• 한국융합학회논문지
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• 제4권2호
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• pp.21-27
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• 2013

점용접은 자동차 산업에서 많이 사용되어지는데 조립공정의 자동화로 인하여 경제성과 차체 중량을 높이지 않아 자동차 연비 개선효과가 있다. 그러나 차량 주행시 노면으로부터 불규칙적인 하중전달 및 진동으로 인하여 점 용접부에 응력집중이 발생하고 피로파괴가 종종 발생한다. 이에 대하여 강성변화를 고려한 점용접부의 피로수명 평가는 필수적이다. 본 논문에서는 선형정적해석을 수행하여 취약부위를 파악하였다. 점용접부의 피로특성을 획득하였고, 시간영역에서 3단계의 하중이력을 도출하여, 준정적 피로해석에 조건으로 설정하여 수행하였다. 또한 점용접부에 대한 피로수명예측 방법은 기존 방법과 피로누적으로 인한 손상방법을 적용하여 나타낸 결과를 가지고 비교분석하였다.

• Nuclear Engineering and Technology
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• 제50권6호
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• pp.971-980
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• 2018

Using the concept of quasi-static decomposition and using three-noded isoparametric locking-free element, this article presents a formulation of the finite element method for Timoshenko beam subjected to spatially different time-dependent motions at supports. To verify the validity of the formulation, three fixed-hinged beams excited by the real seismic motions are examined; one is a slender beam, another is a stocky one, and the other is an intermediate one. The numerical results of time histories of motions of the three beams are compared with corresponding analytical solutions. The internal loads such as bending moment and shearing force at a specific time are also compared with analytic solutions. These comparisons show good agreements. The comparisons between static components of the internal loads and the corresponding total internal loads show that the static components predominate in the stocky beam, whereas the dynamic components predominate in the slender one. Thus, the total internal loads of the stocky beam, which is governed by static components, can be predicted simply by static analysis. Careful numerical experiments indicate that the fundamental frequency of a beam can be used as a parameter identifying such a stocky beam.

• Structural Engineering and Mechanics
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• 제81권4호
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• pp.411-428
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• 2022

This paper presents the Campbell diagram analysis of the rotordynamic system using the full order model (FOM) and the reduced order model (ROM) techniques to determine the critical speeds, identify the stability and reduce the computational time. Due to the spin-speed-dependent matrices (e.g., centrifugal stiffening matrix), several model order reduction (MOR) techniques may be considered, such as the modal superposition (MS) method and the Krylov subspace-based MOR techniques (e.g., Ritz vector (RV), quasi-static Ritz vector (QSRV), multifrequency quasi-static Ritz vector (MQSRV), multifrequency/ multi-spin-speed quasi-static Ritz vector (MMQSRV) and the combined Ritz vector & modal superposition (RV+MS) methods). The proposed MMQSRV method in this study is extended from the MQSRV method by incorporating the rotational-speed-dependent stiffness matrices into the Krylov subspace during the MOR process. Thus, the objective of this note is to respond to the question of whether to use the MS method or the Krylov subspace-based MOR technique in establishing the Campbell diagram of the shaft-disc-blade assembly systems in three-dimensional (3D) finite element analysis (FEA). The Campbell diagrams produced by the FOM and various MOR methods are presented and discussed thoroughly by computing the norm of relative errors (ER). It is found that the RV and the MS methods are dominant at low and high rotating speeds, respectively. More precisely, as the spinning velocity becomes large, the calculated ER produced by the RV method is significantly increased; in contrast, the ER produced by the MS method is smaller and more consistent. From a computational point of view, the MORs have substantially reduced the time computing considerably compared to the FOM. Additionally, the verification of the 3D FE rotordynamic model is also provided and found to be in close agreement with the existing solutions.

• 한국자동차공학회논문집
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• 제4권2호
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• pp.183-188
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• 1996

The compressive stress-strain response of Low Density Polyurethane foam material is modeled using the finite element method. A constitutive equation which include experimental constants based on quasi-static and dynamic uniaxial compression test is proposed. Impact test with different impactor masses and velocities are performed to verify the proposed model. The comparison between impact test and finite element analysis shows good agreements.

• 전산구조공학
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• 제7권3호
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• pp.167-176
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• 1994

균열전파 현상은 항상 형상이 변화하는 대표적인 문제중의 하나이다. 본 연구는 준-정적 균열전파 현상을 해석하기 위하여 들로네이 특성을 이용한 국지 요소재편 알고리즘을 제시하였다. 이 알고리즘은 요소 재편성과 세분화를 모두 수행할 수 있도록 준비되었다. 적용예로 M 적분법을 사용하여 주로 혼합 모우드로 균열이 전파되는 스폴링 현상을 해석하였다.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2003년도 춘계학술대회논문집
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• pp.336-341
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• 2003

In this paper, resonance durability analysis technique is presented for the fatigue life assessment considering dynamic effect of a vehicle system. In the resonance durability analysis, the frequency response and the dynamic load on frequency domain are used. Multi-body dynamic analysis, finite element analysis, and fatigue life prediction method are applied for the virtual durability assessment. To obtain the frequency response and the dynamic load, the computer simulations running over typical pothole and Belgian road are carried out by utilizing vehicle dynamic model. The durability estimations on the rear suspension system of the passenger car are performed by using the presented technique and compared with the quasi-static durability analysis. The study shows that the fatigue life considering resonant frequency of vehicle system can be effectively estimated in early design stage.

