Fatigue damage accumulation and lifetime prediction of defective C35 steel subjected to block loading

This paper deals with the influence of both defect and loading sequence on fatigue damage accumulation of C35 steel containing artificial defects. Tests were carried out using fatigue samples with artificial spherical defects introduced at the surface. Tests were performed using two blocks loading under increasing and decreasing magnitude. The experimental results were compared to the damage calculated by the Miner rule. In the case of defective material; it is shown in both cases a minor influence of sequence’s effect. A lifetime prediction method is then developed to assess the residual lifetime of damaged defective material. The method is based on a multiaxial endurance criterion used to calculate the equivalent local stress distribution around the defect and to inject it in an uniaxial damage cumulative rule. Finally a comparison between experimental and theoretical results is performed. It is observed that the Mesmacque sequential law gives the most accurate lifetime prediction of defective specimens