The growth of short cracks and life prediction

The classical methods of the life prediction and residual life evaluation of cyclically loaded materials and structures are briefly summarised. The principal mechanisms leading to the fatigue damage evolution in crystalline materials are analysed. The stages of fatigue damage evolution are given and their importance in fatigue life is discussed. The role of fatigue crack initiation in materials free of defects and in materials with real defects is emphasised. Main attention is concentrated to the description of short crack growth regime. Characteristic results concerning the crack growth kinetics in terms of plastic strain driven crack growth are presented. The general equation describing fatigue crack growth under cyclic loading is derived. The information concerning the general equation describing the fatigue crack growth is used to propose novel method of the fatigue life prediction and residual fatigue life evaluation. The fatigue life prediction of smooth and notched bodies is is illustrated using simple examples.