A METHOD TO REDUCE THE SCATTER IN FATIGUE-CRACK GROWTH-RATE DATA

The scatter in experimentally determined fatigue crack growth rates is dependent, in part, on the data reduction process applied to the pair ed values of crack length and number of cycles recorded in crack growt h tests. An additional data reduction process is proposed which replac es the original test data by a smooth curve. Analysis of mid-range gro wth rate data for Udimet 720 shows that the introduction of this addit ional data reduction procedure reduces the scatter in the calculated g rowth rates, increases the effectiveness of Walker's method in account ing fbr the effects of stress ratio, and leads to more accurate predic tions of the experimental crack propagation lives of test specimens.