STRESS INTENSITY FACTORS FOR FATIGUE CRACKS AT HOLES UNDER CYCLIC STRESS GRADIENTS (PLATES, INTERPOLATIONS, INTERFEROMETRY).

摘要

The objective of this study is to determine stress intensity factors (K) which may be used to predict the fatigue lives of part-through cracks loaded with variable stress gradients. The two types of cracks considered are surface and corner flaws located at holes in plates subjected to various stress distributions. The approach employs the weight function method which uses information from a reference load case to compute the stress intensity factor for a new load situation of interest. Results obtained for a number of crack sizes and load conditions are tabulated to serve as a data source. A second approach for calculating K by direct interpolation of data is also described. The simplicity of this latter technique makes it ideal for use in fatigue predictions where repetitive determination of K is required.;Results are incorporated in a fatigue crack growth algorithm, which is used to perform specimen life predictions. The crack growth calculations are compared with experiments to test the validity of stress intensity factors from weight functions. The comparisons obtained are satisfactory.