• 한국안전학회지
• /
• 제28권5호
• /
• pp.54-60
• /
• 2013

In this study, a finite element model based on the SU/PG scheme was developed to solve shallow-water equations and the influences of parameters and internal boundary conditions on depth-averaged flow behavior were investigated. To analyze the effect of roughness coefficient and eddy viscosity on flow characteristics, the developed model was applied to rectangular meandering channel with two bends, and transverse velocities and water depth distributions were examined. As the roughness coefficient adjacent to wall increased, the velocities near the wall decreased, and the reduced velocities were compensated by the expanding mid-channel velocities. In addition, the flow characteristics around a circular cylinder were analyzed by varying the internal boundary conditions as free slip and no slip. The assignment of slip condition changed the velocity distribution on the cylinder surface and reduced the magnitude of the shear stress up to one third.

• 한국철도학회논문집
• /
• 제9권5호
• /
• pp.561-568
• /
• 2006

Dynamic equations of motion for the interaction system of bridge and vehicle are derived to investigate the dynamic responses of bridge and vehicles induced by moving automated guide-way transit(AGT) vehicle and surface roughness of bridge. The vehicle model for ACT vehicle is idealized as 11 DOF including yawing, lateral translation and steering of wheels, and the bridges are modeled with finite element method. The AGT vehicle model was verified by experimental study. Parametric studies are carried out to investigate the effect of vehicle speed, surface roughness, stiffness and damping of the suspension system, AGT vehicles and dynamic wheel loads of the AGT vehicles. From the parametric study it can be seen that the dynamic incremental factor of the bridge and dynamic responses of vehicles have a tendency to increase with vehicle speeds, surface roughness and the stiffness of AGT vehicle suspension system. On the other hand those dynamic wheel loads have tendencies to decrease in according to increase of damping of the suspension system.

• 한국전기전자재료학회:학술대회논문집
• /
• 한국전기전자재료학회 2003년도 춘계학술대회 논문집 초전도 자성체 연구회
• /
• pp.84-87
• /
• 2003

The interfacial diffusion in Fe/Cr/MgO(001) multilayers has been studied using synchrotron x-ray techniques, such as x-ray reflectivity, extended x-ray absorption fine structures (EXAFS), and anomalous x-ray scattering (AXS). The results of x-ray reflectivity indicated that the interfacial roughness of Fe/Cr multilayers with Cr-$4{\AA}$-thick was larger than that with Cr-$4{\AA}$-thick. The results of EXAFS indicated that the Fe element dominantly diffuse into the stable Cr layers at the Fe/Cr interface. The AXS was certified the existence of the interdiffused Fe element in the Cr layers. Our study revealed that the rough interface of the Fe/Cr multilayers was caused by the interfacia diffusion of Fe element into the Cr layers.

• 소성∙가공
• /
• 제23권3호
• /
• pp.159-163
• /
• 2014

In the current study, the effect of small surface defects in the starting material including roughness, indentations, or scratches, which are perpendicular to the direction of drawing, on the product quality is investigated using the finite element method. An axisymmetric defect is assumed. Such defects are defined by a cylindrical defect area and two tapered regions connecting the defect area to the non-defective area of the material. Various conditions for these initial surface defects are considered, including defect depth, defect slope and defect length. To describe the plastic deformation of the defect in detail during the simulation, local remeshing is applied. Based on the finite element results, defect disappearance maps were generated. It was found that defect disappearance is significantly dependent on the defect depth and the defect length coupled with the defect slope.

