• 한국지반신소재학회논문집
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• 제3권2호
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• pp.31-38
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• 2004

2종류 지오그리드의 장기안정성의 검토되었다. 멤브레인 연신형 지오그리드는 지수함수형 인장거동을, 섬유형 지오그리드는 파단점에 가까울수록 빠른 인장특성 증가를 나타내었다. 섬유형 지오그리드의 경우 가속 크리프 시험을 실시하였지만 멤브레인 연신형 지오그리드의 경우에는 열적특성 때문에 가속 크리프 시험을 실시할 수 없었다. 멤브레인 연신형 지오그리드의 크리프 변형률은 인장시험에 의한 극한변형률보다 훨씬 큰 값을 나타내었으며, 섬유형 지오그리드의 크리프 변형에 의한 감소인자는 멤브레인 연신형 지오그리드에 비해 작은 값을 나타내었다.

• 대한기계학회논문집A
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• 제31권6호
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• pp.665-670
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• 2007

Alpha-phase alumina TGO(Thermally Grown Oxide) forms on the interface between zirconia top coat and bond coat of thermal barrier coating system for superalloys during exposure to high temperature over $1000^{\circ}C$. It is known to provide a good protection against hot corrosion and to cause surface failure such as rumpling and cracking due to difference in thermal expansion coefficient from the substrate metal and the lateral growth. Consequently, mechanical properties of the alumina TGO at the high temperature are the key parameters determining the integrity of TBC system. In this work, by using Fecralloy foils as the alumina forming substrate, creep tests and tensile tests have been performed with various TGO thicknesses$(h=0{\sim}4{\mu}m)$ and yttrium contents(0, 200ppm) at $1200^{\circ}C$. Displacement-time curves and load-displacement curves for each TGO thickness(h=1,2,..) were measured from the creep and tensile tests, respectively, and compared with the curves without TGO thickness(h=0). As the result, the intrinsic tensile and creep properties of TGO itself were determined.

• 대한금속재료학회지
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• 제49권7호
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• pp.535-540
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• 2011

The tensile and creep behaviors of Alloy 263, which is a wrought Ni-base superalloy used for gas turbine combustion systems, was studied. Anomalous increase of yield strength and abrupt decrease of elongation with increasing temperature were observed after tensile testing at an intermediate temperature. Elongation of the superalloy decreased as the temperature increased to and above 540$^{\circ}C$, and it reached a minimum value at 760$^{\circ}C$. It was found that creep strain was also very low at the same temperature. Inhomogeneous deformation with intensive slip bands was observed in the specimens tested at low temperature. A thermally-assisted dislocation climb process was regularly conducted at high temperature. Twinning was found to be an important mechanism of both tensile and creep deformations of the superalloy at an intermediate temperature where ductility minimum was observed.

• 한국정밀공학회지
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• 제26권7호
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• pp.99-104
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• 2009

Creep characteristic is an important failure mechanism when evaluating engineering materials that are soft as polymers or used as mechanical elements at high temperatures. One of the popular thermo-elastic plastics, Polyethylene(PE) which is used broadly for engineering purposes, as it has good properties and merits compared to other plastics, was studied for creep characteristic at various level of stresses and temperatures. From the experimental results, the creep limit of PE at room temperature is 75% of tensile strength. Also the creep limits decreased exponentially as the temperatures increased, up to 50% of the melting point. Also the secondary stage among the three creep stages was nonexistent nor was there any rupture failure which occurred for many metals.

• 한국정밀공학회지
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• 제27권9호
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• pp.78-85
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• 2010

Creep characteristic is an important failure mechanism when evaluating engineering materials that are soft material as polymers or used as mechanical elements at high temperatures. One of the popular thermo-elastic polymers, Polycarbonate(PC) which is used broadly for engineering polymer, as it has excellent mechanical and thermal properties compared to other polymers, was studied for creep characteristic at various level of stresses and temperatures. From the experimental results, the creep limit of PC at room temperature is 85 % of tensile strength. which is higher than PE (75%)at room temperature. Also the creep limits decreased exponentially as the temperatures increased, up to 50 % of the melting point($267^{\circ}C$). Also the first and third stage among the three creep stages was non-existent nor was there any rupture failure which occurred for many metals.

