• 한국가스학회지
• /
• 제18권5호
• /
• pp.72-77
• /
• 2014

우리나라는 영구 동토지역이 존재하지 않는 기후적 특성으로 인해 건설수요가 없었지만, 최근 지구 온난화 현상으로 인하여 화석연료의 사용 보다 극한지 지역의 에너지 확보가 대두되고 있다. 이에 극한지 지역에서 사용하고 있지 못한 에너지 자원의 관심이 증가함에 따라 알레스카 및 시베리아의 천연가스의 개발이 필요성이 증대하고 있다. 이에 따라 극한지 지역에서 필요한 배관 설계 기술은 현재 국내에서 사용되고 있는 천연가스와 전혀 다른 환경에서 운용될 것이 예상되며, 이에 따른 설계 기초 자료가 필요하다. 그러므로 극한지 환경에서의 토양 물성에 따라 배관에 미치는 영향 분석이 필요하다. 현재 배관의 설계는 응력 기반으로 설계되어있지만 추후 변위를 기초하는 설계법이 필요하며, 우선적으로 이를 위한 영구동토층 및 활동층에 대한 영향 분석이 필요하다. 본 연구에서는 유한요소해석을 이용한 Thermal elasto-plastic analysis를 통해 활동층의 영향에 따른 배관의 응력 및 변위 측정을 알아보고자 한다.

• 대한기계학회논문집B
• /
• 제24권9호
• /
• pp.1166-1174
• /
• 2000

This work presents a two-dimensional quasi-steady state model to study the fluid flow and heat transfer in high-power density welding process of thin AISI-304 stainless steel plates. The enthalpy method and the finite volume method were used for a numerical analysis of the mushy region phase change as well as the heat flow at the weld pool and the heat-affected zone. The results show that the mushy region distributed around the weld pool becomes wider downstream and the surface heat losses by convection and radiation can be significant factors in welding process especially when a welding speed is relatively low.

• 한국안전학회지
• /
• 제20권2호
• /
• pp.18-25
• /
• 2005

This study performed finite element analysis on the pipe bend with various bend angles under loading conditions of internal pressure and combined pressure and bending, to investigate the effect of bend angle on the collapse behavior of pipe bend and on the stress state in the bend region. In the analysis, the pipe bends with bend angle of $5\~90^{\circ}$ were considered, and the bending moment was applied as in-plane closing and opening modes. From the results of analysis, it was found that the collapse moment of pipe bend increases with decreasing bend angle. As the bend angle decreases, also, the equivalent stress at intrados region increases regardless of bending mode. Under closing mode bending especially, the increase in stress at intrados is significant so that the maximum stress region moves from crown to intrados with decreasing bend angle.

• ETRI Journal
• /
• 제11권2호
• /
• pp.109-119
• /
• 1989

Based on the 2-dimensional charge-control simulation[4], a purely analytical model for MODFET's is proposed. In this model, proper treatment of the diffusion effect in the 2-DEG transport due to the gradual channel opening along the 2-DEG channel was made to explain the enhanced mobility and increased thershold voltage. The channel thickness and gate capacitance are experssed as functions of gate vlotage including subthreshold characteristics of the MODFET's analytically. By introducing the finite channel opening and an effective channel-length modulation, the slope of the saturation region of the I-V curves was modeled. The smooth transition of the I-V curves from linear-to-saturation region of the I-V curves was possible using the continuous Troffimenkoff-type of field-dependent mobility. Furthermore, a correction factor f was introduced to account for the finite transtition section forming between the GCA and the saturated section. This factor removes the large discrepanicies in the saturation region fo the I-V curves presicted by existing 1-dimensional models. The fitting parameters chosen in our model were found to be predictable and vary over relatively small range of values.

