The use of Hurst exponent in impedance-based structural health monitoring

This work presents the use of the Hurst exponent in structural health monitoring based on the electromechanical impedance method. This technique uses piezoelectric patches bonded to the structure (or incorporated into) to measure impedance signatures. Any changes between the obtained curves may be related to the existence of damage in the monitored system. Damage metrics are calculated by proper equations used to quantify changes in impedance signatures, which present values very close to zero for undamaged structural condition (pristine) and increases as the damage become more evident. The Hurst exponent will be presented and discussed as a new damage metric to detect changes in impedance signatures due to the existence of damage, as an alternative to other damage metrics already consolidated in the literature. The effectiveness of Hurst exponent for damage detection is evaluated by using a set of experiments that were carried out on small aluminum beams, subjected to tests without and with the existence of damage for different environment temperatures. The damage analysis is performed by considering the comparison of the values obtained from Hurst exponent technique with the values from existing damage metrics. The results show that the Hurst exponent as a damage metric allows for the detection of the existence of damage in all test conditions. The results obtained demonstrate the advantages and disadvantages of the Hurst method in the context of the electromechanical impedance technique for structural health monitoring.