A Study of the Notch Effect and of Specimen Design and Loading on the Fatigue Properties of Cast Steel

Scope of the research report: The purpose of the research included in this report is to extend the knowledge on the fatigue properties of cast steel by presenting a study of the effect of notches on fatigue properties and the effect of specimen design and the method of loading on the fatigue properties of cast steel. Summary of the research report conclusions: (a) Notch Effect—A severe notch (0.015-in. radius) in fatigue testing of cast steel results in a 36 percent reduction in endurance limit based on unnotched specimens. An extremely severe notch (0.001 in. radius) results in a 42 to 53 percent reduction in the endurance limit. The fatigue strength reduction factor K_f for extreme notched specimens is appreciably higher for cast steel in the quenched and tempered condition. (b) Specimen Design and Loading—Cast steel exhibits better endurance properties in reversed torsion than reversed bending. Bending fatigue tests of cast steel tested at 1800 rpm result in lower endurance properties than rotating beam tests at 10,000 rpm. The difference is greater at the higher tensile strength level.