• Journal of Wind Energy
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• v.14 no.4
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• pp.68-74
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• 2023

Research is being actively conducted to increase energy production by increasing the length of wind turbine blades. However, it is difficult to manufacture and transport large-scale blades. Various studies are being conducted on the concept of separate wind turbine blades considering transportation methods and maintenance. In this study, various methods of dividing blades and assembling the divided blades were reviewed. The position of the division when the blades are divided was analyzed.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2011.06a
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• pp.1499-1500
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• 2011

• Proceedings of the KWS Conference
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• 2001.10a
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• pp.140-142
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• 2001

항공기의 제트 엔진을 비롯하여 육상용 발전기, 선박용 엔진, 로켓 엔진 등에 널리 사용되는 터빈 블레이드를 포함한 고온용 가스터빈 부품은 최대 온도 120$0^{\circ}C$ 이상의 고온에 노출되어 가혹한 기계적 응력을 받는 동시에 고온에서의 표면 안정성이 요구되므로 초내열 니켈 합금(superalloy), 티타늄 합금, 내열강 등의 고온강도가 우수한 합금이 사용된다. 그런데 합금성분이 많이 첨가된 내열 합금을 용접하는 경우, 미세균열, 용접부의 기계적 성질의 저하, 용접열영향부의 내식성과 내산화성의 저하, 용접외부 결함에 의한 피로강도 저하 등의 문제가 발생하므로 이를 해결해야 한다. 본고에서는 생산성과 용접품질이 우수한 고밀도 에너지빔 용접의 적용 현황에 관하여 고찰코자 한다.

• Journal of the Korean Society for Nondestructive Testing
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• v.35 no.3
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• pp.179-184
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• 2015

In this study, the flap fatigue test of a 48 m long wind turbine blade was performed for 1 million cycles to evaluate the characteristics of acoustic emission signals generated from fatigue damage of the wind blades. As the number of hits and total energy continued to increase during the first 0.6 million cycles, blade damage was constant. The rise-time result showed that the major aspects of damage were initiation and propagation of matrix cracks. In addition, the signal analysis of each channel showed that the most seriously damaged sections were the joint between the skin and spar, 20 m from the connection, and the spot of actual damage was observable by visual inspection. It turned out that the event source location was related to the change in each channel's total energy. It is expected that these findings will be useful for the optimal design of wind turbine blades.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2017.05a
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• pp.248-250
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• 2017

The Mar-M-247 alloy is one of the most widely used materials for gas turbine components in aerospace filed and it shows excellent high temperature strength properties. Hot section parts, such as turbine nozzle and blade, are difficult to manufacture because of their complicated shape. So, the joining process usually applies to them. In this study, the high-temperature behavior of Mar-M-247 alloy at liquid diffusion bonding was investigated. Thus, we performed the diffusion bonding at $1,121^{\circ}C$ for 7 minutes, and observed changes in high temperature strength. As a result, the strength of the bonded specimens decreased by about 70% at $649^{\circ}C$, 60% at $825^{\circ}C$, and 45% at $1,000^{\circ}C$ compared to the base metal. As a result of observing the strength change with bonding time, the specimen bonded for 720 minutes showed a similar strength with the base metal at $649^{\circ}C$. Inferring this result, the joint is considered to be the one-body part.

• Journal of Applied Reliability
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• v.17 no.3
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• pp.224-235
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• 2017

Purpose: Reliability is the most important factor to detect defects as wind turbines are deployed in large blades. The methods of detecting defects are various, such as non-destructive inspection and thermal imaging inspection. We propose the phased array ultrasonic testing method of non-destructive testing. Methods: We propose the active pressure mechanism for wind power blade. The phase array ultrasonic inspection method is used for fault detection inner blade surface. Controlled pressure of mechanism with respect to z-axis is important for guarantee the result of phase array ultrasonic inspection. The model based control and proposed mechanism are utilized for overall system stability and effectiveness of system. Result: The result of proposed pressure mechanism B is more stable than A. Convergence speed is also faster than A. Conclusion: We confirmed the performance of the proposed constant pressure mechanism through experiments. Non-destructive testing was applied to the specimen to confirm the reliability of detecting defects.

