Abstract
The true relief arising on the surface of cyclically strained materials has been assessed using atomic force microscopy and high resolution scanning electron microscopy. Characteristic features of the surface relief are well-defined persistent slip markings consisting of extrusions and intrusions. The shape of extrusions and intrusions can be obtained by combination of both methods. The growth of extrusions during fatigue life was reported for austenitic and ferritic stainless steels. The comparison of the experimental data with the predictions of the various models of fatigue crack nucleation allows to conclude that the realistic models are based on a continuous redistribution of matter leading to extrusion and intrusion formation.
