Effects of mean stress on fatigue behaviour of a hardened carbon steel

Abstract The effects of mean stress on the cyclic deformation and fatigue life of smooth uniaxial fatigue specimens made from SAE 1045 steel hardened to 55 HRC were investigated. Both compressive and tensile mean stresses were imposed through strain-controlled tests with strain ratios of −2, 0 and 0.5, resulting in fatigue lives ranging from 550 to 106 cycles. Insignificant degrees of mean stress relaxation were observed except at the very short lives. The tensile mean stress was found to decrease life by as much as two orders of magnitude, while compressive mean stress increased life by as much as a factor of five. The experimental mean stress data were used to compare the life prediction capabilities of several fatigue damage parameters that are sensitive to mean stress.