• Proceedings of the KWS Conference
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• 2009.11a
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• pp.12-12
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• 2009

터빈에서 핵심부품인 로터는 블레이드를 원심 운동시키는 대형 단조강이며, 고압의 증기 조건에서 고속회전하며 고온에서 운전과 저온에서 과속시험 동안 높은 원심력을 받는다. 또한 기동/정지 천이 동안 열응력을 받기 때문에, 이러한 운전조건에 부합되는 소재로서는 높은 Creep 강도 및 피로강도를 가지는 CrMoV type의 강종이 사용되어져 왔다. 발전소의 대용량화 및 고온화에 따라 종래의 증기조건에서 사용되어져 왔던 1%CrMoV강은 내산화성 및 내부식성이 문제가 되어 더 이상 사용이 불가하며, 고온/고압하에서도 우수한 소재 특성을 가지는 12%Cr강의 사용이 필수적이다. 그러나 12%Cr강으로 제작되는 로타는 Cr 양이 높기 때문에 저널부에 Galling 또는 Scuffing 이라 불리는 부적절한 마모현상과 사용 중 소착이 발생하기 쉬운 단점이 있기 때문에, 저널부에 Cr 함유량 2~3% 이하의 저합금강을 오버레이 용접하여 육성하는 일체형 가공구조의 로타 저널부가 주목되어 왔다. 따라서 본 연구에서는 Large scale 로타가 용접 도중 급열 및 급냉이 되지 않으면서 균일한 온도로 일정 시간 유지할 수 있는 열관리 장치 개발, 최적 오버레이 용접조건 선정 및 용접부 건전성 시험 평가를 통하여 12%Cr 로타 저널부의 최적 오버레이 용접공정을 확립하고자 하였다. 용접 열관리 장치는 전기저항 가열방식을 적용하고 있으며 용접이 최종 완료되기 전까지 로타 제품 전체는 $93^{\circ}C$이상의 온도로 유지 되어져야 하며, 규정 용접후열처리 온도는 $650^{\circ}C{\pm}14^{\circ}C$ 이다. 또한 로타 오버레이 용접은 모재 Set up $\Rightarrow$ 용접예열 $\Rightarrow$ GTA용접 $\Rightarrow$ SA용접 $\Rightarrow$ 용접후열(Post heating) $\Rightarrow$ 용접후열처리(PWHT) $\Rightarrow$ 정삭가공 $\Rightarrow$ NDE(UT) 순으로 수행 되어진다 실제 로타의 1/3 Scale로 시험편을 제작하여, 오버레이 mockup 시험을 수행한 후 화학성분, 경도 분포, 인장강도, 충격인성 및 굽힘시험을 수행한 결과, 오버레이 용접에서 요구되어지는 용접 물성값을 만족하는 것으로 확인되었다. 또한 균열 등의 선형 결함이나 기공, 슬라그 혼입과 같은 결함은 관찰되지 않았으며, 용접 시 아크의 안정성과 슬라그의 박리성은 양호하였으며 비드의 외관도 미려하여 용접 작업성도 양호하였다.

• Proceedings of the KWS Conference
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• 2009.11a
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• pp.108-108
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• 2009

Precipitation hardening nickel base alloys strengthened by intermetallic compounds are extensively used to manufacture on the components of the hot section of gas turbine engines. To ensure structural stability and maintenance of strength properties for a long time, nickel alloys are normally subjected to complex alloying with elements to form ${\gamma}'$(gamma prime). Such alloys have a limited weldability, are normally welded in high temperature. However, laser welding have a merit that applies in room temperature as easy control of welding parameter and heat input. In this study, $CO_2$ laser welding is applied on STS304 plate with good ductility and precipitation hardening nickel base alloy (GTD111DS) used blade material. Also, several welding parameters are applied on powder, power and travel speed. There are no cracks in Rene 80 and IN 625 powder when STS304 plate is used. But IN 625 powder has no cracks and Rene 80 have some cracks in welds with GTD111DS substrate. Adjusting of welding parameter is tried to apply Rene 80 having a good strength compare to IN 625. In the result of adjusted welding parameter, optimized welding parameters are set with low power, low feed rate and high welding speed. Tensile strength of GTD111DS substrate with Rene 80 powder is same and over than the one of base metal in room temp and high temp($760^{\circ}C$).

• Transactions of the Korean Society of Mechanical Engineers A
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• v.34 no.9
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• pp.1227-1233
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• 2010

In the hot section of a gas turbine, the turbine blades were protected from high temperature by providing a thermal barrier coating (TBC) as well as by cooling air flowing through internal passages within the blades. The cooling air then passed through discrete holes on the blade surface, creating a film of cooling air that further protects the surface from the hot mainstream flow. The holes are subjected to stresses resulting from the lateral growth of thermally grown oxide, the thermal expansion misfit between the constituent layers, and the centrifugal force due to high-speed revolution; these stresses often result in cracking. In this study, the deformation and cracks occurring near a hole on a heat-resistant alloy subjected to thermo-mechanical cycling were investigated. The experiment showed that cracks formed around the hole depending on the applied stress level and the number of cycles. These results could be explained by our analytic solution.