Predicting microstructurally sensitive fatigue-crack path in WE43 magnesium using high-fidelity numerical modeling and three-dimensional experimental characterization

Microstructurally small fatigue-crack growth in polycrystalline materials is highly three-dimensional due to sensitivity to local microstructural features (e.g., grains). One requirement for modeling microstructurally sensitive crack propagation is establishing the criteria that govern crack evolution, including crack deflection. Here, a high-fidelity finite-element modeling framework is used to assess the performance and validity of various crack-growth criteria, including slip-based metrics (e.g., fatigue-indicator parameters), as potential criteria for predicting three-dimensional crack paths in polycrystalline materials. The modeling framework represents cracks as geometrically explicit discontinuities and involves voxel-based remeshing, mesh-gradation control, and a crystal-plasticity constitutive model. The predictions are compared to experimental measurements of WE43 magnesium samples subject to fatigue loading, for which three-dimensional grain structures and fatigue-crack surfaces were measured post-mortem using near-field high-energy x-ray diffraction microscopy and x-ray computed tomography. Findings from this work are expected to improve the predictive capabilities of simulations involving microstructurally small fatigue-crack growth in polycrystalline materials. The performance of potential crack-deflection criteria are assessed for 3D short-crack paths.The predictions are compared to experimental measurements of fatigue-failed WE43 magnesium samples.Blind predictions based on FIP distributions were most sensitive to the local microstructure.These findings expected to improve the predictive capabilities of short-crack simulations.