• Transactions of Materials Processing
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• v.12 no.3
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• pp.194-201
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• 2003

An automatic quadrilateral mesh generator for large deformation finite element analysis such as metal forming simulation was developed. The NURBS interpolation method is used for modeling arbitrary 2-D free surface. This mesh generation technique is the modified paving algorithm, which is an advancing front technique with element-by-element resolving method for paving boundary intersection problem. The mesh density for higher analysis accuracy and less analysis time can be easily controlled with high-density points, maximum and minimum element size. A couple of application to large deformation finite element analysis is given as an example, which shows versatility and applicability of the proposed approach and the developed mesh generator for large deformation finite element analysis.

• Journal of the Korea Computer Graphics Society
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• v.17 no.3
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• pp.43-50
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• 2011

We present a trade-off technique for fast but qualitative planar shape deformation using a layered mesh. We construct a layered mesh that is embedding a planar input shape; the upper-layer is denoted as a control mesh and the other lower-layer as a shape mesh that is defined by mean value coordinates relative to the control mesh. First, we try to preserve some shape properties including user constraints for the control mesh by means of a known existing nonlinear least square optimization technique, which produces deformed positions of the control mesh vertices. Then, we compute the deformed positions of the shape mesh vertices indirectly from the deformed control mesh by means of simple coordinates computation. The control mesh consists of a small number of vertices while the shape layer contains relatively a large number of vertices in order to embed the input shape as tightly as possible. Since the time-consuming optimization technique is applied only to the control mesh, the overall execution is extremely fast; however, the quality of deformation is sacrificed due to the sacrificed quality of the control mesh and its relativity to the shape mesh. In order to change the deformation behavior and consequently to compensate the quality sacrifice, we present a method to control the deformation stiffness by incorporating the orientation into the user constraints. According to our experiments, the proposed technique produces a planar shape deformation fast enough for real-time applications on limited embedded systems such as cell phones and tablet PCs.

• Korean Journal of Computational Design and Engineering
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• v.21 no.2
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• pp.143-150
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• 2016

In shipbuilding, hull assemblies are manufactured by welding. The thermal deformation caused by the welding produces shape deformation. Counter-deformed design methods have been used in shipyards to cope with the weld-induced deformation of ship assembles. Finite element methods (FEMs) are frequently used to estimate welding distortion in the counter-deformed design. For the estimation of welding distortion, producing uniform rectangular elements is required to enter thermal loads on the welding line and obtain accurate analysis results. In this paper, a new automatic mesh generation method is proposed for prediction of welding deformation in FEM. Meshes are constructed for test cases to demonstrate the feasibility of the proposed mesh generation method.

• The Transactions of the Korean Institute of Electrical Engineers B
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• v.52 no.6
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• pp.247-253
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• 2003

A novel finite element mesh regeneration method is presented for 3D shape optimization of electromagnetic devices. The method has its theoretical basis in the structural deformation of an elastic body. When the shape of the electromagnetic devices changes during the optimization process, a proper 3D finite element mesh can be easily obtained using the method from the initial mesh. For real engineering problems, the method guarantees a smooth shape with proper mesh quality, and maintains the same mesh topology as the initial mesh. Application of the optimum design of an electromagnetic shielding plate shows the effectiveness of the presented method.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.29 no.6 s.237
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• pp.895-903
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• 2005

In this paper, we present a cutter location (CL) surface deformation approach for constant scallop height tool path generation from triangular mesh. The triangular mesh model of the stereo lithography (STL) format is offset to the CL surface and then deformed in accordance with the deformation vectors, which are computed by the slope and the curvature of the CL surface. In addition, the tool path which is computed by slicing the deformed CL surface is inversely deformed by those same deformation vectors to a tool path with a constant scallop height. The proposed method is implemented, and a tool path generated by the proposed method is tested by simulation and by numerical control (NC) machining. The scallop height was found to be constant over the entire machined surface, demonstrating much better quality than that of mesh slicing, under the same constraints for machining time.

• Interaction and multiscale mechanics
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• v.5 no.3
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• pp.287-318
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• 2012

We apply a partitioned-solution (iterative-staggered) coupling method based on a fixed Eulerian mesh with the level set function to a large-deformation fluid-structure interaction (FSI) problem where a large-deformable thin structure moves in a high-speed flow field, as an airbag does during deployment. This method combines advanced fluid and structure solvers-specifically, the constrained interpolation profile finite element method (CIP-FEM) for fluid Eulerian mesh and large-deformable structural elements for Lagrangian structural mesh. We express the large-deformable interface as a zero isosurface by the level set function, and introduce virtual nodes with level sets and structural normal velocities to generate the level set function according to the large-deformable interfacial geometry and enforce the kinematic condition at the interface. The virtual nodes are located in the direction normal to the structural mesh. It is confirmed that application of the method to unfolded airbag deployment simulation shows the adequacy of the method.

• Journal of Korea Multimedia Society
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• v.7 no.1
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• pp.80-90
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• 2004

Watermarking algorithm for 3D mesh model using EGI distribution of each patch is proposed. The proposed algorithm divides a 3D mesh model into 6 patches to have the robustness against the partial geometric deformation. Plus, it uses EGI distributions as the consistent factor that has the robustness against the topological deformation. To satisfy both geometric and topological deformation, the same watermark bits for each subdivided patch are embedded by changing the mesh normal vectors. Moreover, the proposed algorithm does not need not only the original mesh model but also the resampling process to extract the watermark. Experimental results verify that the proposed algorithm is imperceptible and robust against geometrical and topological attacks.

• Journal of KIISE:Software and Applications
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• v.32 no.8
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• pp.769-780
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• 2005

This paper addresses a novel application of meshes to analyzing the deformation patterns of 2D signals. The proposed mesh is distinguished form the previous models in that it includes simulated charges in each node that interact with external charges comprising an input pattern. Therelaxation of the mesh given an input is carried out by any of the well-known numerical integration techniques. The result of the relaxation is a deformed mesh. This Paper provides four criterion functions for measuring the pattern deformation. A set of trained meshes was created from the simple average of target patterns. Experimental results show that these measures, although highly intuitive, are not good enough to capture the amount and characteristics of pattern deformation. If more sophisticated measures are found and incorporated into the relaxation process, we expect that a better and high-performance mesh framework is realized.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.12 no.3
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• pp.447-455
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• 1999

An adaptive mesh generation scheme is developed for effective non-linear analysis of the shell structures under large deformation. In particular, based on a posteriori error estimation, remeshing method on each load step is of primary interest here. An advancing front method, called paving method, is adopted for remeshing. It can be known that the adaptive mesh generation using contours of spacing values obtained from stress errors has an advantage in the adaptive analysis of the shell structures.

• Transactions of Materials Processing
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• v.9 no.1
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• pp.59-65
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• 2000

Most studies of failure analysis in ductile metals have been based on the classical plasticity theory using the local constitutive relations. These frequently yields a physically unrealistic solution, in which a numerical prediction of the onset of a deformation localization shows an inherent mesh-size sensitivity. A one way to remedy the spurious mesh sensitivity resulted in the unreasonable results is to incorporate the non-local plasticity into the simulation model, which introduce an internal (material) length-scale parameter into the classical constitutive relations. In this paper, a non-local version of the modified Gurson constitutive relation has been introduced into the finite element formulation of the simulation for plane strain compression of the visco elastic-plastic void material. By introducing the non-local constitutive relations we could successfully removed the inherent mesh-size sensitivity for the prediction of the deformation localization. The effects of non-local constitutive relation are discussed in terms of the load-stroke curve and the strain distributions accross the shear band.