An automatic mesh generation for finite element analysis program has been developed in 2 or 3 dimension. Flexibility for mesh refinement and treatment of difficult-to-mesh geometries are specifically emphasized. Depending on geometrical and material variations, the region to be discretized is manually divided into subregions. Each subregion is described by its boundaries in terms of edges and control points. The inputs for the edges are composed of straight lines, arcs and polynomial curves. No connectivity information of the adjacent subregions is required to be inputed by the user. Inner nodes are automatically generated corresponding to the nodal arrangement along the edges which are given by the user.
The automatic generation of triangular finite elements is done using boundary node lengths and corner angles, such that the generated triangles are about equilateral. The resulting triangulations are always satisfactory, even for very abnormally shaped subregions. The transition between small and large triangles is also very smooth. The generation of tetrahedron elements has been based on Dirichlet Tessellation, resulting in very regular element shapes.
Mesh refinement schemes for triangular, quadrilateral and tetrahedron elements are developed. The triangular mesh refinement is performed by bisectioning of the largest side until no non-conforming element is left. The result is a smooth variation of mesh size. In quadrilateral element case, a subdivision of prescribed elements is used, resulting in variable node elements.
The program based on the algorithms developed, combined with existing preprocessor, PREQB for quadrilateral and brick elements, has greatly enhanced the flexibility and scope of preprocessing capabilities. Nine illustrative examples have been presented to show the details of the method and its capabilities. They include triangular and tetrahedral mesh generation, and several mesh refinements.
