Title: Fatigue Strength and Fatigue Deformation of S50C Steel under Random Load
Abstract: Axial load fatigue tests were carried out on the plain specimens made of S50C carbon steel under loads of random and constant amplitudes with mean stresses 0 and 20kg/mm2. Furthermore, in the case of mean stress 20kg/mm2, the fatigue deformations of specimens were also measured under respective loads.The testing machine was an electro-hydraulic servo type equipment and the signals for random loading tests were supplied by the pseudo-random noise generator, which generated the repeated noise signals with a continuous analog waveform of approximately gaussian distribution in known sequence.It was observed that the endurance limits under random and constant amplitude loads nearly coincided to each other when they were compared on the basis of the maximum peak stress σpmax, and that the increases of fatigue deformation under random and constant amplitude loads showed the tendencies similar to the ordinary creep curves. Some discussions were made on the behaviors of fatigue strains by comparing the values of initial strain, ε0, strain rate A and final strain εN obtained under respective loads.