Effects of Multiple Interacting Cracks on rates of Fatigue Crack Growth

As engineering applications have become more sophisticated, more dangerous and severe failures in structures have occurred. Therefore, Fracture Mechanics, the study of cracks and their growth, began in the 1950s and our understanding of material failures e.g. in aircraft structures has improved significantly since then. This project focuses on developing 2D models of crack growth under cyclic load conditions. The models are being developed using the displacement discontinuity method with known influence functions developed for a single crack element in a half-space. A model of a Mode I pressurized crack in an infinite region was completed. The resulting crack openings were compared to the exact solution, and it was found that as the number of elements (N) used to model the crack increased, so did the accuracy of the crack opening profile. However, the stress intensity factor (K1) which governs the rate of crack growth, failed to converge smoothly as N increased, therefore prompting the need to implement special crack tip elements to improve its accuracy. This was accomplished by dividing the outer crack elements into smaller sub-elements, thus allowing the model to represent a more mathematically accurate and realistic crack. Next steps are to generalize the code to model non-planar cracks and apply cyclic loading to model fatigue crack growth.