• 대한기계학회논문집A
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• 제41권6호
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• pp.499-505
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• 2017

본 연구에서는 선형탄성 유한요소해석 방법과 $m_{\alpha}-tangent$ 방법으로 한계하중을 계산하고 이를 기존의 연구들에 의해 제시된 한계하중 식들과 비교하였다. 해석의 대상은 배관계의 대표 형상인 곡관과분기관을 선정하였다. 곡관과 분기관의 형상 변수를 다양하게 바꿔가면서 $m_{\alpha}-tangent$ 방법의 적용가능성을 살펴보았다. 하중은 내압하중과 면내굽힘하중을 각각 고려하였으며 곡관의 경우에는 기존의 한계하중식과 $m_{\alpha}-tangent$방법이 비교적 잘 일치함을 확인하였다. 하지만 분기관의 경우 형상의 특수성으로 인해 뚜렷한 경향 없이 기존의 한계하중 식과 $m_{\alpha}-tangent$ 방법이 일치하지 않는 것을 확인할 수 있었다. 이는 $m_{\alpha}-tangent$ 방법이 불연속부의 응력집중현상에 의해 왜곡된 결과를 갖기 때문으로 보인다.

• 한국항해항만학회지
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• 제35권3호
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• pp.265-270
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• 2011

본 연구는 건물에너지 효율 향상을 위한 목적으로 기상데이터 변화에 따른 건물 냉 난방부하량을 예측하고 결과를 비교 분석한 것으로, 연구 성과는 다음과 같다. 1)기상청에서 입수데이터를 평가툴인 ESP-r에 활용할 수 있도록 항목별 기상데이터를 개발하였다. 표준기상 데이터의 외기온도, 습도, 풍속은 대부분의 경우 기상청데이터 보다 크거나 높았다. 수평면전일사량은 기상청데이터가 높았고, 직달일사량은 겨울철에는 표준기상데이터가, 여름철에는 기상청데이터가 많은 것으로 나타났다. 2)대학교 캠퍼스 내에 신축된 후생복지관을 대상으로 한 시뮬레이션 결과, 최대난방부하의 경우 표준년도, 2006년, 2009년이 비슷한 반면 2007년은 표준년도 대비 81%, 2008년은 96% 수준이었고, 연간난방부하는 2006년, 2008년의 순으로 난방수요가 많았다. 한편, 냉방부하의 경우에는, 상대적으로 최대냉방부하가 큰 2007년, 2009년의 연간 냉방부하보다 최대냉방부하가 가장 적은 2008년의 연간냉방부하가 더 큰 결과를 보였다. 3)냉 난방기기의 상당시간가동률을 평가한 결과, 표준년도의 최대부하대비 상당시간가동률은 2006~2009년이 표준년도에 비해 대부분 가동률이 낮았다.

• Steel and Composite Structures
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• 제52권3호
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• pp.343-356
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• 2024

This paper presents an analytical solution for correctly predicting the Lateral-Torsional Buckling critical moment of simply supported castellated beams, the solution covers uniformly distributed loads combined with compressive loads. For this purpose, the castellated beam section with hexagonal-type perforation is treated as an arrangement of double "T" sections, composed of an upper T section and a lower T section. The castellated beam with regular openings is considered as a periodic repeating structure of unit cells. According to the kinematic model, the energy principle is applied in the context of geometric nonlinearity and the linear elastic behavior of materials. The differential equilibrium equations are established using Galerkin's method and the tangential stiffness matrix is calculated to determine the critical lateral torsional buckling loads. A Finite Element simulation using ABAQUS software is performed to verify the accuracy of the suggested analytical solution, each castellated beam is modelled with appropriate sizes meshes by thin shell elements S8R, the chosen element has 8 nodes and six degrees of freedom per node, including five integration points through the thickness, the Lanczos eigen-solver of ABAQUS was used to conduct elastic buckling analysis. It has been demonstrated that the proposed analytical solution results are in good agreement with those of the finite element method. A parametric study involving geometric and mechanical parameters is carried out, the intensity of the compressive load is also included. In comparison with the linear solution, it has been found that the linear stability underestimates the lateral buckling resistance. It has been confirmed that when high axial loads are applied, an impressive reduction in critical loads has been observed. It can be concluded that the obtained analytical solution is efficient and simple, and offers a rapid and direct method for estimating the lateral torsional buckling critical moment of simply supported castellated beams.

• Journal of Mechanical Science and Technology
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• 제20권4호
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• pp.513-521
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• 2006

The performances of porous bearings under different operating conditions were experimentally investigated in this study. Material groups studied are 90%Cu + 10%Sn bronze and 1%C + % balance Fe iron-based self-lubricating P/M bearings at constant (85%) density. In the experiments, the variation of the coefficient of friction and wear ratio of those two different group materials for different sliding speeds, loads, and temperatures were investigated. As a result, the variation of the friction coefficient-temperature for both constant load, and constant sliding speed, friction coefficient-average bearing pressure, PV-wear loss and temperature-wear loss curves were plotted and compared with each other for two materials, separately. The test results showed that Cu-based bearings have better friction and wear properties than Fe-based bearings.

