Three-dimensional finite element analysis using crystal plasticity for a parameter study of fatigue crack incubation in a 7075 aluminum alloy

Three-dimensional finite element analysis of a bicrystal using a crystal plasticity constitutive theory was performed to compute the maximum plastic shear strain range Δγmaxp in the matrix, at the particle/matrix interface, and at the bicrystal boundary. Using the finite element analysis results, a design of experiments (DOE) technique was employed to understand and quantify the effects of seven parameters on fatigue crack incubation: applied displacement, load ratio, particle modulus, the number of initially active slip systems, the relative crystallographic misorientation at the grain boundary, the particle aspect ratio, and the normalized particle size. The simulations clearly showed that the applied displacement is the most influential parameter. In most cases, particles were found to be more significant than bicrystal boundaries for incubation. The number of initially active slip systems, the particle aspect ratio, and the normalized particle size showed some influences on fatigue incubation. The particle modulus was the least influential parameter.