• 콘크리트학회지
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• 제2권1호
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• pp.79-90
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• 1990

철근 콘크리트 보의 인장철근이 합리적인 위치에서 체단(Cutoff)되지 않으며, 응력집중 및 부재의 극한강도가 저하되는 등의 문제가 발생될 수 있다. 따라서, 본 연구에서는 이러한 상황에 부합되는 실제건물을 대상으로 실물크기(Full Scale) 및 모형 실험을 함으로써 체단점에서 발생되는 파괴양상과 휨 강도, 실물, 시험체와 모형 시험체의 파괴 진전 상황등을 비교\ulcorner분석하고, 동시에 유한요소법에 의한 해석을 통하여 인장응력 분포 상태등을 검토함으로써 보 설계시 인장철근의 체단등에 관한 기토자료를 제공하고자 하였다. 실험 및 해석의 결과로부터, 체단부가 지점쪽으로 멀리 있을수록 최대내력의 감소는 물론 인장응력의 집중현상등이 나타나고 있는 바, 보부재의 설계시 인장철의 체단보에 대해서는 세심한 주의가 필여하리라 사료된다.

• Journal of Advanced Marine Engineering and Technology
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• 제21권3호
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• pp.246-255
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• 1997

The wave washer springs are expected to behave non-linearly between forces and displace¬ments due to contractions of the height and due to expansions in radial direction. To find out the non -linearity of wave washer springs, the three dimensional plate analysis theory using the finite element method is adopted in this paper. The wave washer springs are considered to be three dimensional plate structures rather than frame structures, because their thickness is normally much smaller than their width. The displacements of nodal points due to small increment of force are calculated by the finite element method and the calculated nodal displacements are added to X - Y Z coordinates of nodal points. The new stiffness matrix of the system using the new coordinates of nodal points is adopted to calculate the another nodal displacements, that is, the step by step method is used in this paper. The relations between the increments of forces and displacements in each step are recorded and plotted in chart. The experimental results are compared with the calculated chart and it is shown that there are good coincidences between measured values and calculated ones.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2002년도 학술대회지
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• pp.517-520
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• 2002

Stereoscopic particle image velocimetry is a measurement technique to acquire of three dimensional velocity field by two cameras. With a laser sheet illumination, the third velocity component can be deduced by out-of-plane velocity components using a stereoscopic matching method. Industrial fluid flows are almost three dimensional turbulent flows, so it is necessary to use the stereoscopic PIV measurement method. However the existing stereoscopic PIV system seems hard to use since it is very expensive and complex. In this study we have developed a Stereoscopic Miniature PIV(MPIV) system based on the concept of the Miniature PIV system which we have already developed. In this paper, we address the design and some first experimental results of the stereoscopic PIV system. The Stereoscopic MPIV system features relatively modest performances, but is considerably smaller, cheaper and easy to handle. The proposed Stereoscopic MPIV system uses two one-chip-only CMOS cameras with digital output. Only two other chips are needed, one for a buffer memory and one for an interfacing logic that controls the system. Images are transferred to a personal computer (PC) via its standard parallel port. No extra hardware is required (in particular, no frame grabber board is needed).

• 대한기계학회:학술대회논문집
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• 대한기계학회 2002년도 학술대회지
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• pp.631-634
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• 2002

The study of the flow characteristics in two types of turbo-fans for a vacuum cleaner was performed in a previous study. In present study an analysis of a new modified model to reduce fan noise was performed by using CFD. The characteristics of three models calculated for various rotating speeds and flow rates are obtained and compared with available measured data. The results show that the modified model gives stable flow characteristics in operating range than the original model, while both models show similar performance characteristics at the range of high flow rate. Since in the modified model it takes much longer for an impeller blade to pass a diffuser blade than in the original model, and thus the peak pressure at BPF can be relieved, it is anticipated that the modified model gives much lower noise level with similar performance than the original one, which remains to be verified by unsteady computation and measurements.

• 수산해양기술연구
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• 제28권1호
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• pp.61-70
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• 1992

In this study, corrosion fatigue test of SAPH45 steel was performed by the use of plane bending fatigue tester in marine environment and investigated fracture surface growth behavior of base metal and heat affected zone corrosion fatigue. The main results obtained are as follows: 1) Fracture surface growth of heat affected zone (HAZ) is delayed more than that of base matel (BM), and they tend to faster in seawater than in air. 2) Corrosion sensitivity to corrosion fatigue life of HAZ is more susceptible than that of BM. 3)In the case of the corner crack by corrosion fatigue, the correlation between the propagation rate of fracture surface area(dA/dN) and stress intensity factor range(ΔK) for SAPH45 are applied to Paris rule as follows: dA/dN=C(ΔK) super(m) where m is the slope of the correlation, and is about 6.60-6.95 in air and about 6.33-6.41 in seawater respectively.

