The effect of bending overloads on torsional fatigue in normalized 1045 steel

Abstract Variable amplitude bending-torsion fatigue experiments were conducted on axle-shafts to determine the effects of overloads on the fatigue life of normalized SAE 1045 steel. Either periodic bending overloads or static bending loads were applied to these shafts to determine their effect on torsional fatigue. It was determined that these yield stress level bending excursions both decrease the torsional fatigue limit and shorten the torsional fatigue life at medium and long lifetimes. The magnitude of this effect is very similar to that of uniaxial overloads, and a multiaxial fatigue parameter was found which causes the uniaxial and multiaxial datasets to fall on a single parameter–life curve. It is postulated that the fatigue strength reduction is due to a reduction in crack face interaction which results in an increase in effective strain intensity.