• Proceedings of the Korean Institute of Navigation and Port Research Conference
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• 2002.11a
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• pp.95-100
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• 2002

The wing in ground effect (WIG) ship is an energy saying vessel that uses the lift from its air-wing along with the lift increase from the ground effect by flying low above the sea surface. The WIG Ship should consist of thin plate in order to float on the sea and to fly in the air. Therefore, the structure of WIG, Ship has very thin and light shell plate and stiffener like stringer and frame has comparatively large cross section area. This structure makes shell plate nearly pure shear field when shell plate is pressed by in-plane load. This complex thin plate structure of WIG Ship can he considered as a closed section beam which makes it possible to analyze structure response of WIG Ship affected by shear load and bending load. In this respect, the present study will show basic theory for analysing shear stress and focus on the analysis of structure strength of model WIC Ship's wing.

• Journal of the Korean Society of Propulsion Engineers
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• v.5 no.1
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• pp.42-48
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• 2001

Over two decades, many researchers have performed studies on strength size effects in composite laminates under tensile and flexural loads. It is well known that there is a tendency for the strength of fibre-reinforced composites to decrease with increasing specimen size. Under compressive load, however, little work has been done on the effect of specimen size to failure strength. This is due to the fact that compressive testing of composite is very difficult. In this paper, the effect of the test specimen size on the compressive strength of composites containing open hole was considered using T300/924C, $>[45/-45/0/90]_{3S}$. For sizing test specimens, the in-plane scaling method is used i.e., the change of two- dimensional specimen area in specimen width and gauge length. The results clearly show that there is a hole size effect in the finite width plates. In addition, the specimens which have the same a/W(hole diameter/specimen width) exhibit a tendency of size effect. In contrast, test results of the unnotched specimens did not show a clear strength size effect.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.25 no.8
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• pp.1277-1286
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• 2001

Aluminum 5052/Aramid Fiber Reinforced Plastic(Al5052/AFRP) laminates are applied to the fuselage-wing intersection. The Al5052/AFRP laminates suffer from the cyclic bending moment of variable amplitude during the service. Therefore, the influence of cyclic bending moment on the delamination and the fatigue crack propagation behavior in Al5052/AFRP laminate was investigated in this study. Al5052/AFRP laminate composite consists of three thin sheets of Al5052 and two layers of unidirectional aramid fibers. The cyclic bending moment fatigue tests were performed with five different levels of bending moment. The shape and size of the delamination zone formed along the fatigue crack between Al5052 sheet and aramid fiber-adhesive layer were measured by an ultrasonic C-scan. The relationships between da/dN and ΔK, between the cyclic bending moment and the delamination zone size, and between the fiber bridging mechanism and the delamination zone were studied. Fiber failures were not observed in the delamination zone in this study. It represents that the fiber bridging modification factor should turn out to increase and that the fatigue crack growth rate should decrease. The shape of delamination zone turns out to be semi-elliptic with the contour decreased non-linearly toward the crack tip.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.18 no.6
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• pp.78-84
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• 2017

Consistent efforts have been made to reduce the weight of automotive parts by using lightweight materials. This has resulted in the replacement of conventional steels in car body structures with high-strength steels, and the current usage rate has reached 50%. This study examines the structural stiffness and energy absorption capability of bumper beams made of high-strength steels. New types of bumper beam cross sections are proposed.The structural stiffness and maximum bending force were computed via finite element analysis as about 25tons and 7.5tons/mm, and there were no significant differences among the proposedcross sections. Dynamic analysis was also carried out to investigate the energy absorption capabilities of the bumper beams, and the effects of materials and thickness reduction were analyzed. High-strength steel can be used to achieve weight reduction with comparable structural performance to conventional bumper beams.

• Journal of the Society of Naval Architects of Korea
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• v.29 no.2
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• pp.115-122
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• 1992

A sandwich element is a special Hybrid structural form of the composite construction, which is consisted of three main parts : thin, stiff and relatively high density faces separated by a thick, light, and weaker core material. In a sandwich construction, the shear deformation of the faces. Therefore, in the calculation of the bending stiffness, the shear effect should be included. In this paper, the minimum weight is selected as an object function, as the weight critical structures are usually composed of these kind of construction. To obtain the minimum weight of sandwich panel, the principle of minimum potential energy is used and as for the design constraints, the allowable bending stress of face material, the allowable shear stress of core material, the allowable value of panel deflection and the wrinkling stress of faces are adopted, as well as the different boundary conditions. For the engineering purpose of sandwich panel design, the results are tabulated, which are calculated by using the nonlinear optimization technique SUMT.