• 한국정밀공학회지
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• 제28권12호
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• pp.1403-1410
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• 2011

Creep characteristic is an important failure mechanism when evaluating engineering materials that are soft material as polymers or used as mechanical elements at high temperatures. One of the popular thermo-elastic polymers, Polymethyl methacrylate(PMMA) which is used broadly for engineering polymer, as it has excellent mechanical and thermal properties compared to other polymers, was studied for creep characteristic at various level of stresses and temperatures. From the experimental results, the creep limit of PMMA at room temperature is 85 % of tensile strength. which is higher than that of PE (75%)at room temperature. Also the creep limits decreased to nil linearly as the temperatures increased, up to $120^{\circ}C$ of the melting point($267^{\circ}C$). Also the first and third stage among the three creep stages were non-existent nor were there any rupture failure which occurred for many metals at high temperatures.

• 동력기계공학회지
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• 제6권4호
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• pp.49-55
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• 2002

In this paper, the elevated temperature tensile properties and short-time creep rupture characteristics were investigated for the friction welded joints of dissimilar materials, Cu-1%Cr-0.5%Zr and STS316L. The joining tests on Cu-1%Cr-0.5%Zr/STS316L by friction welding were performed, and optimum joining conditions of the friction welded joints were determined. The characteristics of the elevated temperature tensile strength, hardness, fractographs were examined, and the creep rupture characteristics for the optimum welded joints were investigated under uniaxal static load at 300, 400 and $500^{\circ}C$.

• 한국해양공학회:학술대회논문집
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• 한국해양공학회 2004년도 학술대회지
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• pp.228-233
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• 2004

The characteristics of the probability distribution for mechanical properties, e.g. tensile strength, reduction of area ana elongation, for STS304 stainless steel in elevated temperature were investigated from tensile test performed by constant cross head speea controls with 1mm/min, Recently, in order to clarify the strengthening mechanisms at high temperature, a new scheme to improve high temperature mechanical properties is desired. Therefore, the test ,technique development of high temperature creep behaviors for this material is very important. In this paper, the creep praperties and creep life prediction by Larson-Miller parameter method for STS304 stainless steel to be used for other high temperature components were presented at the elevated temperatures of 600, 650 and $700^{\circ}C$.

• 한국지반신소재학회논문집
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• 제17권4호
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• pp.213-224
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• 2018

본 연구에서는 접힘홈이 형성된 띠형 섬유보강재를 대상으로, 보강재 종류 및 크리프시험 방법에 따른 크리프특성을 분석하고 크리프 감소계수를 평가하기 위하여 인장강도가 다른 6종류의 띠형 섬유보강재(인장강도 15kN, 25kN, 35kN, 50kN, 70kN, 90kN)에 대한 가속 크리프시험(SIM)을 수행하였다. 또한, 특히 활용 빈도가 높은 인장강도 25kN인 띠형 섬유보강재에 대해서는 장기 크리프시험을 동시에 수행하여 가속 크리프시험 결과와 비교, 분석하였다. 분석 결과, 보강재의 설계수명이 증가할수록 크리프 감소계수가 증가하고, 동일한 소재와 제조방법을 사용한 띠형 섬유보강재는 인장강도가 서로 다르더라도 설계수명에 따라 거의 유사한 크리프 감소계수값을 보여주며, 장기 및 가속 크리프시험 데이터를 모두 사용한 경우의 크리프 감소계수는 장기 크리프시험 데이터만 사용한 경우보다 설계수명 50년~100년을 고려하면 크리프 감소계수가 5.9%~7.1% 정도 작게 평가됨을 알 수 있었다.

• International Journal of Automotive Technology
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• 제1권2호
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• pp.71-77
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• 2000

High temperature materials in service are subjected to mechanical damage due to operating load and metallurgical damage due to operating temperature. Therefore, when designing or assessing life of high temperature components, both factors must be considered. In this paper, the effect of tensile hold time on high temperature fatigue crack growth and long term prior thermal aging heat treatment on creep rupture behavior were investigated using STS 316L and STS 316 austenitic stainless steels, which are widely used for high temperature components like in automotive exhaust and piping systems. In high temperature fatigue crack growth tests using STS 316L, as tensile hold time increased, crack growth rate decreased in relatively short tensile hold time region. In long term aged specimens, cavity type microcracks have been observed at the interface of grain boundary and coarsened carbide.