Reference-free impedance-based crack detection for asymmetric structures: application to tidal turbine blades

Abstract

Impedance-based technique is a promising approach for structural health monitoring due to its high sensitivity to minor local damage, real-time monitoring capability, and cost-effectiveness. Traditional impedance-based methods rely on comparing the current impedance signal with a reference state, however the baseline characteristics may fluctuate under varying and noisy conditions, resulting in unreliable detection. An existing study proposed a reference-free impedance-based method by directly analyzing current-state impedance responses, allowing robust long-term monitoring by eliminating the need for baseline data. However, this method faces challenges for asymmetric structures, where additional mode conversions can obscure damage signatures and cause false detections. This study proposes an improved reference-free approach that enhances damage detection by extracting damage-sensitive features while filtering out irrelevant mode conversions. Numerical simulations on asymmetrical plate structures and a tidal turbine blade demonstrate the effectiveness of the proposed method, which consistently outperforms the existing reference-free technique, particularly in detecting minor damage in asymmetrical structures under highly damped and noisy conditions. The proposed method can be applied to a diverse range of structures, and its robustness and ease of implementation make it a promising solution for long-term structural health monitoring in complex environments.