Asymptotic boundary conditions for finite element analysis of three-dimensional transmission line discontinuities

1990 ◽  
Vol 38 (10) ◽  
pp. 1427-1432 ◽  
Author(s):  
A. Khebir ◽  
A.B. Kouki ◽  
R. Mittra
Author(s):  
Ajay Garg

Abstract Design and analysis of engineering components can be categorized under the theory of continuum mechanics, plates/shells or beams. Closed form solutions for determining deformations and stresses are available for simple structures with simple boundary conditions. In the cases of complex structures, boundary conditions and loads, analytical solutions are not readily available. Finite element analysis (FEA) can be performed to resolve the simulation barrier of these analytically indeterminate structures. Similar to analytical approach, FEA can simulate the components through solid, plate/shell or beam elements. Finite element analysis through 3-D solid elements is costly and may require time in weeks, which may not be at the disposal of an analyst. Axi-symmetric components and components with an infinite radius of curvature (flat surfaces), but with complex cross sections can be modeled by 2-D axi-symmetric and plate elements, respectively. Two dimensional finite elements require less time and hardware support than three-dimensional elements. Two development cases of successful application of 2-D finite elements instead of 3-D finite elements are discussed. Experimental and analytical verification of FEA results, and guidelines for checking finite element mesh discretization error are presented.


Author(s):  
M. T. Rahmati ◽  
G. Alfano ◽  
H. Bahai

In this paper the implementation of two types of boundaries, periodic and fixed in-plane boundaries, for a detailed finite-element model of flexible risers is discussed. By using three-dimensional elements, all layer components are individually modelled and a surface-to-surface frictional contact model is used to simulate their interaction. The approach is applied on several riser models with various lengths and layers. It is shown that the model with periodic boundaries can be effectively employed in a fully-nested (FE2) multiscale analysis based on computational homogenization. In fact, in this model only a small fraction of a flexible pipe is needed for a detailed nonlinear finite-element analysis at the small scale. The advantage of applying periodic boundary conditions in capturing the detailed nonlinear effects and the efficiencies in terms of significant CPU time saving are demonstrated.


Author(s):  
Y B Park ◽  
D Y Yang

In metal forming, there are problems with recurrent geometric characteristics without explicitly prescribed boundary conditions. In such problems, so-called recurrent boundary conditions must be introduced. In this paper, as a practical application of the proposed method, the precision cold forging of a helical gear (which is industrially useful and geometrically complicated) has been simulated by a three-dimensional rigid-plastic finite element method and compared with the experiment. The application of recurrent boundary conditions to helical gear forging analysis is proved to be effective and valid. The three-dimensional deformed pattern by the finite element analysis is shown, and the forging load is compared with the experimental load. The profiles of the free surface of the workpiece show good agreement between the computation and the experiment.


2007 ◽  
Vol 35 (3) ◽  
pp. 226-238 ◽  
Author(s):  
K. M. Jeong ◽  
K. W. Kim ◽  
H. G. Beom ◽  
J. U. Park

Abstract The effects of variations in stiffness and geometry on the nonuniformity of tires are investigated by using the finite element analysis. In order to evaluate tire uniformity, a three-dimensional finite element model of the tire with imperfections is developed. This paper considers how imperfections, such as variations in stiffness or geometry and run-out, contribute to detrimental effects on tire nonuniformity. It is found that the radial force variation of a tire with imperfections depends strongly on the geometrical variations of the tire.


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