Fatigue growth simulation for cracks in notched and unnotched round bars

Fatigue crack growth for various cracks in both unnotched and notched round bars is directly modelled by using an automated numerical technique, which calculates the stress intensity factors at a set of points on the crack front through the three-dimensional finite element method and then applies an appropriate fatigue crack growth law to this set of points to obtain a new crack front. This technique also has the capability of automatic remeshing so that the crack propagation can conveniently be followed. The crack geometries modelled in the present paper include a small internal crack near the free boundary and several initially part-elliptical or irregular surface cracks in a smooth round bar under tension, a surface crack in different semi-circularly notched bars under both tension and bending, a surface crack initiated from the root of a V-notched bar and an initially twin crack configuration within a smooth tension bar. Some fatigue growth characteristics relevant to each type of cracks are also revealed. It is demonstrated that the fatigue growth analyses of various cracks commonly occurring in bars can reliably be made by using the automated finite element technique proposed.