Studies on Impact Fatigue : part II, Inelastic Behavior of S50C Steel under Impact Fatigue Loads

Using plain specimens of annealed S50C carbon steel, fatigue tests were conducted under fully reversed sinusoidal axial stress and under repeated impact stress. Inelastic behavior of specimens was observed using strain gauges mounted on the specimens. Under the impact fatigue stress, fractures occurred at the stress levels lower than the ordinary fatigue limit and in the region of a larger number of stress cycles than 107. The inelastic strains accompanied with a fracture were unexpectedly small comparing with those under sinusoidal stress. And the amount of hysteresis energy accumulated : in the specimen during the impact fatigue test was also less than the corresponding value under sinusoidal stress.