Effect of roller-working and mean stress on fatigue strength of ferritic stainless steel

This paper covers investigations of the effect of mean stress on fatigue properties of non-deformed specimens and the effect of roller-working on fatigue properties of plastically deformed specimens of ferritic stainless steel. In order to evaluate the effect of mean stress on fatigue strength improvement, tensile-compressive fatigue test have been performed on non-deformed specimens. In order to study the effect of plastic deformation due to roller-working on fatigue properties of deformed specimens, rotating bending fatigue test have been done on plastically deformed specimens in several degree of plastic deformation. The results showed that according to increase of the compressive mean stress the fatigue strengths of these specimens increase. Compressive mean stress delays crack initiation and suppresses fatigue crack propagation properties. In case of tensile mean stress, this kind of mean stress decreases the fatigue strength. The fatigue limits of plastically deformed specimen are much higher than that of non-deformed specimen and do not linearly increase with increase of plastic deformation value. The fatigue limit improvement of deformed specimens would be caused by the compressive residual stress in the notch root and workhardening due to roller-working.