Guided wave health monitoring of complex structures by sparse array systems: Influence of temperature changes on performance

Structural health monitoring of complex structures with guided waves is complicated because of the large number of overlapping reflections obtained in time-traces. One of the strategies to avoid having to interpret raw time signals is to use baseline subtraction techniques. However, environmental effects modify the signals, causing large amplitude levels in the subtracted signal which can mask information received from weak reflectors such as defects. A large database of baselines covering environmental effects commonly faced by the structure becomes necessary, and the simple gathering of these baselines becomes a difficult task. This paper investigates how a temperature compensation method can be used to reduce the number of signals required in the database. The strong influence of signal complexity and mode purity on the effectiveness of this method is shown experimentally. Finally, an airframe panel is tested using a temperature compensation strategy developed.