Fatigue Properties Of High Performance Steel

Abstract

A low carbon content, the addition of alloying elements, and improved mill practices have imparted high performance steel (HPS) with superior toughness, strength, and weldability. Its performance in fatigue, however, is not well understood. A research program presently being conducted at the University of Alberta has obtained the necessary material input parameters for fatigue life predictions. The fatigue performance of two different heats of HPS 485W steel is compared to two other grades of structural steel: A7 steel commonly found in older structures, and G40.21 350WT steel, commonly used in modern bridge structures. Stress or strain-controlled smooth specimen fatigue tests were conducted to obtain cyclic stress vs, strain curves, strain and stress amplitude vs. fatigue life curves, and energy per cycle vs. fatigue life curves, and to obtain the fatigue limit. Crack growth rate data were also obtained. The collected material data are used as a basis of comparison of high performance steel with more common grades of structural steel. HPS 485W steel shows high strength, good ductility, high fatigue limit level, and high fracture toughness. The fatigue test results indicate that HPS 485W steel has a fatigue resistance comparable to that of lower strength structural steels in the stable crack growth range. Its higher fatigue endurance limit, however, provides a distinct advantage.