Tri-dimensional numerical modelling of plasticity induced fatigue crack closure

Fatigue crack closure has been studied numerically with 2D finite element models as alternative to experimental methods. In a few cases fatigue crack closure behaviour has been analyzed with tri-dimensional models. In this work, a compact C(T) aluminium specimen has been modelled tri-dimensionally. The minimum element size is smaller than common accepted recommendation. This parameter limits the mesh size along the thickness. The number of divisions of the thickness is a special issue studied in this work. Different thicknesses, range of loads and stress relations have been calculated. The results show the crack behaviour through the thickness. The plastic zone is visualized and quantified. An abrupt transition is observed in a thin external slice of the specimen; only captured with a fine meshing of the thickness. Crack closure/opening along the thickness have been computed. Results show that closure is only relevant in this small external area and its size is not affected by the thickness. Results match experimental observation and have been correlated with experimental tests.