• The Transactions of the Korea Information Processing Society
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• v.6 no.9
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• pp.2504-2511
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• 1999

This paper proposes the scattered data interpolation as an efficient method that is designed for free-form surface. Data interpolation is an essential method of designing for various objects. For the generating free-form surface of complexity construction, the existing method had problems to represent flat area and sharp corner edge, in presenting objects with computing the weight of control points. For solving this problem, we proposes the generating method of new approximation surfaces, using scattered data interpolation. This method obtains B-Spline basis function which calculates main curvature, having optimized value in variable area, on given control points and changed objects, and then computes the changing rate the approximating data, using it's value. We also present this method that generates smoother free-form surface, using the scattered data interpolation with minimum weight.

• Tribology and Lubricants
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• v.24 no.5
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• pp.250-254
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• 2008

The steam generator of nuclear power plant is composed with the bundles of long tubes. It is exposed fluid flow and weak in the vibration. The tubes are supported by anti-vibration bars. Due to vibration the wear damage is called as the fretting wear. It should be minimized for the safety of the plants. The hard coatings are very effective to reduce the amount of wear. The coatings of TiN and CrN are introduced in this study to protect the fretting surfaces. The tube-on-flat type tester was used for fretting wear tests. The results show that the wear amounts of the coated tubes were decreased depending on coating thickness. CrN was very effective to reduce the wear. In case of TiN the wear amounts were dependent on the coating thickness. Thick coating of TiN was very effective for wear resistance.

• Journal of the Korean Society of Industry Convergence
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• v.20 no.2
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• pp.195-204
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• 2017

Predicting the failure life of automated manufacturing systems can reduce overall downtime, maintenance costs, and total plant operation costs. Therefore, there is a growing interest in fatigue failure mechanisms as the safety or service life assessment of manufacturing systems becomes an important issue. In particular, fretting fatigue is caused by repeated tangential stresses that are generated by friction during small amplitude oscillatory movements or sliding between two surfaces pressed together in intimate contact. Previous studies in fretting fatigue have observed size effects related to contact width such that a critical contact width exists where there is drastic change in the fretting fatigue life. However, most of them are the two-dimensional finite element analyses based on the plane strain assumption. The purpose of this study is to investigate the contact size effects on the three-dimensional finite element model of a finite width of a flat specimen and a cylindrical pad exposed to fretting fatigue. The contact size effects were analyzed by means of the stress and strain averages at the element integration points of three-dimensional finite element model. This study shows that the fretting fatigue life of manufacturing systems can be predicted by three-dimensional finite element analysis based on SWT critical plane model.

• Korean Journal of Metals and Materials
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• v.50 no.1
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• pp.59-63
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• 2012

Studying the long-range ordering of nanopores on the anodic aluminum oxide (AAO) membranes under a hard anodization (HA) approach is crucial in producing well-aligned nanopores on the AAO membranes. Electro-polishing in a mixture of ethanol and perchloric acid for 5 min removed marks formed by rolling and produced flat surfaces on aluminum substrates. The AAO was formed by the first HA process, providing seeds for the subsequent production of uniform AAO nanopores. The second HA process carried out on the seeds produced well-aligned, uniform AAO nanopores. The AAO nanopores, varying in size and shape, were observed with voltages applied for HA. This study provides a route for controlling the size and shape of AAO nanopores by changing the applied voltages.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.18 no.11
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• pp.867-873
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• 2006

Vertical falling liquid film is extensively used in heat and mass transfer processes of many applications, such as evaporative coolers, cooling towers, and absorption chillers. In such cases, it is required that the falling film spreads widely in the surface forming thin liquid film to enlarge contact surface. An addition of surface active agent to a falling liquid film or hydrophilic surface treatment affects the fluid physical properties of the film. Surfactant addition not only decreases contact angle between the liquid and solid surface but also changes the surface from hydrophobicity to hydrophilicity. In this study, the effects of contact angle on falling film characteristics over a vertical surface have been investigated experimentally. The contact angle is varied either by an addition of surfactant to the liquid or by hydrophilic surface treatment. It is found that the wetted area is increased and film thickness is decreased by the hydrophilic treatment as compared with those of other surfaces. With this hydrophilic treatment, the falling liquid film spreads out widely in the surface. As surfactant concentration is increased, wetted area is also increased and the film thickness is substantially decreased.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.15 no.8
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• pp.619-629
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• 2003

A grease filter is used to remove grease generated from a cooking appliance in a kitchen. Since the inertial impaction is a dominant particle removal mechanism of the grease filter, the performance of the filter is greatly affected by the geometry. This numerical study has been conducted to investigate the effect of geometry on the performance of grease filters for four models having nominal flowrate of 100 m$^3$/h. Four models were designed by changing the shape of impaction surface, the length of eyelid, and the number of eyelids of the grease filter. The flow field and particle trajectories in the grease filter with a flow chamber were simulated using the commercial code of STAR-CD. The difference of air velocity and pressure distributions among four models was discussed in detail. The collection efficiency curves and the pressure drops of four models were also compared. It was found that the grease filter model with flat top surfaces shows highest performance among four models, having high particle collection efficiency and relatively low pressure drop. The cutoff diameter of this model representing 50-% collection efficiency is about 7.1 ${\mu}{\textrm}{m}$ for water droplets at 100 m$^3$/h.

