• Composites Research
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• v.12 no.3
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• pp.66-74
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• 1999

A modified mixed mode bending test was performed to investigate the mixed mode delamination for carbon/epoxy composite material. Various mixed mode ratios could be produced by changing the applied load position on the loading lever and the bending load position on the specimen. The modified mixed mode bending test was analyzed to obtain strain energy release rates using beam theory, compliance method and finite element method, This results were in good agreement with the experimental result, which confirmed the validity of this test.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2004.05a
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• pp.116-116
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• 2004

편마비 환자의 보행운동 개선을 위한 보조기구로 족부보장구(Ankle Foot Orthosis, A.F.O.)가 활용되고 있다 족부보장구는 Fig. 1에 제시한 바와 같이 보행특성상 무수히 반복되는 충격과 굽힘하중을 받는다. 따라서 족부보장구용 재료는 피로특성이 우수한 탄소섬유 강화재(Carbon Fiber Reinforced Plastic, 이하 CFRP)를 주로 사용한다. 그러나 CFRP의 상용재인 프리프레그(prepreg)는 강한 이방성의 단방향 섬유이므로 섬유방향과 하중작용방향의 관계에 매우 민감하다.(중략)

• Journal of the Korean Society of Hazard Mitigation
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• v.8 no.4
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• pp.39-45
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• 2008

Breakaway support for small signs of size $0.293\;m^2{\sim}0.360\;m^2$ using indented tube type bolt of D12 mm with 6 mm inner diameter has been developed and the structural strength of the support system for the wind load was verified through static shear and tension tests. One important value in understanding the dynamic behavior of sign post and impact vehicle is the fracture energy of the sign support. In this study, fracture energy needed to break the sign support was estimated by pendulum test and computer simulation using LS-DYNA program. Support system composed of 3 indented bolts was found to sustain the 43.1 kg$\sim$51.2 kg wind load safely. Fracture energy for one indented bolt was measured as 163.3J from the pendulum test, and was calculated as 153J from the LS-DYNA simulation. The closeness between these two values verified the validity of the simulation model.

• Aerospace Engineering and Technology
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• v.6 no.2
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• pp.111-118
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• 2007

KSLV-I which is being developed in KARI is composed with two stages, and adaptor ring is used for coupling stage. Cables for interconnecting between stage is exposed on the outside. Also 8 pyro bolts which are installed in adaptor ring are used for separation of stage. In general, cowl is used for protecting exposed parts or structure which are anxious about damage from outer environment. In KSLV-I, two kind of cowls are designed. The one is umbilical cowl, and the other is pyro bolt cowl. Because cowl is exposed on the outside, heat and pressure load developed from air have effect on cowls. Therefore verification of structural strength through static analysis is required. In this study, static analysis in load condition except heat load is accomplished. In result of analysis, structural strength of pyro bolt cowl is verified. But breakage of umbilical cowl is confirmed in pressure load condition. So design of umbilical cowl is modified for satisfying required structural strength. And structural strength of umbilical cowl through analysis is verified.

• Journal of Korean Tunnelling and Underground Space Association
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• v.6 no.2
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• pp.171-182
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• 2004

This study is focused on finding out the mechanical behavior of pillars and the ground adjacent to the tunnel depending on the central tunnel size and the invert during the construction of 2 arch tunnels in the sandy ground. Model tests were performed in the trap door system, which was composed of 3 separately movable plates. Central pillar was installed on the central movable plate to measure the pillar loads during the excavation of pilot tunnel and the main tunnel. The load-transfer and the loosening load were measured at the bottom plates adjacent to the 2 arch tunnels. The ground settlement and displacement of the tunnel lining were also measured. As results, not only pillar load but also the load transfer mechanism was influenced by the construction sequences, central tunnel size, and the invert.