• 한국마린엔지니어링학회:학술대회논문집
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• 한국마린엔지니어링학회 2001년도 추계학술대회 논문집(Proceeding of the KOSME 2001 Autumn Annual Meeting)
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• pp.21-27
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• 2001

Springs are widely utilized in machine element. To find out stiffness of frustum-shaped coil spring, the space beam theory using the finite element method is adopted in this paper In three dimensional space, a space frame element is a straight bar of uniform cross section which is capable of resisting axial forces, bending moments about two principal axes in the plane of its cross section and twisting moment about its centroidal axis. The corresponding displacement degrees of freedom are twelve. To find out load vector of coil spring subjected to distributed compression, principle of virtual work is adapted The displacements of nodal points due to small increment of force are calculated by the finite element method and the calculated nodal displacements are added to coordinates of nodal points. The new stiffness matrix of the system using the new coordinates of nodal points is adopted to calculate the another increments of nodal displacements, that is, the step by step method is used in this paper. The results of the finite element method are fairly well agreed with those of various experiments. Using MATLAB program developed in this paper, spring constants and stresses can be predicted by input of few factors.

• 한국터널지하공간학회 논문집
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• 제5권1호
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• pp.43-54
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• 2003

현재 복개 터널구조물의 해석 및 설계에는 구조공학적 모델링 기법이 널리 적용되고 있으나, 이러한 구조공학적 모델링 기법은 지형적인 영향인자 및 soil arching 등과 같은 지반공학적 측면의 영향인자를 고려하기에 많은 어려움이 있다. 따라서, 본 연구에서는 복개 터널구조물의 합리적이고 경제적인 설계를 위하여 복개 터널구조물의 거동에 영향을 미치는 인자로써 콘크리트 라이닝과 성토체의 계면요소, 굴착사면의 경사, 이격거리 및 성토사면 등을 고려하여 지반공학적 모델링 기법을 이용한 수치해석 수행하였다. 이의 결과를 토대로 각 영향인자 변화에 따른 복개 터널구조물의 역학적 거동특성을 분석하였다.

• 대한기계학회논문집B
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• 제25권5호
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• pp.611-618
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• 2001

The flow characteristics of a turbulent buoyant jet were experimentally investigated using a single-frame PIV system. The Reynolds number based on the nozzle exit velocity and nozzle diameter was about Re=5$\times$10$^3$. The instantaneous velocity fields in the streamwise plane passing the jet axis were measured in the near field X/D <11 with and without the temperature gradient. By ensemble averaging the instantaneous velocity fields, the spatial distributions of mean velocity, vorticity, and higher-order statistics up to third order were obtained. The temperature difference of 10$\^{C}$ does not affect a significant influence to the flow structure in the near field, but the total entrainment rate is increased slightly. The entrainment rate shows a linear variation with the streamwise distance in the region after X/D=5.0.

• 대한기계학회논문집
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• 제17권12호
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• pp.3115-3123
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• 1993

This paper presents a real-time correction method of the movemont errors of a translatory precision machine axis. This method is a null-balances technique in which two plane mirrors are used to generate an interferometric fringe pattern utilizing the optical principles of TwymanGreen interferometry. One mirror is fixed on a reference frame, while the other is placed on the machine axis being supported by three piezoelectric actuators. From the fringe pattern, one translatory and two rotational error components of the machine axis are simultaneously detected by using CCD camera vision and image processing techniques. These errors are then independently suppressed by activating the peizoelectric actuators by real-time feedback control while the machine axis is moving. Experimental results demonstrate that a machine axis can be controlled with movement errors less than 10 nm in vertical straightness, 0.1 arcsec in pitch, and 0.06 arcsec in roll for 50mm travel by adopting the real-time correction method.

• 한국구조물진단유지관리공학회 논문집
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• 제6권2호
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• pp.113-119
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• 2002

In the prestressed concrete structures, stresses are gradually redistributed with time due to the creep and shrinkage of concrete and the stress relaxation of prestressed steel. In this study a numerical procedure and computer program is developed to analyze the behavior of prestressed concrete structures considering the time-dependent properties of material. It accounts for the aging, creep and shrinkage of concrete and the stress relaxation of prestressed steel. The structural model uses two dimensional plane frame elements with three nodal degree of freedom and is analyzed based on the finite element method. Member cross section can consist of concrete, reinforcement and prestressing steel. Two different set of equations for the prediction of time-dependent material properties of concrete are presented, which are ACI, CEB-FIP. Analytical studies for different examples of prestressed concrete structures have been performed to demonstrated the capabilities and practical applicabilities of the developed program.