• Structural Engineering and Mechanics
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• v.78 no.2
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• pp.135-143
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• 2021

In this study, continuous contact problem in the functionally graded (FG) layer loaded with a FG flat punch resting on the elastic semi-infinite plane was analyzed by the finite element method (FEM). It was assumed that the shear modulus and density of the layer and punch varied according to exponentially throughout their depth. FG layer's weight was included to the problem and additionally all surfaces were considered as frictionless. Analysis of FG materials was performed with a special macro which was added to the ANSYS program. Firstly, the shear modulus of the punch was considered to be very rigid and the results of initial separation load (λcr) and distance (xcr) were compared with the analytical solution. Afterwards, results obtained from the contact analysis made according to the inhomogeneity parameters (β, γ) between FG punch-FG layer which had been unprecedented in the literature were discussed. As a result, FG punch's stress values at the punch edges where stress accumulations occurred were found to be smaller than the rigid punch. The security of the structure, longer life of the material and ease of production are directly related to the reduction of the stress values. The results obtained in this study are important in this respect. Also this work is the first study that investigates the effect of FG punch on the FG layer.

• Journal of the Korea Fashion and Costume Design Association
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• v.23 no.2
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• pp.155-163
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• 2021

This design proposal research is meaningful as Jogakbo can retain the traditional value of the it's design as it becomes a contemporary design proposal. As a specific method of research, history was been investigated to find meaning and formative characteristics defined through prior research under the theme of Jogakbo. Ideas, such as silhouettes, details for design, and the making domestic and foreign designer examples were obtained. The fabric used for the works were recycled from past leather works. All materials are sheep skin. There were various processed surfaces used to avoid monotony. Jogakbo's cotton composition focused on free and radial patterns. The pattern was manufactured using a flat and 3D combination, and the selection of items was mainly made with a simple and light silhouette, so that Jogakbo's details, such as dresses, slip dress, and vests could stand out. Color is an important factor in Jogakbo. However, traditions which are relics of the times, do not need to be preserved in their original form. If changes are inherited with reasonable grounds and directions in line with the changing times, the significance and values are retained are sufficient. It is hoped that these design development studies will continue in the future so that our precious cultural heritage can continue to change and develop positively.

• Journal of the Korea Fashion and Costume Design Association
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• v.22 no.4
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• pp.93-104
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• 2020

This paper focuses on the spatial changes that create a three-dimensional or deep feeling on the surface of a scarf centering on the cube shape. Through this, consumers with various tastes were able to satisfy their image presentation. The cube form has simplicity and order and is likely to be used as a formative object. The cube shapes can be expressed in various forms through visual and perceptual spatial changes by presenting various shape changes based on the viewpoint of the two-dimensional silk surface, that is, by changing the eyes' position and orientation. Various visual theorists' discussions about cube-shaped visual changes were discussed. In addition, the three-dimensional spatial illusion caused by the shape and color of Victor Bazaarelli's cube was examined. The cube shape was printed silk surfaces to give a three-dimensional sense of space on a two-dimensional scarf design using the size change, the difference in the length of the line, and the color change. As such, the cube shape has infinite possibilities as a method that can express three-dimensional depth and space on the flat surface of a scarf. Therefore, it is hoped that this study will be applied to various aspects as the basic data for the scarf design that expresses the spatial changes in the form of cubes.

• Design & Manufacturing
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• v.17 no.1
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• pp.33-39
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• 2023

The ball end mill is a type of cutting tool that is widely used to process complex mold shapes including aspheric surfaces. Unlike the flat end mill in which the cutting edge is formed on the cylindrical handle, the cutting edge is formed from the cylindrical handle to the hemispherical shape, which is advantageous for processing curved shapes. However, since the cutting speed continuously changes during machining due to the helix angle of the cutting edge or the machining inclination angle, it is difficult to obtain a precise machined surface. Therefore, in this paper, machining was performed while changing the helix angle of the ball end mill and the angle of the machining slope under the same cutting conditions for STD 11 material, which is widely used as a mold material. Through this, the effect of the two variables on the roughness of the machined surface was analyzed. As a result, if the helix angle was 0 degrees, it showed the best surface roughness of Ra. 0.16 ㎛. When the helix angle was 20 degrees, the best surface roughness of Ra. 0.18 ㎛ was occurred.