The critical distance theory for fatigue analysis of notched aluminium specimens subjected to repeated bending

This paper provides new insights in the use of the critical distance method for fatigue analysis of notched aluminium components subjected to constant amplitude bending loading. A straightforward test setup was developed to load test samples with different stress concentrations in repeated bending at high test frequency. The mean values of the local endurable stress amplitudes are determined with the staircase method and the Dixon and Mood theory using a minimum amount of test samples. The critical distance is determined using these fatigue limits and the corresponding stress gradients determined by means of finite element analysis. The results indicate a unique critical distance of 0.22 mm for fatigue crack initiation. Consequently, the critical distance theory can be successfully applied for fatigue analysis of notched specimens or engineering components of aluminium EN AW 7075 T7351 with geometrical features of various size and shape subjected to fluctuating loading in bending.