Predicting fatigue crack initiation in milled aerospace grade Ti-6Al-4V parts using CPFEM

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Arcidiacono, Mauro Francisco and Violatos, Ioannis and Rahimi, Salaheddin; Cawte, E. R. and Cockings, H. L. and Stekovic, S. and Yates, J. R., eds. (2024) Predicting fatigue crack initiation in milled aerospace grade Ti-6Al-4V parts using CPFEM. In: Proceedings of the 9th Engineering Integrity Society International Conference on Durability & Fatigue. Engineering Integrity Society, GBR, pp. 115-126. ISBN 978-0-9544368-7-2 (https://doi.org/10.5281/zenodo.12705102)

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Abstract

A Crystal Plasticity Finite Element Method (CPFEM) model is proposed for determining the likelihood of fatigue crack initiation and its sites in an aerospace-grade Ti-6Al-4V machined part. The methodology is based on a digitally reconstructed Electron Backscatter Diffraction (EBSD) microstructural model that incorporates the previous deformation history, the residual stress distribution and the roughness profile which result from milling. The constitutive model employs the Armstrong-Frederick nonlinear formulation and implements microstructure sensitive fatigue initiation parameters. Findings suggest that fatigue initiation is significantly influenced by the surface topology and the pre-existing strain and stress fields. The simulation predicts the formation of persistent slip bands within the deformed microstructure and ratcheting that causes local plastic strain accumulation. The model indicates that at the surface and near-surface regions fatigue initiation is mainly driven by local topography, while orientation becomes more dominant at higher depths.

ORCID iDs

Arcidiacono, Mauro Francisco ORCID logoORCID: https://orcid.org/0000-0003-3215-6766, Violatos, Ioannis ORCID logoORCID: https://orcid.org/0000-0002-0669-1741 and Rahimi, Salaheddin ORCID logoORCID: https://orcid.org/0000-0001-6461-988X; Cawte, E. R., Cockings, H. L., Stekovic, S. and Yates, J. R.
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