Volume 17, Issue 5 (September 1989)
Fatigue Performance of AISI 1140 Modified Steel
A study of the fatigue behavior of modified AISI 1140 resulfurized steel containing manganese (1.05 to 1.25%) and sulfur (0.16 to 0.23%) was conducted at room temperature under load-controlled conditions. Monotonic and cyclic mechanical tests were conducted with samples possessing a “C” shaped ring configuration; a finite element analysis was used to establish the stress levels appropriate to the “C”-ring specimen. Quantitative S-N and Goodman (1) diagrams were determined, based on cyclic stresses representing different fractions of the ultimate strength of the material. A toughening mechanism is postulated that accounts for the interaction between the advancing crack front and the duplex microstructure which includes finely oriented manganese sulfide (MnS) stringers encapsulated in the ferrite phase.