• Journal of Satellite, Information and Communications
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• v.5 no.2
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• pp.8-13
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• 2010

Satellite structure should be designed to accommodate and support safely the payload and equipments necessary for its own missions and to secure satellite and payloads from severe launch environments. The launch environments imposed on satellites are quasi-static accelerations, aerodynamic loads, acoustic loads and shock loads. Especially when optical payload is accommodated, satellite structure usually adopts the optical bench consisting of composite material not only to support and secure but also to guarantee good pointing stability against extreme thermal environments. This paper deals with optical bench and support structure which shall be designed to minimize the loads transferred to optical payloads from satellite.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.21 no.12
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• pp.845-856
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• 2020

This study proposes a bridge evaluation system for indivisible permit vehicles such as hydraulic cranes. The permit loads for the bridge evaluation are divided into three categories: routine permit loads, special permit 1 loads, and special permit 2 loads. Routine permit and special permit 1 vehicles are allowed to cross a bridge with normal traffic. For these two permits, the standard lane model in the Korean Highway Bridge Design Code was adopted to consider normal traffic in the same lane. Special permit 2 vehicles are assumed to cross a bridge without other traffic. Structural analyses of two prestressed-beam bridges and two steel box girder bridges were conducted for the proposed permit loads. The rating factors of the four bridges for all permit loads were calculated as sufficiently large values for the moment and shear force so that crossing the bridges can be permitted. A reliability assessment of the bridges was performed to identify the reliability levels for the permit vehicles. It was confirmed that the reliability level of the minimum required strength obtained by the load-resistance factors yields the target reliability index of the design code for the permit vehicles.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.38 no.8
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• pp.767-773
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• 2010

This paper describes development of a non-explosive separation device which can be equipped on small satellites. The spur geared micro DC motor, which has high reliability and advantage of price, is adopted as an actuator. The proposed separation device has resettability and it does not need extra jig to reload. In addition, the simple structure makes it easy to fabricate and assemble. To verify the performance of the proposed device, the response time tests, maximum preload tests and maximum shock level tests were performed. Also, through the vibration tests and thermal vacuum tests, feasibility of the proposed separation device was shown in launching and space environments. Therefore, we expect that the proposed separation device can replace the imported separation devices in near future.

• Composites Research
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• v.29 no.2
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• pp.45-52
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• 2016

An understanding of the failure mechanisms of the adhesive layer is decisive in interpreting the performance of a particular adhesive joint because the delamination is one of the most common failure modes of the laminated composites such as the fiber metal laminates. The interface between different materials, which is the case between the metal and the composite layers in this study, can be loaded through a combination of fracture modes. All loads can be decomposed into peel stresses, perpendicular to the interface, and two in-plane shear stresses, leading to three basic fracture mode I, II and III. To determine the load causing the delamination growth, the energy release rate should be identified in corresponding criterion involving the critical energy release rate ($G_C$) of the material. The critical energy release rate based on these three modes will be $G_{IC}$, $G_{IIC}$ and $G_{IIIC}$. In this study, to evaluate the fracture behaviors in the fracture mode I and II of the adhesive layer in fiber metal laminates, the double cantilever beam and the end-notched flexure tests were performed using the reference adhesive joints. Furthermore, it is confirmed that the experimental results of the adhesive fracture toughness can be applied by the comparison with the finite element analysis using cohesive zone model.

• Journal of Aerospace System Engineering
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• v.17 no.2
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• pp.94-102
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• 2023

A nylon wire holding and release mechanism (HRM) has been widely used for deployable applications of CubeSat owing to its simplicity and low cost. In general, structural safety of solar panel with an HRM has been designed by performing structural analysis under a launch environment. However, previous studies have not performed thermal analysis for HRM in an on-orbit environment. In this study, Launch and Early Orbit Phase (LEOP) thermal analysis was performed to evaluate thermal stability of the mechanism in the orbital thermal environment of the pogo pin-based HRM applied to CubeSat. In addition, the effectiveness of the thermal design and performance of the pogo pin-based HRM were verified through a thermal vacuum test.