Plastic Stress Concentration Factor KF in Fatigue
Palavras-chave:
Short cracks, stress gradient factor, notch-induced plasticity, fatigue plastic stress concentration factor, notch concentrationResumo
This study uses the stress gradient factors (SGFs) ahead of notch tips to determine the notch effects in
fatigue, which are generally smaller than notch stress concentration factor due to the material tolerance to non-
propagating short cracks. Even under elastic nominal stress levels, the notch vicinity may accumulate plastic
strains when the maximum local stress exceeds the material yield strength. Considering the significant role of local
plasticity in the propagation behavior of short cracks within the notch plastic zone and therefore in the notch
sensitivity, a methodology is proposed to take into account the elastic-plastic stress and strain fields modeled by
Neuber’s rule and cyclic Ramberg-Osgood equation. 2D finite element analyses are conducted to compute the
stress intensity factors (SIFs) of smooth and notched specimens, which in turn are used to calculate the SGFs and
finally to obtain plastic fatigue notch factor predictions. To validate the methodology, experimental S-N data of
centre-notched, U-notched and V-notched plate specimens made of different materials and tested at uniaxial load
ratio R=-1, 0 and 0.1 are collected from the literature and compared with simulation results.
