Microcrack propagation and microstructural parameters of fatigue damage

Modern approaches to microstructural analysis of fatigue in metallic materials consider the density and the total length per unit area of propagating surface microcracks as useful indicators of fatigue damage. Such parameters, when observed on a carbon steel studied in a previous paper, have a dispersion similar to that of fatigue life and they are linearly correlated with fatigue endurance. The aim of this paper is to extend the research on fatigue damage in the already studied carbon steel and to examine the scatter of crack propagation rate together with the evolution of surface cracks during fatigue life. The final aim of this work is to study how these two factors are correlated with fatigue life distribution in order to evaluate the effectiveness of damage detection methods.