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035 _a.b11829540
099 9 _aAIT Thesis no. ST-01-13
100 1 _aYin, Xianpu
245 1 3 _aAn enhancement of the element free Galerkin method
260 _aBangkok :
_bAsian Institute of Technology,
_c2001
300 _a53 leaves
490 1 _aThesis ;
_vno. ST-01-13
500 _aA thesis submitted in partial fulfillment of the requirements for the degree of Master of Engineering, School of Civil Engineering
502 _aThesis (M.Eng.) - Asian Institute of Technology, 2001
520 _aElement-Free Galerkin Method (EFGM) is best applied to problems where intensity of responses is not uniform, deformation is excessive, or cracks occur and propagate. This study explores the feasibility and the advantages of varying the domain of influence (DOI) and the integration cells in relation to the intensity of the responses to minimize errors and improve efficiency of EFGM. Several strategies for varying the sizes of DOI and the integration cells are investigated and tested. As a rule of thumb, DOis associated with any node must be large enough to ensure that at least m nodes are visible from each integration point, where m is the number of monomials in basis function. At the same time, integration cells must be fine enough to accurately evaluate the contribution of all visible nodes. In standard EFGM, all DOis are maintained uniform in size. Thus, they must be large enough to cover sufficient number of nodes in the low-gradient areas in order to ensure a good matrix condition in the Moving Least Square (MLS) approximation. However, large DOis will cause a large array of nodes to be coupled; thus solution not only is expensive, but also cannot reflect locality effects. On the issue of numerical integration, the commonly used uniform background cells will yield an inaccurate solution for high node-concentrated area or wastes excessive computing time in the node-sparse area. In this study, for lD problems, integration over the entire problem domain is subdivided into a series of integration sub-domains, each being defined as interval between two nodes. For 2D problems, integration over the entire problem domain is subdivided into a network of triangular sub-domain cells, each being defined as a triangle formed over three nodes. By this procedure, the size of integration cells can be varied with the density of nodes, while the number of integration points in each cell is constant. The numerical tests in this study confirm that the proposed strategy for varying the sizes of DOI and integration cells works effectively for all test examples. This should serve as the initial step towards to a breakthrough in adaptive discretization of EFGM in the future extension of this study. By establishing an algorithm to generate a network of triangular cells based on any given distribution of nodes, the triangulation process can be automated and transparent to users. Thus, with a good estimator of error norm, one can determine if more nodes should be added to the mid-sides of any triangle. Then, all nodes including the new ones will be considered in the new triangulation, and the new discretized domain can be reanalyzed. This process can be repeated until a situation can be achieved where error norms in all triangles are controlled under a specified limit.
650 1 0 _aFinite element method
700 0 _aWorsak Kanok-Nukulchai,
_eChairperson
700 1 _aBarry, William Joseph,
_eExamination Committee
700 1 _aKim, Kidu,
_eExamination Committee
710 2 _aGovernment of Japan,
_eExamination Committee
810 2 _aAsian Institute of Technology.
_tThesis ;
_vno. ST-01-13
856 _3Full-Text
_uhttp://203.159.5.9/ait-thesis/detail.php?q=B09497
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