Statistical size effect in the fatigue limit of steel

Then is always a large quantity of initiated cracks in a specimen subjected to cyclic loading. This kind of specimen forms a sample of initial cracks: the larger the specimen, the larger the sample. A method for the predictio n of the statistical size effect due to the sample size is introduced in th is paper. The statistics of extremes can be used to calculate an estimate o f the largest expectable crack in specimens with varying surface area. Conn ection between the initiated crack size and the fatigue limit is obtained w ith the help of the linear elastic fracture mechanics. The presented method is tested to eight sets of experimental data for cylindrical specimens mad e of steel 34CrNiMo8. The mean fatigue limit tends to decrease and the scat ter increase in proportion to increasing material thickness. If these effec ts can be accounted for, as done in this paper, the constant amplitude fati gue limit can be very accurately predicted. The error of the calculated est imates is within -3% to +6% compared to experimental results. (C) 2001 Else vier Science Ltd. All rights reserved.