• 한국추진공학회:학술대회논문집
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• 한국추진공학회 2008년도 제31회 추계학술대회논문집
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• pp.181-184
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• 2008

오스테나이트 계열 스테인리스강의 경우 뛰어난 내열성으로 인해 가스 터빈 블레이드나 디스코 등으로 많이 사용되고 있다. 본 연구에서는 터빈 블레이드로 사용되는 316 스테인리스강의 고온 인장 및 저주기 피로 물성을 실험적으로 구하였다. 실험 결과 탄성계수와 항복강도, 최대인장강도 모두 온도 증가에 따라 감소하는 것으로 확인되었다. 소성변형률 진폭, 소성변형률 에너지 등의 인자들이 피로파괴에 미치는 영향도 조사하였다. 실험을 통해 얻어진 고온 인장 물성을 이용하여 316 스테인리스강으로 제작된 가스터빈 블레이드의 구조해석을 수행하였다.

• 유체기계공업학회:학술대회논문집
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• 유체기계공업학회 2006년 제4회 한국유체공학학술대회 논문집
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• pp.509-512
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• 2006

The propellant mixture ratio of gas generator changes when thrust control valve operate to change LRE thrust level. The mixture ratio change of gas generator result in gas temperature change and failure of turbine blade or deterioration of LRE specific impulse. The mixture ratio stabilizer has been developed to maintain propellant mixture ratio of gas generator. This article deals with design and static/dynamic characteristic of stabilizer. Also gas generator system simulation test has shown that the stabilizer can maintain propellant mixture ratio effectively within tolerable range.

• 한국추진공학회지
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• 제2권3호
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• pp.1-9
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• 1998

풍력에너지는 자연의 에너지를 이용하므로써 환경문제와 경제적 측면에서 다른 대체 에너지보다 훨씬 유리하여 세계 여러 나라에서 각광을 받고 있다. 경제적인 이유로 풍력발전을 위한 회전날개가 대형화 되고 있으며, 경량화를 위해 복합재 구조등의 첨단 항공기술이 적용되고 있는 추세이다. 본 연구에서는 500㎾급 중형 풍력 발전시스템을 개발함에 있어, 적합한 공력 성능을 갖는 경량화 복합재 회전날개의 개선 설계를 수행하였다. 회전날개의 경량화를 위해 기 설계된 쉘-스파 구조물을 쉘-스파-샌드위치 구조물로 설계를 수정하였고, 배선형 해석을 통해서 경량화에 따른 대변형 문제를 검토하였으며, 파괴응력보다 낮은 상태에서 발생되는 국부좌굴에 의한 구조물의 안전성을 검토하였다. 또한, 허브의 금속재 삽입부분의 전단핀에 의한 핀 홀 주위의 응력해석을 수행하여 충분히 안전함을 확인하였고, 수정 설계된 구조물이 운용구간내에서 공진이 발생하지 않음을 확인하였다.

• Structural Engineering and Mechanics
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• 제37권4호
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• pp.427-442
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• 2011

In fatigue life design of mechanical components, uncertainties arising from materials and manufacturing processes should be taken into account for ensuring reliability. A common practice is to apply a safety factor in conjunction with a physics model for evaluating the lifecycle, which most likely relies on the designer's experience. Due to conservative design, predictions are often in disagreement with field observations, which makes it difficult to schedule maintenance. In this paper, the Bayesian technique, which incorporates the field failure data into prior knowledge, is used to obtain a more dependable prediction of fatigue life. The effects of prior knowledge, noise in data, and bias in measurements on the distribution of fatigue life are discussed in detail. By assuming a distribution type of fatigue life, its parameters are identified first, followed by estimating the distribution of fatigue life, which represents the degree of belief of the fatigue life conditional to the observed data. As more data are provided, the values will be updated to reduce the credible interval. The results can be used in various needs such as a risk analysis, reliability based design optimization, maintenance scheduling, or validation of reliability analysis codes. In order to obtain the posterior distribution, the Markov Chain Monte Carlo technique is employed, which is a modern statistical computational method which effectively draws the samples of the given distribution. Field data of turbine components are exploited to illustrate our approach, which counts as a regular inspection of the number of failed blades in a turbine disk.

