ABSTRACT
The fatigue of a machine part depends strongly on its surface layer condition. The experience shows that fatigue failure begins in most cases at the surface. This is due to the fact that surface layers bear the greatest load and that they are exposed to environmental effects. Crack initiation and propagation, in most cases, can be attributed to surface integrity which includes surface roughness, structure and stress conditions of the surface layer and material properties. The importance of surface integrity rises as the conditions of loading, temperature, speed and vibration increase. Fatigue strength of machine parts may be improved by the choice of methods and conditions which will offer the optimal combination of surface integrity parameters. The fatigue strength of a machine part is affected by surface integrity, including surface roughness, cold work, residual stresses and structural transformations in the surface layer.
