Fatigue Analysis Based on the Field Theory of Deformation and Fracture

We are developing a physics-based numerical model for fatigue using the Field Theory of Deformation and Fracture (Field Theory). The interferometric technique Electronic Speckle-Pattern Interferometry (ESPI) is used to analyze the spatiotemporal behavior of the displacement field formed while a specimen experiences cyclic loads. Numerical models solve wave equations derived from the Field Theory under conditions assimilated with physical experiment. The Field Theory describes deformation dynamics of elastic, plastic, and fracture stages, using the same theoretical foundation. Hence, the Field Theory defines each stage with specific spatiotemporal features. The ESPI experiment exhibits these features at each stage with corresponding fringe patterns that are consistent with stress-strain characteristics. The numerical results exhibit similar spatiotemporal behavior of the displacement field observed in experiment in the respective stages. Fringe patterns in numerical analysis and experiments are the same in the x and y directions prior to fracture, which is one of the spatiotemporal features defined by the Field Theory. Thus, we can verify that the Field Theory can be used to model fatigue fracture dynamics. This makes the theory useful for aerospace engineers to study fatigue.