Automatic and Adaptive Finite Element Mesh Generation For Full 3D Fatigue Crack Growth

G.Cook, C.Timbrell, P.W.Claydon

STRUCENG & FEMCAD Conference, Grenoble, France, 1990

A method is presented for automatically generating meshes containing 3D crack fronts. Further, an adaptive meshing scheme is presented for automatically updating meshes during full 3D fatigue crack growth prediction.
Cracks are introduced into a valid mesh of the intact component by a mapping scheme which replaces standard 20 noded brick elements with 'superelements'. In the context of this paper, the term 'superelement' refers to a set of 20 noded brick elements which models a quarter circular or through crack front using collapsed 'quarter point node' brick elements. Replacement of elements in a mesh allows introduction of one or more distinct crack fronts, with more than one superelement permitted on each distinct crack front. A special mapping controls the crack size in each superelement and maintains original isoparametric surfaces thus creating a valid mesh for the cracked component. Following incremental fatigue crack growth prediction, all superelements are re-mapped to obtain a mesh with the new crack position. The mapping scheme allows non-planar crack growth in 3D geometries.
The procedure has been found to be flexible, efficient and a great time saver in 3D fatigue crack growth analyses. Good agreement with experimental fatigue crack growth data has been demonstrated using this meshing scheme.