| A smooth specimen subjected to cyclic loading undergoes different stages of crack growth behavior; three distinct crack growth regimes exist, namely the regime of microstructually small cracks, the regime of physically small cracks and the long crack regime. The limits of these different crack growth regimes can be evaluated in terms of characteristic crack lengths which are functions of material and mechanical parameters. A log △σ-log a diagram is used to derive estimates of these characteristic. crack lengths. The approach presented relies on relations between material strength and grain size, on the one side, and on fracture mechanics quantities depending on the applied load such as the size of the plastic zone ahead of the crack tip, on the other side. |
|
