Theoretical determination of the fatigue strength limit of electrical discharge machined (EDM) AISI 8740 steel

AISI 8740 is an alloy steel which is frequently preferred in plane and aerospace engineering. In this study, it was machined by electro-erosion and fatigue life of the surface structure is theoretically evaluated. For this purpose, AISI 8740 steel is processed with different processing parameters with EDM and the surface roughness and hardness of the produced surfaces are measured. Using these values in $\sqrt{area}$ fatigue model, the effect of surface structure on the fatigue endurance limit of the AISI 8740 steel was evaluated. It is the result of study that, surface roughness increases with increasing processing current and pulse duration and as a result fatigue strength limit decreases.