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하도준,김병수,김인근,송호인,이영재,Ha, Do-Jun,Kim, Byoung-Soo,Kim, In-Keun,Song, Ho-In,Lee, Young-Jae 한국군사과학기술학회 2012 한국군사과학기술학회지 Vol.15 No.3
This paper presents a study on characteristics of precession motion of a smart munition. It's a kind of the Sensor Fuzed Weapon. The particular thing for the smart munition is that it has precession motion in the air while the sensor is searching the ground to detect ground vehicles such as tanks. The smart munition has a cylindrical shape and has a sensor attached on its side. Due to its non-uniform mass distribution, its center of gravity(CG) is located away from the center of volume(CV). In order for the smart munition to detect the target effectively, the ground searching pattern of sensor should have an uniform circular form, and for this, the precession motion of smart munition should be in its steady-state. Finally, it is necessary to choose the right initial conditions at the moment of firing, for the steady-state precession motion during flight.
항공기 착륙장치 장착 구조 균열원인 및 품질개선에 관한 연구
하도준,이경찬,최형준 국방기술품질원 2021 국방품질연구논집 Vol.3 No.2
This quality improvement study aims to investigate the cause of structural defects that occur during aircraft operation and to confirm structural health for the improvement configuration. Aircraft are exposed to various loads due to harsh environments and rapid maneuver during operation and mission performance. The influence of various and complex factors such as vibration, shock load, and repeated load is a potential hindrance to flight safety due to structural strength degradation and cracking compared to design load. Therefore, quality improvement is essential through inspection and cracking of vulnerable areas of the aircraft structure and analysis of structural strength, fatigue, and life. In particular, it was analyzed for defects in the structure of the landing device in which static loads and repetitive loads are concentrated during takeoff and landing. After improving the quality for defects, it was confirmed through structural strength and lifespan analysis.
작은 활차가 적용된 비행조종계통의 케이블 내구성 시험을 통한 피로 수명 비교
박혜은,박응선,김윤환,김승현,하도준 한국항공우주학회 2013 한국항공우주학회 학술발표회 논문집 Vol.2013 No.11
항공기 내 직접조종방식 비행조종계통에 사용되는 Cable 및 Pulley(활차)를 이용하여 Cable 내구수명 시험을 수행하였다. 협소한 장착 공간으로 인해 권장 사이즈보다 작은 사이즈의 Pulley 가 적용되어있는 경우가 있는 데, 실제 내구성 시험 수행을 통해 Pulley 사이즈가 Cable 내구 수명에 미치는 영향성과 Cable 종류를 교체함으로써 요구되는 피로 수명을 만족할 수 있는 지에 대해 연구해보고자 한다. 시험 결과, 항공기 설계 시 권장 사이즈보다 작은 Pulley 를 사용하더라도 Cable 의 최적 선정을 통해 요구되는 피로 수명(3 배 이상의 피로수명 개선 필요) 확보가 가능함을 확인하였다. In this study, we performed cable endurance test with cable and pulley used in manual flight control system(MFCS). Since there is no enough space in the aircraft to apply the recommended size of pulley, the smaller size one is used for this test. It is studied that the effect of pulley size on cable’s fatigue life and be satisfied with required fatigue life by changing the cable type. This paper includes the implementation and result analysis of cable’s endurance test. As a result of this test, it is determined that using optimally selected cable secures the cable’s fatigue life (need to improve fatigue life more than 3 times) even though using smaller pulley than the recommended size.
항공기용 유압 펌프의 맥동 압력에 의한 감쇄기 용접부위 균열 개선 연구
신재혁(Jae Hyuk Shin),김태환(Tae Hwan Kim),강구헌(Gu Heon Kang),하도준(Do Jun Ha) 한국산학기술학회 2017 한국산학기술학회논문지 Vol.18 No.7
항공기는 운용 중에 엔진, 유압펌프, 공력 등에 의한 진동 환경에 노출이 되어 기계구조와 각종 구성품이 고주기 피로로 인해 균열이나 파괴가 될 수 있다. 통상적으로 항공기용 유압 펌프는 액셜 피스톤 타입이 주로 적용되고 있으며, 펌프의 특성상 연속적인 회전에 의한 유량 맥동 발생은 필연적으로 수반된다. 이러한 유압펌프 맥동에 의한 진동을 감소시키기 위해 설치된 Dampener Fitting의 용접 부위에서 균열이 발생하였다. 용접 부위 균열의 원인 파악을 위해 파단면 분석 및 성분 분석을 수행하였고, 균열 방지를 위한 설계 개선사항으로 일체형 Fitting 가공 방식을 적용하였다. 일체형 Fitting의 적용 타당성에 대한 설계검증을 위해 구조건전성 응력 해석, 피로수명 해석, 인증시험 및 항공기 체계 장착 시험을 수행하였다. 개선방안에 대한 해석 결과 재료의 요구수명 및 각종 시험의 요구조건에 만족하는 결과를 얻었으며, 개선방안을 운영 항공기에 적용 할 수 있는 것을 객관적으로 검증하였다. Aircraft can often be exposed to a variety of environments and vibrations such as engine, hydraulic pump, aerodynamic force. These may cause cracking and destruction of the mechanical structure and sub-components by high-cycle fatigue. The axial piston type pump which is usually applied to the aircraft hydraulic pump can be necessarily accompanied by the fluid pulsation by continuous rotation of the axial piston. The fatigue crack was identified at the dampener fitting welding zone to prevent vibration damping during the running of aircraft equipped with this type of pulsation hydraulic pump. In order to understand the root cause of this matter, fracture and component analyses were carried out and also integral type dampener fitting was applied to prevent recurrence of the crack as a subject of design improvements. Structural integrity stress analysis, fatigue analysis, qualification test and aircraft system equipped test was conducted to verify the design validity in application to integral type dampener fitting. The test results were sufficiently satisfactory with the demand lifetime of the material from the various types of test as conducted and the subject of design improvement in this study could be objectively evaluated that shall be applied to the operational aircraft.