LONG LIFE SPECTRUM FATIGUE OF CARBON AND STAINLESS STEEL WELDS

Abstract— Fatigue tests of non-load carrying carbon and stainless steel fillet welds have been performed using spectrum loading typical for rail vehicles. The proportion of spectrum cycles exceeding the constant amplitude fatigue limit ranged between 0.86% and 100% and cycles to failure ranged from 4.2 ± 10⁵ to 2.1 ± 10⁷. For the longest tests, the majority of fatigue damage was contributed by cycles with stress ranges less than the constant amplitude fatigue limit. For the carbon steel welds a significant portion of fatigue damage was produced by cycles with stress ranges less than 50% of the fatigue limit but only a small fraction of damage was produced by cycles of this size for the stainless steel welds. The carbon steel welds had slightly better fatigue strength at lives less than 10⁷ cycles but results suggest that stainless steels may have superior long-life variable amplitude fatigue strength when a greater portion of life is spent in the early stages of crack nucleation and growth.