Defect Analysis by Computed Tomography in Metallic Materials: Optimisation, Uncertainty Quantification and Classification
DOI:
https://doi.org/10.62679/9eykx120Keywords:
Computed Tomography, Additive Manufacturing, Titanium alloy, Uncertainty quantification, Defect classificationAbstract
This paper presents a novel methodology for optimising the X-ray Computed Tomography (CT) post-processing protocol for defect detection in metallic materials, assessing the associated uncertainties and performing a reliable defect classification. The approach aims to remove the systematic error that impacts defect reconstruction, thereby improving the accuracy of defect size and morphology assessment, which is essential for fatigue life prediction, particularly in materials produced through additive manufacturing (AM). The performance and robustness are evaluated by analysing eleven titanium alloy samples produced via electron beam melting (EBM). The developed methodology entails an iterative comparison of CT defect reconstructions with fractographic measurements to identify optimal parameters for CT post-processing. This aimed, in particular, to reduce the systematic error related to the renowned Murakami's parameter √area. The uncertainty of various defect features, such as equivalent diameter, sphericity and aspect ratio, is calculated by propagating the remaining stochastic uncertainty of √area. A K-means clustering algorithm is trained to cluster unlabelled defects into three major categories often encountered in AM, e.g. gas pore (GP), key hole (KH), and lack of fusion (LOF). Eventually, the labelled defects are processed through a support vector machine (SVM) to infer the analytical form of the decision boundaries.
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