• Bulletin of the Society of Naval Architects of Korea
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• v.27 no.1
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• pp.24-34
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• 1990

In this paper, the formulation of a new simplified finite element is made to analyze the ultimate strength of damaged tubular members subjected to combined axial force and end moment. A damaged tubular member that has the bending deformation and the local dent is modeled by beam elements. Tangent elastic stiffness matrix of a beam element which contains the effect of the geometric nonlinearity is derived by using the updated Lagrangian approach. Here the contribution of the stiffness in the dented area is neglected since its resistance against the external loads is considered to be small. A fully plastic interaction curve of the element under combined loads taking account of the local dent effect is selected as a yielding criterion at each nodal point. Also tangent elasto-plastic stiffness matrix of the element is formulated by plastic node method. Comparison with the present solution and the existing experimental results is made showing that the present method gives quite an accurate solution.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2017.10a
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• pp.598-601
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• 2017

The purpose of this study is to evaluate the effects of Ankle Exercise Program on Muscle Strength and Balance in Middle Aged Woman. Subjects of this study, among the patients who were diagnosed with obesity in the study, for patients total of 8 people have agreed to research. Experimental group 4 people, control group 4 people, was a total of 8 people. Group-specific arbitration method, was applied to Unstable supporting surface exercise program(experimental group) and stable supporting surface exercise program(control group). Each training courses 30 minutes for 6 weeks, examined the changes in Functional Reach Test(FRT) and One Leg Standing(OLST), Dorsi Flexion(DF) and Plantar Flexion(PF) ability to examine a total of 6-week course effectively. The intervention were compared by measuring before and after. There were significant improvements in the subscales of the muscle strength and balance test of those who practiced with the unstable supporting surface exercsie program, while the control group showed no significant changes. Therefore, unstable supporting surface exercsie program is effective in improvement of to improve the muscle strength and balance in woman with obesity.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.37 no.12
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• pp.1541-1546
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• 2013

The stress concentration of lock-claws, which are one of the important parts for pneumatic fitting for a flexible tube connection, was investigated by finite element simulation. In this study, the generation of the local plastic deformation was predicted when the tube was hooked up to a pneumatic fitting in order to disperse the stress concentration, and design optimization was carried out using the Taguchi method. For the optimization, the outer width, bending angle, and inner radius of the lock-claws are used as main variables. As a result, their respective contribution ratios are revealed as 81.3%, 10.9%, and 1.5%. The ratio of the total stress distribution was improved by 4% compared with the initial design of the lock-claws.

• Journal of the Korean Society for Nondestructive Testing
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• v.20 no.6
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• pp.490-500
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• 2000

A new technique for the source location of acoustic emission (AE) in plates whose thichness are close to or thinner than the wavelength has been studied by introducing wavelet transform de-noising technique. The detected AE signals were pre-processed using wavelet transform to be decomposed into the low-frequency, high-amplitude flexural components and the high-frequency, low-amplitude extensional components. If the wavelet transform de-noising was employed, we could successfully filter out the extensional wave component, one of the critical errors of source location in plates by arrival time difference method. The accuracy of source location appeared to be significantly improved and independent of the setting of gain and threshold, plate thickness, sensor-to-sensor distance, and the relative position of source to sensors. Since the method utilizes the flexural component of relatively high amplitude, it could be applied to very large, thin-walled structures in practice.

• Journal of Biomedical Engineering Research
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• v.22 no.1
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• pp.69-80
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• 2001

본 연구에서는 환자의 골다공증 유무에 따른 내고정 장치 시술 직후 및 융합 후의 안정성을 평가하기 위해 다양한 하중 모드에서 C5-C6 운동분절의 생체역학적 거동을 분석하였다. 이러한 목적으로 먼저, C5-C6 경추부의 유한요소 모델을 구현하여 검증하였다. 모델의 결과는 기존 실험치와 유사하여 신뢰성이 부여되었다. 검증된 모델은 Smith-Robinson 방식으로 골이식물을 삽입한 후 전방 내고정 장치를 적용한 시술 상황을 재현하기 위해 수정되었다. 수정된 모델은 두 종류로 구현되었다. (1) 첫 번째 모델에서는, 시술 직후의 상황을 재현하기 위해 골이식물과 종판의 경계면에 접촉요소를 사용하였다. (2)두 번째 모델에서는 완전히 융합된 상황을 나타내기 위해 골이식물을 종판에 고정하였다. 골다공증의 효과를 예측하기 위하여 두 모델의 해면골에 대한 탄성계수를 변화시켰다(정상: 100MPa, 골다공증: 40MPa). 각 모델의 C5 주체의 상위면에 73.6N의 압축 하중을 가한 후에 108Nm의 굴곡/신전, 굽힘, 비틀림 하중을 가하였으며, C6 추체의 하단면은 모든 방향에 대하여 구속하였다. 전체적인 결과에 있어서 상대적 회전운동, 미끄럼운동, 골이식물 내에서의 von Mises 응력의 경우 정상 모델에 비해 골다공증 모델에서 증가함을 보였으며, 특히 시술 직후의 모델에서 비틀림 하중이 가해진 경우, 상대적 회전운동 및 미끄럼 운동이 가장 높게 예측되었다. 이는 골다공증환자에게 전방 내고정 장치를 시술한 경우 골이식물의 파단 및 유합의 실패가 비틀림 하중에서 발생할 수 있음을 나타낸다. 해면골의 von Mises 응력은 시술 직후에 골다공증 모델의 모든 하중 모드에서, 유합 후에는 굽힘 하중 외의 모든 하중에서 ultimate strength를 초과하는 것으로 나타나 골다공증 환자에게 screw의 해리가 발생할 가능성이 높은 것으로 예측되었다. 따라서 골다공증 환자에게 과도한 운동이 발생하지 않도록 하기 위해서 시술 후 세심한 주의와 halo 같은 견고한 정형술이 필요할 것으로 사료된다.