• Journal of the Computational Structural Engineering Institute of Korea
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• v.12 no.2
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• pp.223-231
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• 1999

본 연구는 복합하중을 받는 구조물에 있어서 구조물의 안정경계점을 계산하는 방법을 제시하고 있다. 여기에서는 우선 안정경계점에 놓여 있는 기지의 점에 대한 선형해를 일반역행열을 이용하여 선형 증분 평형방정식의 여해와 특이해의 선형결합으로 나타내었다. 다음으로 두 개의 하중계수를 구속하는 선형조건을 도입하고, 그 구속조건하에서 하중계수 비가 일정하게 되도록 반복계산을 수행하므로써, 안정경계점위의 다음 목표점이 얻어진다. 얻어진 이 점을 초기점으로 이용한다. 평형경로를 추적할 때, 본래의 두 개의 하중계수 문제는 하중계수의 비가 일정하다는 조건을 도입하여 단일 하중계수의 문제로 된다. 두 개의 예를 들어 수치해석을 행하였으며, 얻어진 결과로부터 본 연구에서 채택된 방법은 구조물의 경계안정점을 찾는 문제에 적합하며 더욱 개발할 여지가 있음을 보여주고 있다.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.39 no.5
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• pp.453-460
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• 2015

Since the Fukushima nuclear accident, several researchers are extensively studying the effect of torsion on the piping systems In nuclear power plants. Piping installations in power plants with a circumferential crack can be operated under combined loading conditions such as bending and torsion. ASME Code provides flaw evaluations for fully plastic fractures using limit load criteria for the structural integrity of the cracked pipes. According to the recent version of Code, combined loadings are provided only for the membrane and bending. Even though actual operating conditions have torsion loading, the methodology for evaluating torsion load is not established. This paper provides the results of limit load analyses by using finite element models for circumferentially cracked pipes under pure bending, pure torsion, and combined bending and torsion with tension. Theoretical limit load solutions based on net-section fully plastic criteria are suggested and verified with the results of finite element analyses.

• Journal of Korean Society of Coastal and Ocean Engineers
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• v.33 no.5
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• pp.195-202
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• 2021

Offshore wind turbine (OWT) receive a combined vertical-horizontal- moment load by wind, waves, and the structure's own weight. In this study, the bearing capacity for the combined load of the suction foundation of OWT installed on the sandy soil was calculated by finite element analysis. In addition, the stress state of the soil around the suction foundation was analyzed in detail under the condition that a combined load was applied. Based on the results of the analyses, new equations are proposed to calculate the horizontal and moment bearing capacities as well as to define the capacity envelopes under general combined loads.

• Proceedings of the Korean Society for Agricultural Machinery Conference
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• 2017.04a
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• pp.16-16
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• 2017

국내 농업인구 감소 대비 식품소비량이 증가함에 따라 농가의 인력을 대체하고 다양한 작업이 가능하며 가격이 저렴한 국내 기계화 기술이 필요하다. 무동력 디스크해로우 작업기는 경운과 배토가 가능한 복합작업기로서 작업기를 구성하는 주요 구성품들은 필드작업에 의해 발생되는 하중에 구조적 강도와 신뢰성이 충분히 확보되어야 한다. 또한, 실제로 필드 작업 시 작업기에 걸리는 하중은 복합하중 형태로 전달되기 때문에 단순한 형태 하중에 비해 하중계측에 어려운 점이 있으므로 하중계측점의 선정이 매우 중요하다. 본 논문에서는 하중계측점을 선정하기 위하여 복합기의 주요 구성품인 치즐(chisel) 및 디스크해로우암(disk harrow arm)에 대하여 구조해석을 수행하였으며, 3축 방향의 단위하중 응력 계산결과로부터 load reconstruction을 위한 스트레인 게이지 위치를 선정하였다. 또한, 스트레인 게이지의 신호가 하중해석에 적절한 값이 되도록 기존의 형상을 수정하였다.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.38 no.11
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• pp.1207-1214
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• 2014

Under excessive plasticity, the fracture toughness of a material depends on its size and geometry. Under fully yielded conditions, the stresses in a material near its crack tip are not unique but rather depend on the geometry. Therefore, the single-parameter J-approach is limited to a high-constraint crack geometry. The JQ theory has been proposed for establishing the crack geometry constraints. This approach assumes that the crack-tip fields have two degrees of freedom. In this study, the crack-tip stress field of a fully circumferential surface-cracked pipe under combined loads is investigated on the basis of the JQ theory by using finite element analysis. The combined loads are a tensile axial force and the thermal gradient in the radial direction. Q-stresses of the crack geometry and its loading state are used to determine the constraint effects. The constraint effects of secondary loading are found to be greater than those of primary loading. Therefore, thermal shock is believed to be the most severe loading condition of constraint effects.

