• Tribology and Lubricants
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• 제29권6호
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• pp.366-371
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• 2013

Various heat treatment and surface coating methods have been applied to machine parts. Nowadays, diamond-like carbon (DLC) coatings are widely used because of their excellent tribological characteristics. Despite the numerous studies on DLC-coated engineering surfaces, the exact wear mechanisms related to the coating thickness and elastic modulus have not been fully examined. In this study, a sliding contact problem between a small spherical hard particle and a DLC-coated steel surface is analyzed using a nonlinear finite element code, MARC. The maximum principal stress distributions and deformed surfaces are compared for different coating thicknesses and Young's modulus values. Plastically deformed surface shapes such as a groove and torus indicate that the most dominant wear mechanism for a DLC-coated surface is abrasive wear. Fatigue wear can also play a role in a case where the coating thickness is relatively large and the elastic modulus is high.

• 항공우주기술
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• 제12권1호
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• pp.54-63
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• 2013

항공기의 자세제어를 담당하는 각각의 비행 조종면에 중복안정성 등의 이유로 여러 개의 작동기를 연결하여 사용하고 있다. 다중 작동기들이 동시에 정확하게 같은 위치로 이동하지 않으면 비행조종면에 변형이 발생한다. 그 결과 변형된 조종면이 원래 상태로 복원하려는 힘에 의해 작동기들 간에 force fighting이 발생한다. 게다가 force fighting은 각 장치들의 초기 허용 오차 등에 의해서도 발생한다. 다중 작동기간의 force fighting 현상은 제어정밀도에 영향을 미치고 피로파괴의 원인이 되어 작동기와 비행조종면의 수명을 단축할 수도 있다. 본 논문에서는 두 개의 서보작동기를 사용하는 시스템의 force fighting을 감소하기 위하여 힘되먹임제어를 사용하는 제어기를 설계하였다.

• 한국정밀공학회지
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• 제15권4호
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• pp.58-67
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• 1998

A sectional analysis of sheet metal forming process with an arbitrary tool shape is proposed in the present work. To improve the numerical convergence in the conventional membrane sectional analysis, the Bending Energy Augmented Membrane (BEAM) elements had been developed. The BEAM elements particularly improve the stability and convergence of the finite element method for the case of deep drawing. In this work, the FERGUBON spline (C$^2$-continuous) was used to fit the deformed mesh to smooth the given curves and calculate the local curvature of the deformed sheet. The fittings of the deformed sheet and tool surface profile ensure the stability and the convergence of the finite element analysis of highly nonlinear stamping processes. A center floor section and front fender section are analyzed to show the accuracy and robustness of the approach. The results obtained by the proposed approach are compared with the available experimental data.

• 한국전산유체공학회:학술대회논문집
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• 한국전산유체공학회 2008년도 춘계학술대회논문집
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• pp.498-501
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• 2008

Knowledge of airflow characteristics in nasal cavities is essential to understand the physiological and pathological aspects of nasal breathing. Several studies have utilized physical models of the healthy nasal cavity to investigate the relationship between nasal anatomy and airflow. In our laboratory, there have been a series of experimental investigations on the nasal airflow in normal, abnormal, and deformed nasal cavity models cavity models by PIV under both constant and periodic flow conditions. In this time normal and several deformed nasal cavity models, which simulate surgical operation, Turbinectomy, are investigated numerically by the FVM general purpose code and PIV analysis. The comparisons of these results are appreciated. Dense CT data and careful treatment of model surface under the ENT doctor's advice provide more sophisticated cavity models. The Davis (LaVision Co.) code is used for PIV flow analysis. Average and RMS distributions have been obtained for inspirational and expirational nasal airflows in the normal and deformed nasal cavities.

• Journal of Welding and Joining
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• 제22권3호
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• pp.62-68
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• 2004

The strip Au bumps are bonded using longitudinal ultrasonic far the electronic package. Au bumps on the chip and substrate are aligned in a crossed shape, and the ultrasonic is imposed on the chip to form the solid-state bond between the Au bumps. Deformed bump shapes are calculated using the finite element method, and the bond strength is measured experimentally. The crossed strip Au bumps are deformed similar to the saddle, which provides larger contact surface area and higher friction force. Compared with the previous bonding method between the Au bump and planar pad, higher bond strength is obtained using the crossed strip bumps.

