On the influence of overloads on the fatigue performance of deep rolled steel SAE 1045

The present paper analyzes the influence of overloads on the fatigue strength and residual stress stability for a tempered and deep rolled steel SAE 1045. Deep rolling has been conducted at room temperature and 250 degrees C. A single overload as well as blocks of 10 and 100 overloads were applied at two different overload levels of 25% and 50%. A single baseline amplitude of 800 MPa at a stress ratio of R = -1 was considered for fatigue testing. It is shown that overloads negatively influence the near surface areas resulting in significant reduction of the fatigue life up to about 75%. The consequences of overloads on residual stress stability and plastic strain behavior were assessed in depth. Findings presented clearly reveal that residual stress relaxation as well as an increase of plastic strain upon overloading are affected by both the absolute value and the number of overload cycles. Furthermore, conditions deep rolled at elevated temperature, showing superior performance under constant amplitude loading, most severely suffer from overloads.