Assessment of Source of Non-Linearities in Guided Wave Sensing: a comparative study

Non-linear wave features are considered for damage detection in structures. The idea comes from the fact that, healthy structures are mostly linear, and any non-linearity such as crack, or delamination will lead to non-linear wave behaviour, which can be detected for damage diagnosis as well as damage localization. The application of these features to guided waves (GW) based monitoring is challenging. Often, the source of the non-linearity is not the damage, but the acquisition system. Furthermore, the non-linear features from GW data are often masked in the measurement noise. To continue their utilization for reference-free structural health monitoring (SHM) the sources of non-linearity should be thoroughly investigated. Hence, in this work, we compare the sensing of non linear features with three measurement techniques: non-contact LDV, FBG, and PZT-based sensors. The study is carried out on two aluminium beams one linear sample and another with known non-linearities.