Uncertainty-aware deep kernel learning: An end-to-end approach for crack localization in turbine blades

Early and reliable crack localization in jet turbine blades is important for structural health monitoring in aerospace systems. This study presents an uncertainty-aware Deep Kernel Learning (DKL) framework that integrates a deep residual feature extractor with a Sparse Variational Gaussian Process (SVGP) model for crack location regression from modal frequency data. The model is trained end-to-end, enabling the learned latent representation to be optimized jointly with the Gaussian Process objective while providing predictive uncertainty estimates. A finite element simulation dataset consisting of 901 samples was generated by parametrically varying crack positions along the turbine blade and extracting modal frequency features. To ensure a comprehensive evaluation, robustness analyses were conducted under both Gaussian noise (σ = 0.01, 0.05, 0.10) and synthetic dataset shifts (± 5% and ± 10%). In addition, a more realistic evaluation was performed using non-uniform stochastic perturbations that simulate feature-wise variability, sensor drift, and environmental noise. The proposed DKL model was compared with classical machine learning methods (Random Forest, SVR, XGBoost) as well as modern uncertainty-aware deep learning approaches, including MC Dropout and Deep Ensemble. Results show that all models achieve high predictive accuracy under clean conditions due to the smooth and deterministic nature of the simulation dataset. Under stochastic perturbations, Deep Ensemble achieves the lowest prediction error, while the proposed DKL model maintains competitive accuracy and provides more conservative and stable uncertainty estimates. These findings indicate that the proposed DKL framework offers a balanced trade-off between predictive performance and uncertainty awareness. However, further validation on real-world sensor data is required to assess its applicability in practical structural health monitoring scenarios.