• 대한기계학회논문집
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• 제6권2호
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• pp.101-106
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• 1982

This study was undertaken to determine tensile properties and low-cycle fatigue behavior of 0.6%C high carbon steel used of structural purposes at temperatures up to 500.deg.C. In the low-cycle fatigue test the upper limit was decided by elongation(i.e. the total strain range), while the lower limit was defined by the load (i.e. zero load). The following results were obtained. Both, the ultimate tensile strength and low-cycle fatigue resistance attain the maximum values near 250.deg.C. Above this temperature the values decrease rapidly as the temperature increases. The low-cycle fatigue resistance decreases whenever there is an increase of the total strain range. Because the hardness of cycle fatigued specimen correlates cyclic hardening and cyclic softening, therefore the hardness of cycle fatigued specimen is smaller than that of the nonfatigued specimen at room temperature and 500.deg.C but much larger than the hardness of the nonfatigued specimen near 250.deg.C.

• 열처리공학회지
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• 제11권4호
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• pp.295-304
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• 1998

The effects of retained austenite and carbon content in the retained austenite on the tensile strength-elongation balance and spot weldability of TRIP high strength steel sheet have been investigated. The retained austenite of granular type increased with increasing intercritical annealing and austempering temperature, and film type was increased with the increase of austempering time. The volume fraction of retained austenite increased with decreasing intereritical annealing temperature, and the maximum value was obtained at austempering temperature of $400^{\circ}C$. The values of tensile strength-elongation balance increased with decreasing intercritical annealing temperature and maximum value was obtained at austempering temperature of $400^{\circ}C$. The maximum value of tensile strength-elongation balance was obtained at a retained austenite content of about 12%. Tensile shear strength of the specimens with retained austenite was higher than that of the normalizing specimens. With increasing welding current and time, the tensile shear strengh and nugget diameter increased, while nugget thickness showed the peak value and then decreased. The optimum range of welding condition at the given welding pressure of 350kgf was 7~11kA and 10~15 cycles.

• 콘크리트학회논문집
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• 제24권1호
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• pp.53-60
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• 2012

이 연구의 목적은 자연모래를 사용한 콘크리트(NSC)와 부순모래를 사용한 콘크리트(CSC)의 고온 하에서의 물리, 역학적인 특성을 조사하는 것이다. 시험체를 $23^{\circ}C$에서 $800^{\circ}C$ 범위에 노출시켜 육안검사와 중량손실을 측정하였으며, 압축강도 시험과 할렬 인장강도 시험을 수행하였다. 그 결과 중량손실률은 노출 온도가 증가할수록 감소하였으며, NSC와 CSC의 감소율은 비슷하였다. 압축강도, 할렬 인장강도와 탄성계수 또한 노출온도가 증가할수록 감소하였다. NSC의 잔존 압축강도는 $200^{\circ}C$와 $400^{\circ}C$에서 CSC보다 급격히 감소했으며, NSC의 잔존 할렬 인장강도 또한 $200^{\circ}C$에서 CSC 보다 급격하게 감소했다. 하지만 CSC와 NSC 공히 $800^{\circ}C$에 노출되었을 때는 비슷한 잔존강도를 나타내었다.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 1998년도 가을 학술발표회 논문집(I)
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• pp.42-47
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• 1998

Experimental investigation was undertaken to determine early-age strength development and the relationships between the mechanical properties of type I, V and V/fly ash cement concrete with different curing temperature. The tests for mechanical properties, i.e., compressive strength, splitting tensile strength and modulus of elasticity were carried out for type, I, V and V with 15% replacement with fly ash cement concrete. For this purpose 480 concrete cylinders cured at isothermal conditions of 10, 23, 35 and 5$0^{\circ}C$ were tested at ages of 1, 3, 7 and 28days. According to the experiments, the concrete subjected to high temperature at early age got greater strength at early age, however eventually lower strength at late age. The derived relationships between compressive strength and splitting tensile strength and elastic modulus of elasticity appeared to be identical for all types of cement.

• 한국소성가공학회:학술대회논문집
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• 한국소성가공학회 2005년도 추계학술대회 논문집
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• pp.126-129
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• 2005

Microstructures and tensile properties of low carbon steels, 5083 Al alloy and Ti-6Al-4V alloy fabricated by equal channel angular pressing (ECAP) were examined in order to understand their deformation response associated with a formation of an ultrafine grained (UFG) structure. Room temperature tensile properties of UFG low carbon ferrite/pearlite steels and UFG ferrite/martensite dual phase steel were compared for exploring a feasibility enhancing the strain hardening capability of UFG materials. In addition, low temperature and high strain rate superplasticity of the two grades of the UFG 5083 Al alloy, and Ti-6Al-4V alloy were presented. From the analysis of a series of experiments, it was found that UFG materials exhibited the enhanced mechanical properties compared to coarse grained counterparts.

