• Proceedings of the Korean Society of Precision Engineering Conference
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• 2004.05a
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• pp.66-66
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• 2004

중량은 항공기의 성능을 좌우하는 주요 변수로써, 최소의 중량 달성이 100여 년 전 라이트 형제가 최초의 비행을 성공한 후, 항공기 개발자들의 주요 관심사였다. 일반 구조물의 최적화를 통한 설계는 구조물의 강도를 유지하면서 중량절감, 비용절감을 위해 널리 사용되고 있다. 하지만, 현재 항공기 구조물에 대해서는 아직 최적화론 통한 설계가 널리 적용되지 않고 있다. 그래서, 항공기에서는 중량절감을 위해 가벼우면서 강도를 큰 알루미늄이 주재료로 사용되고 있다.(중략)

• Journal of the Korea Academia-Industrial cooperation Society
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• v.13 no.5
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• pp.1983-1989
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• 2012

This paper presents the stability analysis of UH-60 helicopter with external store such like chaff/flare dispenser. An external store can affect the natural frequency of the aircraft and induce the resonance, which cause the failure of structures. In this paper, therefore, Rayleigh method is used to investigate the resonance with aircraft and external store, and transmission formula is used to determine the vibration load. Structural analysis with local modeling method are performed to present the robust design of aircraft with external store. The ground and flight test are also done to verify the stability of the aircraft.

• Journal of Aerospace System Engineering
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• v.15 no.5
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• pp.106-112
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• 2021

In this study, we performed a design and structural analysis of a blade-shaped antenna installation on the rear fuselage of a rotary wing aircraft operated by the military. When the structure is damaged while the aircraft is in operation, it is separated from the aircraft main structure and may collide with the rotor or blades to cause the aircraft to crash. Therefore, structural safety for the modified structure must be secured. The design requirement for the newly installed modified part were established, and the load condition was constructed by applying the load that may occur in the aircraft after the modification. Structure safety for the modified structure was secured by performing structure analysis. To analysis stress and deformation of aircraft structure, we developed finite element model and verified it by using hand calculation method. We confirmed the safety of the modified structure through the final structural integrity analysis.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.40 no.12
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• pp.1070-1079
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• 2012

The impact energy absorbing is a very important characteristic of an aircraft to enhance the survivability of occupants when an aircraft is under the survivable accident such as an emergency landing condition. The impact energy is generally transmitted into the occupant and absorbed through a landing gear, a subfloor (lower structure of fuselage), and a seat. The characteristic of crash energy absorbing of a subfloor depends on the type of an aircraft, a shape of structure, and an applied material. Therefore, the study of crashworthiness characteristics of a subfloor structure is very important work to improve the safety of an aircraft. In this study, a finite element model of a narrow body fuselage section for the 80~90 seats regional aircraft was developed and crash simulation was executed using an explicit finite element analysis. Through survey of the impact energy distribution of each structural part of a fuselage and floor-level acceleration response, the crashworthiness characteristics and performance was evaluated.

• Journal of Aerospace System Engineering
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• v.14 no.1
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• pp.28-35
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• 2020

This paper presents the design improvements made for the crack which is in the mounting structure of the mechanical structure of rotary wing aircraft. The doubler added to the mounting structure of rotary wing aircraft was designed and manufactured based on the load at the development stage, and a crack was found in the surface of doubler at a certain point during the operation of the aircraft. To identify the cause of the crack, the initial deformation of the structure, which may occur as a result of fastening condition, was considered and the dynamic analysis of the natural frequency of the structure comparing to the blade passing frequency of the aircraft were additionally reviewed. As a result of this study, a shim was added to remove the physical gap of the fastening area, and a doubler with thickened reinforcement was installed. The increase of structural strength is shown by reviewing the results of dynamic analysis for the structural verification of the improved design, and the fatigue evaluation complied to the requirement of the aircraft lifetime.