• 한국구조물진단유지관리공학회 논문집
• /
• 제17권6호
• /
• pp.50-60
• /
• 2013

본 연구에서는 교량의 노면조도 및 교량과 차량 사이의 상호작용을 고려한 수치해석방법을 사용하여 도로교설계기준에 규정된 표준트럭 하중인 KL-510에 의한 강판형교의 동적응답을 연구하였다. 대상교량은 건설부에서 제정한 "도로교 상부구조 표준도"에 수록되어 있는 지간이 20m, 30m와 40m인 단순 강판형교를 사용하고. "보통의 도로"에 대하여 생성시킨 10개의 노면조도를 사용하였다. 차량은 5축 트랙터-트레일러인 표준트럭하중 KL-510을 3차원 차량으로 모델링하고, 교량은 주형을 보요소로, 콘크리트 바닥판은 쉘요소로, 주형과 콘크리트 바닥판 사이는 Rigid Link를 사용하여 3차원으로 모델링하였다. 이와 같은 노면조도 및 차량을 사용하여 강판형교의 충격계수와 DLA를 구하고 각국의 설계기준과 비교 검토하였다.

• 대한기계학회논문집
• /
• 제14권1호
• /
• pp.37-42
• /
• 1990

본 연구에서는 수직 밀링에서 탄소섬유 에폭시 복합재료를 절삭할 경우 절삭 조건에 따른 공구마멸 형태를 조사하였으며, 여유면 마멸량을 측정하여 Taylor 지수를 구하였다. 또한 절삭조건 및 측정 방향에 따른 표면거칠기를 조사하여 탄소섬유 에 폭시 복합재료의 가공특성을 조사하였다.

• 한국정밀공학회지
• /
• 제17권4호
• /
• pp.69-80
• /
• 2000

Generally, die polishing is a lime consuming process, resulting in 30∼50％ of the whole die manufacturing time. However, die polishing has not been automated yet, since it needs a great deal of experience and skill. This paper describes a new development of automated system for die polishing and focuses on the successful achievements of the element techniques to realize from hand skill to automation, as followings: (1) The 5 axes polishing system by the aid of robot with 2 degrees of freedom, is developed for the application of curved surface die. (2) The CAM system realizes a 5 axes tool path control for polishing and measuring. (3) The conductive elastic tool is able to meet curved surfaces of die and gives a high efficient and quality polishing characteristics. (4) The surface roughness measurement device with noncontact laser is developed and has a high reliability without surface damage.

• 한국지반공학회:학술대회논문집
• /
• 한국지반공학회 2006년도 춘계 학술발표회 논문집
• /
• pp.896-905
• /
• 2006

Several soil parameters such as particle characteristics, geological element, drainage and loading conditions are influenced on the shear strength of soil. The characteristics of soil particles are important factor to the shear strength of soil. However, this component is not well considered in the determination of soil strength in Korea. The particle shape of sand was analyzed by utilizing SEM(Scanning Electron Micrograph) and compared its results in terms of aspect ratio, angularity and roughness. Based on the determined soil parameters, the ultimate bearing capacity of sandy ground was estimated by using Terzaghi bearing capacity equation.

• 대한기계학회논문집
• /
• 제18권9호
• /
• pp.2443-2453
• /
• 1994

The structure of turbulence of fully developed flow through four concentric annuli with the rough outer wall was investigated experimentally for a Reynolds number range Re=15, 000-93, 000. Turbulence intensities were measured in three(u, v, w) directions, and turbulence shear stresses in annuli of radius=0.13, 0.26, 0.4 and 0.56, respectively. Due to the square roughness element attached periodically along the axial direction, the radial velocity fluctuations show similar distribution regardless of the different .alpha.cases. However, the axial and circumferential velocity fluctuation profiles demonstrate the longitudinal turbulence structures are strongly influenced by the .alpha. values. The turbulent eddy viscosity deduced form mean velocity distributions and the measured Reynolds shear stresses are also presented and discussed.

• 한국공작기계학회논문집
• /
• 제10권4호
• /
• pp.33-39
• /
• 2001

During the turning of the workpiece, cutting heat causes thermal deformation of the cutting tool which influences the surface characteristics of the machined part. This paper presents a study of thermal deformation of the cutting tool. For this purpose, cutting tool is modeled based of Pro/Engineering and the thermal deformation is simulated by means of the finite element method. The thermal effect on the surface roughness profile is simulated by using surface-shaping system. It has been shown that the results of simulation are similar to those of experiment.