Energy Correlated Damage Indices in Fatigue Crack Extent Quantification

Signals received by piezoelectric transducers (PZT) network can be influenced by many factors. Apart from environmental conditions, whose variability should be compensated, significant difference in a signal can be also caused by relative geometry changes of a designed sensor's node, e.g. the damage localization and its orientation with respect to sensors location in the node. In the adopted approach a set of Damage Indices (DI's), carrying marginal signal information content and correlated with the total energy received by a given sensor are proposed. These are sensitive to the two main modes of guided wave interaction with a fatigue crack, i.e. its transmission and reflection from a damage. Detailed description of DI's detection capabilities are delivered in the paper. Two dimensional reduction techniques: Principal Component Analysis and Fisher's Linear Discriminant are compared. The results of the data collected from specimen fatigue tests are used to compare several classification models based on the emerged effective Damage Indices.