite Structures
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• 제3권3호
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• pp.153-168
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• 2003

This paper discusses the results and observations from a large-scale fire test conducted on a slim floor system, comprising asymmetric beams, rectangular hollow section beams and a composite floor slab. The structure was subjected to a fire where the fire load (combustible material) was higher that that found in typical office buildings and the ventilation area was artificially controlled during the test. Although the fire behaviour was not realistic it was designed to follow as closely as possible the time-temperature response used in standard fire tests, which are used to assess individual structural members and forms the bases of current fire design methods. The presented test results are limited, due to the malfunction of the instrumentation measuring the atmosphere and member temperatures. The lack of test data hinders the presentation of definitive conclusions. However, the available data, together with observations from the test, provides for the first time a useful insight into the behaviour of the slim floor system in its entirety. Analysis of the test results show that the behaviour of the beam-to-column connections had a significant impact on the overall structural response of the system, particularly when the end-plate of one of the connections fractured, during the fire.

• Advances in concrete construction
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• 제15권3호
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• pp.179-190
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• 2023

The effect of glass fibres (GF) and polypropylene fibres (PPF) on the fresh properties and mechanical properties of lightweight concrete (LWC) exposed to high temperatures is investigated in this study. In this study, fifteen LWC mixtures were carried out in three different groups reinforced with PPF or GF fibers by 0%, 0.2%, and 0.4% by volume of concrete. The first group included aluminum powder (AP) as an air agent at 0.03% with the normal weight coarse aggregate (NWCA) by 100% of the weight of coarse aggregate. In the second group, 33% of the NWCA weight was replaced by lightweight coarse aggregate (LWCA). In the third group, 67% of the NWCA weight was replaced by LWCA. The slump, unit weight, Compressive strength (CS), tensile strength (TS), and flexural strength (FS) were examined. For two hours, the CS and FS were subjected to elevated temperatures of 200℃, 400℃, and 600℃, in addition to microstructure analysis of concrete. In comparison to the reference mixture, the fresh properties and bulk density of LWC decreased with the use of the air agent or the replacement of 67% of the NWCA with LWCA. As a result of the fiber addition, both the slump test and the bulk density decreased. The addition of fibers increased the CS; the highest CS was 38.5 MPa when 0.4% GF was added, compared to 28.9 MPa for the reference mixture at the test age of 28 days. In addition, flexural and TS increased by 53% and 38%, respectively, for 0.4% GF mixes. As well as, adding 0.4% GF to LWC maintained a higher CS than other mixtures.

• Elastomers and Composites
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• 제1권1호
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• pp.56-62
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• 1966

The aging characteristics of vulcanized rubber products manufactured in Korean industries have been studied, especially in terms of relationship between aging temperature and time, and also the comparison of results between Geer's oven testing and tube testing was made. It was assessed from changes in tensile properties resulting from conditioning at elevated temperatures for specified period of time. Even though the recipe of each sample is different, the results, as would be expected, has shown that at lower aging temperature the change of tensile strength indicate moderately and at the elovated severely as shown in Figure 9. Consequently, in spite of that the results from conditioning at various temperatures for certain specified period of time must be equivalent to each other, it shows inignorable tolerance. The results of Geer's oven test and tube test have shown slightly different value. It seemed to be caused by the result of migration phenomena on aging in Geer's oven.

• Advanced Composite Materials
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• 제17권1호
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• pp.75-87
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• 2008

Aerospace structural applications, along with high performance marine and automotive applications, require high-strength efficiency, which can be achieved using metal matrix composites (MMCs). Rotating components, such as jet-engine blades and gas turbine parts, require materials that maximize strength efficiency and metallurgical stability at elevated temperatures. Titanium matrix composites (TMCs) are well suited in such applications, since they offer an enhanced resistance to temperature effects as well as corrosion resistance, in addition to optimum strength efficiency. The overall behavior of the composite system largly depends on the properties of the interface between fiber and matrix. Characterization of the fiber.matrix interface at operating temperatures is therefore essential for the developemt of these materials. The fiber fragmentation test shows good reproducibility of results in determining interface properties. This paper deals with the evaluation of fiber fragmentation characteristics in TMCs at elevated temperature and the results are compared with tests at ambient temperature. It was observed that tensile testing at $650^{\circ}C$ of single-fiber TMCs led to limited fiber fragmentation behavior. This indicates that the load transfer from the matrix to the fiber occurs due to interfacial friction, arising predominantly from mechanical clamping of the fiber by radial compressive residual and Poisson stresses. The present work also demonstrates that composite processing conditions can significantly affect the nature of the fiber.matrix interface and the resulting fragmentation of the fiber.

