Multiple surface crack propagation: numerical simulations and experimental tests

In house made experimental observations of three-dimensional fatigue crack growth are compared to numerical predictions by the Boundary Element code BEASY. Fracture analysis results for a complex geometry specimen, undergoing a general load spectrum, are presented with regard to 3D crack propagation and mode coupling effects. The specimens under consideration are cracked tension specimens, with a through crack or a quarter/semicircular crack that proceed inclined to the remote loading direction. Mixed mode conditions along the crack edge are characterised: the stress intensity factors are determined using the crack opening displacement method (COD) and the crack growth direction is computed by the minimum strain energy density criterion. Effects of specimen complex geometry, produced by a part-through the thickness hole nearby the initial saw cut notch, on fracture crack path are analysed. Moreover multiple interacting 3D cracks are simulated correspondingly to experiments: a satisfactory agreement between numerical and experimental crack growth direction and crack growth rates are displayed.