Three-dimensional finite element simulations of microstructurally small fatigue crack growth in 7075 aluminium alloy

ABSTRACT Three‐dimensional finite element simulations were performed to study the growth of microstructurally small fatigue cracks in aluminium alloy 7075‐T651. Fatigue crack propagation through five different crystallographic orientations was simulated using crystal plasticity theory, and plasticity‐induced crack opening stresses were calculated. The computed crack opening stresses were used to construct small crack da/dN‐ΔK diagrams. The generated da/dN‐ΔK curves compared well with experimental small crack data from the literature. The variance observed among the da/dN‐ΔK results, which occurred as a consequence of the different crystallographic orientations employed, was found to be of the same order of magnitude as commonly observed variability in small fatigue crack growth data. This suggests that grain orientation is a major contributor to observed small fatigue crack data scatter.