• 한국음향학회지
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• 제34권5호
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• pp.360-370
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• 2015

무한 길이를 가진 도파관 구조물에 유한 길이를 가진 구조물이 결합되어 있는 경우, 결합된 구조물의 응답을 수치해석으로 구하기 위해서는 파동 방법과 모드 방법을 함께 적용하여 해석하는 것이 필요하다. 본 논문에서는 무한 길이 도파관구조물에 대해서는 파수유한요소법을, 유한 길이 구조물에 대해서는 유한요소법을 적용하여 결합 지점에서의 각 하부 구조물 임피던스 또는 모빌리티를 구하고 이를 연성하여 전체 구조물의 응답을 해석하는 방법에 대하여 다루었다. 해석 대상 구조물로는 내부에 사각 평판 구조물이 네 꼭지점에서 결합되어 있는 무한 길이 원통형 실린더를 선정하였으며, 네 결합지점이 강결합 또는 탄성마운트로 결합된 경우에 대하여 살펴보았다. 본 연구를 통해 임피던스 연성을 통한 파동 방법(파수유한요소법)과 모드 방법(유한요소법)의 결합이 적용 가능함을 확인하였다.

• 한국주조공학회지
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• 제38권6호
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• pp.111-120
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• 2018

In this study, the effects of two different casting methods (gravity casting and, diecasting) and various solid-solution conditions on the mechanical properties of ASC (Al-10.5wt%Si-1.75wt%Cu) and ALDC12 (Al-10.3wt%Si-1.72wt%Cu-0.76wt%Fe-0.28wt% Mn-0.32wt%Mg-0.9wt%Zn) alloys were investigated. A thermodynamic solidification analysis program (PANDAT) was used to predict the liquidus, solidus, and phases of the used alloys. In the results of an XRD analysis, ${\beta}$-AlFeSi peaks were observed only in the ALDC12 alloy regardless of the casting method or SST (solid-solution treatment) conditions. However, according to the results of a FE-SEM observation, both ${\theta}(Al_2Cu)$ and ${\beta}$-AlFeSi were found to exist besides ${\alpha}$-Al and eutectic Si in the gravity-casted ASC alloy at $500^{\circ}C$ after a SST of 120min. The ${\alpha}$-AlFeSi and ${\beta}$-AlFeSi phases including the eutectic phases were also found to exist in the ALDC12 alloy. The results of a microstructural observation and analyses by XRD, FE-SEM and EDS were in good agreement with the PANDAT results. The gravity-casted ALDC12 and ASC specimens showed the highest Y.S. and UTS values after aging for three hours at $180^{\circ}C$ after a SST at $500^{\circ}C$ for 30min. At longer solid-solution treatment times at $500^{\circ}C$ in the gravity-casted ALDC12 and ASC specimens, the elongations of the ASC alloys increased, whereas they decreased slightly in the ALDC12 alloys.

• 한국자기학회지
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• 제13권4호
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• pp.171-175
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• 2003

Czochralski방법으로 성장된 정비조성 LiTaO$_3$ 단결정내에 불순물로 첨가되어 있는 Fe$^{3+}$ 이온에 대하여 상온에서 전자 상자성 공명(EPR : Electron Paramagnetic Resonance) 실험을 실행하였다. X-band(9.447 ㎓) 스펙트로미터를 사용하여 Fe$^{3+}$ 이온에 대한 공명 흡수선을 결정학적 주평면에서 시료를 돌려가면서 자기장을 가하여 각도의존 데이터를 얻었다. 이렇게 얻은 공명 자기장을 유효 스핀하밀토니안을 사용하여 분광학적 분리인자 g 및 영자기장 갈라지기(ZFS: Zero Field Splitting) 상수 b$_{2}$sup 0/ (=D)를 계산하였다. 분석결과 정비조성으로 성장시킨 LiTaO$_3$ 단결정에서 얻은 Fe$^{3+}$ 공명중심은 기존에 발표된 congruent 조성으로 성장시킨 단결정의 것과는 다른 것으로 밝혀졌다. 또한 Fe$^{3+}$ 이온에 관한 온도의존 공명 흡수선을 분석한 결과 실험 온도 구간에서는 LiTaO$_3$ 단결정의 어떠한 상변화도 없는 것으로 나타났다.

• 대한조선학회논문집
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• 제58권5호
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• pp.314-321
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• 2021

In the existing whole ship analysis, topside was modeled as mass element. However recently, the topside is modeled as beam element due to the owner's requirement to improve the maturity of the whole ship FE model. To follow the owner'srequirement, detailed information for topside drawing and modeling, which may delay analysis schedule, is needed. However, it is hard to respond effectively to this matter due to the lack of study on the topside from the hull perspective. Therefore in this study, the effect of the topside on the hull is investigated when the topside is modeled as a mass element or beam element respectively. In addition, the interface modeling method is analyzed to verify modeling method used in the existing whole ship analysis. The results indicate that the interface and topside modeling method used in existing whole ship analysis are appropriate. This conclusion will be the technical basis for responding to owner's requirement about the topside modeling method.

