Abstract
For stainless steel, it was pointed out that fatigue life did not decrease due to mean stress because the mean stress caused plastic shakedown and that reduced the strain amplitude under the same stress amplitude. However, it may reduce the fatigue life of work hardening material due to the mean stress. In this study, the effect of the mean stress on fatigue life of cold-worked material was investigated in detail using Type 316 stainless steel which introduced 20% plastic strain. Axial fatigue tests were conducted in ambient air and room temperature. It was shown that fatigue life of stainless steel was not reduced by introducing the plastic strain because non-elastic strain amplitude of cold-worked materials under the same stress amplitude decreased due to the work hardening. Fatigue life correlated better with the strain amplitude than the stress amplitude regardless of degree of cold-work. It was found that fatigue life of the cold-worked material decreases with increase the mean stress because crack opening point decreased with increase the mean stress. It was concluded that fatigue life well correlated with effective strain range, which corresponded to the crack opening range regardless of degree of cold-work and mean stress.