• 대한금속재료학회지
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• 제46권1호
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• pp.1-5
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• 2008

This study has been investigated the deformation behavior of a hot-extruded Mg-Zn-RE (RE: rare earth elements) alloy containing $Mg_{12}$(RE) particles at the elevated temperatures. The particles are intrinsically produced by breaking the eutectic structure of the alloy during the hot-extrusion process. The grain size of the extruded Mg-Zn-RE alloy developed via dynamic recrystallization is around $10{\mu}m$. Under the heat treatment at 200o C up to 48 hr, no change has been observed on the microstructure and mechanical properties due to the pinning effect of the thermally stable particles. Under the tensile test condition in the initial strain-rate range of $1\times10^{-3}s^{-1}$ and the temperature range up to $200^{\circ}C$, the alloy shows yield strength of 270 MPa and elongation to failure around 9% at room temperature and yield strength of 135 MPa at $200^{\circ}C$. Furthermore, although the alloy contains large amount of the second phase particles around 15%, it shows excellent hot-workability possibly due to the presence of the thermally stable interface between the particles and the matrix.

• Journal of Acupuncture Research
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• 제33권3호
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• pp.75-87
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• 2016

Objectives : The purpose of this study is to investigate the effects of acupuncture and moxibustion treatment at SP6(Sanyinjiao) on the temperature change of feet in healthy adults and evaluate whether SP6 has an effect on cold hypersensitivity of feet. Methods : Subjects of this study were 61 healthy adults consisting of 21 in the acupuncture treatment group, 21 in the moxibustion treatment group and 19 in the control group, selected at random. After starting the experiment, the subjects laid straight on their back and relaxed for 30 minutes. Pictures were then taken of their feet by DITI 3 times before and after treatment. The treatment was carried out by either 15 minutes of acupuncture or 2 pieces of moxibustion at SP6. Whilst the control group rested lying straight. After taking pictures the temperatures of LR2, GB42, ST42, KI1, center of the plantar, and center of the calcaneus were checked and the SPSS for Windows Version 20.0 was used to evaluate the statistical significance by the paired t-test, Wilcoxon signed-ranks test(in group) and the Mann-Whitney U-test(between the groups). Results : Some temperature changes before and after treatment were observed in each of the 12 areas, most of which were not significant. But as a result of comparing the temperature difference of all the samples without dividing the area of each group, the mean temperatures in the acupuncture and moxibustion group were significantly elevated. A comparison between the groups showed the mean temperature of the acupuncture and moxibustion group to be significantly elevated, more so than the control group. Conclusion : The result of this study suggests acupuncture and moxibustion treatment at SP6 has the effect of the rising temperature of feet temporarily.

• Steel and Composite Structures
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• 제5권1호
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• pp.71-86
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• 2005

Based on the test data of Nippon Steel Corporation, the formulas for calculating mechanical properties of fire-resistant (FR) steel at elevated temperatures have been established. A practical approach for fire safety design of FR steel members, including axially compressed members, flexural members and eccentrically compressed members, is developed in this paper. Compared with the full-scale specimen experiments and FEM numerical analysis, this practical approach for fire safety design of FR steel members is demonstrated to be effective and precise.

• 한국추진공학회:학술대회논문집
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• 한국추진공학회 2008년도 제30회 춘계학술대회논문집
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• pp.40-45
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• 2008

본 연구는 항공구조재로 널리 사용되고 있는 AISI 304강에 대한 상온 및 고온 인장특성을 신뢰성 기법을 이용하여 실험한 결과를 정리한 것이다. 인장실험은 ASTM 규정에 의하여 수행하였고, 정규확률지를 이용하여 항공구조설계 시 적용할 수 있는 A-Basis 및 B-Basis 강도를 평가하는 신뢰성 해석을 수행하였다.

• 한국강구조학회 논문집
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• 제18권3호
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• pp.395-403
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• 2006

최근 건설되는 강교량은 지간의 장대화 및 교량으로서의 기능은 물론이고 외적 조형미, 유지관리, 공사기간과 수명주기 비용 등을고려한 구조적 단순함을 요한다. 이러한 요구를 충족시키기 위해 극후판이나 TMCP 강과 같은 고성능 강의 사용이 요구된다. TMCP (Thermo-Mechanical Control Proces)법에 의해 제조되는 TMCP 강은 탄소당량이 적고, 조직이 미세하며, 강도 및 인성이 좋다. 최근에는 인장강도 60MPa급의 고강도 TMCP 강인 SM570-TMC 강이 개발되어 토목구조물에 일부 적용되고 있으며, 점차 그 영역을 확장하려는 추세에 있다. 하지만 이러한 고강도 TMCP 강을 강구조물에 적용하기 위해서는 그 재료적 특성뿐만 아니라 용접 시 발생하는 접합부의 역학적 특징을 명확히 할 필요가 있다. 따라서 본 연구에서는 고온인장실험을 통해서 SM570-TMC 강의 고온시의 기 계적 특성을 조사하였고, 이를 잔류응력 특징을 명확히 하였다.