The use of nondestructive evaluation methods in fatigue: A review

Efforts to understand fatigue in materials generally rely on defining relationships between the material response to fatigue loading and the evolving remaining material life portion. Typical measurements and data associated with such relationships include load (stress), displacement (strain), and associated properties (eg, mean stress and strain, energy dissipation, and residual stiffness). In addition to obtaining such measurements, efforts have been made to leverage nondestructive evaluation (NDE) methods to obtain additional information and enhance the description of the material fatigue response, especially its evolution due to interacting material-microstructure-property relationships. Given the range of available NDE methods and the number of materials they can be applied to, a critical overview of related investigations is presented in this article. Specifically, the state of the art of applying optical, thermal, acoustic, electromagnetic, X-ray, and other diffraction NDE methods in fatigue investigations is provided and discussed. The methods are individually described for background and defining their relationship to fatigue, followed by descriptions of their current uses and contributions to enhancing the understanding of fatigue, and their limitations and ways that improvements could be made.