Effect of variable amplitude on fatigue life of 17CrNi steel beyond 10⁷ cycles

To study the effect of the variable amplitude on the carburised 17CrNi high-strength steel, very high cycle fatigue tests were performed on smooth specimens under the stress ratios of 0 and −1. After the experiment, the characteristics of the fracture surfaces were investigated by means of an optical microscope and a scanning electron microscope. Circular-formed marks were found around the inclusion inside the fisheye. Finally, based on five damage models, the fatigue life of the carburised 17CrNi high-strength steel was predicted. The comparison of the calculated lives with the experimental data shows that the modified Miner’s criterion is the most accurate and it can adequately characterise the fatigue life of the 17CrNi steel.