Dynamic time warping based on signal instantaneous phase difference for guided wave structural health monitoring under load variation

Structural load variations have significant effects on the propagation of guided waves and therefore can lead to the increasing of diagnostic difficulty of the guided wave-based structural health monitoring, which may cause the diagnostic error of damage and limit the practical application of the method. In order to mitigate the load effect, a dynamic time warping load compensation method based on signal instantaneous phase difference is developed in this study, which can compensate the phase of the guide wave signal. The effectiveness of the proposed method is validated by the composite panel experiment and damage monitoring of composite T-joint under tensile load. The results show that the proposed method can effectively mitigate the load effect on the phase of guide wave signal and identify the damage of composite T-joint under tensile load accurately.