Effect of prestrain on and prediction of fatigue limit in carbon steel

The effect of prestrain on the fatigue limit of 0.1% (annealed) and 0.5% (quenched and tempered) carbon steel was investigated. Formulas for predicting the fatigue limit of carbon steels were proposed. The fatigue limit of 0.1% carbon steel increased with increasing surface hardness and surface compressive residual stress imposed by prestrain. The fatigue limit decreased when precracks were generated on the surface, in spite of a large surface compressive residual stress in the case of 0.5% carbon steel. The precrack, variation of surface hardness and surface residual stress were considered to be parameters applicable in formulas for predicting the fatigue limit of prestrained carbon steels. The calculated results of such formulas showed good agreement with the experimental results.