• Structural Engineering and Mechanics
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• 제50권4호
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• pp.441-457
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• 2014

This paper presents a finite element based numerical model to solve two dimensional bi-material problems. A bi-material beam consisting of two phase materials ceramic and metal is modelled by finite element method. The beam is subjected simultaneously to mechanical and thermal loadings. The main objective of this study is the analysis of crack deviation located in the brittle material near the interface. The effect of temperature gradient, the residual stresses and applied loads on crack initiation, propagation and deviation are examined and highlighted.

• 대한기계학회논문집A
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• 제26권7호
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• pp.1302-1308
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• 2002

Thermo-mechanical and flexural behavior of a wire-bond plastic ball grid array (WB-PBGA) package are characterized by high sensitive moire interferometry. Moire fringe patterns are recorded and analyzed for several bending loads and temperatures. At the temperature higher than $100^{\circ}C$, the inelastic deformation in solder balls become more dominant, so that the bending of the molding compound decreases while temperature increases. The deformation caused by thermally induced bending is compared with that caused by mechanical bending. The strain results show that the solder ball located at the edge of the chip has largest shear strain by the thermal load while the maximum average shear strain by the bending moment occurs in the end solder.

• 전력전자학회:학술대회논문집
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• 전력전자학회 2006년도 전력전자학술대회 논문집
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• pp.107-109
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• 2006

The purpose of this paper is to introduce the new products for replacing on the old technical cooperation products which have 24 kinds of industrial inverter model. The core algorithm for vector control and sensorless control and the operation program for LCD operator have been developed. Through the continuous test, the improvement of speed/torque control performance and the control program for special target loads will be performed.

• Journal of the Korean Wood Science and Technology
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• 제44권4호
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• pp.505-514
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• 2016

To study mechanical properties of fiberglass reinforced wood-based composite (FRWC), fiberglass with a diameter of $20{\mu}m$ was selected to prepare test specimens. Mechanical properties of fiberglass reinforced wood-based composite were determined by three-point-bending test while its microstructure was characterizes by scanning electron microscopy (SEM). The results showed that mechanical properties of fiberglass reinforced wood-based composite were superior to that of the wood fiberboard based on the contrasting mechanical curves and the analysis of fracture mechanism. It is believed that the material design with this "sandwich" structure brings a unique buffering capacity of fiberglass into play in the composites. So the specimen did not produce a sudden fracture failure at high level of applied loads because it had a bearing ability. The SEM analysis showed that the working strength of PVAc adhesive was high; under a bearing force, it could properly transfer a load. In addition, glass fiber mesh and wood fiber board combined well.

• Nuclear Engineering and Technology
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• 제46권5호
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• pp.689-698
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• 2014

Reactor internals are sensitive to dynamic loads such as earthquakes and flow induced vibration. Thus, it is essential to identify the dynamic characteristics to evaluate the seismic integrity of the structures. However, a full-sized system is too large to perform modal experiments, making it difficult to extract data on its modal characteristics. In this research, we constructed a finite element model of the APR1400 reactor internals to identify their modal characteristics. The commercial reactor was selected to reflect the actual boundary conditions. Our FE model was constructed based on scale-similarity analysis and fluid-structure interaction investigations using a fabricated scaled-down model.

• 대한기계학회논문집A
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• 제39권5호
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• pp.453-460
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• 2015

후쿠시마 원전 사고 이후로 원자력 발전 플랜트의 배관 시스템에 가해지는 비틀림 하중의 영향에 대한 연구가 여러 연구자들에 의해서 수행되었다. 발전 플랜트의 원주방향 균열을 포함한 배관은 정상운전 조건이나 갑자기 발생한 사고에 의해서 굽힘과 비틀림과 같은 하중을 받을 수 있다. ASME 코드에서는 균열 배관의 구조건전성 확보를 위해서 한계하중 기법을 사용해서 완전소성 파단에 대한 결함평가를 제공한다. 최근 개정된 코드에 따르면, 복합하중은 막응력과 굽힘 응력만을 포함하고 있다. 실제로 운전 환경에서 비틀림 하중이 가해질 수 있음에도 불구하고, 비틀림 하중을 평가하는 방법론에 대해서는 언급하지 않았다. 본 논문에서는 한계하중 분석을 기반으로 원주방향 균열 존재하는 배관에 단순 굽힘과 단순 비틀림, 인장을 포함한 굽힘 비틀림 복합하중이 가해질 경우에 대한 유한요소해석 결과를 포함하고 있다. 전단면 완전항복 기준을 만족하는 한계하중 이론해를 제안하고 유한요소해석을 통해서 이를 검증하였다.