• 한국공작기계학회:학술대회논문집
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• 한국공작기계학회 1998년도 추계학술대회 논문집
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• pp.204-209
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• 1998

The acceleration of the performance of machine tools influences the development of the semi-conductor and optical technology as the development of NC and measurement technology. We can mention that a traction role of the acceleration for the development like that depends on the development of the measurement technics Stylus instrument method, STM, SEM, Laser interferometer method which are used for measuring the quasi-static error of machine tools. Because the measurement has been done to unload condition without considering of mechanical stiffness in the case of machining center as we measure the quasi-static error of machine tools on general studies, people who works on the spot has many problems on the data value. Therefor we will help working more accurately on the spot by measuring, analyzing, displaying the deflection of the table and support shaft when we load on the table and the support shaft of machining center using laser interferometer. Also we try to settle new conception of the measurement method and more accurate grasp of the deflection tendency by verifing the tendency of the error measured through the comparison of the simulated error using ANSYS, a common finite element analysis program, which is able to measure heat deformation, material deformation, and error resulted form this study.

• 한국자동차공학회논문집
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• 제12권1호
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• pp.106-113
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• 2004

Most of mechanical structures are composed of many substructures connected to one another by various types of mechanical joints. In automotive engineering, it is important to study these connected structures under various dynamic forces for the evaluations of fatigue life and stress concentration exactly. In this study, the dynamic response of vehicle structure to external forces is classified an inverse problem involving strains from the experiment and the analysis. The practical dynamic forces are determined by the combination of the analytical and experimental method with analyzed strain by quasi-static finite element analysis under unit force and with measured strain by a strain gage under driving load, respectively. In a stressed body, inter-molecular chemical bonds are failed beyond the certain magnitude. The failure of molecular structure in material is considered as a time process of which rate is determined by mechanical stress. That is, the failure of inter-molecular chemical bonds is the fatigue lift of material. This kinetic concept is expressed as lethargy coefficient. And S-N curve is obtained with the lethargy coefficient from quasi-static tensile test. Equivalent practical dynamic force is obtained from the identification of practical dynamic force for one loading point. Using the practical dynamic force and S-N curve, fatigue life of a window pillar is analyzed with FEM under the identified force by the procedure of above mentioned.

• Smart Structures and Systems
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• 제4권2호
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• pp.247-259
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• 2008

The potential use of Cu-based shape memory alloys (SMA) in retrofitting historical monuments is investigated in this paper. This study is part of the ongoing work conducted in Tunisia within the framework of the FP6 European Union project (WIND-CHIME) on the use of appropriate modern seismic protective systems in the conservation of Mediterranean historical buildings in earthquake-prone areas. The present investigation consists of a finite element simulation, as a preliminary to an experimental study where a cantilever masonry wall, representing a part of a historical monument, is subjected to monotonic and quasi-static cyclic loadings around a horizontal axis at the base level. The wall was retrofitted with an array of copper SMA wires with different cross-sectional areas. A new model is proposed for heat-treated copper SMAs and is validated based on published experimental results. A series of nonlinear finite element analyses are then performed on the wall for the purpose of assessing the SMA device retrofitting capabilities. Simulation results show an improvement of the wall response for the case of monotonic and quasi-static cyclic loadings.

• 한국전산구조공학회논문집
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• 제31권2호
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• pp.105-114
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• 2018

본 연구에서 페리다이나믹 이론 모델을 이용하여 준정적하중과 동적 하중, 균열전파와 분기균열 패턴 그리고 등방성재료, 직교 이방성 재료의 균열 진전 해석 등 다양한 조건을 고려한 전산 시뮬레이션을 수행하여 그 적합성을 검토하였다. 초기 균열은 없지만 중심에 홀이 있는 등방성 재료, 초기 균열이 존재하는 등방성 및 이방성 재료에 대한 전산 시뮬레이션이 수행되었다. 조정 동적 완화 기법이 사용되어 준정적 하중을 모사하였고, 이방성 재료 해석에서는 고전 연속체 역학과 페리다이나믹의 변형률 에너지를 고려한 균질화 방법이 사용되었다. 균열 전파와 분기 균열이 성공적으로 확인되었으며 파괴 거동의 시작과 그 방향 역시 페리다이나믹 이론으로 확인되었다. 페리다이나믹을 균질화 방법을 사용하여 비교적 복잡한 이방성 재료에 적용한 경우 역시 실험 결과 값과 비교하여 검증하였다.