• Proceedings of the Computational Structural Engineering Institute Conference
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• 1998.10a
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• pp.298-305
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• 1998

The purpose of this study is to propose the method of determining the initial fabric membrane structures surface and membrane patterning procedures. Tension structure, such as, fabric membrane structures and cable-net, is stabilized by their initial prestress and boundary condition. The process to find initial structural overall shape of tension structures produced by initial prestress called Shape Finding or Shape Analysis. One of the most important factor for the design of membrane structures is to search initial smooth surface, because unlike steel or concrete building elements which resist loads in bending, all tension structure forces are carried within the surface by membrane stress or cable tension. To obtain initial surface of fabric membrane element in large deformation analysis, the membrane element is idealized as cable using a technique with Force-density method. and that result is compared with well-known nonlinear numerical method, such as Newton-raphson method and Dynamic relaxation method. The shape resulting from Force-density method has been dealt with as the initial membrane shape and used patterning procedures.

• Journal of the Korean Society for Heat Treatment
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• v.18 no.2
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• pp.105-111
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• 2005

In sheet metal forming, drawbeads are often used to control uneven material flow, which may cause defects such as wrinkles, fractures, surface distortion and springback. Appropriate setting and adjusting of the drawbead force is one of the most important parameters in sheet forming process control. Therefore in this study, drawbead test was performed at various bead surface treatment conditions to clarify the frictional characteristics between sheet and drawbead. Furthermore, the differences in drawing force between circular and rectangular shape beads have also been measured to estimate the effectiveness of bead shape on the material flow control. The results show that drawing and friction characteristic were strongly influenced by surface treatments of bead and bead shapes.

• Journal of Computing Science and Engineering
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• v.6 no.3
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• pp.219-226
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• 2012

Recently, shape analysis of human organs has achieved much attention, owing to its potential to localize structural abnormalities. For a group-wise shape analysis, it is important to accurately restore the shape of a target structure in each subject and to build the inter-subject shape correspondences. To accomplish this, we propose a shape modeling method based on the Laplacian deformation framework. We deform a template model of a target structure in the segmented images while restoring subject-specific shape features by using Laplacian surface representation. In order to build the inter-subject shape correspondences, we implemented the progressive weighting scheme for adaptively controlling the rigidity parameter of the deformable model. This weighting scheme helps to preserve the relative distance between each point in the template model as much as possible during model deformation. This area-preserving deformation allows each point of the template model to be located at an anatomically consistent position in the target structure. Another advantage of our method is its application to human organs of non-spherical topology. We present the experiments for evaluating the robustness of shape modeling against large variations in shape and size with the synthetic sets of the second cervical vertebrae (C2), which has a complex shape with holes.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 1995.10a
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• pp.210-213
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• 1995

In this study,the effect of both process parameters (wheel velocity, friction coefficients between die and billet, etc) and die-shape (abutment height and shape, flash gap, etc.) on the surface defect on forming process is theoretically investigated. For this work, computer simulation was performed by using the DEFORM, a commercial FEM code. Through numerous simulations with different parameters and die shapes, We propose one optimal die shape for CONFORM process which can remove surface defect.

• Journal of the Korean Society for Precision Engineering
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• v.17 no.4
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• pp.97-105
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• 2000

One of the most important steps to determine the blank shape and dimensions in deep drawing process is to calculate the surface area of the product. In general, the surface area of axisymmetric products is calculated by mathematical or graphical methods. However, in the case of non-axisymmetric products, it is difficult to calculate the exact surface area due to errors as separated components. Fortunately, it is possible for elliptical products to recognize the geometry of the product in the long side and short side by drafting in another two layers on AutoCAD software. So, in this study, a surface area calculating system is constructed for a design of blank shape of deep drawing products. This system consists of input geometry recognition module and three dimensional modeling module, respectively. The suitability of this system is verified by applying to a real deep drawing product. The system constructed in this study would be very useful to reduce lead time and cost for determining the blank shape and dimensions.

• Journal of Institute of Control, Robotics and Systems
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• v.21 no.5
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• pp.459-464
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• 2015

An on-line quality control of hot steel products is one of the important issues in the steel industry because of cost minimization. In recent years, relative depth information of surface defects is increasingly required for strict quality control. In this paper, a 3D shape reconstruction scheme for defects on a hot steel surface based on a multi-spectral photometric stereo method is proposed. After simultaneously illuminating a hot steel surface by using vertical/horizontal linearly polarized lights of green and blue light sources, the corresponding 4 images are obtained. The photometric stereo method is then applied with the aid of a GPU (Graphic Processing Unit) to reconstruct the shape of the target surface based on these images. The proposed scheme was validated through experiments.

• Proceedings of the Korean Society of Tribologists and Lubrication Engineers Conference
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• 1998.10a
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• pp.115-123
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• 1998

The morphological analysis of wear particle is a very effective means for machine condition monitoring and fault diagnosis. In order to describe morphology of various wear particle, the wear test was carried out under different experimental conditions. And fractal descriptors was applied to boundary and surface of wear particle with image processing system. These descriptors to analyze shape and surface wear particle are shape fractal dimension and surface fractal dimension. The shape fractal dimension can be derived from the boundary profile and surface fractal dimension can be determined by sum of intensity difference of surface pixel. The morphology of wear particles can be effectively obtained by two fractal dimensions.

• Korean Journal of Computational Design and Engineering
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• v.12 no.6
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• pp.441-451
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• 2007

In this paper, the method to modify a surface through three dimensional vector field technique is presented, In this method two guide surfaces are required as a shape reference. One is the shape of original surface, the other is the target shape for the result surface. Proposed method is consists of two steps. The first step is to calculate the mapping points on original and target guide surfaces so that the shape error may be minimized. The second step is to construct the smooth vector field from mapping points of the first step. The developed method is applied to shoe design system which makes the surface modeling very easy and effective.

• Journal of the Institute of Electronics Engineers of Korea SC
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• v.49 no.4
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• pp.1-9
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• 2012

A method to estimate the 3-D shape of surface with specular reflection is proposed, where the difference between the images reflected from a flat surface and a curved surface is used. First, we analyzed the geometry of the spatial reflection at specular surface and the variation of reflected light due to curved surface, whose results are used to estimate 3-D shape. The proposed method is shown to be effective via experiments using the illumination with spatially distributed light source and the CCD camera to capture the light reflected from a surface. In experiments, the captured images from curved surface with specular reflection are processed to approximately estimate 3-D shape.

• 한국전산유체공학회:학술대회논문집
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• 2008.03a
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• pp.186-196
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• 2008

The dependence of the rheological properties of blood on shape, aggregation, and deformability of red blood cells (RBCs) has been investigated using hybrid systems by coupling fluid with solid models. We present a simple approach for simulating blood as a multi-component fluid, in which RBCs are modeled as droplets of acquired biconcave shape. We used lattice Boltzmann method (LBM) due to its excellent numerical stability as a simulation tool. The model enables us to control the droplet static shape by imposing non-isotropic surface tension force on the interface between the two components. The use of the proposed non-isotropic surface tension method is justified by the Norris hypothesis. This hypothesis states that the shape of the RBC is due to a non-uniform interfacial surface tension force acting on the RBC periphery. This force is caused by the unbalanced distribution of the lipid molecules on the surface of the RBC. We also used the same concept to investigate the dynamic shape change of the RBC while flowing through the microvasculature, and to explore the physics of the Fahraeus, and the Fahraeus-Lindqvist effects.