• Journal of the Korean Society for Nondestructive Testing
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• v.36 no.5
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• pp.345-352
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• 2016

As aircrafts are being operated at high altitude, wing structures experience various fatigue loadings under cryogenic environments. As a result, fatigue damage such as a crack could be develop that could eventually lead to a catastrophic failure. For this reason, fatigue damage monitoring is an important process to ensure efficient maintenance and safety of structures. To implement damage detection in real-world flight environments, a special cooling chamber was built. Inside the chamber, the temperature was maintained at the cryogenic temperature, and harmonic fatigue loading was given to a wing structure. In this study, piezoelectric active-sensing based guided waves were used to detect the fatigue damage. In particular, a beamforming technique was applied to efficiently measure the scattering wave caused by the fatigue damage. The system was used for detection, growth monitoring, and localization of a fatigue crack. In addition, a sensor diagnostic process was also applied to ensure the proper operation of piezoelectric sensors. Several experiments were implemented and the results of the experiments demonstrated that this process could efficiently detect damage in such an extreme environment.

• Proceedings of the Korean Institute of Industrial Safety Conference
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• 2003.10a
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• pp.101-106
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• 2003

항공기 외부 장착물인 POD는 전자전 방해장치(ECM, electronic counter measures)로서 전자방해 장비 및 부분 부품인 전ㆍ후방 러그(lug)와 외부 케이스로 이루어져 있다. POD는 항공기 외부 동체 하단부 및 파일런(pylon)에 장착되어 작동하므로 항공기의 운용중 이륙부터 착륙간의 기동에 의한 피로하중을 주로 받게 되므로 POD 부품들에 대한 구조 건전성 확보하기 위해서는 MIL-STD-1530의 요구에 따라 내구성(durability) 및 손상허용설계(damage tolerance design) 의 평가가 요구되고 있다.(중략)

• Journal of Aerospace System Engineering
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• v.12 no.4
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• pp.106-111
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• 2018

Hydrodynamic ram phenomenon could be generated by external threats such as impact and blast in the aircraft. High strain rate deformation caused by the hydrodynamic ram phenomenon is one of the main factors to influence structural survivability. Mechanical properties of composite structure change rapidly under conditions of high strain rate. Therefore, it is necessary to experimentally investigate the influence of strain rates for aircraft structural survivability. In this paper, tensile tests of composite material were conducted for low and high strain rates to investigate the influence of the various strain rates. Tensile modulus increases more compared to tensile strength at high strain rate under hydrodynamic ram condition. Regression analysis was conducted to predict tensile modulus at various strain rates because it is one of the main damaging factors for composite structures under high strain rate conditions. Also, the mechanical properties of composite materials were acquired and analyzed under high strain rate conditions. It is hypothesized that the results from this study would be used for designing aircraft composite structures and evaluation considering structural survivability.

• Composites Research
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• v.25 no.4
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• pp.105-109
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• 2012

Recently, development of a small aircraft has been carried out for the BASA(Bilateral Aviation Safety Agreement) program in Korea. This aircraft adopted all composite structures for environmental friendly by low fuel consumption due to its lightness behavior. However the composite structure has disadvantage which is very weak against impact damages. Therefore, damage allowable design of aircraft structure must be performed considering compressive fracture strength. This point is very important for certification of composite structure aircraft. In this paper, it is performed the research on damage tolerance of thick laminate adopting aircraft structure. The damage tolerance of three different types of thick laminates such as no damage, open hole and impact damage is evaluated under compression loading.

• Journal of the KSME
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• v.28 no.4
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• pp.408-414
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• 1988

근년에 항공 산업이 많은 관심을 불러일으키고 있음에 즈음하여 독자적인 항공기 구조개발시 구조적 안전성 확보를 위해서는 구조시험 기술의 확보가 필수적이다. 또한 구조시험 관련기술은 다른 기계 구조물의 초기 설계단계에서 구조 강도 및 피로 강도의 확인을 위해서도 응력될 수 있어 구조물의 설계 및 제작공정 결정에 큰 도움이 될 수 있으므로 기업체나 연구소에서도 충 분히 응용할 수 있도록 노력을 기울여야 할 분야이다.