Abstract Lesiuk

Mean stress effect, stress ratio R in Fatigue Crack Growth Rate description - from Dimensional Analysis to generalization of Paris law

The main problem with the description of FCGR (Fatigue Crack Growth Rate) is a strong dependency on stress ratio R. It is clear that the mean stress effect is reflected in various semi-empirical equations. However, in some energy-based models, observing different descriptions of FCGR phenomena using strain energy density parameters like dissipated energy is possible. During the lecture, it will be performed a simplified review of energy models and my research results of FCGR description in several kinds of steels under mode I and mixed mode concerning different stress ratios. As it can be concluded, the main advantage of the energy approach is the R-ratio invariant description of FCGR. A generalized Paris law will be discussed in the light of uniaxial and multiaxial loading with different approaches including phenomenological - based on Dimensional Analysis (analytical) up to empirical equations based on measured fracture mechanics parameters for elasto-plastic load cases.