• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2000년도 춘계학술대회 논문집 유기절연재료 방전 플라즈마
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• pp.46-49
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• 2000

This paper studied development of the program for estimation the life time of insullating materials and the longtime breakdown voltage. First, short-time breakdown voltage of Epoxy and insulating oil was measured. Life exponent was gained from measurement of insulating breakdown time of the specimens. Life time is presumed from program. The estimation program is based on the "Inverse Power Law", defined $V^nt$ is constant. After gaining the life exponent n, it is mapping the longtime breakdown voltages. On the base of life exponent, the estimation the lifetime and usefulness of the insulation systems are possible, furthermore easy calculation is possible.

• 소성∙가공
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• 제18권4호
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• pp.347-353
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• 2009

The apparent activation energy, the applied stress exponent, and rupture life have been measured from creep experiments over the range of $200^{\circ}C$ to $220^{\circ}C$ and the applied stress range of 64MPa to 94MPa. The materials were used AZ31 magnesium alloys treated by plasma electrolytic oxidation of $20{\mu}m$ and $40{\mu}m$ at surface to investigate the its influence on creep behavior, and creep tests were carried out under constant applied stress and temperature. The experimental results showed that the dipper the thickness of surface treatment the higher the activation energy and stress exponent. And the higher temperature and applied stress, the lower stress exponent and activation energy, respectively. Also the dipper the thickness of surface treatment the longer creep rupture time.

• 한국건설순환자원학회논문집
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• 제4권3호
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• pp.259-268
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• 2016

염해에 노출된 콘크리트 구조물의 내구수명 평가는 크게 결정론적 방법과 확률론적 방법으로 분류할 수 있으며, 다양한 설계인자에 따라 내구수명은 크게 변화한다. 본 연구에서는 시간의존성 확산계수 및 내부영향인자(기본확산계수, 임계염화물량, 시간지수)를 고려하여 변화하는 내구적 파괴확률과 이에 따른 내구수명을 도출하였다. 임계 염화물량이 133.3% 증가할 때, 내구수명은 결정론적 방법에서 134.0~145.4%의 증가비를 나타내었으며, 확률론적 방법에서는 149.2%~152.5% 증가비를 나타내었다. 시간지수가 200% 증가할 경우, 내구수명의 증가비율은 결정론적 방법에서 323.8%, 확률론적 방법에서 346.0%로 증가하였다. 시간의존성 확산계수를 사용하여 과다설계를 방지할 수 있는 합리적인 확률론적 내구설계를 수행할 수 있었으며, 혼화재료를 사용하여 시간지수를 증가시키는 것이 매우 효과적인 내구수명 연장방안임을 알 수 있었다.

• 한국표면공학회지
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• 제33권4호
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• pp.222-228
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• 2000

The life time of cutting tool was studied in the relation with the properties of TiN coating tools. The purpose of this study is to compare the cutting conditions of the TiN coated tools with those of the non-coated tools and to find out the optimal cutting condition of the TiN coated tool. The coated tools were prepared by the sputtering process at $4$\times$10^{-3}$Torr. When the cutting speed is increased 22.2% from 90m/min, the limited life of coating bite was decreased by 60.61%, but non-coating bite was decreased by 64.05%. In the tool lifetime equation of the coated tools "a"(exponent of feed rate) was not much changed in comparison with that of the non-coated tools but "n" (exponent of tool′s life) was increased by 9.3% and "b" (exponent of cutting depth) was increased by 2.4%. It was thought to be that TiN coated tools was used for higher cutting speed than non-coated tools to improve the lifetime of the coated tools.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 1999년도 춘계학술대회 논문집
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• pp.57-61
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• 1999

Electrical stress makes insulating materials aged finally resulting in the dielectric failure. It becomes more and more important to recognize the degree of aging and the life time of the insulating materials since it is directly concerned with the reliability of the insulation system. In this paper, the life time of the Cross-linked Polyethylene(XLPE), the insulation layer in the 154kV-grade power cable, is expected and calculated using statistical and mathematical methods. The simulated results are compared with experimental ones and the life exponent of the material is obtained.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 1997년도 추계학술대회 논문집
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• pp.360-363
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• 1997