• Composites Research
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• v.27 no.6
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• pp.213-218
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• 2014

This paper predicted the strength of mechanical joint of composites under bending load by means of the characteristic curve method. The method has been employed only for tensile and compression load conditions, but in this study, this method was extended to the bending load condition. For the finite element analysis (FEA), the nonlinear analysis was conducted considering the contact and friction effects between composite material and pin. The failure strength and mode on characteristic curve were evaluate with Tsai-Wu failure theory. To validate the results of FEA, the experiments were conducted to find out the failure load by applying bending moment on the composite specimens. The results showed reasonable agreements with theoretical results. These results lead to a conclusion that the characteristic curve method can be applied to predict the bending strength of mechanical joint of composites.

• Journal of the Korean GEO-environmental Society
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• v.17 no.10
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• pp.13-22
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• 2016

An optimized spudcan was designed for the Southwestern Sea, an area mostly comprised of sand and soft clay layers. The spudcan was designed using guidelines by SNAME, ISO, and InSafeJIP, as well as the yield surface for combined loads. The probe test method was applied to define a yield surface used in estimating spudcan stability. Numerical analyses that considered vertical, horizontal, and moment loads in Southwestern Sea resulted in a design of 8 m diameter spudcan. Additionally, the empirical equations suggested by previous studies can estimate a reasonable spudcan bearing capacity at shallow depth. Each yield surface calculated from Mohr Coulomb and Hardening soil model showed different shapes, however the yield surface also grew with increasing spudcan diameter. This yield surface is a useful reference, along with site investigation results and published guidelines, to estimate the stability of a spudcan in the Southwestern Sea.

• Aerospace Engineering and Technology
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• v.10 no.2
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• pp.146-153
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• 2011

Some methods of calculation of test load value from design load data were investigated which will be applied at strap installed full-scale airframe of composite aircraft. These methods were applied to left wing of KC-100 composite aircraft and the calculated test load values were compared with each others. Generally since test load values are differently calculated according to each aircraft type and position of straps, all calculation methods mentioned at this study need to be applied and compared to each aircraft. Finally the most appropriate method needs to be selected.

• Proceedings of the Korean Society For Composite Materials Conference
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• 1999.11a
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• pp.246-250
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• 1999

항공기 날개 및 동체의 보강재로 사용되는 스트링거가 압축하중을 받게되면 플렌지와 웹에서의 부분좌굴이 발생하고 이는 좌굴이 발생하지 않은 부분에 과도한 하중이 걸리게 하여 스트링거의 전체적인 하중지지능력을 현저히 감소시킨다. 이러한 손상의 형태가 크리플링(Crippling)이다. (중략)

• Proceedings of the KAIS Fall Conference
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• 2011.05b
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• pp.602-604
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• 2011

본 연구에서는 알루미늄 폼 샌드위치 복합재료와 알루미늄 허니컴 샌드위치 복합재료의 면내 외 방향 압축실험으로 하중-변위의 관계를 분석하고 압축 특성을 비교하였다. 만능재료시험기로 1 mm/min 의 속도로 압축을 하였으며, 카메라로 실험과정을 촬영하고 로드셀에서 나오는 데이터를 컴퓨터로 저장하였다. 압축실험의 결과로 알루미늄 폼 및 허니컴 샌드위치 복합재료에서 하중이 증가함에 따라 심재에 좌굴이 발생하였다. 면내 방향 압축실험에서 알루미늄 폼 및 허니컴 샌드위치 시험편에 작용하는 압축 최대하중은 비슷하지만 비중을 고려하면 알루미늄 허니컴 샌드위치 복합재료가 더 우수한 것으로 판단되며, 면외 방향 압축실험에서도 알루미늄 허니컴 샌드위치 복합재료의 압축 최대하중이 알루미늄 폼 샌드위치 복합재료보다 높게 나왔다.