• 한국지반공학회논문집
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• 제18권4호
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• pp.215-228
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• 2002

동반논문(오세붕, 2002)에서는 전체 변형도 영역의 거동을 모델할 수 있는 GUX( 구성모델을 ABAQUS 코드(Hibbit 등, 2001)에 구현하였다. 먼저 정확도 해석을 통하여 동반논문에서 구현한 내재적 응력적분 기법이 해의 정확도를 확보함을 알 수 있었다. GUX 모델은 전응력 개념에 의거한 비등방경화 탄소성 구성모델이므로 완전 배수 또는 비배수 삼축시힘시 응력-변형도 관계를 입력하여 대상문제를 배수 및 비배수조건에 따라 해석할 수 있다. 본 연구에서는 연약지반 및 풍화토 지반상 성토시 안정성 문제와 지반-말뚝계의 축하중 재하시 거동에 대한 예제 해석을 수행하였다. 그리고 대변형 해석을 통하여 기하학적 비선형성을 고려하였고 전체 변형도 거동을 합리적으로 모델하는 GUX 모델을 이용한 결과를 Mises 모델 결과와 비교하였다.

• 터널과지하공간
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• 제22권5호
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• pp.339-345
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• 2012

동적하중 하에서 암석의 변형거동 및 파괴강도는 발파, 지진 또는 암반돌출의 지진동에 의한 지하구조물의 안정해석에 중요하다. 본 연구에서는 스플릿 홉킨슨 압력봉(SHPB) 충격실험시스템을 석회암시료의 일축압축시험과 압열인장시험에 적용하여 고변형률과 동적강도 평가를 수행하였다. 충격봉의 발사속도를 제어하여 파괴강도 이하 동적응력 상태에서의 석회암시료의 동적응력-변형거동을 분석하였다. 시료 내 파괴여부 및 파괴양상을 파악하기 위하여 Micro-focus X-ray 단층촬영을 수행하였다. 동적 압축강도 실험결과, 석회암시료의 동적압축강도는 변형율속도 의존성을 보였으며, 동적 압축파괴강도는 140 MPa 이상으로 평가되었다. 동적 압열 인장 실험결과, 석회암시료의 동적 압열인장강도는 21 MPa 이상으로 정적 압열인장강도보다 3배 이상 높은 것으로 평가되었다.

• 한국윤활학회:학술대회논문집
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• 한국윤활학회 1999년도 제30회 추계학술대회
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• pp.323-330
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• 1999

The conventional analysis for the numerical computation of fluid film thickness with elastic deformation of contact region. is performed by Newton-Rephson method for its 18st convergence characteristics. However, both high load and relatively low sliding velocity frequently make it impossible for Newton-Rahpson method to get both converged and stable solutions. In particular, this method cannot provide converged Solution under the condition of high load above 1.0 GPa which frequently occurs in line contact of EHL problem. Multigird multi-level method for the solver of non-linear partial differential equation including solid deformation is preferred to Newton-Rshpson method for better convergence and stability and is applied to line contact EHL behavior in this study.

• 한국생산제조학회지
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• 제21권6호
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• pp.938-945
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• 2012

This research proposes FEM analysis for Tandem welding process used in wind tower and predicts optimal welding process to improve the stability of welded structures. Three dimensional elasto-plastic analyses are employed to evaluate thermo-mechanical behavior of residual stress and deformation during Tandem welding for different distance between two touches. To confirm the thermal distribution, Goldak's ellipse heat source model and the real size wind tower pipe model are utilized. Four different analyses are being performed, where in each case the distance between two electrode torches is being changed and residual stress and welding deformation are predicted. Depending on base material state, each case is divided into: Liquid (100mm), Austenite+Liquid (200mm), Austenite+Cementite (400mm), Pearlite+Cementite (800mm).

• Structural Engineering and Mechanics
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• 제24권2호
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• pp.247-268
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• 2006

The parts of pile, above the soil and embedded in the soil are called the first region and second region, respectively. The forth order differential equations of both region for critical buckling load of partially embedded pile with shear deformation are obtained using the small-displacement theory and Winkler hypothesis. It is assumed that the behavior of material of the pile is linear-elastic and that axial force along the pile length and modulus of subgrade reaction for the second region to be constant. Shear effect is included in the differential equations by considering shear deformation in the second derivative of the elastic curve function. Critical buckling loads of the pile are calculated for by differential transform method (DTM) and analytical method, results are given in tables and variation of critical buckling loads corresponding to relative stiffness of the pile are presented in graphs.