• 대한기계학회논문집A
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• 제34권6호
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• pp.695-700
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• 2010

가스터빈 날개를 덮고 있는 덮개판(Lock plate)의 재료 물성을 유도초음파를 이용하여 측정을 하였다. Lock plate는 가스터빈 발전소에서 아무 극한 환경에서 작동을 하는 부분 중 하나이다. 초음파 속도와 감쇠계수가 서로 다른 3가지 조건의 열처리상태의 재료 물성을 측정하는데 사용되었다. 일반적인 기계적 파괴 인장실험과 비교했을 때, 인코넬 x-750의 재료특성은 다른 열처리 조건에서 탄성계수와 포아슨비를 활용하여 비파괴적인 방법으로 더 효과적으로 알아냈다. 초음파 속도와 인코넬 x-750의 강도는 서로 비례관계에 있으며, 이러한 재료물성 측정은 여러 산업 분야에서 손상 측정에 활용될 수 있다. 또한 유도초음파 기법을 활용하여 장거리, 광범위한 진단으로 시간과 비용을 절감하는데 도움이 되리라 기대된다.

• Tribology and Lubricants
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• 제37권2호
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• pp.48-53
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• 2021

Wind energy is considered as the most competitive energy source in terms of power generation cost and efficiency. The power train of the pitch drive for a wind turbine uses a 3-stage complex planetary gear system in being developed locally. A gear train of the pitch drive consists of an electric or hydraulic motor and a planetary decelerator, which optimizes the pitch angle of the blade for wind generators in response to the change in wind speed. However, it is prone to many problems, such as excessive repair costs in case of failure. Complex planetary gears are very important parts of a pitch drive system because of strength problem. When gears are designed for the power train of a pitch drive, it is necessary to analyze the fatigue strength of gears. While calculating the specifications of the complex planetary gears along with the bending and compressive stresses of the gears, it is necessary to analyze the fatigue strength of gears to obtain an optimal design of the complex planetary gears in terms of cost and reliability. In this study, the specifications of planetary gears are calculated using a self-developed gear design program. The actual gear bending and compressive stresses of the planetary gear system were analyzed using the Lewes and Hertz equation. Additionally, the calculated specifications of the complex planetary gears were verified by evaluating the results from the Stress - No. of cycles curves of gears.

• 대한기계학회논문집A
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• 제32권7호
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• pp.569-575
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• 2008

In this study, disk type of thermal barrier coating system for gas turbine blade was isothermally aged in the furnace changing exposure time and temperature. For each aging condition, bond tests for three samples were conducted for evaluating degradation of adhesive or cohesive strength of thermal barrier coating system. For as-sprayed condition, the location of fracture in the bond test was in the middle of epoxy which have bond strength of 57 MPa. As specimens are degraded by thermal aging, bond strength gradually decreased and the location of failure was also changed from within top coat at the earlier stage of thermal aging to the interface between top coat and TGO at the later stage due to the delamination in the coating.

• 한국표면공학회지
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• 제37권4호
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• pp.226-233
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• 2004

The residual stresses on the surfaces of low carbon 12Cr steels used as a nuclear steam turbine blade material have been studied by controlling the flame hardening surface treatments. The temperature cycles on the surfaces of 12Cr steel were controlled precisely as a function of both the surface temperature and cooling rate. The final residual stress state generated by flame hardening was dominated by two opposite competitive contributions; one is tensile stress due to phase transformation and the other is compressive stress due to thermal contraction on cooling. The optimum processing temperatures required for the desirable residual stress and hardness were in the range of $850^{\circ}C$ to $960^{\circ}C$ on the basis of the specification of GE power engineering. It was also observed that the high residual tensile stress generated by flame hardening induced the cracks on the surfaces, especially across the prior austenite grain boundaries, and the material failure virtually, which might limit practical use of the surface engineered parts by flame hardening.