The influence of machined surface roughness on the fatigue life of S355JR steel has been investigated. The specimen have been machined with three roughness levels and tested under plane fatigue. The surface roughness parameters were used to estimate the effective stress concentration factors Kt using the Arola-Ramulu model and Neuber model. In this paper it is proposed a modification for both models. Based on the experimental results was obtained the evolution of the effective stress concentration factor for the original Arola-Ramulu and Neuber models and also for the modified ones.