The method of estimating life time of epoxy composites which be widely used for transformers has been studied in this paper. The breakdown properties of specimens are observed by appling high AC voltage at the room temperature from a series of the experiments. Afterwards, the breakdown time was determined under the constant voltage below the lowest breakdown voltage. Also, V-t properties were found out using weibull distribution widely used in the applications of discrete data for estimating life time of epoxy composites and life exponent n was gained properly. when life exponent is gained is found out, the tong breakdown life time at used voltage can be estimated from breakdown experiments in short time using reverse law of n power.

• 한국전기전자재료학회논문지
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• 제13권7호
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• pp.607-611
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• 2000

The characteristics on the interface between Epoxy and EPDM which are materials of the underground insulation systems of power delivery have studied. The breakdown strength of specimens are observed by applying high AC voltage at the room temperature. The breakdown times under the constant voltage below the breakdown voltage were gained. As constant voltage is applied the breakdown time is proportion to the breakdown strength. The life exponent n is gained by inverse power law and the long breakdown life time can be evaluated. AC breakdown strength and life time is improved by oiling to the interface. When the low viscosity oil is spread interface has the highest life time.

• 한국정밀공학회지
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• 제20권2호
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• pp.129-135
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• 2003

The fatigue life of a structure can be enhanced by improving the mechanical and metallurgical aspects to strengthen the material around regions of high stress. Coldworking of holes in structures is one of the mechanical methods of strengthening material. The material for this research is A12024-T351 which is used for the primary member or aircraft. Specimens were tested under constant amplitude loading and residual stresses measured by X-ray diffraction technique. Fatigue crack initiation life was evaluated by a strain-life equation which was considered initial residual stress and residual stress relaxation exponent as a function of the strain amplitude. The predictions on fatigue crack initiation life were compared with experimental results. A wide range of discrepancies between them was found.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2000년도 하계학술대회 논문집
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• pp.775-778
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• 2000

In this paper, the life-time of macro interface between Epoxy/EPDM which consists in underground power cable joints is predicted. The electrode system of specimen is designed by FEM(finite elements method). The breakdown strength of specimens are observed by applying high AC voltage at the room temperature. The breakdown times under the constant voltage below the breakdown voltage were gained. As constant voltage is applied, the breakdown time is proportion to the breakdown strength. The life exponent n is gained by inverse power law, and the long breakdown life time can be evaluated.

• 감성과학
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• 제8권4호
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• pp.415-422
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• 2005

본 연구에서는 행동활성화체계(Behavioral Activation System : BAS)와 행동억제 체계(Behavioral Inhibition System : BIS)의 성향이 청년층과 노인층의 뇌파 특성에 차이를 보이는지를 조사하였다. 실험은 19명의 청년층과 31명의 노인층을 대상으로 하여 이루어졌고, 안정 상태의 양측 전전두엽 뇌파를 측정하였다. 분석은 비선형 지수 중 하나인 1/f스케일링 지수를 사용하였다. 그 결과, BAS 성향에서 1/f스케일 지수가 유의한 차이를 보였다. 즉, 좌측 전전두엽(Fpl)에서는 청년층의 1/f스케일 지수가 노인층의 1/f스케일 지수보다 통계적으로 유의하게 높은 값을 보였고, 우측 전전두엽(Fp2)에서도 청년층이 노인층에 비해 높은 1/f스케일 지수를 나타내는 경향을 보였다. 1/f 스케일 지수가 클수록 복잡도는 감소하고, 반면 확률분포에 관련된 정보의 양은 증가하는 것으로 해석 가능하다. 본 연구를 통해, 주관적 평가 결과로서 행동 활성화체계가 강한 성향을 가진 경우, 노인층은 청년층에 비해 양측 전전두엽의 복잡도가 높은 상태임을 알 수 있다 본 연구의 결과는 BAS성향과 연령 사이의 연관성에 대한 가능성을 시사한다.