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General 3D Offsetting of a Triangular Net Using an Implicit Function and the Distance Fields
유동진 한국정밀공학회 2009 International Journal of Precision Engineering and Vol. No.
A novel approach which uses the distance fields based on cell subdivision and an implicit surface interpolation based on the radial basis function is proposed in order to get an accurate and error-free offset model of arbitrary shapes composed of a large number of triangle meshes. In the method, the space bounding the original model is divided into smaller cells. For the efficient calculation of distance fields, valid cells which will generate a portion of offset model are selected previously by the proposed detection algorithm. These valid cells are divided again into much smaller voxels which assure required accuracy. At each voxel, the distance fields are created by calculating the minimum distances between the corner points of voxels and the triangle meshes. For the more efficient calculation of distance fields, valid vertices among the triangle meshes which will generate minimum distances with current cell are selected by checking the intersection between current cell and a cone prism generated at each vertex of triangle meshes. In addition, a new approach based on an implicit surface interpolation scheme is proposed to perform two types of offsetting operations including uniform and non-uniform offsetting in the same framework. In the method, a smooth implicit surface is generated from the discrete offset distance values given by the user. After generating the whole distance fields, the offset surface was constructed by using the conventional marching cube algorithm together with mesh smoothing scheme. The effectiveness and validity of this new offset method was demonstrated by performing numerical experiments for the various types of triangle meshes.
New Paradigms in Cellular Material Design and Fabrication
유동진 한국정밀공학회 2015 International Journal of Precision Engineering and Vol. No.
This paper presents an effective method for designing three dimensional (3D) cellular materials containing complex internal cellular microstructures. The volumetric distance field (VDF) strategy is developed to eliminate voxelization and interpolation processes required in the conventional voxel based DF method. By introducing a hybrid method based on the VDF and triply periodic minimal surface (TPMS) cellular topology, we can design a variety of 3D cellular materials with intricate internal microstructures and arbitrarily-shaped external surfaces with unprecedented efficiency and accuracy. Experimental results show that the proposed design method has the capability to combine the perfectly interconnected channel networks based on the TPMS microstructures and the given object geometries in a consistent framework irrespective of the complexity of objects. In addition, in order to show the generality and versatility of the proposed method, a set of valuable applications are also illustrated through the innovative heat sink, heat exchanger, and enhanced lightweight cellular structure designs. Our findings suggest that the proposed design principles offered by TPMS-based cellular topology and VDF can be applied to create a wide range of advanced 3D cellular materials.
유동진 대진대학교 생산기술연구소 1998 생산기술연구소 논문집 Vol.1 No.-
The stamping process consists of two stages : First. the blank is held by the blank holder and then it is further formed into the die cavity by punch stroke. In the stamping process. accurate prediction of binder wrap is an indispensable step in sheet metal forming analysis. since the initial plastic buckling induced by improper die design is directly related with fatal defect at the final forming stage. In the present work, an approach including the gravity effect of blank material and proper consideration of contact and friction is proposed. Computations are carried out for several actual auto-body parts using 3D FEM code to investigate the validity of the proposed methodology. Comparisons with experimental results show that the suggested scheme can be effectively applied to the precise prediction of binder wrap for arbitrarily curved die faces in which gravity and contact effect shoud be taken into account.