• 대한수학회지
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• 제37권2호
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• pp.193-223
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• 2000

In the late 1970's, M. Kuranishi proposed to control the moduli of the germ of a normal Stein space by deformations of the CR structure on the boundary. I this paper, we will see that it is naturally accomplished by considering stably embeddable deformations of CR structures.

• Structural Engineering and Mechanics
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• 제60권3호
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• pp.507-527
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• 2016

The use of shape memory alloys (SMAs) has been seriously considered in seismic engineering due to their capabilities, such as the ability to tolerate cyclic deformations and dissipate energy. Five 3-D extended end-plate connection models have been created, including one conventional connection and four connections with Nitinol bolts of four different prestress forces. Their cyclic behaviors have been investigated using the finite element method software ANSYS. Subsequently, the moment-rotation responses of the connections have been derived by subjecting them to cyclic loading based on SAC protocol. The results obtained in this research indicate that the conventional connections show residual deformations despite their high ductility and very good energy dissipation; therefore, they cannot be repaired after loading. However, while having good energy dissipation and high ductility, the connections equipped with Nitinol bolts have good recentering capability. Moreover, a connection with the mentioned specifications has been modeled, except that only the external bolts replaced with SMA bolts and assessed for seismic loading. The suggested connection shows high ductility, medium energy dissipation and very good recentering. The main objective of this research is to concentrate the deformations caused by cyclic loading on the connection in order to form super-elastic hinge in the connection by the deformations of the shape memory alloy bolts.

• 한국공작기계학회논문집
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• 제11권4호
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• pp.12-18
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• 2002

Silicon on insulator(SOI) wafer is used in a variety of microsensor applications in which thermal deformations and other mechanical effects may dominate device Performance. One of major Problems associated with the manufacturing Processes of the microaccelerometer based on the tunneling current concept is thermal deformations and thermal stresses. This paper deals with finite element analysis(FEA) of residual thermal deformations causing popping up, which are induced in micrormaching processes of a microaccelerometer. The reason for this Popping up phenomenon in manufacturing processes of microaccelerometer may be the bending of the whole wafer or it may come from the way the underetching occurs. We want to seek after the real cause of this popping up phenomenon and diminish this by changing manufacturing processes of mic개accelerometer. In microaccelerometer manufacturing process, this paper intend to find thermal deformation change of the temperature distribution by tunnel gap and additional beams. The thermal behaviors analysis intend to use ANSYS V5.5.3.

• 해양환경안전학회지
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• 제21권2호
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• pp.194-199
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• 2015

본 연구에서는 도그 피스 설치량에 따른 용접 변형 실험을 수행하여 용접 변형 감소 효과를 정량적으로 평가하였고, 도그 피스 설치를 고려한 용접 변형 해석 방법을 제안하였다. 용접 변형 실험 결과, 도그 피스 설치량이 증가할수록 용접 변형이 감소하며 최대 74%의 변형 감소 효과가 있음을 확인하였다. 원판형 열속 모델을 사용한 열탄소성 유한요소 해석을 활용하여 도그 피스 설치를 고려한 용접 변형 해석 방법을 제안하고, 해석 결과와 실험 결과가 좋은 유사성을 보이고 있음을 확인하였다. 본 해석 방법은 현행 도그 피스 설치량에 대한 적정 여부를 평가하거나 도그 피스 사용량을 절감할 수 있는 설치 가이드를 마련하기 위한 해석적 툴로 활용될 수 있다.

• 대한조선학회논문집
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• 제36권3호
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• pp.122-133
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• 1999

완성되어진 블록을 이용한 탑재의 과정에서 발생하는 블록 경계간의 판재 겹쳐짐 현상, 과도한 간격 및 단차의 발생현상은 선박의 건조비용과 공수를 증가시키는 요인이 된다. 본 논문에서는 블록의 조립 및 탑재에 관한 시뮬레이션 시스템을 제안하고 이중 조립에 관한 시뮬레이션을 용접순서에 따라 용접변형 및 자중을 고려하여 유한요소해석을 ANSYS를 이용하여 수행하였다. 용접에 의한 변형은 실험에 의한 변형량을 이용한 등가강성에 따른 등가 하중을 사용하여 탄성적인 해석법을 수행하여 예측하였으며 선체 이중저 평블록을 패널 조립법에 근거한 조립순서에 따라 시뮬레이션을 수행하였다. 시뮬레이션을 통한 변형으로부터 조립순서에 따른 중간 제품의 형상의 변화에 의한 강성의 변화에 기인한 변형량의 차이를 확인 할 수 있었으며, 자중의 효과를 반드시 고려하여야 함을 확인 할 수 있었다.

