THE EFFECT OF BENDING OVERLOADS ON TORSIONAL FATIGUE IN NORMALIZED 1045-STEEL

Variable amplitude bending-torsion fatigue experiments were conducted on axle-shafts to determine the effects of overloads on the fatigue li fe of normalized SAE 1045 steel. Either periodic bending overloads or static bending loads were applied to these shafts to determine their e ffect 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 uniaxi al and multiaxial datasets to fall on a single parameter-life curve. I t is postulated that the fatigue strength reduction is due to a reduct ion in crack face interaction which results-in an increase in effectiv e strain intensity. (C) 1998 Elsevier Science Ltd. All rights reserved .