• Nuclear Engineering and Technology
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• 제56권3호
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• pp.772-784
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• 2024

The hexagonal nodal code RENUS has been enhanced to handle irregularly deformed hexagonal assemblies. The underlying RENUS methods involving triangle-based polynomial expansion nodal (T-PEN) and corner point balance (CPB) were extended in a way to use line and surface integrals of polynomials in a deformed hexagonal geometry. The nodal calculation is accelerated by the coarse mesh finite difference (CMFD) formulation extended to unstructured geometry. The accuracy of the unstructured nodal solution was evaluated for a group of 2D SFR core problems in which the assembly corner points are arbitrarily displaced. The RENUS results for the change in nuclear characteristics resulting from fuel deformation were compared with those of the reference McCARD Monte Carlo code. It turned out that the two solutions agree within 18 pcm in reactivity change and 0.46% in assembly power distribution change. These results demonstrate that the proposed unstructured nodal method can accurately model heterogeneous thermal expansion in hexagonal fueled cores.

• International Journal of Naval Architecture and Ocean Engineering
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• 제5권2호
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• pp.263-276
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• 2013

Most yacht sails are made of thin fabric, and they have a cambered shape to generate lift force; however, their shape can be easily deformed by wind pressure. Deformation of the sail shape changes the flow characteristics over the sail, which in turn further deforms the sail shape. Therefore, fluid-structure interaction (FSI) analysis is applied for the precise evaluation or optimization of the sail design. In this study, fluid flow analyses are performed for the main sail of a 30-foot yacht, and the results are applied to loading conditions for structural analyses. By applying the supporting forces from the rig, such as the mast and boom-end outhaul, as boundary conditions for structural analysis, the deformed sail shape is identified. Both the flow analyses and the structural analyses are iteratively carried out for the deformed sail shape. A comparison of the flow characteristics and surface pressures over the deformed sail shape with those over the initial shape shows that a considerable difference exists between the two and that FSI analysis is suitable for application to sail design.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 2004년도 춘계 학술발표회 제16권1호
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• pp.124-127
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• 2004

This study is to investigate the bond characteristics of glass fiber reinforced polymer(GFRP) reinforcing bars in concrete by pullout test experimentally. Three different types of GFRP bars with different surface deformations were considered in this study. Also, standard deformed steel reinforcing bar with or without epoxy-coating were included for the comparisons of bond strength. All test procedures including specimens preparation, test apparatus and measuring devices were made according to the recommendation of CSA(Canadian Standards Association) Standard S806-02. From the test results, it was found that small surface indentations contributed to increase the bond strength of GFRP bar significantly. Based on the limited test results till now, the bond strength of GFRP bar with sand-coated deformation commercially available in foreign market is around $80\%$ of that of steel deformed bars.

• 한국반도체및디스플레이장비학회:학술대회논문집
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• 한국반도체및디스플레이장비학회 2003년도 추계학술대회 발표 논문집
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• pp.207-211
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• 2003

In this study, the geometric modeling has been conducted for a new model of 12 inch hot-cold chuck using three-dimensional solid modeler, SolidWorks. Then, the heat transfer analysis and the thermal deformation analysis using FEM have been performed. The results of the analysis show the temperature distribution and the deformed shape of a new model of 12 inch hot-cold chuck. The evaluation for the surface flatness of a new model has been performed based on the deformed shape obtained from ANSYS.

• Journal of Korean Vacuum Science & Technology
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• 제3권1호
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• pp.54-58
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• 1999

We deposited diamond-like carbon (DLC) films using ion beam sputtering of a graphite target on flat substrates for use as a thin film field emitter. An n-type silicon wafer, titanium-coated silicon, and indium tin oxide (ITO) coated glass were used as a substrate. All films exhibited a sudden increase in the emission after a breakdown occurred at high voltage. The morphology of the films after the breakdown depended on the substrate. On ITO and Ti substrates, the DLC film peeled off upon breakdown, but on the Si substrate the surface melting due to breakdown resulted in the formation of various structures such as a sharp point, mound, and crater. By scanning the deformed surface with a tip anode, we found that the emission was concentrated at the deformed sites, indicating that the field enhancement due to the morphology change was responsible for the increased emission.