• Structural Engineering and Mechanics
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• 제30권4호
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• pp.427-444
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• 2008

A mathematical model for the nonlinear dynamics of a rotating beam with flexible root attached to a rotating hub with elastic foundation is developed. The model is developed based on the large planar and flexural deformation theory and the potential energy method to account for axial shortening due to bending deformation. In addition the exact nonlinear curvature is used in the system potential energy. The Lagrangian dynamics and the assumed mode method is used to derive the nonlinear coupled equations of motion hub rotation, beam tip deflection and hub horizontal and vertical displacements. The derived nonlinear model is simulated numerically and the results are presented and discussed for the effect of root flexibility, hub stiffness, torque type, torque period and excitation frequency and amplitude on the dynamic behavior of the rotating beam-hub and on its stability.

• Geomechanics and Engineering
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• 제12권4호
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• pp.561-577
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• 2017

Vast parts of the east of Tabriz city have been covered by Baghmisheh formation marls. These marls can be classified into three types based on their color as identified in yellow, green, and gray marls. Many high-rise buildings and other projects were founded and now is constructing on these marls. Baghmisheh formation marls are classified as stiff soil to very weak rock, therefore they undergo considerable consolidation settlement under foundation loads. This study presents the physical properties and consolidation behavior of these marls. According to the XRD tests, major clay minerals of marls are Illite, Kaolinite, Montmorillonite and Chloride. Uniaxial compressive strength are 100-250, 300-480 and 500-560 kPa for yellow, green and gray marls, respectively. Consolidation and creep behavior of Baghmisheh marls investigated by using of one dimensional consolidation apparatus under stress level up to 5 MPa. The results indicate that yellow marls have high compressibility, settlement and deformation modules. Green marls have an intermediate compressibility and settlement and while gray marls have low compressibility and settlement and from the foundation point of view have high stability. According to the creep test results, all types of marls have not been entered to progressive creep phase up to pressure 5 MPa.

• 터널과지하공간
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• 제10권4호
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• pp.533-543
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• 2000

본 연구에서는 지하공간의 굴착에 따른 수직파이프 구조물의 변형거동 및 안정성을 수치해석적으로 검토하였다. 지반의 수직거동은 파이프의 압축변형 및 압축응력을 발생시키며, 수평거동은 파이프의 굴곡변형 및 쉽응력을 발생시킨다. 또한, 지반의 수평응력은 파이프를 압착시켜 접선응력을 발생시킨다. 본 연구의 해석대상 구조물은 지하 천연가스의 생산정으로 서, 인접 지반의 굴착이 파이프에 미치는 영향과 최대 영향 요소를 고찰하였다. 이를 위해 보안탄주의 폭과 가스생산정의 위치가 서로 다른 세 가지 사례를 해석하고 비교하였다. 두께 2.5m인 탄층이 심도 237.5m에 위치할 때 45.8m 폭의 보안탄주는 외경 10$\frac{3}{4}$ in., 두께 0.4 in.인 API-55 강철 파이프 구조물을 안전하게 보호할 수 있다. 또한, 실제로 파괴가 발생한 가스생산정을 검토한 결과, 발생된 전단음력이 강철 재료의 허용음력을 초과하였다.

• 한국생산제조학회지
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• 제23권3호
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• pp.259-265
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• 2014

When the brakes of a vehicle are applied, large amounts of heat are generated on the surfaces of the brake discs owing to friction between the discs and the brake pads. A high temperature gradient on the disc surfaces leads to thermal deformation and severe disc abrasion. Ultimately, the thermal deformation and disc wear give rise to a thermal judder phenomenon, which has a major effect on the stability of the vehicle. To investigate and propose a solution to these problems, thermoelastic instabilities under applied thermal and mechanical loads were analyzed using the commercial finite element package ANSYS by considering the contact surfaces between the discs and pads. Direct-contact three-dimensional finite elements between the discs and pads were applied to investigate the disc friction temperature, thermal deformation, and contact stress so that the thermal judder phenomenon on the surface of the disc could be predicted.

• Korea-Australia Rheology Journal
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• 제12권2호
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• pp.119-124
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• 2000

Employing the Phan-Thien tanner (PTT) fluids model, dynamic behavior of the non-isothermal melt spinning has been investigated. Subjects such as draw resonance instability, the effects of spinline cooling and of the fluid viscoelasticity on the spinning dynamics have been studied using the governing equations of the system. In particular, the draw resonance criterion based on the traveling times of various kinematic waves in the spinline has been confirmed, the reason why the spinline cooling is stabilizing is analyzed, and the effect of fluid viscoelasticity on the spinline stability is summarized. It is believed that the same method as in this study can be applied with equal ease to other extension deformation processes like film casting and film blowing.