AN ALGORITHM TO GENERATE QUADRILATERAL OR TRIANGULAR ELEMENT SURFACE MESHES IN ARBITRARY DOMAINS WITH APPLICATIONS TO CRACK-PROPAGATION

A new hybrid algorithm for automatically generating either an all-quad rilateral or an all-triangular element mesh within an arbitrarily shap ed domain is described. The input consists of one or more closed loops of straight-line segments that bound the domain. Internal mesh densit y is inferred from the boundary density using a recursive spatial deco mposition (quadtree) procedure. All-triangular element meshes are gene rated using a boundary contraction procedure. All-quadrilateral elemen t meshes are generated by modifying the boundary contraction procedure to produce a mixed element mesh at half the density of the final mesh and then applying a polygon-splitting procedure. The final meshes exh ibit good transitioning properties and are compatible with the given b oundary segments which are not altered. The algorithm can support disc rete crack growth simulation wherein each step of crack growth results in an arbitrarily shaped region of elements deleted about each crack tip. The algorithm is described and examples of the generated meshes a re provided for a representative selection of cracked and uncracked st ructures.