Short fatigue crack parameters describing the lifetime of unnotched steel specimens

The progressive fatigue damage of a material is closely related to the whole population of cracks on the surface of an unnotched specimen. In order to understand which parameter, such as the crack density, the total crack length and the total crack area, is a useful indicator of fatigue damage, rotatory bending fatigue tests are carried out using smooth specimens of medium-carbon steel. The behavior of short crack propagation and the evolution of surface cracks during fatigue are examined. The aim of this paper is to extend the research on fatigue damage in the already studied steel and to study how these damage parameters are correlated with the process of fatigue damage in order to evaluate the effectiveness of damage detection methods.