• Proceedings of the KAIS Fall Conference
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• 2011.12b
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• pp.635-638
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• 2011

항공기 착륙 시 발생되는 높은 충격하중에서 승무원 및 기체를 보호하기 위해 높은 충격흡수율이 요구된다. 따라서 착륙 시 발생하는 충격을 효과적으로 흡수할 수 있는 착륙장치는 항공기 핵심 구성요소이다. 다양한 종류의 완충장치가 존재하나, 소형항공기 주착륙장치에는 판스프링 방식을 이용하여 충격에너지를 흡수할 수 있다. 착륙장치의 완충 성능은 반드시 낙하시험을 통해 입증하여야 하며, 이는 미 연방 항공 규정에서 요구하고 있는 사항이다. 이 논문에서는 소형항공기 낙하시험을 위한 설비, 시험 절차 및 낙하시험 수행 결과를 제시한다.

• Proceedings of the KAIS Fall Conference
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• 2011.12b
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• pp.631-634
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• 2011

항공기용 착륙장치의 완충기 충격흡수 성능은 해석 과정을 거쳐 예측한 값과 낙하시험을 수행하여 그 성능을 입증하여야 한다. 이는 미 연방 항공 규정에서 요구하고 있는 사항이다. 본 논문에서는 착륙장치 낙하시험을 위한 설비, 시험절차 및 시험방법과 낙하시험 수행 결과를 제시한다.

• Advances in aircraft and spacecraft science
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• v.2 no.4
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• pp.391-401
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• 2015

Crashworthiness design and certification have been and will continue to be the main concern in aviation safety. The effects of roll angles on fuselage section crashworthiness for typical civil transport category aircrafts were investigated. A fuselage section with waved-plates under cargo floor is suggested, and the finite element model of fuselage section is developed to simulate drop test subjected to 7 m/s impact velocity under conditions of 0-deg, 5-deg, 10-deg and 15-deg roll angles, respectively. A comparative analysis of failure modes, acceleration responses, and energy absorption of fuselage section under various conditions are given. The results show that the change of roll angles will significantly affect fuselage deformation, seat peak overloads, and energy absorption. The crashworthiness capability of aircraft can be effectively improved by choosing appropriate landing way.

• Ocean Systems Engineering
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• v.10 no.3
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• pp.267-287
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• 2020

The dropped objects are identified as one of the top ten causes of fatalities and serious injuries in the oil and gas industry. It is of importance to understand dynamics of dropped objects under water to accurately predict the motion of dropped objects and protect the underwater structures and facilities from being damaged. In this paper, we study non-dimensionalization of two-dimensional (2D) theory for dropped cylindrical objects. Non-dimensionalization helps to reduce the number of free parameters, identify the relative size of effects of force and moments, and gain a deeper insight of the essential nature of dynamics of dropped cylindrical objects under water. The resulting simulations of dimensionless trajectory confirms that drop angle, trailing edge and drag coefficient have the significant effects on dynamics of trajectories and landing location of dropped cylindrical objects under water.

• Physical Therapy Korea
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• v.9 no.4
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• pp.37-44
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• 2002

이 연구의 목적은 발목에 테이핑을 한 후 40 cm의 높이에서 한 발로 수직착지를 할 때 발목관절에서의 테이핑 효과를 분석하는 것이었다. 대상자는 20대의 건강한 성인 14명(남자 4명, 여자 10명) 이었다. 대상자에게 적용한 조건은 테이핑 전, 테이핑 적용, 30분 동안 트레드밀에서 걷기, 테이핑 제거상태 이었고 맥리플렉스(MacReflex)를 이용하여 발끝이 지면에 닿은 상태에서 발목이 최대 배측굴곡(dorsiflexion) 되기까지 걸린 시간, 발목관절 각도변화, 각속도를 측정한 후 반복측정에 의한 분산분석으로 비교하였다. 그 결과 네 개의 조건간에는 통계학적으로 유의한 차이가 없었다(p>.05). 따라서 발목 테이핑은 수직착지시 발목의 배측굴곡을 제한하는 효과는 없다고 판단된다.

