Quantifying and Correcting for Residual Stress Effects on Fatigue Crack Growth Rate Measurements

Fatigue crack growth rate (FCGR) test data play a critical role in the design and reliability of engineering structural components. Residual stress, a common side effect of many additive manufacturing (AM) techniques, can significantly impact the fatigue crack growth rates (FCGRs) observed in standard tests, which may then bias the interpretation of the performance of AM materials. In the present work, the on-line crack compliance (OLCC) method was used to determine the residual stress intensity factor, K_res, while simultaneously collecting fatigue crack growth rate data in edge crack compact (C(T)) specimens of AM material. The measured residual stress intensity factor, K_res, was then used to quantitatively account for the influence of residual stress on the observed FCGRs. Corrected data were compared to the FCGR behavior of annealed wrought material. The results for the materials processed by the different methods were brought into good agreement for the range of applied ∆K evaluated, demonstrating the importance of accounting for residual stress when interpreting fatigue crack growth data in AM materials.