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Abstract 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.
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Passive atomic-scale optical sensors for mapping light flux in ultra-small cavities
Abstract Understanding light propagation and attenuation in cavities is limited by lack of applicable light sensing technologies. Here we demonstrate the use of light-sensitive metastable states in wide bandgap aluminosilicates (feldspar) as passive optical sensors for high-resolution mapping of light flux. We develop non-destructive, infrared photoluminescence (IRPL) imaging of trapped electrons in cracks as thin as 50 µm width to determine the spatio-temporal evolution of light sensitive metastable states in response to light exposure. Modelling of these data yields estimates of relative light flux at different depths along the crack surfaces. Contrary to expectation, the measured light flux does not scale with the crack width, and it is independent of crack orientation suggesting the dominance of diffused light propagation within the cracks. This work paves way for understanding of how light attenuates in the minutest of cavities for applications in areas as diverse as geomorphology, biology/ecology and civil engineering.
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- Award ID(s):
- 1839148
- PAR ID:
- 10507723
- Publisher / Repository:
- Nature
- Date Published:
- Journal Name:
- Scientific Reports
- Volume:
- 13
- Issue:
- 1
- ISSN:
- 2045-2322
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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Accepted Manuscript1.0
- Journal Article:
- https://doi.org/10.1038/s41598-023-32010-y
