Fatigue Crack Growth Life Assessment Using 3D Finite Element Analysis

Damage tolerance and fatigue crack growth life assessments allow manufactures to predict the in-service behaviour of high-risk components. Fatigue crack growth solutions are mostly generated using reduced order models that are based on simple geometries (i.e., corner crack at a bolt hole or surface crack in a plate) with the assumption that cracks hold an elliptical shape during propagation. A new finite element-based modelling process that takes into account component geometry, service loading conditions and minimizes simplifications with respect to crack front shape or planarity of the crack growth path is demonstrated. A 3D finite element-based approach to fatigue crack growth propagation was evaluated as an alternative to reduced order modeling. The modelling approach was verified and validated in three main stages: simple plate geometry, specimens with multiple out of plane cracks, and full-sized specimen panel. A MATLAB analytical solution-based model was developed to estimate crack front evolution and fatigue crack growth life for surface, corner and internal cracks. The analytical results are verified with 3D finite element (FE) based approach implemented in SimModeler Crack. A set of experimental fatigue crack growth measurements based on Al 2024-T3 specimens containing multiple cracks was used to validate the 3D FE modelling solutions. Lastly, fatigue crack growth measurements from a full-sized spar experiment were used to ascertain the accuracy of the proposed FE model