• Korean Journal of Applied Biomechanics
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• v.21 no.3
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• pp.335-343
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• 2011

Patellofemoral pain syndrome is the most common problem involving the knee, accounting for 25% of knee injuries. Repetitive, overuse activities cause increased force at the patellofemoral joint, resulting in pain during flexion and extension activities. Most research have been conducted in exploring the patellofemoral compressive force in gait, squat and lunges, even though in real cases, possibilities in landing exist. The purpose of this study was to compare the differences in patellofemoral compressive force according to two different height. Sixteen collegiate male students(age: 22.25 ${\pm}$ 3.30 yrs, height: 177.25 ${\pm}$ 4.44 cm, weight: 77.50 ${\pm}$ 8.18 kg) were chosen. The subjects performed drop landings in 45 cm, 60 cm. The findings demonstrated that higher height showed peak knee extension moment, quadriceps contraction force, patellofemoral compressive force with increased VGRF. Regarding the patellofemoral joint compressive force, it increased by quadriceps contraction force with knee flexion during landing, yet, it showed no difference in maximal knee flexion. To minimize patellofemoral joint stress and reduce the likelihood of developing PFPS, we recommend that predesigned quadriceps and hip muscle group strengthening are needed during conditioning and training.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.35 no.8
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• pp.971-976
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• 2011

This paper presents the design concepts of a protector for a launch-reconnaissance robot that is to be deployed for data-collection in hazardous regions. The protector protects the reconnaissance robot inside from shock induced during the process of launch, flight, and landing. Since the outer shells of the protector are automatically opened wide by the unlocking mechanism during the landing stage, the reconnaissance robot can easily exit the protector and move around to carry out its mission. We carefully simulated a finite-element model of the protector with the robot and compared the results with the actual dynamic behavior of the system. Shock- response tests using a droptable showed that the proposed protector filled with silicon material successfully attenuated external shock.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.47 no.1
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• pp.26-34
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• 2019

In this paper, a coarse lunar soil model is developed using discrete element method and its computed physical properties are compared with those of the actual lunar soil for its validation. The surface of the actual moon consists of numerous craters and rocks of various sizes, and it is covered with fine dry soil which seriously affects the landing stability of the lunar lander. Therefore, in consideration of the environment of the lunar regolith, the lunar soil is realized using discrete element method. To validate the coarse model of lunar soil, the simulations of the indentation test and the direct shear test are performed to check the physical properties(indentation depth, cohesion stress, internal friction angle). To examine the performance of the proposed model, the drop simulation of finite element model of single-leg landing gear is performed on proposed soil models with different particle diameters. The impact load delivered to the strut of the lander is compared to test results.

• Journal of Mechanical Science and Technology
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• v.20 no.9
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• pp.1361-1370
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• 2006

An electronic beam mis-landing phenomenon on the RGB (red/green/blue) -fluorescent surface has been considered as one of serious problems to be solved in cathode-ray tube (CRT), which is generally caused by mechanical shock and vibration. In this work, structural design concepts on the major parts of the CRT, such as a frame, a shadow mask, and a spring, are studied to improve the mechanical shockproof character of a CRT by FEM-analyses and experimental approaches ; a frame is newly designed to have strength employing the double-corner-beads which reduces considerably the distortion of the frame and the shadow mask : the edge-bead of a shadow-mask is redesigned to maintain the wide curved surface of a shadow-mask after mechanical shock : finally, a spring supporting the frame and the shadow-mask is designed to have enough flexibility along drop-direction. As an example, a conventional type of a 15inch CRT was utilized to demonstrate the feasibility and usefulness of this work. Overall, some favorable information on the structural design of the CRT is achieved, and the mechanical shockproof character of a 15-inch CRT is improved in the degree of 3G $(1G=9.81m/s^2)$ as an average-value.

• Korean Journal of Applied Biomechanics
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• v.15 no.1
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• pp.259-274
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• 2005

The purpose of this study was to compare the kinematic and kinetic parameters of lower extremity joints between novice and experienced sports aerobic dancers during two heights of depth jumps. Four male dancers were participated in this study and they performed 40cm and 60cm height depth jump three times, respectively. Four ProReflex MCU cameras (100frame/sec) and a Kistler force plate (1000Hz) were used for data collection. The results indicated that the duration of contact phase of experienced group was shorter than that of novice group regardless of jump height. For minimum angle of hip, knee, and ankle joints, the novice group had tendency to decrease the angle but the experienced group had increased the joint angle with jump height. There was no difference of total ground reaction force between the groups but the reaction force had tendency to increase with jump height. Thus, this study implied that repetition of jump and landing may induce joint related injury and further study such as. EMG analysis of lower extremity can be needed to verify the relationship between injury and ground reaction force.