• Structural Engineering and Mechanics
• /
• 제77권5호
• /
• pp.651-659
• /
• 2021

In this study, a new constitutive model has been developed to predict the elastic behavior of plain weave textile composites, using the finite element (FE) method. The geometric conditions and basic assumptions of this model are based on the basics of a continuum theory developed for the plane curved composites. In this model, the mechanical properties of the weave region and pure matrix region is calculated separately and then imported for the FE analysis. This new constitutive model is used to implement the mechanical properties of weave region in the representative volume element (RVE). The constitutive relations are implemented as user-material subroutine code (UMAT) in ABAQUS® FE software. The results of FE analysis have been compared with experimental results and other data available in the literature. These comparisons confirmed the capability of the presented model for the prediction of effective elastic properties of plain weave fabric composites.

• 한국정밀공학회:학술대회논문집
• /
• 한국정밀공학회 2008년도 추계학술대회 논문집
• /
• pp.637-638
• /
• 2008

• Tribology and Lubricants
• /
• 제8권1호
• /
• pp.38-43
• /
• 1992

In solving the Reynolds equation in dynamically loaded bearing problem, it is almost impossible to find the squeeze velocity and the cavitation region by analytical method. Finite Element Method was applied to the piston-ring lubrication analysis to solve the complementary problem. The method was very efficient and any convergence problem was not encountered.

• 한국토양환경학회지
• /
• 제5권1호
• /
• pp.3-12
• /
• 2000

다영역 모델은 Preferential 흐름에 대한 해석을 위하여 토양을 여러개의 공극군으로 나누고 각 토양의 수리학적 특성을 이용하여 토양내의 흐름을 표현한 방정식이다. 이 모델을 유한차분법을 이용하여 수치적으로 풀이할 때 해의 정확도와 일관성을 분석하기위해 수정등가편미분방정식(MEPDE)을 구하고, 안정성을 분석하기위해 Von Neumann법을 이용한다. 수정등가편미분방정식을 이용하여 얻은 유한차분계에 대한 평가는 모델방정식에 대하여 일관성이 있는 것으로 나타났고 모델방정식에 대한 유한차분법은 2차의 정확도를 얻었다. 모델방정식의 안정성 해석은 Von Neumann방법을 이용하여 진폭도와 위상지연을 구하고 이를 분석하였다. 유한차분계의 진폭비는 Peclet수의 변화에 관계없이 비분산적이었으며 Peclet수가 1.0일때 가장 큰 값을 나타냈고, 위상지연은 참값에 대한 빈도요소보다 더 느리게 파동함을 나타냈다. 모델방정식의 안정성 해석 결과, 모델의 영역분해는 보다 정확한 결과를 얻기 위해서 Peclet수는 1.0보다 작고 Courant수는 3.0보다 작은 범위 안에서 분해하는 것이 좋은 것으로 분석된다.

• Smart Structures and Systems
• /
• 제14권3호
• /
• pp.285-305
• /
• 2014

This study employs a novel beam-type wavelet finite element model (WFEM) to fulfill an adaptive-scale damage detection strategy in which structural modeling scales are not only spatially varying but also dynamically changed according to actual needs. Dynamical equations of beam structures are derived in the context of WFEM by using the second-generation cubic Hermite multiwavelets as interpolation functions. Based on the concept of modal strain energy, damage in beam structures can be detected in a progressive manner: the suspected region is first identified using a low-scale structural model and the more accurate location and severity of the damage can be estimated using a multi-scale model with local refinement in the suspected region. Although this strategy can be implemented using traditional finite element methods, the multi-scale and localization properties of the WFEM considerably facilitate the adaptive change of modeling scales in a multi-stage process. The numerical examples in this study clearly demonstrate that the proposed damage detection strategy can progressively and efficiently locate and quantify damage with minimal computation effort and a limited number of sensors.

• Tribology and Lubricants
• /
• 제18권4호
• /
• pp.249-254
• /
• 2002

Adhesive contact characteristics of torus-shaped bumps were analyzed using the finite element technique considering the adhesive force. Analyses focused on the effect of rim and bump radii on the adhesive contact behavior such as the jump-to-contact behavior, adhesion hysteresis, pull-off forces, contact region and pressure, and surface and subsurface stresses. Analysis results in the absence of adhesive force were also included to examine the effect of adhesive force. The applicability of torus-shaped bumps to the MEMS structure for reduction of friction is discussed.