Constant-Amplitude Versus K-Control in Fatigue Crack Growth Rate Testing

This study compared K-control to constant-amplitude fatigue crack growth rate testing to determine under what conditions K-control testing should be used for K-increasing tests. The results showed that there is no significant difference between the data generated from constant-amplitude and K-control testing for compact-tension specimens when the normalized K-gradient ranged from 1.65 to 5.00 (1/in.) and test time was improved by as much as 70 % for the K-control tests. In most cases, and especially for small test specimens, K-Control K-increasing tests are recommended as a more efficient alternative to constant-amplitude testing.