Quantitative evaluation of the effect of surface roughness on fatigue strength (Effect of depth and pitch of roughness)

Abstract

In order to investigate the effect of surface roughness on fatigue strength, fatigue tests for a medium carbon steel, which was annealed and free of residual stress (HV≅170) and quenched and tempered (HV≅650), were carried out. To simulate the actual surface roughness, extremely shallow periodical notches with a constant pitch but irregular depth were introduced. The equivalent defect size √areaR for roughness was defined to evaluate the effect of irregularly shaped roughness using the √area parameter model. The fatigue limits of the annealed medium carbon steel specimens with artificial surface roughness are much higher than those of the specimen with a single notch because of the interference effect of notches. The fatigue limits predicted by the √area parameter model are in good agreement with the experimental results.