• Interaction and multiscale mechanics
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• 제2권4호
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• pp.375-396
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• 2009

In the present work, the elasto-viscoplastic behavior, interactions between grains, and the texture evolution in polycrystalline materials subjected to finite deformations are modeled using a multiscale analysis procedure within a finite element framework. Computational homogenization is used to relate the grain (meso) scale to the macroscale. Specifically, a polycrystal is modeled by a material representative volume element (RVE) consisting of an aggregate of grains, and a periodic distribution of such unit cells is considered to describe material behavior locally on the macroscale. The elastic behavior is defined by a hyperelastic potential, and the viscoplastic response is modeled by a simple power law complemented by a work hardening equation. The finite element framework is based on a Lagrangian formulation, where a kinematic split of the deformation gradient into volume preserving and volumetric parts together with a three-field form of the Hu-Washizu variational principle is adopted to create a stable finite element method. Examples involving simple deformations of an aluminum alloy are modeled to predict inhomogeneous fields on the grain scale, and the macroscopic effective stress-strain curve and texture evolution are compared to those obtained using both upper and lower bound models.

• 한국정밀공학회지
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• 제16권8호
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• pp.138-148
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• 1999

Thermal deformations of tension mask under localized heating are analyzed using finite element method and electron beam landing shifts are predicted by the analysis results. In CRT, electron beam landing shifts due to thermal deformations of the tension mask make the color purity of screen worse. In order to get the final results of thermal deformations, firstly the tension processes of the mask and following welding processes between the tensional mask and rail must be analyzed sequentially. And then, nonlinear transient thermo-elastic finite element analysis is performed on every part inside CRT including tension mask, wherein thermal radiation is a main heat transfer mechanism. Because the tension mask has numerous slits, the effective thermal conductivity and effective and effective elastic modulus is calculated, and the tension mask is modeled as a shell without slits. From the displacement results of tension mask, electron beam landing shifts is calculated directly. Experiments are performed to confirm our analysis results. Temperature distributions and beam landing shifts of tension mask are measured and the results are in good agreement with those of analyses.

• 건축역사연구
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• 제4권1호
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• pp.9-28
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• 1995

How have they preserved the regional historic buildings in Korea? Do they preserve the original value as a historic building. Are there any artificial deformations deteriorating the quality of the buildings? Is the regional system for preservation effective agalnst the artificial deformations of the buildings? These questions are involved in the purposes of this paper. I investigated the historic buildings designated by Kyong-Nam provincial government. As the resuit, variouse patterns of artificial deformation were found. I found that the deformations may deteriorate the original quality of historic building, and it is related somehow to the limitations of regional system for preservation. So I suggest some alternative ideas for preserving the quality of historic buildings against artificial deformation : a. Present system for preservation is not effective for preserving various architectural value such as urban context and landscape, site planning techniques, function of a space, etc. Regional system should be revised for preserving their architectural value or meaning. b. Historic buildings should be classified and should have proper protecting area according to each architectural values or meanings, respectibly: Historic buildings with Urban context and landscape Historic buildings as a part of a complex Historic buildings as a behavorial setting. c. Historic buildings should be graded based on their quality. And standard and criteria for acceptable deformations should be established. d. Periodical inspections by experts should be carried out to check out the deformation.

• 한국해양공학회지
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• 제20권4호
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• pp.24-30
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• 2006

Different methods exist for the estimation of thermaldeformation of plates in the line heating process. These are based on the assumption of residual strains in the heat-affected zone, known as the method of inherent strains, or simulated relations between heating conditions and residual deformations. The purpose of this paper is to develop a simulator of thermal deformation in the line heating, using the artificial neural network. Curvature deformations for the plate-forming are investigated, which can be used as a prime deformation parameter in the process. The curvature of plates are calculated using the approximation of plate surface by NURBS. Line heating experiments for 11 specimens of different thickness and heating conditions were performed. Two neural networks predicting the maximum temperature and curvature deformations at the heating line are studied. It was concluded that the thermal deformations predicted by the neural network can be used in a line heating simulator, which is considered an attractive and practical alternative to the existing methods.

• 비파괴검사학회지
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• 제31권5호
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• pp.543-551
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• 2011

Steam generator tubes for nuclear power plants contain the local shape transitions on their inner or outer surface such as dent, bulge, over-expansion, eccentricity, deflection, and so on by the application of physical force during the tube manufacturing and steam generator assembling and by the sludge (that is, corrosion products) produced during the plant operation. The structural integrity of tubes will be degraded by generating the corrosive crack at that location. The profilometry using the traditional bobbin probes which are currently applied for measuring the profile change of tubes gives us basic information such as axial locations and average magnitudes of deformations. However, the three-dimensional quantitative evaluation on circumferential locations, distributional angle, and size of deformations will have to be conducted to understand the effects of residual stresses increased by local deformations on corrosive cracking of tubes. Steam generator tubes of Korean standard nuclear power plants expanded within their tube-sheets by the explosive expansion method and suffered from corrosive cracks in the early stage of power operation. Thus, local deformations of steam generator tubes at the top of tube-sheet were measured with an advanced rotating probe and a laser profiling system for the two cases where the tubes expanded by the explosive expansion method and hydraulic expansion. Also, the trends of eccentricity, deflection, and over-expansion of tubes were evaluated. The advanced eddy current profilometry was confirmed to provide accurate information of local deformations compared with laser profilometry.