• Journal of Mechanical Science and Technology
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• 제16권11호
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• pp.1359-1366
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• 2002

The measurement of residual stresses by the hole-drilling method has been used to evaluate residual stresses in structural members. In this method, eccentricity can usually occur between the hole center and rosette gage center. In this study, we obtained the magnitude of the error due to eccentricity of a hole through the finite element analysis. To predict the magnitude of the error due to eccentricity of a hole in the biaxial residual stress field, it could be learned through the back propagation neural network. The prediction results of the error using the trained neural network showed good agreement with FE analyzed results.

• 한국해양공학회:학술대회논문집
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• 한국해양공학회 2003년도 추계학술대회 논문집
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• pp.41-46
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• 2003

In this paper, two different methods are developed to be used for the design of noncontact dry gas seal which is used to prevent gas leakage of high speed rotating shaft-housing machineries. First method is using FEA to compute the deformation of seal face and the other is using Influence Coefficient Method in order to save computation of FEA. In both cases, heat load and mechanical loads are applied such as heat generation, bulk temperature and nodal force, bulk pressure, centrifugal force, respectively. ICM method is verified correct and effective and both methods give reliable and useful deformation results for the design of mechanical seals.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2000년도 학술대회 논문집 전문대학교육위원
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• pp.99-103
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• 2000

The finite element method (FEM) is suitable for the analysis of a complicated region that includes nonlinear materials, whereas the boundary element method (BEM) is naturally effective for analyzing a very large region with linear characteristics. Therefore, considering the advantages in both methods, a novel algorithm for the alternate application of the FEM and BEM to magnetic field problems with the open boundary is presented. This approach avoids the disadvantages of the typical numerical methods with the open boundary problem such as a great number of unknown values for the FEM and non-symmetric matrix for the Hybrid FE-BE method. The solution of the overall problems is obtained by iterative calculations accompanied with the new acceleration method.

• 대한기계학회논문집A
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• 제24권9호
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• pp.2292-2301
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• 2000

We propose an accurate and efficient estimation method of transverse shear stresses for analysis and design of laminated composite structures by 4-node quadrilateral degenerated shell elements. To get proper distributions of transverse shear stresses in each layer, we use 3-dimensional equilibrium equations instead of constitutive equations with shear correction factors which vary diversely according to the shapes of shell sections. Three dimensional equilibrium equations are integrated through the thickness direction with complete polynomial membrane stress fields, which are recovered by REP (Recovery by Equilibrium in Patches) recovery method. The 4-node quadrilateral degenerated shell element used in this paper has drilling degrees of freedom and shear stresses derived from assumed strain fields that are set up at natural coordinate systems. The numerical results demonstrate that the proposed estimation method attains reasonable accuracy and efficiency compared with other methods and FE analysis using 4-node degenerated shell elements.

• 한국철도학회:학술대회논문집
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• 한국철도학회 2008년도 추계학술대회 논문집
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• pp.1697-1702
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• 2008

The objective of the review is to introduce the evaluation method of welding joint designs by using forces extracted from FE models. This evaluation method is currently being used for the Southeastern Pennsylvania Transportation Authority (SEPTA) project in the United States by request of the customer Engineer. The evaluation method was applied to critical joints connected by Fillet or Partial Joint Penetration (PJP) welds in car body structure for SEPTA project. The additional manual analysis is required based on the fact that Technical Specification in the United States requires the Contractor to apply Complete Joint Penetration (CJP) welds to all structural connections in Car body. However, in the car body design for Septa project there are some areas where CJP welds are not applied due to structural and manufacturing problems.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2007년도 학술대회 논문집 전문대학교육위원
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• pp.183-186
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• 2007

Realistic deformation of computer simulated anatomical structures is computationally intensive. As a result, simple methodologies not based in continuum mechanics have been employed for achieving real time deformation of virtual reality. Since the graphical interpolations and simple spring models commonly used in these simulations are not based on the biomechanical properties of tissue structures, these "quick and dirty"methods typically do not accurately represent the complex deformations and force-feedback interactions that can take place during surgery. Finite Element(FE) analysis is widely regarded as the most appropriate alternative to these methods. However, because of the highly computational nature of the FE method, its direct application to real time force feedback and visualization of tissue deformation has not been practical for most simulations. If the mathematics are optimized through pre-processing to yield only the information essential to the simulation task run-time computation requirements can be drastically reduced. To apply the FEM, We examined a various in verse matrix method and a deformed material model is produced and then the graphic deformation with this model is able to force. As our simulation program is reduced by the real-time calculation and simplification because the purpose of this system is to transact in the real time.