• 열처리공학회지
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• 제10권2호
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• pp.109-120
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• 1997

Microstructure and mechanical properties of Fe-Si-Mn-P high strength steel sheet have been investigated by controlling the cooling rate. Bainite and ferrite were obtatined by annealing in the ferrite pluse austenite region, and ferrite and austenite were obtatined after annealing in the fully austenite region. Ferrite and pearlite were obtained when the cooling rate was controlled from the annealing temperature above $760^{\circ}C$ and bainite showed with increasing cooling rate, however below $760^{\circ}C$ ferrite and bainite were obtained. Tensile strengths and hardness nearly unchanged with increasing cooling rate after control the cooling rate from the temperature above $760^{\circ}C$, while tensile strengths increased and elongation decreased with increasing cooling rate when the cooling rate was controlled from the tempeature below $760^{\circ}C$. Without regard to annealing temperature, tensile strength increased and elongation decreased with increasing cooling rate. Tensile strengths and elongation values heat treated in the ferrite plus austenite region were higher than those in the fully austenite region. Retained austenite and strength-elongation balance showed the maximum value at $780^{\circ}C$ and decreased with increasing annealing temperature. Strength-elongation balance value was controlled by the retained austenite.

• 한국주조공학회지
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• 제29권6호
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• pp.257-264
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• 2009

The effects of silicon and molybdenum on the temperature-dependent properties of high silicon and high molybdenum ductile cast iron were investigated. Microstructure was composed of ferrite, cell boundary complex carbide, carbide precipitated in the grain and graphite. The number and size of carbide decreased with the increase of silicon content and increased with the increase of molybdenum content, however, the size of cell boundary carbide increased above 0.81wt%Mo. The room temperature tensile strength increased with the increase of silicon and molybdenum contents. That did not increase with the latter with more than 0.8wt%. Meanwhile the high temperature tensile strength showed the similar trend to that of room temperature one, that of the specimen with 0.55wt%Mo was the highest. The $A_1$ transformation temperature increased with the silicon and molybdenum contents, and showed similar tendency with the variation of strength. It was discussed due to the solubility limit of Molybdenum in ferrite, of which value was assumed to be in the vicinity of 0.81wt%Mo. The weight after oxidation at 1,173K showed the result caused by the difference in solubility of molybdenum in the matrix. That and the thickness change after oxidation did not show any consistent trend with the silicon and molybdenum contents.

• 한국도로학회논문집
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• 제18권2호
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• pp.1-9
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• 2016

PURPOSES : The performance properties (indirect tensile strength, rutting resistance, and resilient modulus) of recycled aged CRM mixtures and their correlation with Superpave binder properties (viscosity, high failure temperature, $G^*sin{\delta}$, and stiffness) were investigated. METHODS: A series of Superpave binder tests was performed by using a rotational viscometer, DSR, and BBR to evaluate the performance properties. In addition, the CRM mixes were artificially aged through accelerated aging processes, and their properties were evaluated. The correlation between the properties of recycled aged CRM binders and the engineering properties of recycled aged CRM mixtures was experimentally determined. RESULTS : The rut depth values decreased and the ITS values increased with increasing high failure temperature. In general, the resilient modulus properties seemed to be poorly correlated with the high-temperature values, regardless of the aggregate source. CONCLUSIONS: The recycled aged CRM binders and mixtures can lead to satisfactory performance, and the properties of these binders are strongly correlated with the engineering properties of the mixtures.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2003년도 제5회 영호남 학술대회 논문집
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• pp.3-6
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• 2003

The electrical and mechanical properties of dielectric paper and cable at cryogenic temperature have been investigated to optimum insulating design of high-Tc superconducting(HTS) cable. From the results, Tensile strength of PPLP in liquid nitrogen was high more than that of air, but tensile strain could know that decrease sharply. According as tensile strength increases, the breakdown stress of PPLP in liquid nitrogen was decreased because PPLP was degradated. According as bending radius multiple is decrese, breakdown voltage decreased sharply. And bending radius multiple is thought that more than about 25 is suitable.

• 펄프종이기술
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• 제44권3호
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• pp.70-78
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• 2012

For evaluating the printing suitability of electronic copying papers in the aspect of climate conditions, 12 samples of copying papers being generally used in Korea and worldwide were collected. The copying papers were controlled by various temperature and humidity options in conditioning equipment in order to simulate the specific circumstances of dry, temperate or tropical climate, and the pre-heating system of photocopying machines during printing. As results, some copying papers showed several physical problems, especially in recycled copying papers and a normal paper with original printing faulty. These problems of copying papers were mostly resulted in extremely high moisture circumstance, and in lower levels of tensile strength and tensile stiffness. The moisture contents of copying papers during passing through the pre-heater system of photocopying machine could be rapidly decreased because paper is exposed to high temperature around the pre-heating zone. The copying paper, for example of XR3 sample, containing low moisture contents below 2% had high exfoliating possibility of toner transfer from copying paper.