Fatigue life prediction of semi-elliptical surface crack in 14MnNbq bridge steel

The fatigue life prediction of semi-elliptical surface crack in 14MnNbq bridge steel is discussed in this paper. The FCG rates under different stress ratios R as well as FCG behavior under tensile and bending loading conditions are investigated experimentally. Moreover, an approach to predict surface crack growth is discussed, and the advantage of the approach is that the data used in the prediction is obtained from the testing of through-thickness cracks. The effects of crack closure on predictions are also considered and the data corrected by crack closure of through-thickness crack is used. Comparison results show that the corrected prediction with consideration of crack closure provides much better predictions than the normal ones. And reasonable agreement is obtained between the predicted and experimental results.